139 lines
4.2 KiB
Java
139 lines
4.2 KiB
Java
/*
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* Copyright (C) 2008 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.os;
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import android.util.Log;
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/**
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* Schedule a countdown until a time in the future, with
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* regular notifications on intervals along the way.
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*
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* Example of showing a 30 second countdown in a text field:
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*
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* <pre class="prettyprint">
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* new CountdownTimer(30000, 1000) {
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*
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* public void onTick(long millisUntilFinished) {
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* mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
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* }
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*
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* public void onFinish() {
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* mTextField.setText("done!");
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* }
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* }.start();
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* </pre>
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*
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* The calls to {@link #onTick(long)} are synchronized to this object so that
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* one call to {@link #onTick(long)} won't ever occur before the previous
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* callback is complete. This is only relevant when the implementation of
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* {@link #onTick(long)} takes an amount of time to execute that is significant
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* compared to the countdown interval.
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*/
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public abstract class CountDownTimer {
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/**
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* Millis since epoch when alarm should stop.
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*/
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private final long mMillisInFuture;
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/**
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* The interval in millis that the user receives callbacks
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*/
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private final long mCountdownInterval;
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private long mStopTimeInFuture;
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/**
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* @param millisInFuture The number of millis in the future from the call
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* to {@link #start()} until the countdown is done and {@link #onFinish()}
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* is called.
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* @param countDownInterval The interval along the way to receive
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* {@link #onTick(long)} callbacks.
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*/
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public CountDownTimer(long millisInFuture, long countDownInterval) {
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mMillisInFuture = millisInFuture;
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mCountdownInterval = countDownInterval;
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}
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/**
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* Cancel the countdown.
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*/
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public final void cancel() {
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mHandler.removeMessages(MSG);
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}
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/**
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* Start the countdown.
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*/
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public synchronized final CountDownTimer start() {
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if (mMillisInFuture <= 0) {
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onFinish();
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return this;
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}
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mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture;
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mHandler.sendMessage(mHandler.obtainMessage(MSG));
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return this;
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}
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/**
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* Callback fired on regular interval.
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* @param millisUntilFinished The amount of time until finished.
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*/
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public abstract void onTick(long millisUntilFinished);
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/**
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* Callback fired when the time is up.
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*/
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public abstract void onFinish();
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private static final int MSG = 1;
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// handles counting down
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private Handler mHandler = new Handler() {
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@Override
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public void handleMessage(Message msg) {
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synchronized (CountDownTimer.this) {
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final long millisLeft = mStopTimeInFuture - SystemClock.elapsedRealtime();
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if (millisLeft <= 0) {
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onFinish();
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} else if (millisLeft < mCountdownInterval) {
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// no tick, just delay until done
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sendMessageDelayed(obtainMessage(MSG), millisLeft);
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} else {
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long lastTickStart = