M7350/base/services/java/com/android/server/am/ActivityStack.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.am;

import com.android.internal.app.HeavyWeightSwitcherActivity;
import com.android.internal.os.BatteryStatsImpl;
import com.android.server.am.ActivityManagerService.PendingActivityLaunch;

import android.app.Activity;
import android.app.AppGlobals;
import android.app.IActivityManager;
import static android.app.IActivityManager.START_CLASS_NOT_FOUND;
import static android.app.IActivityManager.START_DELIVERED_TO_TOP;
import static android.app.IActivityManager.START_FORWARD_AND_REQUEST_CONFLICT;
import static android.app.IActivityManager.START_INTENT_NOT_RESOLVED;
import static android.app.IActivityManager.START_PERMISSION_DENIED;
import static android.app.IActivityManager.START_RETURN_INTENT_TO_CALLER;
import static android.app.IActivityManager.START_SUCCESS;
import static android.app.IActivityManager.START_SWITCHES_CANCELED;
import static android.app.IActivityManager.START_TASK_TO_FRONT;
import android.app.IApplicationThread;
import android.app.PendingIntent;
import android.app.ResultInfo;
import android.app.IActivityManager.WaitResult;
import android.content.ComponentName;
import android.content.Context;
import android.content.IIntentSender;
import android.content.Intent;
import android.content.IntentSender;
import android.content.pm.ActivityInfo;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.content.res.Configuration;
import android.net.Uri;
import android.os.Binder;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.PowerManager;
import android.os.RemoteException;
import android.os.SystemClock;
import android.util.EventLog;
import android.util.Log;
import android.util.Slog;
import android.view.WindowManagerPolicy;
import com.android.internal.app.ActivityTrigger;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * State and management of a single stack of activities.
 */
public class ActivityStack {
    static final String TAG = ActivityManagerService.TAG;
    static final boolean localLOGV = ActivityManagerService.localLOGV;
    static final boolean DEBUG_SWITCH = ActivityManagerService.DEBUG_SWITCH;
    static final boolean DEBUG_PAUSE = ActivityManagerService.DEBUG_PAUSE;
    static final boolean DEBUG_VISBILITY = ActivityManagerService.DEBUG_VISBILITY;
    static final boolean DEBUG_USER_LEAVING = ActivityManagerService.DEBUG_USER_LEAVING;
    static final boolean DEBUG_TRANSITION = ActivityManagerService.DEBUG_TRANSITION;
    static final boolean DEBUG_RESULTS = ActivityManagerService.DEBUG_RESULTS;
    static final boolean DEBUG_CONFIGURATION = ActivityManagerService.DEBUG_CONFIGURATION;
    static final boolean DEBUG_TASKS = ActivityManagerService.DEBUG_TASKS;
    
    static final boolean VALIDATE_TOKENS = ActivityManagerService.VALIDATE_TOKENS;
    
    // How long we wait until giving up on the last activity telling us it
    // is idle.
    static final int IDLE_TIMEOUT = 10*1000;
    
    // How long we wait until giving up on the last activity to pause.  This
    // is short because it directly impacts the responsiveness of starting the
    // next activity.
    static final int PAUSE_TIMEOUT = 500;

    // How long we can hold the launch wake lock before giving up.
    static final int LAUNCH_TIMEOUT = 10*1000;

    // How long we wait until giving up on an activity telling us it has
    // finished destroying itself.
    static final int DESTROY_TIMEOUT = 10*1000;
    
    // How long until we reset a task when the user returns to it.  Currently
    // 30 minutes.
    static final long ACTIVITY_INACTIVE_RESET_TIME = 1000*60*30;
    
    // How long between activity launches that we consider safe to not warn
    // the user about an unexpected activity being launched on top.
    static final long START_WARN_TIME = 5*1000;
    
    // Set to false to disable the preview that is shown while a new activity
    // is being started.
    static final boolean SHOW_APP_STARTING_PREVIEW = true;
    
    enum ActivityState {
        INITIALIZING,
        RESUMED,
        PAUSING,
        PAUSED,
        STOPPING,
        STOPPED,
        FINISHING,
        DESTROYING,
        DESTROYED
    }

    final ActivityManagerService mService;
    final boolean mMainStack;
    
    final Context mContext;
    
    /**
     * The back history of all previous (and possibly still
     * running) activities.  It contains HistoryRecord objects.
     */
    final ArrayList mHistory = new ArrayList();
    
    /**
     * List of running activities, sorted by recent usage.
     * The first entry in the list is the least recently used.
     * It contains HistoryRecord objects.
     */
    final ArrayList mLRUActivities = new ArrayList();

    /**
     * List of activities that are waiting for a new activity
     * to become visible before completing whatever operation they are
     * supposed to do.
     */
    final ArrayList<ActivityRecord> mWaitingVisibleActivities
            = new ArrayList<ActivityRecord>();

    /**
     * List of activities that are ready to be stopped, but waiting
     * for the next activity to settle down before doing so.  It contains
     * HistoryRecord objects.
     */
    final ArrayList<ActivityRecord> mStoppingActivities
            = new ArrayList<ActivityRecord>();

    /**
     * Animations that for the current transition have requested not to
     * be considered for the transition animation.
     */
    final ArrayList<ActivityRecord> mNoAnimActivities
            = new ArrayList<ActivityRecord>();

    /**
     * List of activities that are ready to be finished, but waiting
     * for the previous activity to settle down before doing so.  It contains
     * HistoryRecord objects.
     */
    final ArrayList<ActivityRecord> mFinishingActivities
            = new ArrayList<ActivityRecord>();
    
    /**
     * List of people waiting to find out about the next launched activity.
     */
    final ArrayList<IActivityManager.WaitResult> mWaitingActivityLaunched
            = new ArrayList<IActivityManager.WaitResult>();
    
    /**
     * List of people waiting to find out about the next visible activity.
     */
    final ArrayList<IActivityManager.WaitResult> mWaitingActivityVisible
            = new ArrayList<IActivityManager.WaitResult>();
    
    /**
     * Set when the system is going to sleep, until we have
     * successfully paused the current activity and released our wake lock.
     * At that point the system is allowed to actually sleep.
     */
    final PowerManager.WakeLock mGoingToSleep;

    /**
     * We don't want to allow the device to go to sleep while in the process
     * of launching an activity.  This is primarily to allow alarm intent
     * receivers to launch an activity and get that to run before the device
     * goes back to sleep.
     */
    final PowerManager.WakeLock mLaunchingActivity;

    /**
     * When we are in the process of pausing an activity, before starting the
     * next one, this variable holds the activity that is currently being paused.
     */
    ActivityRecord mPausingActivity = null;

    /**
     * This is the last activity that we put into the paused state.  This is
     * used to determine if we need to do an activity transition while sleeping,
     * when we normally hold the top activity paused.
     */
    ActivityRecord mLastPausedActivity = null;

    /**
     * Current activity that is resumed, or null if there is none.
     */
    ActivityRecord mResumedActivity = null;
    
    /**
     * This is the last activity that has been started.  It is only used to
     * identify when multiple activities are started at once so that the user
     * can be warned they may not be in the activity they think they are.
     */
    ActivityRecord mLastStartedActivity = null;
    
    /**
     * Set when we know we are going to be calling updateConfiguration()
     * soon, so want to skip intermediate config checks.
     */
    boolean mConfigWillChange;

    /**
     * Set to indicate whether to issue an onUserLeaving callback when a
     * newly launched activity is being brought in front of us.
     */
    boolean mUserLeaving = false;
    
    long mInitialStartTime = 0;
    
    static final int PAUSE_TIMEOUT_MSG = 9;
    static final int IDLE_TIMEOUT_MSG = 10;
    static final int IDLE_NOW_MSG = 11;
    static final int LAUNCH_TIMEOUT_MSG = 16;
    static final int DESTROY_TIMEOUT_MSG = 17;
    static final int RESUME_TOP_ACTIVITY_MSG = 19;
    
    static final ActivityTrigger mActivityTrigger = new ActivityTrigger();

    final Handler mHandler = new Handler() {
        //public Handler() {
        //    if (localLOGV) Slog.v(TAG, "Handler started!");
        //}

        public void handleMessage(Message msg) {
            switch (msg.what) {
                case PAUSE_TIMEOUT_MSG: {
                    IBinder token = (IBinder)msg.obj;
                    // We don't at this point know if the activity is fullscreen,
                    // so we need to be conservative and assume it isn't.
                    Slog.w(TAG, "Activity pause timeout for " + token);
                    activityPaused(token, null, true);
                } break;
                case IDLE_TIMEOUT_MSG: {
                    if (mService.mDidDexOpt) {
                        mService.mDidDexOpt = false;
                        Message nmsg = mHandler.obtainMessage(IDLE_TIMEOUT_MSG);
                        nmsg.obj = msg.obj;
                        mHandler.sendMessageDelayed(nmsg, IDLE_TIMEOUT);
                        return;
                    }
                    // We don't at this point know if the activity is fullscreen,
                    // so we need to be conservative and assume it isn't.
                    IBinder token = (IBinder)msg.obj;
                    Slog.w(TAG, "Activity idle timeout for " + token);
                    activityIdleInternal(token, true, null);
                } break;
                case DESTROY_TIMEOUT_MSG: {
                    IBinder token = (IBinder)msg.obj;
                    // We don't at this point know if the activity is fullscreen,
                    // so we need to be conservative and assume it isn't.
                    Slog.w(TAG, "Activity destroy timeout for " + token);
                    activityDestroyed(token);
                } break;
                case IDLE_NOW_MSG: {
                    IBinder token = (IBinder)msg.obj;
                    activityIdleInternal(token, false, null);
                } break;
                case LAUNCH_TIMEOUT_MSG: {
                    if (mService.mDidDexOpt) {
                        mService.mDidDexOpt = false;
                        Message nmsg = mHandler.obtainMessage(LAUNCH_TIMEOUT_MSG);
                        mHandler.sendMessageDelayed(nmsg, LAUNCH_TIMEOUT);
                        return;
                    }
                    synchronized (mService) {
                        if (mLaunchingActivity.isHeld()) {
                            Slog.w(TAG, "Launch timeout has expired, giving up wake lock!");
                            mLaunchingActivity.release();
                        }
                    }
                } break;
                case RESUME_TOP_ACTIVITY_MSG: {
                    synchronized (mService) {
                        resumeTopActivityLocked(null);
                    }
                } break;
            }
        }
    };
    
    ActivityStack(ActivityManagerService service, Context context, boolean mainStack) {
        mService = service;
        mContext = context;
        mMainStack = mainStack;
        PowerManager pm =
            (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        mGoingToSleep = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "ActivityManager-Sleep");
        mLaunchingActivity = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "ActivityManager-Launch");
        mLaunchingActivity.setReferenceCounted(false);
    }
    
    final ActivityRecord topRunningActivityLocked(ActivityRecord notTop) {
        int i = mHistory.size()-1;
        while (i >= 0) {
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (!r.finishing && r != notTop) {
                return r;
            }
            i--;
        }
        return null;
    }

    final ActivityRecord topRunningNonDelayedActivityLocked(ActivityRecord notTop) {
        int i = mHistory.size()-1;
        while (i >= 0) {
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (!r.finishing && !r.delayedResume && r != notTop) {
                return r;
            }
            i--;
        }
        return null;
    }

    /**
     * This is a simplified version of topRunningActivityLocked that provides a number of
     * optional skip-over modes.  It is intended for use with the ActivityController hook only.
     * 
     * @param token If non-null, any history records matching this token will be skipped.
     * @param taskId If non-zero, we'll attempt to skip over records with the same task ID.
     * 
     * @return Returns the HistoryRecord of the next activity on the stack.
     */
    final ActivityRecord topRunningActivityLocked(IBinder token, int taskId) {
        int i = mHistory.size()-1;
        while (i >= 0) {
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            // Note: the taskId check depends on real taskId fields being non-zero
            if (!r.finishing && (token != r) && (taskId != r.task.taskId)) {
                return r;
            }
            i--;
        }
        return null;
    }

    final int indexOfTokenLocked(IBinder token) {
        int count = mHistory.size();

        // convert the token to an entry in the history.
        int index = -1;
        for (int i=count-1; i>=0; i--) {
            Object o = mHistory.get(i);
            if (o == token) {
                index = i;
                break;
            }
        }

        return index;
    }

    private final boolean updateLRUListLocked(ActivityRecord r) {
        final boolean hadit = mLRUActivities.remove(r);
        mLRUActivities.add(r);
        return hadit;
    }

    /**
     * Returns the top activity in any existing task matching the given
     * Intent.  Returns null if no such task is found.
     */
    private ActivityRecord findTaskLocked(Intent intent, ActivityInfo info) {
        ComponentName cls = intent.getComponent();
        if (info.targetActivity != null) {
            cls = new ComponentName(info.packageName, info.targetActivity);
        }

        TaskRecord cp = null;

        final int N = mHistory.size();
        for (int i=(N-1); i>=0; i--) {
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (!r.finishing && r.task != cp
                    && r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
                cp = r.task;
                //Slog.i(TAG, "Comparing existing cls=" + r.task.intent.getComponent().flattenToShortString()
                //        + "/aff=" + r.task.affinity + " to new cls="
                //        + intent.getComponent().flattenToShortString() + "/aff=" + taskAffinity);
                if (r.task.affinity != null) {
                    if (r.task.affinity.equals(info.taskAffinity)) {
                        //Slog.i(TAG, "Found matching affinity!");
                        return r;
                    }
                } else if (r.task.intent != null
                        && r.task.intent.getComponent().equals(cls)) {
                    //Slog.i(TAG, "Found matching class!");
                    //dump();
                    //Slog.i(TAG, "For Intent " + intent + " bringing to top: " + r.intent);
                    return r;
                } else if (r.task.affinityIntent != null
                        && r.task.affinityIntent.getComponent().equals(cls)) {
                    //Slog.i(TAG, "Found matching class!");
                    //dump();
                    //Slog.i(TAG, "For Intent " + intent + " bringing to top: " + r.intent);
                    return r;
                }
            }
        }

        return null;
    }

    /**
     * Returns the first activity (starting from the top of the stack) that
     * is the same as the given activity.  Returns null if no such activity
     * is found.
     */
    private ActivityRecord findActivityLocked(Intent intent, ActivityInfo info) {
        ComponentName cls = intent.getComponent();
        if (info.targetActivity != null) {
            cls = new ComponentName(info.packageName, info.targetActivity);
        }

        final int N = mHistory.size();
        for (int i=(N-1); i>=0; i--) {
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (!r.finishing) {
                if (r.intent.getComponent().equals(cls)) {
                    //Slog.i(TAG, "Found matching class!");
                    //dump();
                    //Slog.i(TAG, "For Intent " + intent + " bringing to top: " + r.intent);
                    return r;
                }
            }
        }

        return null;
    }

    final boolean realStartActivityLocked(ActivityRecord r,
            ProcessRecord app, boolean andResume, boolean checkConfig)
            throws RemoteException {

        r.startFreezingScreenLocked(app, 0);
        mService.mWindowManager.setAppVisibility(r, true);

        // Have the window manager re-evaluate the orientation of
        // the screen based on the new activity order.  Note that
        // as a result of this, it can call back into the activity
        // manager with a new orientation.  We don't care about that,
        // because the activity is not currently running so we are
        // just restarting it anyway.
        if (checkConfig) {
            Configuration config = mService.mWindowManager.updateOrientationFromAppTokens(
                    mService.mConfiguration,
                    r.mayFreezeScreenLocked(app) ? r : null);
            mService.updateConfigurationLocked(config, r);
        }

        r.app = app;

        if (localLOGV) Slog.v(TAG, "Launching: " + r);

        int idx = app.activities.indexOf(r);
        if (idx < 0) {
            app.activities.add(r);
        }
        mService.updateLruProcessLocked(app, true, true);

        try {
            if (app.thread == null) {
                throw new RemoteException();
            }
            List<ResultInfo> results = null;
            List<Intent> newIntents = null;
            if (andResume) {
                results = r.results;
                newIntents = r.newIntents;
            }
            if (DEBUG_SWITCH) Slog.v(TAG, "Launching: " + r
                    + " icicle=" + r.icicle
                    + " with results=" + results + " newIntents=" + newIntents
                    + " andResume=" + andResume);
            if (andResume) {
                EventLog.writeEvent(EventLogTags.AM_RESTART_ACTIVITY,
                        System.identityHashCode(r),
                        r.task.taskId, r.shortComponentName);
            }
            if (r.isHomeActivity) {
                mService.mHomeProcess = app;
            }
            mService.ensurePackageDexOpt(r.intent.getComponent().getPackageName());
            app.thread.scheduleLaunchActivity(new Intent(r.intent), r,
                    System.identityHashCode(r),
                    r.info, r.icicle, results, newIntents, !andResume,
                    mService.isNextTransitionForward());
            
            if ((app.info.flags&ApplicationInfo.FLAG_CANT_SAVE_STATE) != 0) {
                // This may be a heavy-weight process!  Note that the package
                // manager will ensure that only activity can run in the main
                // process of the .apk, which is the only thing that will be
                // considered heavy-weight.
                if (app.processName.equals(app.info.packageName)) {
                    if (mService.mHeavyWeightProcess != null
                            && mService.mHeavyWeightProcess != app) {
                        Log.w(TAG, "Starting new heavy weight process " + app
                                + " when already running "
                                + mService.mHeavyWeightProcess);
                    }
                    mService.mHeavyWeightProcess = app;
                    Message msg = mService.mHandler.obtainMessage(
                            ActivityManagerService.POST_HEAVY_NOTIFICATION_MSG);
                    msg.obj = r;
                    mService.mHandler.sendMessage(msg);
                }
            }
            
        } catch (RemoteException e) {
            if (r.launchFailed) {
                // This is the second time we failed -- finish activity
                // and give up.
                Slog.e(TAG, "Second failure launching "
                      + r.intent.getComponent().flattenToShortString()
                      + ", giving up", e);
                mService.appDiedLocked(app, app.pid, app.thread);
                requestFinishActivityLocked(r, Activity.RESULT_CANCELED, null,
                        "2nd-crash");
                return false;
            }

            // This is the first time we failed -- restart process and
            // retry.
            app.activities.remove(r);
            throw e;
        }

        r.launchFailed = false;
        if (updateLRUListLocked(r)) {
            Slog.w(TAG, "Activity " + r
                  + " being launched, but already in LRU list");
        }

        if (andResume) {
            // As part of the process of launching, ActivityThread also performs
            // a resume.
            r.state = ActivityState.RESUMED;
            r.icicle = null;
            r.haveState = false;
            r.stopped = false;
            mResumedActivity = r;
            r.task.touchActiveTime();
            completeResumeLocked(r);
            pauseIfSleepingLocked();                
        } else {
            // This activity is not starting in the resumed state... which
            // should look like we asked it to pause+stop (but remain visible),
            // and it has done so and reported back the current icicle and
            // other state.
            r.state = ActivityState.STOPPED;
            r.stopped = true;
        }

        // Launch the new version setup screen if needed.  We do this -after-
        // launching the initial activity (that is, home), so that it can have
        // a chance to initialize itself while in the background, making the
        // switch back to it faster and look better.
        if (mMainStack) {
            mService.startSetupActivityLocked();
        }
        
        return true;
    }

    private final void startSpecificActivityLocked(ActivityRecord r,
            boolean andResume, boolean checkConfig) {
        // Is this activity's application already running?
        ProcessRecord app = mService.getProcessRecordLocked(r.processName,
                r.info.applicationInfo.uid);
        
        if (r.launchTime == 0) {
            r.launchTime = SystemClock.uptimeMillis();
            if (mInitialStartTime == 0) {
                mInitialStartTime = r.launchTime;
            }
        } else if (mInitialStartTime == 0) {
            mInitialStartTime = SystemClock.uptimeMillis();
        }
        
        if (app != null && app.thread != null) {
            try {
                realStartActivityLocked(r, app, andResume, checkConfig);
                return;
            } catch (RemoteException e) {
                Slog.w(TAG, "Exception when starting activity "
                        + r.intent.getComponent().flattenToShortString(), e);
            }

            // If a dead object exception was thrown -- fall through to
            // restart the application.
        }

        mService.startProcessLocked(r.processName, r.info.applicationInfo, true, 0,
                "activity", r.intent.getComponent(), false);
    }
    
    void pauseIfSleepingLocked() {
        if (mService.mSleeping || mService.mShuttingDown) {
            if (!mGoingToSleep.isHeld()) {
                mGoingToSleep.acquire();
                if (mLaunchingActivity.isHeld()) {
                    mLaunchingActivity.release();
                    mService.mHandler.removeMessages(LAUNCH_TIMEOUT_MSG);
                }
            }

            // If we are not currently pausing an activity, get the current
            // one to pause.  If we are pausing one, we will just let that stuff
            // run and release the wake lock when all done.
            if (mPausingActivity == null) {
                if (DEBUG_PAUSE) Slog.v(TAG, "Sleep needs to pause...");
                if (DEBUG_USER_LEAVING) Slog.v(TAG, "Sleep => pause with userLeaving=false");
                startPausingLocked(false, true);
            }
        }
    }
    
    private final void startPausingLocked(boolean userLeaving, boolean uiSleeping) {
        if (mPausingActivity != null) {
            RuntimeException e = new RuntimeException();
            Slog.e(TAG, "Trying to pause when pause is already pending for "
                  + mPausingActivity, e);
        }
        ActivityRecord prev = mResumedActivity;
        if (prev == null) {
            RuntimeException e = new RuntimeException();
            Slog.e(TAG, "Trying to pause when nothing is resumed", e);
            resumeTopActivityLocked(null);
            return;
        }
        if (DEBUG_PAUSE) Slog.v(TAG, "Start pausing: " + prev);
        mResumedActivity = null;
        mPausingActivity = prev;
        mLastPausedActivity = prev;
        prev.state = ActivityState.PAUSING;
        prev.task.touchActiveTime();

        mService.updateCpuStats();
        
        if (prev.app != null && prev.app.thread != null) {
            if (DEBUG_PAUSE) Slog.v(TAG, "Enqueueing pending pause: " + prev);
            try {
                EventLog.writeEvent(EventLogTags.AM_PAUSE_ACTIVITY,
                        System.identityHashCode(prev),
                        prev.shortComponentName);
                prev.app.thread.schedulePauseActivity(prev, prev.finishing, userLeaving,
                        prev.configChangeFlags);
                if (mMainStack) {
                    mService.updateUsageStats(prev, false);
                }
            } catch (Exception e) {
                // Ignore exception, if process died other code will cleanup.
                Slog.w(TAG, "Exception thrown during pause", e);
                mPausingActivity = null;
                mLastPausedActivity = null;
            }
        } else {
            mPausingActivity = null;
            mLastPausedActivity = null;
        }

        // If we are not going to sleep, we want to ensure the device is
        // awake until the next activity is started.
        if (!mService.mSleeping && !mService.mShuttingDown) {
            mLaunchingActivity.acquire();
            if (!mHandler.hasMessages(LAUNCH_TIMEOUT_MSG)) {
                // To be safe, don't allow the wake lock to be held for too long.
                Message msg = mHandler.obtainMessage(LAUNCH_TIMEOUT_MSG);
                mHandler.sendMessageDelayed(msg, LAUNCH_TIMEOUT);
            }
        }


        if (mPausingActivity != null) {
            // Have the window manager pause its key dispatching until the new
            // activity has started.  If we're pausing the activity just because
            // the screen is being turned off and the UI is sleeping, don't interrupt
            // key dispatch; the same activity will pick it up again on wakeup.
            if (!uiSleeping) {
                prev.pauseKeyDispatchingLocked();
            } else {
                if (DEBUG_PAUSE) Slog.v(TAG, "Key dispatch not paused for screen off");
            }

            // Schedule a pause timeout in case the app doesn't respond.
            // We don't give it much time because this directly impacts the
            // responsiveness seen by the user.
            Message msg = mHandler.obtainMessage(PAUSE_TIMEOUT_MSG);
            msg.obj = prev;
            mHandler.sendMessageDelayed(msg, PAUSE_TIMEOUT);
            if (DEBUG_PAUSE) Slog.v(TAG, "Waiting for pause to complete...");
        } else {
            // This activity failed to schedule the
            // pause, so just treat it as being paused now.
            if (DEBUG_PAUSE) Slog.v(TAG, "Activity not running, resuming next.");
            resumeTopActivityLocked(null);
        }
    }
    
    final void activityPaused(IBinder token, Bundle icicle, boolean timeout) {
        if (DEBUG_PAUSE) Slog.v(
            TAG, "Activity paused: token=" + token + ", icicle=" + icicle
            + ", timeout=" + timeout);

        ActivityRecord r = null;

        synchronized (mService) {
            int index = indexOfTokenLocked(token);
            if (index >= 0) {
                r = (ActivityRecord)mHistory.get(index);
                if (!timeout) {
                    r.icicle = icicle;
                    r.haveState = true;
                }
                mHandler.removeMessages(PAUSE_TIMEOUT_MSG, r);
                if (mPausingActivity == r) {
                    r.state = ActivityState.PAUSED;
                    completePauseLocked();
                } else {
                    EventLog.writeEvent(EventLogTags.AM_FAILED_TO_PAUSE,
                            System.identityHashCode(r), r.shortComponentName, 
                            mPausingActivity != null
                                ? mPausingActivity.shortComponentName : "(none)");
                }
            }
        }
    }

    private final void completePauseLocked() {
        ActivityRecord prev = mPausingActivity;
        if (DEBUG_PAUSE) Slog.v(TAG, "Complete pause: " + prev);
        
        if (prev != null) {
            if (prev.finishing) {
                if (DEBUG_PAUSE) Slog.v(TAG, "Executing finish of activity: " + prev);
                prev = finishCurrentActivityLocked(prev, FINISH_AFTER_VISIBLE);
            } else if (prev.app != null) {
                if (DEBUG_PAUSE) Slog.v(TAG, "Enqueueing pending stop: " + prev);
                if (prev.waitingVisible) {
                    prev.waitingVisible = false;
                    mWaitingVisibleActivities.remove(prev);
                    if (DEBUG_SWITCH || DEBUG_PAUSE) Slog.v(
                            TAG, "Complete pause, no longer waiting: " + prev);
                }
                if (prev.configDestroy) {
                    // The previous is being paused because the configuration
                    // is changing, which means it is actually stopping...
                    // To juggle the fact that we are also starting a new
                    // instance right now, we need to first completely stop
                    // the current instance before starting the new one.
                    if (DEBUG_PAUSE) Slog.v(TAG, "Destroying after pause: " + prev);
                    destroyActivityLocked(prev, true);
                } else {
                    mStoppingActivities.add(prev);
                    if (mStoppingActivities.size() > 3) {
                        // If we already have a few activities waiting to stop,
                        // then give up on things going idle and start clearing
                        // them out.
                        if (DEBUG_PAUSE) Slog.v(TAG, "To many pending stops, forcing idle");
                        Message msg = Message.obtain();
                        msg.what = IDLE_NOW_MSG;
                        mHandler.sendMessage(msg);
                    }
                }
            } else {
                if (DEBUG_PAUSE) Slog.v(TAG, "App died during pause, not stopping: " + prev);
                prev = null;
            }
            mPausingActivity = null;
        }

        if (!mService.mSleeping && !mService.mShuttingDown) {
            resumeTopActivityLocked(prev);
        } else {
            if (mGoingToSleep.isHeld()) {
                mGoingToSleep.release();
            }
            if (mService.mShuttingDown) {
                mService.notifyAll();
            }
        }
        
        if (prev != null) {
            prev.resumeKeyDispatchingLocked();
        }

        if (prev.app != null && prev.cpuTimeAtResume > 0
                && mService.mBatteryStatsService.isOnBattery()) {
            long diff = 0;
            synchronized (mService.mProcessStatsThread) {
                diff = mService.mProcessStats.getCpuTimeForPid(prev.app.pid)
                        - prev.cpuTimeAtResume;
            }
            if (diff > 0) {
                BatteryStatsImpl bsi = mService.mBatteryStatsService.getActiveStatistics();
                synchronized (bsi) {
                    BatteryStatsImpl.Uid.Proc ps =
                            bsi.getProcessStatsLocked(prev.info.applicationInfo.uid,
                            prev.info.packageName);
                    if (ps != null) {
                        ps.addForegroundTimeLocked(diff);
                    }
                }
            }
        }
        prev.cpuTimeAtResume = 0; // reset it
    }

    /**
     * Once we know that we have asked an application to put an activity in
     * the resumed state (either by launching it or explicitly telling it),
     * this function updates the rest of our state to match that fact.
     */
    private final void completeResumeLocked(ActivityRecord next) {
        next.idle = false;
        next.results = null;
        next.newIntents = null;

        // schedule an idle timeout in case the app doesn't do it for us.
        Message msg = mHandler.obtainMessage(IDLE_TIMEOUT_MSG);
        msg.obj = next;
        mHandler.sendMessageDelayed(msg, IDLE_TIMEOUT);

        if (false) {
            // The activity was never told to pause, so just keep
            // things going as-is.  To maintain our own state,
            // we need to emulate it coming back and saying it is
            // idle.
            msg = mHandler.obtainMessage(IDLE_NOW_MSG);
            msg.obj = next;
            mHandler.sendMessage(msg);
        }

        if (mMainStack) {
            mService.reportResumedActivityLocked(next);
        }
        
        next.thumbnail = null;
        if (mMainStack) {
            mService.setFocusedActivityLocked(next);
        }
        next.resumeKeyDispatchingLocked();
        ensureActivitiesVisibleLocked(null, 0);
        mService.mWindowManager.executeAppTransition();
        mNoAnimActivities.clear();

        // Mark the point when the activity is resuming
        // TODO: To be more accurate, the mark should be before the onCreate,
        //       not after the onResume. But for subsequent starts, onResume is fine.
        if (next.app != null) {
            synchronized (mService.mProcessStatsThread) {
                next.cpuTimeAtResume = mService.mProcessStats.getCpuTimeForPid(next.app.pid);
            }
        } else {
            next.cpuTimeAtResume = 0; // Couldn't get the cpu time of process
        }
    }

    /**
     * Make sure that all activities that need to be visible (that is, they
     * currently can be seen by the user) actually are.
     */
    final void ensureActivitiesVisibleLocked(ActivityRecord top,
            ActivityRecord starting, String onlyThisProcess, int configChanges) {
        if (DEBUG_VISBILITY) Slog.v(
                TAG, "ensureActivitiesVisible behind " + top
                + " configChanges=0x" + Integer.toHexString(configChanges));

        // If the top activity is not fullscreen, then we need to
        // make sure any activities under it are now visible.
        final int count = mHistory.size();
        int i = count-1;
        while (mHistory.get(i) != top) {
            i--;
        }
        ActivityRecord r;
        boolean behindFullscreen = false;
        for (; i>=0; i--) {
            r = (ActivityRecord)mHistory.get(i);
            if (DEBUG_VISBILITY) Slog.v(
                    TAG, "Make visible? " + r + " finishing=" + r.finishing
                    + " state=" + r.state);
            if (r.finishing) {
                continue;
            }
            
            final boolean doThisProcess = onlyThisProcess == null
                    || onlyThisProcess.equals(r.processName);
            
            // First: if this is not the current activity being started, make
            // sure it matches the current configuration.
            if (r != starting && doThisProcess) {
                ensureActivityConfigurationLocked(r, 0);
            }
            
            if (r.app == null || r.app.thread == null) {
                if (onlyThisProcess == null
                        || onlyThisProcess.equals(r.processName)) {
                    // This activity needs to be visible, but isn't even
                    // running...  get it started, but don't resume it
                    // at this point.
                    if (DEBUG_VISBILITY) Slog.v(
                            TAG, "Start and freeze screen for " + r);
                    if (r != starting) {
                        r.startFreezingScreenLocked(r.app, configChanges);
                    }
                    if (!r.visible) {
                        if (DEBUG_VISBILITY) Slog.v(
                                TAG, "Starting and making visible: " + r);
                        mService.mWindowManager.setAppVisibility(r, true);
                    }
                    if (r != starting) {
                        startSpecificActivityLocked(r, false, false);
                    }
                }

            } else if (r.visible) {
                // If this activity is already visible, then there is nothing
                // else to do here.
                if (DEBUG_VISBILITY) Slog.v(
                        TAG, "Skipping: already visible at " + r);
                r.stopFreezingScreenLocked(false);

            } else if (onlyThisProcess == null) {
                // This activity is not currently visible, but is running.
                // Tell it to become visible.
                r.visible = true;
                if (r.state != ActivityState.RESUMED && r != starting) {
                    // If this activity is paused, tell it
                    // to now show its window.
                    if (DEBUG_VISBILITY) Slog.v(
                            TAG, "Making visible and scheduling visibility: " + r);
                    try {
                        mService.mWindowManager.setAppVisibility(r, true);
                        r.app.thread.scheduleWindowVisibility(r, true);
                        r.stopFreezingScreenLocked(false);
                    } catch (Exception e) {
                        // Just skip on any failure; we'll make it
                        // visible when it next restarts.
                        Slog.w(TAG, "Exception thrown making visibile: "
                                + r.intent.getComponent(), e);
                    }
                }
            }

            // Aggregate current change flags.
            configChanges |= r.configChangeFlags;

            if (r.fullscreen) {
                // At this point, nothing else needs to be shown
                if (DEBUG_VISBILITY) Slog.v(
                        TAG, "Stopping: fullscreen at " + r);
                behindFullscreen = true;
                i--;
                break;
            }
        }

        // Now for any activities that aren't visible to the user, make
        // sure they no longer are keeping the screen frozen.
        while (i >= 0) {
            r = (ActivityRecord)mHistory.get(i);
            if (DEBUG_VISBILITY) Slog.v(
                    TAG, "Make invisible? " + r + " finishing=" + r.finishing
                    + " state=" + r.state
                    + " behindFullscreen=" + behindFullscreen);
            if (!r.finishing) {
                if (behindFullscreen) {
                    if (r.visible) {
                        if (DEBUG_VISBILITY) Slog.v(
                                TAG, "Making invisible: " + r);
                        r.visible = false;
                        try {
                            mService.mWindowManager.setAppVisibility(r, false);
                            if ((r.state == ActivityState.STOPPING
                                    || r.state == ActivityState.STOPPED)
                                    && r.app != null && r.app.thread != null) {
                                if (DEBUG_VISBILITY) Slog.v(
                                        TAG, "Scheduling invisibility: " + r);
                                r.app.thread.scheduleWindowVisibility(r, false);
                            }
                        } catch (Exception e) {
                            // Just skip on any failure; we'll make it
                            // visible when it next restarts.
                            Slog.w(TAG, "Exception thrown making hidden: "
                                    + r.intent.getComponent(), e);
                        }
                    } else {
                        if (DEBUG_VISBILITY) Slog.v(
                                TAG, "Already invisible: " + r);
                    }
                } else if (r.fullscreen) {
                    if (DEBUG_VISBILITY) Slog.v(
                            TAG, "Now behindFullscreen: " + r);
                    behindFullscreen = true;
                }
            }
            i--;
        }
    }

    /**
     * Version of ensureActivitiesVisible that can easily be called anywhere.
     */
    final void ensureActivitiesVisibleLocked(ActivityRecord starting,
            int configChanges) {
        ActivityRecord r = topRunningActivityLocked(null);
        if (r != null) {
            ensureActivitiesVisibleLocked(r, starting, null, configChanges);
        }
    }
    
    /**
     * Ensure that the top activity in the stack is resumed.
     *
     * @param prev The previously resumed activity, for when in the process
     * of pausing; can be null to call from elsewhere.
     *
     * @return Returns true if something is being resumed, or false if
     * nothing happened.
     */
    final boolean resumeTopActivityLocked(ActivityRecord prev) {
        // Find the first activity that is not finishing.
        ActivityRecord next = topRunningActivityLocked(null);

        // Remember how we'll process this pause/resume situation, and ensure
        // that the state is reset however we wind up proceeding.
        final boolean userLeaving = mUserLeaving;
        mUserLeaving = false;

        if (next == null) {
            // There are no more activities!  Let's just start up the
            // Launcher...
            if (mMainStack) {
                return mService.startHomeActivityLocked();
            }
        }

        next.delayedResume = false;
        
        // If the top activity is the resumed one, nothing to do.
        if (mResumedActivity == next && next.state == ActivityState.RESUMED) {
            // Make sure we have executed any pending transitions, since there
            // should be nothing left to do at this point.
            mService.mWindowManager.executeAppTransition();
            mNoAnimActivities.clear();
            return false;
        }

        // If we are sleeping, and there is no resumed activity, and the top
        // activity is paused, well that is the state we want.
        if ((mService.mSleeping || mService.mShuttingDown)
                && mLastPausedActivity == next && next.state == ActivityState.PAUSED) {
            // Make sure we have executed any pending transitions, since there
            // should be nothing left to do at this point.
            mService.mWindowManager.executeAppTransition();
            mNoAnimActivities.clear();
            return false;
        }
        
        // The activity may be waiting for stop, but that is no longer
        // appropriate for it.
        mStoppingActivities.remove(next);
        mWaitingVisibleActivities.remove(next);

        if (DEBUG_SWITCH) Slog.v(TAG, "Resuming " + next);

        mActivityTrigger.activityResumeTrigger(next.intent);

        // If we are currently pausing an activity, then don't do anything
        // until that is done.
        if (mPausingActivity != null) {
            if (DEBUG_SWITCH) Slog.v(TAG, "Skip resume: pausing=" + mPausingActivity);
            return false;
        }

        // Okay we are now going to start a switch, to 'next'.  We may first
        // have to pause the current activity, but this is an important point
        // where we have decided to go to 'next' so keep track of that.
        // XXX "App Redirected" dialog is getting too many false positives
        // at this point, so turn off for now.
        if (false) {
            if (mLastStartedActivity != null && !mLastStartedActivity.finishing) {
                long now = SystemClock.uptimeMillis();
                final boolean inTime = mLastStartedActivity.startTime != 0
                        && (mLastStartedActivity.startTime + START_WARN_TIME) >= now;
                final int lastUid = mLastStartedActivity.info.applicationInfo.uid;
                final int nextUid = next.info.applicationInfo.uid;
                if (inTime && lastUid != nextUid
                        && lastUid != next.launchedFromUid
                        && mService.checkPermission(
                                android.Manifest.permission.STOP_APP_SWITCHES,
                                -1, next.launchedFromUid)
                        != PackageManager.PERMISSION_GRANTED) {
                    mService.showLaunchWarningLocked(mLastStartedActivity, next);
                } else {
                    next.startTime = now;
                    mLastStartedActivity = next;
                }
            } else {
                next.startTime = SystemClock.uptimeMillis();
                mLastStartedActivity = next;
            }
        }
        
        // We need to start pausing the current activity so the top one
        // can be resumed...
        if (mResumedActivity != null) {
            if (DEBUG_SWITCH) Slog.v(TAG, "Skip resume: need to start pausing");
            startPausingLocked(userLeaving, false);
            return true;
        }

        if (prev != null && prev != next) {
            if (!prev.waitingVisible && next != null && !next.nowVisible) {
                prev.waitingVisible = true;
                mWaitingVisibleActivities.add(prev);
                if (DEBUG_SWITCH) Slog.v(
                        TAG, "Resuming top, waiting visible to hide: " + prev);
            } else {
                // The next activity is already visible, so hide the previous
                // activity's windows right now so we can show the new one ASAP.
                // We only do this if the previous is finishing, which should mean
                // it is on top of the one being resumed so hiding it quickly
                // is good.  Otherwise, we want to do the normal route of allowing
                // the resumed activity to be shown so we can decide if the
                // previous should actually be hidden depending on whether the
                // new one is found to be full-screen or not.
                if (prev.finishing) {
                    mService.mWindowManager.setAppVisibility(prev, false);
                    if (DEBUG_SWITCH) Slog.v(TAG, "Not waiting for visible to hide: "
                            + prev + ", waitingVisible="
                            + (prev != null ? prev.waitingVisible : null)
                            + ", nowVisible=" + next.nowVisible);
                } else {
                    if (DEBUG_SWITCH) Slog.v(TAG, "Previous already visible but still waiting to hide: "
                        + prev + ", waitingVisible="
                        + (prev != null ? prev.waitingVisible : null)
                        + ", nowVisible=" + next.nowVisible);
                }
            }
        }

        // We are starting up the next activity, so tell the window manager
        // that the previous one will be hidden soon.  This way it can know
        // to ignore it when computing the desired screen orientation.
        if (prev != null) {
            if (prev.finishing) {
                if (DEBUG_TRANSITION) Slog.v(TAG,
                        "Prepare close transition: prev=" + prev);
                if (mNoAnimActivities.contains(prev)) {
                    mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
                } else {
                    mService.mWindowManager.prepareAppTransition(prev.task == next.task
                            ? WindowManagerPolicy.TRANSIT_ACTIVITY_CLOSE
                            : WindowManagerPolicy.TRANSIT_TASK_CLOSE);
                }
                mService.mWindowManager.setAppWillBeHidden(prev);
                mService.mWindowManager.setAppVisibility(prev, false);
            } else {
                if (DEBUG_TRANSITION) Slog.v(TAG,
                        "Prepare open transition: prev=" + prev);
                if (mNoAnimActivities.contains(next)) {
                    mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
                } else {
                    mService.mWindowManager.prepareAppTransition(prev.task == next.task
                            ? WindowManagerPolicy.TRANSIT_ACTIVITY_OPEN
                            : WindowManagerPolicy.TRANSIT_TASK_OPEN);
                }
            }
            if (false) {
                mService.mWindowManager.setAppWillBeHidden(prev);
                mService.mWindowManager.setAppVisibility(prev, false);
            }
        } else if (mHistory.size() > 1) {
            if (DEBUG_TRANSITION) Slog.v(TAG,
                    "Prepare open transition: no previous");
            if (mNoAnimActivities.contains(next)) {
                mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
            } else {
                mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_ACTIVITY_OPEN);
            }
        }

        if (next.app != null && next.app.thread != null) {
            if (DEBUG_SWITCH) Slog.v(TAG, "Resume running: " + next);

            // This activity is now becoming visible.
            mService.mWindowManager.setAppVisibility(next, true);

            ActivityRecord lastResumedActivity = mResumedActivity;
            ActivityState lastState = next.state;

            mService.updateCpuStats();
            
            next.state = ActivityState.RESUMED;
            mResumedActivity = next;
            next.task.touchActiveTime();
            mService.updateLruProcessLocked(next.app, true, true);
            updateLRUListLocked(next);

            // Have the window manager re-evaluate the orientation of
            // the screen based on the new activity order.
            boolean updated = false;
            if (mMainStack) {
                synchronized (mService) {
                    Configuration config = mService.mWindowManager.updateOrientationFromAppTokens(
                            mService.mConfiguration,
                            next.mayFreezeScreenLocked(next.app) ? next : null);
                    if (config != null) {
                        next.frozenBeforeDestroy = true;
                    }
                    updated = mService.updateConfigurationLocked(config, next);
                }
            }
            if (!updated) {
                // The configuration update wasn't able to keep the existing
                // instance of the activity, and instead started a new one.
                // We should be all done, but let's just make sure our activity
                // is still at the top and schedule another run if something
                // weird happened.
                ActivityRecord nextNext = topRunningActivityLocked(null);
                if (DEBUG_SWITCH) Slog.i(TAG,
                        "Activity config changed during resume: " + next
                        + ", new next: " + nextNext);
                if (nextNext != next) {
                    // Do over!
                    mHandler.sendEmptyMessage(RESUME_TOP_ACTIVITY_MSG);
                }
                if (mMainStack) {
                    mService.setFocusedActivityLocked(next);
                }
                ensureActivitiesVisibleLocked(null, 0);
                mService.mWindowManager.executeAppTransition();
                mNoAnimActivities.clear();
                return true;
            }
            
            try {
                // Deliver all pending results.
                ArrayList a = next.results;
                if (a != null) {
                    final int N = a.size();
                    if (!next.finishing && N > 0) {
                        if (DEBUG_RESULTS) Slog.v(
                                TAG, "Delivering results to " + next
                                + ": " + a);
                        next.app.thread.scheduleSendResult(next, a);
                    }
                }

                if (next.newIntents != null) {
                    next.app.thread.scheduleNewIntent(next.newIntents, next);
                }

                EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY,
                        System.identityHashCode(next),
                        next.task.taskId, next.shortComponentName);
                
                next.app.thread.scheduleResumeActivity(next,
                        mService.isNextTransitionForward());
                
                pauseIfSleepingLocked();

            } catch (Exception e) {
                // Whoops, need to restart this activity!
                next.state = lastState;
                mResumedActivity = lastResumedActivity;
                Slog.i(TAG, "Restarting because process died: " + next);
                if (!next.hasBeenLaunched) {
                    next.hasBeenLaunched = true;
                } else {
                    if (SHOW_APP_STARTING_PREVIEW && mMainStack) {
                        mService.mWindowManager.setAppStartingWindow(
                                next, next.packageName, next.theme,
                                next.nonLocalizedLabel,
                                next.labelRes, next.icon, null, true);
                    }
                }
                startSpecificActivityLocked(next, true, false);
                return true;
            }

            // From this point on, if something goes wrong there is no way
            // to recover the activity.
            try {
                next.visible = true;
                completeResumeLocked(next);
            } catch (Exception e) {
                // If any exception gets thrown, toss away this
                // activity and try the next one.
                Slog.w(TAG, "Exception thrown during resume of " + next, e);
                requestFinishActivityLocked(next, Activity.RESULT_CANCELED, null,
                        "resume-exception");
                return true;
            }

            // Didn't need to use the icicle, and it is now out of date.
            next.icicle = null;
            next.haveState = false;
            next.stopped = false;

        } else {
            // Whoops, need to restart this activity!
            if (!next.hasBeenLaunched) {
                next.hasBeenLaunched = true;
            } else {
                if (SHOW_APP_STARTING_PREVIEW) {
                    mService.mWindowManager.setAppStartingWindow(
                            next, next.packageName, next.theme,
                            next.nonLocalizedLabel,
                            next.labelRes, next.icon, null, true);
                }
                if (DEBUG_SWITCH) Slog.v(TAG, "Restarting: " + next);
            }
            startSpecificActivityLocked(next, true, true);
        }

        return true;
    }

    private final void startActivityLocked(ActivityRecord r, boolean newTask,
            boolean doResume) {
        final int NH = mHistory.size();

        int addPos = -1;
        
        if (!newTask) {
            // If starting in an existing task, find where that is...
            boolean startIt = true;
            for (int i = NH-1; i >= 0; i--) {
                ActivityRecord p = (ActivityRecord)mHistory.get(i);
                if (p.finishing) {
                    continue;
                }
                if (p.task == r.task) {
                    // Here it is!  Now, if this is not yet visible to the
                    // user, then just add it without starting; it will
                    // get started when the user navigates back to it.
                    addPos = i+1;
                    if (!startIt) {
                        mHistory.add(addPos, r);
                        r.inHistory = true;
                        r.task.numActivities++;
                        mService.mWindowManager.addAppToken(addPos, r, r.task.taskId,
                                r.info.screenOrientation, r.fullscreen);
                        if (VALIDATE_TOKENS) {
                            mService.mWindowManager.validateAppTokens(mHistory);
                        }
                        return;
                    }
                    break;
                }
                if (p.fullscreen) {
                    startIt = false;
                }
            }
        }

        // Place a new activity at top of stack, so it is next to interact
        // with the user.
        if (addPos < 0) {
            addPos = NH;
        }
        
        // If we are not placing the new activity frontmost, we do not want
        // to deliver the onUserLeaving callback to the actual frontmost
        // activity
        if (addPos < NH) {
            mUserLeaving = false;
            if (DEBUG_USER_LEAVING) Slog.v(TAG, "startActivity() behind front, mUserLeaving=false");
        }
        
        // Slot the activity into the history stack and proceed
        mHistory.add(addPos, r);
        r.inHistory = true;
        r.frontOfTask = newTask;
        r.task.numActivities++;
        if (NH > 0) {
            // We want to show the starting preview window if we are
            // switching to a new task, or the next activity's process is
            // not currently running.
            boolean showStartingIcon = newTask;
            ProcessRecord proc = r.app;
            if (proc == null) {
                proc = mService.mProcessNames.get(r.processName, r.info.applicationInfo.uid);
            }
            if (proc == null || proc.thread == null) {
                showStartingIcon = true;
            }
            if (DEBUG_TRANSITION) Slog.v(TAG,
                    "Prepare open transition: starting " + r);
            if ((r.intent.getFlags()&Intent.FLAG_ACTIVITY_NO_ANIMATION) != 0) {
                mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
                mNoAnimActivities.add(r);
            } else if ((r.intent.getFlags()&Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET) != 0) {
                mService.mWindowManager.prepareAppTransition(
                        WindowManagerPolicy.TRANSIT_TASK_OPEN);
                mNoAnimActivities.remove(r);
            } else {
                mService.mWindowManager.prepareAppTransition(newTask
                        ? WindowManagerPolicy.TRANSIT_TASK_OPEN
                        : WindowManagerPolicy.TRANSIT_ACTIVITY_OPEN);
                mNoAnimActivities.remove(r);
            }
            mService.mWindowManager.addAppToken(
                    addPos, r, r.task.taskId, r.info.screenOrientation, r.fullscreen);
            boolean doShow = true;
            if (newTask) {
                // Even though this activity is starting fresh, we still need
                // to reset it to make sure we apply affinities to move any
                // existing activities from other tasks in to it.
                // If the caller has requested that the target task be
                // reset, then do so.
                if ((r.intent.getFlags()
                        &Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
                    resetTaskIfNeededLocked(r, r);
                    doShow = topRunningNonDelayedActivityLocked(null) == r;
                }
            }
            if (SHOW_APP_STARTING_PREVIEW && doShow) {
                // Figure out if we are transitioning from another activity that is
                // "has the same starting icon" as the next one.  This allows the
                // window manager to keep the previous window it had previously
                // created, if it still had one.
                ActivityRecord prev = mResumedActivity;
                if (prev != null) {
                    // We don't want to reuse the previous starting preview if:
                    // (1) The current activity is in a different task.
                    if (prev.task != r.task) prev = null;
                    // (2) The current activity is already displayed.
                    else if (prev.nowVisible) prev = null;
                }
                mService.mWindowManager.setAppStartingWindow(
                        r, r.packageName, r.theme, r.nonLocalizedLabel,
                        r.labelRes, r.icon, prev, showStartingIcon);
            }
        } else {
            // If this is the first activity, don't do any fancy animations,
            // because there is nothing for it to animate on top of.
            mService.mWindowManager.addAppToken(addPos, r, r.task.taskId,
                    r.info.screenOrientation, r.fullscreen);
        }
        if (VALIDATE_TOKENS) {
            mService.mWindowManager.validateAppTokens(mHistory);
        }

        if (doResume) {
            resumeTopActivityLocked(null);
        }
    }

    /**
     * Perform a reset of the given task, if needed as part of launching it.
     * Returns the new HistoryRecord at the top of the task.
     */
    private final ActivityRecord resetTaskIfNeededLocked(ActivityRecord taskTop,
            ActivityRecord newActivity) {
        boolean forceReset = (newActivity.info.flags
                &ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0;
        if (taskTop.task.getInactiveDuration() > ACTIVITY_INACTIVE_RESET_TIME) {
            if ((newActivity.info.flags
                    &ActivityInfo.FLAG_ALWAYS_RETAIN_TASK_STATE) == 0) {
                forceReset = true;
            }
        }
        
        final TaskRecord task = taskTop.task;
        
        // We are going to move through the history list so that we can look
        // at each activity 'target' with 'below' either the interesting
        // activity immediately below it in the stack or null.
        ActivityRecord target = null;
        int targetI = 0;
        int taskTopI = -1;
        int replyChainEnd = -1;
        int lastReparentPos = -1;
        for (int i=mHistory.size()-1; i>=-1; i--) {
            ActivityRecord below = i >= 0 ? (ActivityRecord)mHistory.get(i) : null;
            
            if (below != null && below.finishing) {
                continue;
            }
            if (target == null) {
                target = below;
                targetI = i;
                // If we were in the middle of a reply chain before this
                // task, it doesn't appear like the root of the chain wants
                // anything interesting, so drop it.
                replyChainEnd = -1;
                continue;
            }
        
            final int flags = target.info.flags;
            
            final boolean finishOnTaskLaunch =
                (flags&ActivityInfo.FLAG_FINISH_ON_TASK_LAUNCH) != 0;
            final boolean allowTaskReparenting =
                (flags&ActivityInfo.FLAG_ALLOW_TASK_REPARENTING) != 0;
            
            if (target.task == task) {
                // We are inside of the task being reset...  we'll either
                // finish this activity, push it out for another task,
                // or leave it as-is.  We only do this
                // for activities that are not the root of the task (since
                // if we finish the root, we may no longer have the task!).
                if (taskTopI < 0) {
                    taskTopI = targetI;
                }
                if (below != null && below.task == task) {
                    final boolean clearWhenTaskReset =
                            (target.intent.getFlags()
                                    &Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET) != 0;
                    if (!finishOnTaskLaunch && !clearWhenTaskReset && target.resultTo != null) {
                        // If this activity is sending a reply to a previous
                        // activity, we can't do anything with it now until
                        // we reach the start of the reply chain.
                        // XXX note that we are assuming the result is always
                        // to the previous activity, which is almost always
                        // the case but we really shouldn't count on.
                        if (replyChainEnd < 0) {
                            replyChainEnd = targetI;
                        }
                    } else if (!finishOnTaskLaunch && !clearWhenTaskReset && allowTaskReparenting
                            && target.taskAffinity != null
                            && !target.taskAffinity.equals(task.affinity)) {
                        // If this activity has an affinity for another
                        // task, then we need to move it out of here.  We will
                        // move it as far out of the way as possible, to the
                        // bottom of the activity stack.  This also keeps it
                        // correctly ordered with any activities we previously
                        // moved.
                        ActivityRecord p = (ActivityRecord)mHistory.get(0);
                        if (target.taskAffinity != null
                                && target.taskAffinity.equals(p.task.affinity)) {
                            // If the activity currently at the bottom has the
                            // same task affinity as the one we are moving,
                            // then merge it into the same task.
                            target.task = p.task;
                            if (DEBUG_TASKS) Slog.v(TAG, "Start pushing activity " + target
                                    + " out to bottom task " + p.task);
                        } else {
                            mService.mCurTask++;
                            if (mService.mCurTask <= 0) {
                                mService.mCurTask = 1;
                            }
                            target.task = new TaskRecord(mService.mCurTask, target.info, null,
                                    (target.info.flags&ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0);
                            target.task.affinityIntent = target.intent;
                            if (DEBUG_TASKS) Slog.v(TAG, "Start pushing activity " + target
                                    + " out to new task " + target.task);
                        }
                        mService.mWindowManager.setAppGroupId(target, task.taskId);
                        if (replyChainEnd < 0) {
                            replyChainEnd = targetI;
                        }
                        int dstPos = 0;
                        for (int srcPos=targetI; srcPos<=replyChainEnd; srcPos++) {
                            p = (ActivityRecord)mHistory.get(srcPos);
                            if (p.finishing) {
                                continue;
                            }
                            if (DEBUG_TASKS) Slog.v(TAG, "Pushing next activity " + p
                                    + " out to target's task " + target.task);
                            task.numActivities--;
                            p.task = target.task;
                            target.task.numActivities++;
                            mHistory.remove(srcPos);
                            mHistory.add(dstPos, p);
                            mService.mWindowManager.moveAppToken(dstPos, p);
                            mService.mWindowManager.setAppGroupId(p, p.task.taskId);
                            dstPos++;
                            if (VALIDATE_TOKENS) {
                                mService.mWindowManager.validateAppTokens(mHistory);
                            }
                            i++;
                        }
                        if (taskTop == p) {
                            taskTop = below;
                        }
                        if (taskTopI == replyChainEnd) {
                            taskTopI = -1;
                        }
                        replyChainEnd = -1;
                        if (mMainStack) {
                            mService.addRecentTaskLocked(target.task);
                        }
                    } else if (forceReset || finishOnTaskLaunch
                            || clearWhenTaskReset) {
                        // If the activity should just be removed -- either
                        // because it asks for it, or the task should be
                        // cleared -- then finish it and anything that is
                        // part of its reply chain.
                        if (clearWhenTaskReset) {
                            // In this case, we want to finish this activity
                            // and everything above it, so be sneaky and pretend
                            // like these are all in the reply chain.
                            replyChainEnd = targetI+1;
                            while (replyChainEnd < mHistory.size() &&
                                    ((ActivityRecord)mHistory.get(
                                                replyChainEnd)).task == task) {
                                replyChainEnd++;
                            }
                            replyChainEnd--;
                        } else if (replyChainEnd < 0) {
                            replyChainEnd = targetI;
                        }
                        ActivityRecord p = null;
                        for (int srcPos=targetI; srcPos<=replyChainEnd; srcPos++) {
                            p = (ActivityRecord)mHistory.get(srcPos);
                            if (p.finishing) {
                                continue;
                            }
                            if (finishActivityLocked(p, srcPos,
                                    Activity.RESULT_CANCELED, null, "reset")) {
                                replyChainEnd--;
                                srcPos--;
                            }
                        }
                        if (taskTop == p) {
                            taskTop = below;
                        }
                        if (taskTopI == replyChainEnd) {
                            taskTopI = -1;
                        }
                        replyChainEnd = -1;
                    } else {
                        // If we were in the middle of a chain, well the
                        // activity that started it all doesn't want anything
                        // special, so leave it all as-is.
                        replyChainEnd = -1;
                    }
                } else {
                    // Reached the bottom of the task -- any reply chain
                    // should be left as-is.
                    replyChainEnd = -1;
                }
                
            } else if (target.resultTo != null) {
                // If this activity is sending a reply to a previous
                // activity, we can't do anything with it now until
                // we reach the start of the reply chain.
                // XXX note that we are assuming the result is always
                // to the previous activity, which is almost always
                // the case but we really shouldn't count on.
                if (replyChainEnd < 0) {
                    replyChainEnd = targetI;
                }

            } else if (taskTopI >= 0 && allowTaskReparenting
                    && task.affinity != null
                    && task.affinity.equals(target.taskAffinity)) {
                // We are inside of another task...  if this activity has
                // an affinity for our task, then either remove it if we are
                // clearing or move it over to our task.  Note that
                // we currently punt on the case where we are resetting a
                // task that is not at the top but who has activities above
                // with an affinity to it...  this is really not a normal
                // case, and we will need to later pull that task to the front
                // and usually at that point we will do the reset and pick
                // up those remaining activities.  (This only happens if
                // someone starts an activity in a new task from an activity
                // in a task that is not currently on top.)
                if (forceReset || finishOnTaskLaunch) {
                    if (replyChainEnd < 0) {
                        replyChainEnd = targetI;
                    }
                    ActivityRecord p = null;
                    for (int srcPos=targetI; srcPos<=replyChainEnd; srcPos++) {
                        p = (ActivityRecord)mHistory.get(srcPos);
                        if (p.finishing) {
                            continue;
                        }
                        if (finishActivityLocked(p, srcPos,
                                Activity.RESULT_CANCELED, null, "reset")) {
                            taskTopI--;
                            lastReparentPos--;
                            replyChainEnd--;
                            srcPos--;
                        }
                    }
                    replyChainEnd = -1;
                } else {
                    if (replyChainEnd < 0) {
                        replyChainEnd = targetI;
                    }
                    for (int srcPos=replyChainEnd; srcPos>=targetI; srcPos--) {
                        ActivityRecord p = (ActivityRecord)mHistory.get(srcPos);
                        if (p.finishing) {
                            continue;
                        }
                        if (lastReparentPos < 0) {
                            lastReparentPos = taskTopI;
                            taskTop = p;
                        } else {
                            lastReparentPos--;
                        }
                        mHistory.remove(srcPos);
                        p.task.numActivities--;
                        p.task = task;
                        mHistory.add(lastReparentPos, p);
                        if (DEBUG_TASKS) Slog.v(TAG, "Pulling activity " + p
                                + " in to resetting task " + task);
                        task.numActivities++;
                        mService.mWindowManager.moveAppToken(lastReparentPos, p);
                        mService.mWindowManager.setAppGroupId(p, p.task.taskId);
                        if (VALIDATE_TOKENS) {
                            mService.mWindowManager.validateAppTokens(mHistory);
                        }
                    }
                    replyChainEnd = -1;
                    
                    // Now we've moved it in to place...  but what if this is
                    // a singleTop activity and we have put it on top of another
                    // instance of the same activity?  Then we drop the instance
                    // below so it remains singleTop.
                    if (target.info.launchMode == ActivityInfo.LAUNCH_SINGLE_TOP) {
                        for (int j=lastReparentPos-1; j>=0; j--) {
                            ActivityRecord p = (ActivityRecord)mHistory.get(j);
                            if (p.finishing) {
                                continue;
                            }
                            if (p.intent.getComponent().equals(target.intent.getComponent())) {
                                if (finishActivityLocked(p, j,
                                        Activity.RESULT_CANCELED, null, "replace")) {
                                    taskTopI--;
                                    lastReparentPos--;
                                }
                            }
                        }
                    }
                }
            }
            
            target = below;
            targetI = i;
        }
        
        return taskTop;
    }
    
    /**
     * Perform clear operation as requested by
     * {@link Intent#FLAG_ACTIVITY_CLEAR_TOP}: search from the top of the
     * stack to the given task, then look for
     * an instance of that activity in the stack and, if found, finish all
     * activities on top of it and return the instance.
     *
     * @param newR Description of the new activity being started.
     * @return Returns the old activity that should be continue to be used,
     * or null if none was found.
     */
    private final ActivityRecord performClearTaskLocked(int taskId,
            ActivityRecord newR, int launchFlags, boolean doClear) {
        int i = mHistory.size();
        
        // First find the requested task.
        while (i > 0) {
            i--;
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (r.task.taskId == taskId) {
                i++;
                break;
            }
        }
        
        // Now clear it.
        while (i > 0) {
            i--;
            ActivityRecord r = (ActivityRecord)mHistory.get(i);
            if (r.finishing) {
                continue;
            }
            if (r.task.taskId != taskId) {
                return null;
            }
            if (r.realActivity.equals(newR.realActivity)) {
                // Here it is!  Now finish everything in front...
                ActivityRecord ret = r;
                if (doClear) {
                    while (i < (mHistory.size()-1)) {
                        i++;
                        r = (ActivityRecord)mHistory.get(i);
                        if (r.finishing) {
                            continue;
                        }
                        if (finishActivityLocked(r, i, Activity.RESULT_CANCELED,
                                null, "clear")) {
                            i--;
                        }
                    }
                }
                
                // Finally, if this is a normal launch mode (that is, not
                // expecting onNewIntent()), then we will finish the current
                // instance of the activity so a new fresh one can be started.
                if (ret.launchMode == ActivityInfo.LAUNCH_MULTIPLE
                        && (launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) == 0) {
                    if (!ret.finishing) {
                        int index = indexOfTokenLocked(ret);
                        if (index >= 0) {
                            finishActivityLocked(ret, index, Activity.RESULT_CANCELED,
                                    null, "clear");
                        }
                        return null;
                    }
                }
                
                return ret;
            }
        }

        return null;
    }

    /**
     * Find the activity in the history stack within the given task.  Returns
     * the index within the history at which it's found, or < 0 if not found.
     */
    private final int findActivityInHistoryLocked(ActivityRecord r, int task) {
        int i = mHistory.size();
        while (i > 0) {
            i--;
            ActivityRecord candidate = (ActivityRecord)mHistory.get(i);
            if (candidate.task.taskId != task) {
                break;
            }
            if (candidate.realActivity.equals(r.realActivity)) {
                return i;
            }
        }

        return -1;
    }

    /**
     * Reorder the history stack so that the activity at the given index is
     * brought to the front.
     */
    private final ActivityRecord moveActivityToFrontLocked(int where) {
        ActivityRecord newTop = (ActivityRecord)mHistory.remove(where);
        int top = mHistory.size();
        ActivityRecord oldTop = (ActivityRecord)mHistory.get(top-1);
        mHistory.add(top, newTop);
        oldTop.frontOfTask = false;
        newTop.frontOfTask = true;
        return newTop;
    }

    final int startActivityLocked(IApplicationThread caller,
            Intent intent, String resolvedType,
            Uri[] grantedUriPermissions,
            int grantedMode, ActivityInfo aInfo, IBinder resultTo,
            String resultWho, int requestCode,
            int callingPid, int callingUid, boolean onlyIfNeeded,
            boolean componentSpecified) {

        int err = START_SUCCESS;

        ProcessRecord callerApp = null;
        if (caller != null) {
            callerApp = mService.getRecordForAppLocked(caller);
            if (callerApp != null) {
                callingPid = callerApp.pid;
                callingUid = callerApp.info.uid;
            } else {
                Slog.w(TAG, "Unable to find app for caller " + caller
                      + " (pid=" + callingPid + ") when starting: "
                      + intent.toString());
                err = START_PERMISSION_DENIED;
            }
        }

        if (err == START_SUCCESS) {
            Slog.i(TAG, "Starting: " + intent + " from pid "
                    + (callerApp != null ? callerApp.pid : callingPid));
            mActivityTrigger.activityStartTrigger(intent);
        }

        ActivityRecord sourceRecord = null;
        ActivityRecord resultRecord = null;
        if (resultTo != null) {
            int index = indexOfTokenLocked(resultTo);
            if (DEBUG_RESULTS) Slog.v(
                TAG, "Sending result to " + resultTo + " (index " + index + ")");
            if (index >= 0) {
                sourceRecord = (ActivityRecord)mHistory.get(index);
                if (requestCode >= 0 && !sourceRecord.finishing) {
                    resultRecord = sourceRecord;
                }
            }
        }

        int launchFlags = intent.getFlags();

        if ((launchFlags&Intent.FLAG_ACTIVITY_FORWARD_RESULT) != 0
                && sourceRecord != null) {
            // Transfer the result target from the source activity to the new
            // one being started, including any failures.
            if (requestCode >= 0) {
                return START_FORWARD_AND_REQUEST_CONFLICT;
            }
            resultRecord = sourceRecord.resultTo;
            resultWho = sourceRecord.resultWho;
            requestCode = sourceRecord.requestCode;
            sourceRecord.resultTo = null;
            if (resultRecord != null) {
                resultRecord.removeResultsLocked(
                    sourceRecord, resultWho, requestCode);
            }
        }

        if (err == START_SUCCESS && intent.getComponent() == null) {
            // We couldn't find a class that can handle the given Intent.
            // That's the end of that!
            err = START_INTENT_NOT_RESOLVED;
        }

        if (err == START_SUCCESS && aInfo == null) {
            // We couldn't find the specific class specified in the Intent.
            // Also the end of the line.
            err = START_CLASS_NOT_FOUND;
        }

        if (err != START_SUCCESS) {
            if (resultRecord != null) {
                sendActivityResultLocked(-1,
                    resultRecord, resultWho, requestCode,
                    Activity.RESULT_CANCELED, null);
            }
            return err;
        }

        final int perm = mService.checkComponentPermission(aInfo.permission, callingPid,
                callingUid, aInfo.exported ? -1 : aInfo.applicationInfo.uid);
        if (perm != PackageManager.PERMISSION_GRANTED) {
            if (resultRecord != null) {
                sendActivityResultLocked(-1,
                    resultRecord, resultWho, requestCode,
                    Activity.RESULT_CANCELED, null);
            }
            String msg = "Permission Denial: starting " + intent.toString()
                    + " from " + callerApp + " (pid=" + callingPid
                    + ", uid=" + callingUid + ")"
                    + " requires " + aInfo.permission;
            Slog.w(TAG, msg);
            throw new SecurityException(msg);
        }

        if (mMainStack) {
            if (mService.mController != null) {
                boolean abort = false;
                try {
                    // The Intent we give to the watcher has the extra data
                    // stripped off, since it can contain private information.
                    Intent watchIntent = intent.cloneFilter();
                    abort = !mService.mController.activityStarting(watchIntent,
                            aInfo.applicationInfo.packageName);
                } catch (RemoteException e) {
                    mService.mController = null;
                }
    
                if (abort) {
                    if (resultRecord != null) {
                        sendActivityResultLocked(-1,
                            resultRecord, resultWho, requestCode,
                            Activity.RESULT_CANCELED, null);
                    }
                    // We pretend to the caller that it was really started, but
                    // they will just get a cancel result.
                    return START_SUCCESS;
                }
            }
        }
        
        ActivityRecord r = new ActivityRecord(mService, this, callerApp, callingUid,
                intent, resolvedType, aInfo, mService.mConfiguration,
                resultRecord, resultWho, requestCode, componentSpecified);

        if (mMainStack) {
            if (mResumedActivity == null
                    || mResumedActivity.info.applicationInfo.uid != callingUid) {
                if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid, "Activity start")) {
                    PendingActivityLaunch pal = new PendingActivityLaunch();
                    pal.r = r;
                    pal.sourceRecord = sourceRecord;
                    pal.grantedUriPermissions = grantedUriPermissions;
                    pal.grantedMode = grantedMode;
                    pal.onlyIfNeeded = onlyIfNeeded;
                    mService.mPendingActivityLaunches.add(pal);
                    return START_SWITCHES_CANCELED;
                }
            }
        
            if (mService.mDidAppSwitch) {
                // This is the second allowed switch since we stopped switches,
                // so now just generally allow switches.  Use case: user presses
                // home (switches disabled, switch to home, mDidAppSwitch now true);
                // user taps a home icon (coming from home so allowed, we hit here
                // and now allow anyone to switch again).
                mService.mAppSwitchesAllowedTime = 0;
            } else {
                mService.mDidAppSwitch = true;
            }
         
            mService.doPendingActivityLaunchesLocked(false);
        }
        
        return startActivityUncheckedLocked(r, sourceRecord,
                grantedUriPermissions, grantedMode, onlyIfNeeded, true);
    }
  
    final int startActivityUncheckedLocked(ActivityRecord r,
            ActivityRecord sourceRecord, Uri[] grantedUriPermissions,
            int grantedMode, boolean onlyIfNeeded, boolean doResume) {
        final Intent intent = r.intent;
        final int callingUid = r.launchedFromUid;
        
        int launchFlags = intent.getFlags();
        
        // We'll invoke onUserLeaving before onPause only if the launching
        // activity did not explicitly state that this is an automated launch.
        mUserLeaving = (launchFlags&Intent.FLAG_ACTIVITY_NO_USER_ACTION) == 0;
        if (DEBUG_USER_LEAVING) Slog.v(TAG,
                "startActivity() => mUserLeaving=" + mUserLeaving);
        
        // If the caller has asked not to resume at this point, we make note
        // of this in the record so that we can skip it when trying to find
        // the top running activity.
        if (!doResume) {
            r.delayedResume = true;
        }
        
        ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
                != 0 ? r : null;

        // If the onlyIfNeeded flag is set, then we can do this if the activity
        // being launched is the same as the one making the call...  or, as
        // a special case, if we do not know the caller then we count the
        // current top activity as the caller.
        if (onlyIfNeeded) {
            ActivityRecord checkedCaller = sourceRecord;
            if (checkedCaller == null) {
                checkedCaller = topRunningNonDelayedActivityLocked(notTop);
            }
            if (!checkedCaller.realActivity.equals(r.realActivity)) {
                // Caller is not the same as launcher, so always needed.
                onlyIfNeeded = false;
            }
        }

        if (sourceRecord == null) {
            // This activity is not being started from another...  in this
            // case we -always- start a new task.
            if ((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) == 0) {
                Slog.w(TAG, "startActivity called from non-Activity context; forcing Intent.FLAG_ACTIVITY_NEW_TASK for: "
                      + intent);
                launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
            }
        } else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
            // The original activity who is starting us is running as a single
            // instance...  this new activity it is starting must go on its
            // own task.
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
        } else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
            // The activity being started is a single instance...  it always
            // gets launched into its own task.
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
        }

        if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
            // For whatever reason this activity is being launched into a new
            // task...  yet the caller has requested a result back.  Well, that
            // is pretty messed up, so instead immediately send back a cancel
            // and let the new task continue launched as normal without a
            // dependency on its originator.
            Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
            sendActivityResultLocked(-1,
                    r.resultTo, r.resultWho, r.requestCode,
                Activity.RESULT_CANCELED, null);
            r.resultTo = null;
        }

        boolean addingToTask = false;
        if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
                (launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
            // If bring to front is requested, and no result is requested, and
            // we can find a task that was started with this same
            // component, then instead of launching bring that one to the front.
            if (r.resultTo == null) {
                // See if there is a task to bring to the front.  If this is
                // a SINGLE_INSTANCE activity, there can be one and only one
                // instance of it in the history, and it is always in its own
                // unique task, so we do a special search.
                ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
                        ? findTaskLocked(intent, r.info)
                        : findActivityLocked(intent, r.info);
                if (taskTop != null) {
                    if (taskTop.task.intent == null) {
                        // This task was started because of movement of
                        // the activity based on affinity...  now that we
                        // are actually launching it, we can assign the
                        // base intent.
                        taskTop.task.setIntent(intent, r.info);
                    }
                    // If the target task is not in the front, then we need
                    // to bring it to the front...  except...  well, with
                    // SINGLE_TASK_LAUNCH it's not entirely clear.  We'd like
                    // to have the same behavior as if a new instance was
                    // being started, which means not bringing it to the front
                    // if the caller is not itself in the front.
                    ActivityRecord curTop = topRunningNonDelayedActivityLocked(notTop);
                    if (curTop != null && curTop.task != taskTop.task) {
                        r.intent.addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
                        boolean callerAtFront = sourceRecord == null
                                || curTop.task == sourceRecord.task;
                        if (callerAtFront) {
                            // We really do want to push this one into the
                            // user's face, right now.
                            moveTaskToFrontLocked(taskTop.task, r);
                        }
                    }
                    // If the caller has requested that the target task be
                    // reset, then do so.
                    if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
                        taskTop = resetTaskIfNeededLocked(taskTop, r);
                    }
                    if (onlyIfNeeded) {
                        // We don't need to start a new activity, and
                        // the client said not to do anything if that
                        // is the case, so this is it!  And for paranoia, make
                        // sure we have correctly resumed the top activity.
                        if (doResume) {
                            resumeTopActivityLocked(null);
                        }
                        return START_RETURN_INTENT_TO_CALLER;
                    }
                    if ((launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
                        // In this situation we want to remove all activities
                        // from the task up to the one being started.  In most
                        // cases this means we are resetting the task to its
                        // initial state.
                        ActivityRecord top = performClearTaskLocked(
                                taskTop.task.taskId, r, launchFlags, true);
                        if (top != null) {
                            if (top.frontOfTask) {
                                // Activity aliases may mean we use different
                                // intents for the top activity, so make sure
                                // the task now has the identity of the new
                                // intent.
                                top.task.setIntent(r.intent, r.info);
                            }
                            logStartActivity(EventLogTags.AM_NEW_INTENT, r, top.task);
                            top.deliverNewIntentLocked(callingUid, r.intent);
                        } else {
                            // A special case: we need to
                            // start the activity because it is not currently
                            // running, and the caller has asked to clear the
                            // current task to have this activity at the top.
                            addingToTask = true;
                            // Now pretend like this activity is being started
                            // by the top of its task, so it is put in the
                            // right place.
                            sourceRecord = taskTop;
                        }
                    } else if (r.realActivity.equals(taskTop.task.realActivity)) {
                        // In this case the top activity on the task is the
                        // same as the one being launched, so we take that
                        // as a request to bring the task to the foreground.
                        // If the top activity in the task is the root
                        // activity, deliver this new intent to it if it
                        // desires.
                        if ((launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
                                && taskTop.realActivity.equals(r.realActivity)) {
                            logStartActivity(EventLogTags.AM_NEW_INTENT, r, taskTop.task);
                            if (taskTop.frontOfTask) {
                                taskTop.task.setIntent(r.intent, r.info);
                            }
                            taskTop.deliverNewIntentLocked(callingUid, r.intent);
                        } else if (!r.intent.filterEquals(taskTop.task.intent)) {
                            // In this case we are launching the root activity
                            // of the task, but with a different intent.  We
                            // should start a new instance on top.
                            addingToTask = true;
                            sourceRecord = taskTop;
                        }
                    } else if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) == 0) {
                        // In this case an activity is being launched in to an
                        // existing task, without resetting that task.  This
                        // is typically the situation of launching an activity
                        // from a notification or shortcut.  We want to place
                        // the new activity on top of the current task.
                        addingToTask = true;
                        sourceRecord = taskTop;
                    } else if (!taskTop.task.rootWasReset) {
                        // In this case we are launching in to an existing task
                        // that has not yet been started from its front door.
                        // The current task has been brought to the front.
                        // Ideally, we'd probably like to place this new task
                        // at the bottom of its stack, but that's a little hard
                        // to do with the current organization of the code so
                        // for now we'll just drop it.
                        taskTop.task.setIntent(r.intent, r.info);
                    }
                    if (!addingToTask) {
                        // We didn't do anything...  but it was needed (a.k.a., client
                        // don't use that intent!)  And for paranoia, make
                        // sure we have correctly resumed the top activity.
                        if (doResume) {
                            resumeTopActivityLocked(null);
                        }
                        return START_TASK_TO_FRONT;
                    }
                }
            }
        }

        //String uri = r.intent.toURI();
        //Intent intent2 = new Intent(uri);
        //Slog.i(TAG, "Given intent: " + r.intent);
        //Slog.i(TAG, "URI is: " + uri);
        //Slog.i(TAG, "To intent: " + intent2);

        if (r.packageName != null) {
            // If the activity being launched is the same as the one currently
            // at the top, then we need to check if it should only be launched
            // once.
            ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
            if (top != null && r.resultTo == null) {
                if (top.realActivity.equals(r.realActivity)) {
                    if (top.app != null && top.app.thread != null) {
                        if ((launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TOP
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
                            logStartActivity(EventLogTags.AM_NEW_INTENT, top, top.task);
                            // For paranoia, make sure we have correctly
                            // resumed the top activity.
                            if (doResume) {
                                resumeTopActivityLocked(null);
                            }
                            if (onlyIfNeeded) {
                                // We don't need to start a new activity, and
                                // the client said not to do anything if that
                                // is the case, so this is it!
                                return START_RETURN_INTENT_TO_CALLER;
                            }
                            top.deliverNewIntentLocked(callingUid, r.intent);
                            return START_DELIVERED_TO_TOP;
                        }
                    }
                }
            }

        } else {
            if (r.resultTo != null) {
                sendActivityResultLocked(-1,
                        r.resultTo, r.resultWho, r.requestCode,
                    Activity.RESULT_CANCELED, null);
            }
            return START_CLASS_NOT_FOUND;
        }

        boolean newTask = false;

        // Should this be considered a new task?
        if (r.resultTo == null && !addingToTask
                && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
            // todo: should do better management of integers.
            mService.mCurTask++;
            if (mService.mCurTask <= 0) {
                mService.mCurTask = 1;
            }
            r.task = new TaskRecord(mService.mCurTask, r.info, intent,
                    (r.info.flags&ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0);
            if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
                    + " in new task " + r.task);
            newTask = true;
            if (mMainStack) {
                mService.addRecentTaskLocked(r.task);
            }
            
        } else if (sourceRecord != null) {
            if (!addingToTask &&
                    (launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0) {
                // In this case, we are adding the activity to an existing
                // task, but the caller has asked to clear that task if the
                // activity is already running.
                ActivityRecord top = performClearTaskLocked(
                        sourceRecord.task.taskId, r, launchFlags, true);
                if (top != null) {
                    logStartActivity(EventLogTags.AM_NEW_INTENT, r, top.task);
                    top.deliverNewIntentLocked(callingUid, r.intent);
                    // For paranoia, make sure we have correctly
                    // resumed the top activity.
                    if (doResume) {
                        resumeTopActivityLocked(null);
                    }
                    return START_DELIVERED_TO_TOP;
                }
            } else if (!addingToTask &&
                    (launchFlags&Intent.FLAG_ACTIVITY_REORDER_TO_FRONT) != 0) {
                // In this case, we are launching an activity in our own task
                // that may already be running somewhere in the history, and
                // we want to shuffle it to the front of the stack if so.
                int where = findActivityInHistoryLocked(r, sourceRecord.task.taskId);
                if (where >= 0) {
                    ActivityRecord top = moveActivityToFrontLocked(where);
                    logStartActivity(EventLogTags.AM_NEW_INTENT, r, top.task);
                    top.deliverNewIntentLocked(callingUid, r.intent);
                    if (doResume) {
                        resumeTopActivityLocked(null);
                    }
                    return START_DELIVERED_TO_TOP;
                }
            }
            // An existing activity is starting this new activity, so we want
            // to keep the new one in the same task as the one that is starting
            // it.
            r.task = sourceRecord.task;
            if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
                    + " in existing task " + r.task);

        } else {
            // This not being started from an existing activity, and not part
            // of a new task...  just put it in the top task, though these days
            // this case should never happen.
            final int N = mHistory.size();
            ActivityRecord prev =
                N > 0 ? (ActivityRecord)mHistory.get(N-1) : null;
            r.task = prev != null
                ? prev.task
                : new TaskRecord(mService.mCurTask, r.info, intent,
                        (r.info.flags&ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0);
            if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
                    + " in new guessed " + r.task);
        }

        if (grantedUriPermissions != null && callingUid > 0) {
            for (int i=0; i<grantedUriPermissions.length; i++) {
                mService.grantUriPermissionLocked(callingUid, r.packageName,
                        grantedUriPermissions[i], grantedMode, r.getUriPermissionsLocked());
            }
        }

        mService.grantUriPermissionFromIntentLocked(callingUid, r.packageName,
                intent, r.getUriPermissionsLocked());

        if (newTask) {
            EventLog.writeEvent(EventLogTags.AM_CREATE_TASK, r.task.taskId);
        }
        logStartActivity(EventLogTags.AM_CREATE_ACTIVITY, r, r.task);
        startActivityLocked(r, newTask, doResume);
        return START_SUCCESS;
    }

    final int startActivityMayWait(IApplicationThread caller,
            Intent intent, String resolvedType, Uri[] grantedUriPermissions,
            int grantedMode, IBinder resultTo,
            String resultWho, int requestCode, boolean onlyIfNeeded,
            boolean debug, WaitResult outResult, Configuration config) {
        // Refuse possible leaked file descriptors
        if (intent != null && intent.hasFileDescriptors()) {
            throw new IllegalArgumentException("File descriptors passed in Intent");
        }

        boolean componentSpecified = intent.getComponent() != null;
        
        // Don't modify the client's object!
        intent = new Intent(intent);

        // Collect information about the target of the Intent.
        ActivityInfo aInfo;
        try {
            ResolveInfo rInfo =
                AppGlobals.getPackageManager().resolveIntent(
                        intent, resolvedType,
                        PackageManager.MATCH_DEFAULT_ONLY
                        | ActivityManagerService.STOCK_PM_FLAGS);
            aInfo = rInfo != null ? rInfo.activityInfo : null;
        } catch (RemoteException e) {
            aInfo = null;
        }

        if (aInfo != null) {
            // Store the found target back into the intent, because now that
            // we have it we never want to do this again.  For example, if the
            // user navigates back to this point in the history, we should
            // always restart the exact same activity.
            intent.setComponent(new ComponentName(
                    aInfo.applicationInfo.packageName, aInfo.name));

            // Don't debug things in the system process
            if (debug) {
                if (!aInfo.processName.equals("system")) {
                    mService.setDebugApp(aInfo.processName, true, false);
                }
            }
        }

        synchronized (mService) {
            int callingPid;
            int callingUid;
            if (caller == null) {
                callingPid = Binder.getCallingPid();
                callingUid = Binder.getCallingUid();
            } else {
                callingPid = callingUid = -1;
            }
            
            mConfigWillChange = config != null
                    && mService.mConfiguration.diff(config) != 0;
            if (DEBUG_CONFIGURATION) Slog.v(TAG,
                    "Starting activity when config will change = " + mConfigWillChange);
            
            final long origId = Binder.clearCallingIdentity();
            
            if (mMainStack && aInfo != null &&
                    (aInfo.applicationInfo.flags&ApplicationInfo.FLAG_CANT_SAVE_STATE) != 0) {
                // This may be a heavy-weight process!  Check to see if we already
                // have another, different heavy-weight process running.
                if (aInfo.processName.equals(aInfo.applicationInfo.packageName)) {
                    if (mService.mHeavyWeightProcess != null &&
                            (mService.mHeavyWeightProcess.info.uid != aInfo.applicationInfo.uid ||
                            !mService.mHeavyWeightProcess.processName.equals(aInfo.processName))) {
                        int realCallingPid = callingPid;
                        int realCallingUid = callingUid;
                        if (caller != null) {
                            ProcessRecord callerApp = mService.getRecordForAppLocked(caller);
                            if (callerApp != null) {
                                realCallingPid = callerApp.pid;
                                realCallingUid = callerApp.info.uid;
                            } else {
                                Slog.w(TAG, "Unable to find app for caller " + caller
                                      + " (pid=" + realCallingPid + ") when starting: "
                                      + intent.toString());
                                return START_PERMISSION_DENIED;
                            }
                        }
                        
                        IIntentSender target = mService.getIntentSenderLocked(
                                IActivityManager.INTENT_SENDER_ACTIVITY, "android",
                                realCallingUid, null, null, 0, intent,
                                resolvedType, PendingIntent.FLAG_CANCEL_CURRENT
                                | PendingIntent.FLAG_ONE_SHOT);
                        
                        Intent newIntent = new Intent();
                        if (requestCode >= 0) {
                            // Caller is requesting a result.
                            newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_HAS_RESULT, true);
                        }
                        newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_INTENT,
                                new IntentSender(target));
                        if (mService.mHeavyWeightProcess.activities.size() > 0) {
                            ActivityRecord hist = mService.mHeavyWeightProcess.activities.get(0);
                            newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_CUR_APP,
                                    hist.packageName);
                            newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_CUR_TASK,
                                    hist.task.taskId);
                        }
                        newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_NEW_APP,
                                aInfo.packageName);
                        newIntent.setFlags(intent.getFlags());
                        newIntent.setClassName("android",
                                HeavyWeightSwitcherActivity.class.getName());
                        intent = newIntent;
                        resolvedType = null;
                        caller = null;
                        callingUid = Binder.getCallingUid();
                        callingPid = Binder.getCallingPid();
                        componentSpecified = true;
                        try {
                            ResolveInfo rInfo =
                                AppGlobals.getPackageManager().resolveIntent(
                                        intent, null,
                                        PackageManager.MATCH_DEFAULT_ONLY
                                        | ActivityManagerService.STOCK_PM_FLAGS);
                            aInfo = rInfo != null ? rInfo.activityInfo : null;
                        } catch (RemoteException e) {
                            aInfo = null;
                        }
                    }
                }
            }
            
            int res = startActivityLocked(caller, intent, resolvedType,
                    grantedUriPermissions, grantedMode, aInfo,
                    resultTo, resultWho, requestCode, callingPid, callingUid,
                    onlyIfNeeded, componentSpecified);
            
            if (mConfigWillChange && mMainStack) {
                // If the caller also wants to switch to a new configuration,
                // do so now.  This allows a clean switch, as we are waiting
                // for the current activity to pause (so we will not destroy
                // it), and have not yet started the next activity.
                mService.enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION,
                        "updateConfiguration()");
                mConfigWillChange = false;
                if (DEBUG_CONFIGURATION) Slog.v(TAG,
                        "Updating to new configuration after starting activity.");
                mService.updateConfigurationLocked(config, null);
            }
            
            Binder.restoreCallingIdentity(origId);
            
            if (outResult != null) {
                outResult.result = res;
                if (res == IActivityManager.START_SUCCESS) {
                    mWaitingActivityLaunched.add(outResult);
                    do {
                        try {
                            mService.wait();
                        } catch (InterruptedException e) {
                        }
                    } while (!outResult.timeout && outResult.who == null);
                } else if (res == IActivityManager.START_TASK_TO_FRONT) {
                    ActivityRecord r = this.topRunningActivityLocked(null);
                    if (r.nowVisible) {
                        outResult.timeout = false;
                        outResult.who = new ComponentName(r.info.packageName, r.info.name);
                        outResult.totalTime = 0;
                        outResult.thisTime = 0;
                    } else {
                        outResult.thisTime = SystemClock.uptimeMillis();
                        mWaitingActivityVisible.add(outResult);
                        do {
                            try {
                                mService.wait();
                            } catch (InterruptedException e) {
                            }
                        } while (!outResult.timeout && outResult.who == null);
                    }
                }
            }
            
            return res;
        }
    }
    
    void reportActivityLaunchedLocked(boolean timeout, ActivityRecord r,
            long thisTime, long totalTime) {
        for (int i=mWaitingActivityLaunched.size()-1; i>=0; i--) {
            WaitResult w = mWaitingActivityLaunched.get(i);
            w.timeout = timeout;
            if (r != null) {
                w.who = new ComponentName(r.info.packageName, r.info.name);
            }
            w.thisTime = thisTime;
            w.totalTime = totalTime;
        }
        mService.notifyAll();
    }
    
    void reportActivityVisibleLocked(ActivityRecord r) {
        for (int i=mWaitingActivityVisible.size()-1; i>=0; i--) {
            WaitResult w = mWaitingActivityVisible.get(i);
            w.timeout = false;
            if (r != null) {
                w.who = new ComponentName(r.info.packageName, r.info.name);
            }
            w.totalTime = SystemClock.uptimeMillis() - w.thisTime;
            w.thisTime = w.totalTime;
        }
        mService.notifyAll();
    }

    void sendActivityResultLocked(int callingUid, ActivityRecord r,
            String resultWho, int requestCode, int resultCode, Intent data) {

        if (callingUid > 0) {
            mService.grantUriPermissionFromIntentLocked(callingUid, r.packageName,
                    data, r.getUriPermissionsLocked());
        }

        if (DEBUG_RESULTS) Slog.v(TAG, "Send activity result to " + r
                + " : who=" + resultWho + " req=" + requestCode
                + " res=" + resultCode + " data=" + data);
        if (mResumedActivity == r && r.app != null && r.app.thread != null) {
            try {
                ArrayList<ResultInfo> list = new ArrayList<ResultInfo>();
                list.add(new ResultInfo(resultWho, requestCode,
                        resultCode, data));
                r.app.thread.scheduleSendResult(r, list);
                return;
            } catch (Exception e) {
                Slog.w(TAG, "Exception thrown sending result to " + r, e);
            }
        }

        r.addResultLocked(null, resultWho, requestCode, resultCode, data);
    }

    private final void stopActivityLocked(ActivityRecord r) {
        if (DEBUG_SWITCH) Slog.d(TAG, "Stopping: " + r);
        if ((r.intent.getFlags()&Intent.FLAG_ACTIVITY_NO_HISTORY) != 0
                || (r.info.flags&ActivityInfo.FLAG_NO_HISTORY) != 0) {
            if (!r.finishing) {
                requestFinishActivityLocked(r, Activity.RESULT_CANCELED, null,
                        "no-history");
            }
        } else if (r.app != null && r.app.thread != null) {
            if (mMainStack) {
                if (mService.mFocusedActivity == r) {
                    mService.setFocusedActivityLocked(topRunningActivityLocked(null));
                }
            }
            r.resumeKeyDispatchingLocked();
            try {
                r.stopped = false;
                r.state = ActivityState.STOPPING;
                if (DEBUG_VISBILITY) Slog.v(
                        TAG, "Stopping visible=" + r.visible + " for " + r);
                if (!r.visible) {
                    mService.mWindowManager.setAppVisibility(r, false);
                }
                r.app.thread.scheduleStopActivity(r, r.visible, r.configChangeFlags);
            } catch (Exception e) {
                // Maybe just ignore exceptions here...  if the process
                // has crashed, our death notification will clean things
                // up.
                Slog.w(TAG, "Exception thrown during pause", e);
                // Just in case, assume it to be stopped.
                r.stopped = true;
                r.state = ActivityState.STOPPED;
                if (r.configDestroy) {
                    destroyActivityLocked(r, true);
                }
            }
        }
    }
    
    final ArrayList<ActivityRecord> processStoppingActivitiesLocked(
            boolean remove) {
        int N = mStoppingActivities.size();
        if (N <= 0) return null;

        ArrayList<ActivityRecord> stops = null;

        final boolean nowVisible = mResumedActivity != null
                && mResumedActivity.nowVisible
                && !mResumedActivity.waitingVisible;
        for (int i=0; i<N; i++) {
            ActivityRecord s = mStoppingActivities.get(i);
            if (localLOGV) Slog.v(TAG, "Stopping " + s + ": nowVisible="
                    + nowVisible + " waitingVisible=" + s.waitingVisible
                    + " finishing=" + s.finishing);
            if (s.waitingVisible && nowVisible) {
                mWaitingVisibleActivities.remove(s);
                s.waitingVisible = false;
                if (s.finishing) {
                    // If this activity is finishing, it is sitting on top of
                    // everyone else but we now know it is no longer needed...
                    // so get rid of it.  Otherwise, we need to go through the
                    // normal flow and hide it once we determine that it is
                    // hidden by the activities in front of it.
                    if (localLOGV) Slog.v(TAG, "Before stopping, can hide: " + s);
                    mService.mWindowManager.setAppVisibility(s, false);
                }
            }
            if (!s.waitingVisible && remove) {
                if (localLOGV) Slog.v(TAG, "Ready to stop: " + s);
                if (stops == null) {
                    stops = new ArrayList<ActivityRecord>();
                }
                stops.add(s);
                mStoppingActivities.remove(i);
                N--;
                i--;
            }
        }

        return stops;
    }

    final void activityIdleInternal(IBinder token, boolean fromTimeout,
            Configuration config) {
        if (localLOGV) Slog.v(TAG, "Activity idle: " + token);

        ArrayList<ActivityRecord> stops = null;
        ArrayList<ActivityRecord> finishes = null;
        ArrayList<ActivityRecord> thumbnails = null;
        int NS = 0;
        int NF = 0;
        int NT = 0;
        IApplicationThread sendThumbnail = null;
        boolean booting = false;
        boolean enableScreen = false;

        synchronized (mService) {
            if (token != null) {
                mHandler.removeMessages(IDLE_TIMEOUT_MSG, token);
            }

            // Get the activity record.
            int index = indexOfTokenLocked(token);
            if (index >= 0) {
                ActivityRecord r = (ActivityRecord)mHistory.get(index);

                if (fromTimeout) {
                    reportActivityLaunchedLocked(fromTimeout, r, -1, -1);
                }
                
                // This is a hack to semi-deal with a race condition
                // in the client where it can be constructed with a
                // newer configuration from when we asked it to launch.
                // We'll update with whatever configuration it now says
                // it used to launch.
                if (config != null) {
                    r.configuration = config;
                }
                
                // No longer need to keep the device awake.
                if (mResumedActivity == r && mLaunchingActivity.isHeld()) {
                    mHandler.removeMessages(LAUNCH_TIMEOUT_MSG);
                    mLaunchingActivity.release();
                }

                // We are now idle.  If someone is waiting for a thumbnail from
                // us, we can now deliver.
                r.idle = true;
                mService.scheduleAppGcsLocked();
                if (r.thumbnailNeeded && r.app != null && r.app.thread != null) {
                    sendThumbnail = r.app.thread;
                    r.thumbnailNeeded = false;
                }

                // If this activity is fullscreen, set up to hide those under it.

                if (DEBUG_VISBILITY) Slog.v(TAG, "Idle activity for " + r);
                ensureActivitiesVisibleLocked(null, 0);

                //Slog.i(TAG, "IDLE: mBooted=" + mBooted + ", fromTimeout=" + fromTimeout);
                if (mMainStack) {
                    if (!mService.mBooted && !fromTimeout) {
                        mService.mBooted = true;
                        enableScreen = true;
                    }
                }
                
            } else if (fromTimeout) {
                reportActivityLaunchedLocked(fromTimeout, null, -1, -1);
            }

            // Atomically retrieve all of the other things to do.
            stops = processStoppingActivitiesLocked(true);
            NS = stops != null ? stops.size() : 0;
            if ((NF=mFinishingActivities.size()) > 0) {
                finishes = new ArrayList<ActivityRecord>(mFinishingActivities);
                mFinishingActivities.clear();
            }
            if ((NT=mService.mCancelledThumbnails.size()) > 0) {
                thumbnails = new ArrayList<ActivityRecord>(mService.mCancelledThumbnails);
                mService.mCancelledThumbnails.clear();
            }

            if (mMainStack) {
                booting = mService.mBooting;
                mService.mBooting = false;
            }
        }

        int i;

        // Send thumbnail if requested.
        if (sendThumbnail != null) {
            try {
                sendThumbnail.requestThumbnail(token);
            } catch (Exception e) {
                Slog.w(TAG, "Exception thrown when requesting thumbnail", e);
                mService.sendPendingThumbnail(null, token, null, null, true);
            }
        }

        // Stop any activities that are scheduled to do so but have been
        // waiting for the next one to start.
        for (i=0; i<NS; i++) {
            ActivityRecord r = (ActivityRecord)stops.get(i);
            synchronized (mService) {
                if (r.finishing) {
                    finishCurrentActivityLocked(r, FINISH_IMMEDIATELY);
                } else {
                    stopActivityLocked(r);
                }
            }
        }

        // Finish any activities that are scheduled to do so but have been
        // waiting for the next one to start.
        for (i=0; i<NF; i++) {
            ActivityRecord r = (ActivityRecord)finishes.get(i);
            synchronized (mService) {
                destroyActivityLocked(r, true);
            }
        }

        // Report back to any thumbnail receivers.
        for (i=0; i<NT; i++) {
            ActivityRecord r = (ActivityRecord)thumbnails.get(i);
            mService.sendPendingThumbnail(r, null, null, null, true);
        }

        if (booting) {
            mService.finishBooting();
        }

        mService.trimApplications();
        //dump();
        //mWindowManager.dump();

        if (enableScreen) {
            mService.enableScreenAfterBoot();
        }
    }

    /**
     * @return Returns true if the activity is being finished, false if for
     * some reason it is being left as-is.
     */
    final boolean requestFinishActivityLocked(IBinder token, int resultCode,
            Intent resultData, String reason) {
        if (DEBUG_RESULTS) Slog.v(
            TAG, "Finishing activity: token=" + token
            + ", result=" + resultCode + ", data=" + resultData);

        int index = indexOfTokenLocked(token);
        if (index < 0) {
            return false;
        }
        ActivityRecord r = (ActivityRecord)mHistory.get(index);

        // Is this the last activity left?
        boolean lastActivity = true;
        for (int i=mHistory.size()-1; i>=0; i--) {
            ActivityRecord p = (ActivityRecord)mHistory.get(i);
            if (!p.finishing && p != r) {
                lastActivity = false;
                break;
            }
        }
        
        // If this is the last activity, but it is the home activity, then
        // just don't finish it.
        if (lastActivity) {
            if (r.intent.hasCategory(Intent.CATEGORY_HOME)) {
                return false;
            }
        }
        
        finishActivityLocked(r, index, resultCode, resultData, reason);
        return true;
    }

    /**
     * @return Returns true if this activity has been removed from the history
     * list, or false if it is still in the list and will be removed later.
     */
    final boolean finishActivityLocked(ActivityRecord r, int index,
            int resultCode, Intent resultData, String reason) {
        if (r.finishing) {
            Slog.w(TAG, "Duplicate finish request for " + r);
            return false;
        }

        r.finishing = true;
        EventLog.writeEvent(EventLogTags.AM_FINISH_ACTIVITY,
                System.identityHashCode(r),
                r.task.taskId, r.shortComponentName, reason);
        r.task.numActivities--;
        if (index < (mHistory.size()-1)) {
            ActivityRecord next = (ActivityRecord)mHistory.get(index+1);
            if (next.task == r.task) {
                if (r.frontOfTask) {
                    // The next activity is now the front of the task.
                    next.frontOfTask = true;
                }
                if ((r.intent.getFlags()&Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET) != 0) {
                    // If the caller asked that this activity (and all above it)
                    // be cleared when the task is reset, don't lose that information,
                    // but propagate it up to the next activity.
                    next.intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
                }
            }
        }

        r.pauseKeyDispatchingLocked();
        if (mMainStack) {
            if (mService.mFocusedActivity == r) {
                mService.setFocusedActivityLocked(topRunningActivityLocked(null));
            }
        }

        // send the result
        ActivityRecord resultTo = r.resultTo;
        if (resultTo != null) {
            if (DEBUG_RESULTS) Slog.v(TAG, "Adding result to " + resultTo
                    + " who=" + r.resultWho + " req=" + r.requestCode
                    + " res=" + resultCode + " data=" + resultData);
            if (r.info.applicationInfo.uid > 0) {
                mService.grantUriPermissionFromIntentLocked(r.info.applicationInfo.uid,
                        resultTo.packageName, resultData, 
                        resultTo.getUriPermissionsLocked());
            }
            resultTo.addResultLocked(r, r.resultWho, r.requestCode, resultCode,
                                     resultData);
            r.resultTo = null;
        }
        else if (DEBUG_RESULTS) Slog.v(TAG, "No result destination from " + r);

        // Make sure this HistoryRecord is not holding on to other resources,
        // because clients have remote IPC references to this object so we
        // can't assume that will go away and want to avoid circular IPC refs.
        r.results = null;
        if(r.pendingResults != null) {
           r.pendingResults.clear();
           r.pendingResults = null;
        }
        r.newIntents = null;
        r.icicle = null;
        
        if (mService.mPendingThumbnails.size() > 0) {
            // There are clients waiting to receive thumbnails so, in case
            // this is an activity that someone is waiting for, add it
            // to the pending list so we can correctly update the clients.
            mService.mCancelledThumbnails.add(r);
        }

        if (mResumedActivity == r) {
            boolean endTask = index <= 0
                    || ((ActivityRecord)mHistory.get(index-1)).task != r.task;
            if (DEBUG_TRANSITION) Slog.v(TAG,
                    "Prepare close transition: finishing " + r);
            mService.mWindowManager.prepareAppTransition(endTask
                    ? WindowManagerPolicy.TRANSIT_TASK_CLOSE
                    : WindowManagerPolicy.TRANSIT_ACTIVITY_CLOSE);
    
            // Tell window manager to prepare for this one to be removed.
            mService.mWindowManager.setAppVisibility(r, false);
                
            if (mPausingActivity == null) {
                if (DEBUG_PAUSE) Slog.v(TAG, "Finish needs to pause: " + r);
                if (DEBUG_USER_LEAVING) Slog.v(TAG, "finish() => pause with userLeaving=false");
                startPausingLocked(false, false);
            }

        } else if (r.state != ActivityState.PAUSING) {
            // If the activity is PAUSING, we will complete the finish once
            // it is done pausing; else we can just directly finish it here.
            if (DEBUG_PAUSE) Slog.v(TAG, "Finish not pausing: " + r);
            return finishCurrentActivityLocked(r, index,
                    FINISH_AFTER_PAUSE) == null;
        } else {
            if (DEBUG_PAUSE) Slog.v(TAG, "Finish waiting for pause of: " + r);
        }

        return false;
    }

    private static final int FINISH_IMMEDIATELY = 0;
    private static final int FINISH_AFTER_PAUSE = 1;
    private static final int FINISH_AFTER_VISIBLE = 2;

    private final ActivityRecord finishCurrentActivityLocked(ActivityRecord r,
            int mode) {
        final int index = indexOfTokenLocked(r);
        if (index < 0) {
            return null;
        }

        return finishCurrentActivityLocked(r, index, mode);
    }

    private final ActivityRecord finishCurrentActivityLocked(ActivityRecord r,
            int index, int mode) {
        // First things first: if this activity is currently visible,
        // and the resumed activity is not yet visible, then hold off on
        // finishing until the resumed one becomes visible.
        if (mode == FINISH_AFTER_VISIBLE && r.nowVisible) {
            if (!mStoppingActivities.contains(r)) {
                mStoppingActivities.add(r);
                if (mStoppingActivities.size() > 3) {
                    // If we already have a few activities waiting to stop,
                    // then give up on things going idle and start clearing
                    // them out.
                    Message msg = Message.obtain();
                    msg.what = IDLE_NOW_MSG;
                    mHandler.sendMessage(msg);
                }
            }
            r.state = ActivityState.STOPPING;
            mService.updateOomAdjLocked();
            return r;
        }

        // make sure the record is cleaned out of other places.
        mStoppingActivities.remove(r);
        mWaitingVisibleActivities.remove(r);
        if (mResumedActivity == r) {
            mResumedActivity = null;
        }
        final ActivityState prevState = r.state;
        r.state = ActivityState.FINISHING;

        if (mode == FINISH_IMMEDIATELY
                || prevState == ActivityState.STOPPED
                || prevState == ActivityState.INITIALIZING) {
            // If this activity is already stopped, we can just finish
            // it right now.
            return destroyActivityLocked(r, true) ? null : r;
        } else {
            // Need to go through the full pause cycle to get this
            // activity into the stopped state and then finish it.
            if (localLOGV) Slog.v(TAG, "Enqueueing pending finish: " + r);
            mFinishingActivities.add(r);
            resumeTopActivityLocked(null);
        }
        return r;
    }

    /**
     * Perform the common clean-up of an activity record.  This is called both
     * as part of destroyActivityLocked() (when destroying the client-side
     * representation) and cleaning things up as a result of its hosting
     * processing going away, in which case there is no remaining client-side
     * state to destroy so only the cleanup here is needed.
     */
    final void cleanUpActivityLocked(ActivityRecord r, boolean cleanServices) {
        if (mResumedActivity == r) {
            mResumedActivity = null;
        }
        if (mService.mFocusedActivity == r) {
            mService.mFocusedActivity = null;
        }

        r.configDestroy = false;
        r.frozenBeforeDestroy = false;

        // Make sure this record is no longer in the pending finishes list.
        // This could happen, for example, if we are trimming activities
        // down to the max limit while they are still waiting to finish.
        mFinishingActivities.remove(r);
        mWaitingVisibleActivities.remove(r);
        
        // Remove any pending results.
        if (r.finishing && r.pendingResults != null) {
            for (WeakReference<PendingIntentRecord> apr : r.pendingResults) {
                PendingIntentRecord rec = apr.get();
                if (rec != null) {
                    mService.cancelIntentSenderLocked(rec, false);
                }
            }
            r.pendingResults.clear();
            r.pendingResults = null;
        }

        if (cleanServices) {
            cleanUpActivityServicesLocked(r);            
        }

        if (mService.mPendingThumbnails.size() > 0) {
            // There are clients waiting to receive thumbnails so, in case
            // this is an activity that someone is waiting for, add it
            // to the pending list so we can correctly update the clients.
            mService.mCancelledThumbnails.add(r);
        }

        // Get rid of any pending idle timeouts.
        mHandler.removeMessages(PAUSE_TIMEOUT_MSG, r);
        mHandler.removeMessages(IDLE_TIMEOUT_MSG, r);
    }

    private final void removeActivityFromHistoryLocked(ActivityRecord r) {
        if (r.state != ActivityState.DESTROYED) {
            mHistory.remove(r);
            r.inHistory = false;
            r.resultTo = null;
            r.state = ActivityState.DESTROYED;
            mService.mWindowManager.removeAppToken(r);
            if (VALIDATE_TOKENS) {
                mService.mWindowManager.validateAppTokens(mHistory);
            }
            cleanUpActivityServicesLocked(r);
            r.removeUriPermissionsLocked();
        }
    }
    
    /**
     * Perform clean-up of service connections in an activity record.
     */
    final void cleanUpActivityServicesLocked(ActivityRecord r) {
        // Throw away any services that have been bound by this activity.
        if (r.connections != null) {
            Iterator<ConnectionRecord> it = r.connections.iterator();
            while (it.hasNext()) {
                ConnectionRecord c = it.next();
                mService.removeConnectionLocked(c, null, r);
            }
            r.connections.clear();
            r.connections = null;
        }
    }
    
    /**
     * Destroy the current CLIENT SIDE instance of an activity.  This may be
     * called both when actually finishing an activity, or when performing
     * a configuration switch where we destroy the current client-side object
     * but then create a new client-side object for this same HistoryRecord.
     */
    final boolean destroyActivityLocked(ActivityRecord r,
            boolean removeFromApp) {
        if (DEBUG_SWITCH) Slog.v(
            TAG, "Removing activity: token=" + r
              + ", app=" + (r.app != null ? r.app.processName : "(null)"));
        EventLog.writeEvent(EventLogTags.AM_DESTROY_ACTIVITY,
                System.identityHashCode(r),
                r.task.taskId, r.shortComponentName);

        boolean removedFromHistory = false;
        
        cleanUpActivityLocked(r, false);

        final boolean hadApp = r.app != null;
        
        if (hadApp) {
            if (removeFromApp) {
                int idx = r.app.activities.indexOf(r);
                if (idx >= 0) {
                    r.app.activities.remove(idx);
                }
                if (mService.mHeavyWeightProcess == r.app && r.app.activities.size() <= 0) {
                    mService.mHeavyWeightProcess = null;
                    mService.mHandler.sendEmptyMessage(
                            ActivityManagerService.CANCEL_HEAVY_NOTIFICATION_MSG);
                }
                if (r.app.activities.size() == 0) {
                    // No longer have activities, so update location in
                    // LRU list.
                    mService.updateLruProcessLocked(r.app, true, false);
                }
            }

            boolean skipDestroy = false;
            
            try {
                if (DEBUG_SWITCH) Slog.i(TAG, "Destroying: " + r);
                r.app.thread.scheduleDestroyActivity(r, r.finishing,
                        r.configChangeFlags);
            } catch (Exception e) {
                // We can just ignore exceptions here...  if the process
                // has crashed, our death notification will clean things
                // up.
                //Slog.w(TAG, "Exception thrown during finish", e);
                if (r.finishing) {
                    removeActivityFromHistoryLocked(r);
                    removedFromHistory = true;
                    skipDestroy = true;
                }
            }

            r.app = null;
            r.nowVisible = false;
            
            if (r.finishing && !skipDestroy) {
                r.state = ActivityState.DESTROYING;
                Message msg = mHandler.obtainMessage(DESTROY_TIMEOUT_MSG);
                msg.obj = r;
                mHandler.sendMessageDelayed(msg, DESTROY_TIMEOUT);
            } else {
                r.state = ActivityState.DESTROYED;
            }
        } else {
            // remove this record from the history.
            if (r.finishing) {
                removeActivityFromHistoryLocked(r);
                removedFromHistory = true;
            } else {
                r.state = ActivityState.DESTROYED;
            }
        }

        r.configChangeFlags = 0;
        
        if (!mLRUActivities.remove(r) && hadApp) {
            Slog.w(TAG, "Activity " + r + " being finished, but not in LRU list");
        }
        
        return removedFromHistory;
    }

    final void activityDestroyed(IBinder token) {
        synchronized (mService) {
            mHandler.removeMessages(DESTROY_TIMEOUT_MSG, token);
            
            int index = indexOfTokenLocked(token);
            if (index >= 0) {
                ActivityRecord r = (ActivityRecord)mHistory.get(index);
                if (r.state == ActivityState.DESTROYING) {
                    final long origId = Binder.clearCallingIdentity();
                    removeActivityFromHistoryLocked(r);
                    Binder.restoreCallingIdentity(origId);
                }
            }
        }
    }
    
    private static void removeHistoryRecordsForAppLocked(ArrayList list, ProcessRecord app) {
        int i = list.size();
        if (localLOGV) Slog.v(
            TAG, "Removing app " + app + " from list " + list
            + " with " + i + " entries");
        while (i > 0) {
            i--;
            ActivityRecord r = (ActivityRecord)list.get(i);
            if (localLOGV) Slog.v(
                TAG, "Record #" + i + " " + r + ": app=" + r.app);
            if (r.app == app) {
                if (localLOGV) Slog.v(TAG, "Removing this entry!");
                list.remove(i);
            }
        }
    }

    void removeHistoryRecordsForAppLocked(ProcessRecord app) {
        removeHistoryRecordsForAppLocked(mLRUActivities, app);
        removeHistoryRecordsForAppLocked(mStoppingActivities, app);
        removeHistoryRecordsForAppLocked(mWaitingVisibleActivities, app);
        removeHistoryRecordsForAppLocked(mFinishingActivities, app);
    }
    
    final void moveTaskToFrontLocked(TaskRecord tr, ActivityRecord reason) {
        if (DEBUG_SWITCH) Slog.v(TAG, "moveTaskToFront: " + tr);

        final int task = tr.taskId;
        int top = mHistory.size()-1;

        if (top < 0 || ((ActivityRecord)mHistory.get(top)).task.taskId == task) {
            // nothing to do!
            return;
        }

        ArrayList moved = new ArrayList();

        // Applying the affinities may have removed entries from the history,
        // so get the size again.
        top = mHistory.size()-1;
        int pos = top;

        // Shift all activities with this task up to the top
        // of the stack, keeping them in the same internal order.
        boolean first = true;
        while (pos >= 0) {
            ActivityRecord r = (ActivityRecord)mHistory.get(pos);
            if (localLOGV) Slog.v(
                TAG, "At " + pos + " ckp " + r.task + ": " + r);
            if (r.task.taskId == task) {
                if (localLOGV) Slog.v(TAG, "Removing and adding at " + top);
                mHistory.remove(pos);
                mHistory.add(top, r);
                moved.add(0, r);
                top--;
                if (first && mMainStack) {
                    mService.addRecentTaskLocked(r.task);
                    first = false;
                }
            }
            pos--;
        }

        if (DEBUG_TRANSITION) Slog.v(TAG,
                "Prepare to front transition: task=" + tr);
        if (reason != null &&
                (reason.intent.getFlags()&Intent.FLAG_ACTIVITY_NO_ANIMATION) != 0) {
            mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
            ActivityRecord r = topRunningActivityLocked(null);
            if (r != null) {
                mNoAnimActivities.add(r);
            }
        } else {
            mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_TASK_TO_FRONT);
        }
        
        mService.mWindowManager.moveAppTokensToTop(moved);
        if (VALIDATE_TOKENS) {
            mService.mWindowManager.validateAppTokens(mHistory);
        }

        finishTaskMoveLocked(task);
        EventLog.writeEvent(EventLogTags.AM_TASK_TO_FRONT, task);
    }

    private final void finishTaskMoveLocked(int task) {
        resumeTopActivityLocked(null);
    }

    /**
     * Worker method for rearranging history stack.  Implements the function of moving all 
     * activities for a specific task (gathering them if disjoint) into a single group at the 
     * bottom of the stack.
     * 
     * If a watcher is installed, the action is preflighted and the watcher has an opportunity
     * to premeptively cancel the move.
     * 
     * @param task The taskId to collect and move to the bottom.
     * @return Returns true if the move completed, false if not.
     */
    final boolean moveTaskToBackLocked(int task, ActivityRecord reason) {
        Slog.i(TAG, "moveTaskToBack: " + task);
        
        // If we have a watcher, preflight the move before committing to it.  First check
        // for *other* available tasks, but if none are available, then try again allowing the
        // current task to be selected.
        if (mMainStack && mService.mController != null) {
            ActivityRecord next = topRunningActivityLocked(null, task);
            if (next == null) {
                next = topRunningActivityLocked(null, 0);
            }
            if (next != null) {
                // ask watcher if this is allowed
                boolean moveOK = true;
                try {
                    moveOK = mService.mController.activityResuming(next.packageName);
                } catch (RemoteException e) {
                    mService.mController = null;
                }
                if (!moveOK) {
                    return false;
                }
            }
        }

        ArrayList moved = new ArrayList();

        if (DEBUG_TRANSITION) Slog.v(TAG,
                "Prepare to back transition: task=" + task);
        
        final int N = mHistory.size();
        int bottom = 0;
        int pos = 0;

        // Shift all activities with this task down to the bottom
        // of the stack, keeping them in the same internal order.
        while (pos < N) {
            ActivityRecord r = (ActivityRecord)mHistory.get(pos);
            if (localLOGV) Slog.v(
                TAG, "At " + pos + " ckp " + r.task + ": " + r);
            if (r.task.taskId == task) {
                if (localLOGV) Slog.v(TAG, "Removing and adding at " + (N-1));
                mHistory.remove(pos);
                mHistory.add(bottom, r);
                moved.add(r);
                bottom++;
            }
            pos++;
        }

        if (reason != null &&
                (reason.intent.getFlags()&Intent.FLAG_ACTIVITY_NO_ANIMATION) != 0) {
            mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_NONE);
            ActivityRecord r = topRunningActivityLocked(null);
            if (r != null) {
                mNoAnimActivities.add(r);
            }
        } else {
            mService.mWindowManager.prepareAppTransition(WindowManagerPolicy.TRANSIT_TASK_TO_BACK);
        }
        mService.mWindowManager.moveAppTokensToBottom(moved);
        if (VALIDATE_TOKENS) {
            mService.mWindowManager.validateAppTokens(mHistory);
        }

        finishTaskMoveLocked(task);
        return true;
    }
    
    private final void logStartActivity(int tag, ActivityRecord r,
            TaskRecord task) {
        EventLog.writeEvent(tag,
                System.identityHashCode(r), task.taskId,
                r.shortComponentName, r.intent.getAction(),
                r.intent.getType(), r.intent.getDataString(),
                r.intent.getFlags());
    }

    /**
     * Make sure the given activity matches the current configuration.  Returns
     * false if the activity had to be destroyed.  Returns true if the
     * configuration is the same, or the activity will remain running as-is
     * for whatever reason.  Ensures the HistoryRecord is updated with the
     * correct configuration and all other bookkeeping is handled.
     */
    final boolean ensureActivityConfigurationLocked(ActivityRecord r,
            int globalChanges) {
        if (mConfigWillChange) {
            if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                    "Skipping config check (will change): " + r);
            return true;
        }
        
        if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                "Ensuring correct configuration: " + r);
        
        // Short circuit: if the two configurations are the exact same
        // object (the common case), then there is nothing to do.
        Configuration newConfig = mService.mConfiguration;
        if (r.configuration == newConfig) {
            if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                    "Configuration unchanged in " + r);
            return true;
        }
        
        // We don't worry about activities that are finishing.
        if (r.finishing) {
            if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                    "Configuration doesn't matter in finishing " + r);
            r.stopFreezingScreenLocked(false);
            return true;
        }
        
        // Okay we now are going to make this activity have the new config.
        // But then we need to figure out how it needs to deal with that.
        Configuration oldConfig = r.configuration;
        r.configuration = newConfig;
        
        // If the activity isn't currently running, just leave the new
        // configuration and it will pick that up next time it starts.
        if (r.app == null || r.app.thread == null) {
            if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                    "Configuration doesn't matter not running " + r);
            r.stopFreezingScreenLocked(false);
            return true;
        }
        
        // Figure out what has changed between the two configurations.
        int changes = oldConfig.diff(newConfig);
        if (DEBUG_SWITCH || DEBUG_CONFIGURATION) {
            Slog.v(TAG, "Checking to restart " + r.info.name + ": changed=0x"
                    + Integer.toHexString(changes) + ", handles=0x"
                    + Integer.toHexString(r.info.configChanges)
                    + ", newConfig=" + newConfig);
        }
        if ((changes&(~r.info.configChanges)) != 0) {
            // Aha, the activity isn't handling the change, so DIE DIE DIE.
            r.configChangeFlags |= changes;
            r.startFreezingScreenLocked(r.app, globalChanges);
            if (r.app == null || r.app.thread == null) {
                if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                        "Switch is destroying non-running " + r);
                destroyActivityLocked(r, true);
            } else if (r.state == ActivityState.PAUSING) {
                // A little annoying: we are waiting for this activity to
                // finish pausing.  Let's not do anything now, but just
                // flag that it needs to be restarted when done pausing.
                if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                        "Switch is skipping already pausing " + r);
                r.configDestroy = true;
                return true;
            } else if (r.state == ActivityState.RESUMED) {
                // Try to optimize this case: the configuration is changing
                // and we need to restart the top, resumed activity.
                // Instead of doing the normal handshaking, just say
                // "restart!".
                if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                        "Switch is restarting resumed " + r);
                relaunchActivityLocked(r, r.configChangeFlags, true);
                r.configChangeFlags = 0;
            } else {
                if (DEBUG_SWITCH || DEBUG_CONFIGURATION) Slog.v(TAG,
                        "Switch is restarting non-resumed " + r);
                relaunchActivityLocked(r, r.configChangeFlags, false);
                r.configChangeFlags = 0;
            }
            
            // All done...  tell the caller we weren't able to keep this
            // activity around.
            return false;
        }
        
        // Default case: the activity can handle this new configuration, so
        // hand it over.  Note that we don't need to give it the new
        // configuration, since we always send configuration changes to all
        // process when they happen so it can just use whatever configuration
        // it last got.
        if (r.app != null && r.app.thread != null) {
            try {
                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Sending new config to " + r);
                r.app.thread.scheduleActivityConfigurationChanged(r);
            } catch (RemoteException e) {
                // If process died, whatever.
            }
        }
        r.stopFreezingScreenLocked(false);
        
        return true;
    }

    private final boolean relaunchActivityLocked(ActivityRecord r,
            int changes, boolean andResume) {
        List<ResultInfo> results = null;
        List<Intent> newIntents = null;
        if (andResume) {
            results = r.results;
            newIntents = r.newIntents;
        }
        if (DEBUG_SWITCH) Slog.v(TAG, "Relaunching: " + r
                + " with results=" + results + " newIntents=" + newIntents
                + " andResume=" + andResume);
        EventLog.writeEvent(andResume ? EventLogTags.AM_RELAUNCH_RESUME_ACTIVITY
                : EventLogTags.AM_RELAUNCH_ACTIVITY, System.identityHashCode(r),
                r.task.taskId, r.shortComponentName);
        
        r.startFreezingScreenLocked(r.app, 0);
        
        try {
            if (DEBUG_SWITCH) Slog.i(TAG, "Switch is restarting resumed " + r);
            r.app.thread.scheduleRelaunchActivity(r, results, newIntents,
                    changes, !andResume, mService.mConfiguration);
            // Note: don't need to call pauseIfSleepingLocked() here, because
            // the caller will only pass in 'andResume' if this activity is
            // currently resumed, which implies we aren't sleeping.
        } catch (RemoteException e) {
            return false;
        }

        if (andResume) {
            r.results = null;
            r.newIntents = null;
            if (mMainStack) {
                mService.reportResumedActivityLocked(r);
            }
        }

        return true;
    }
}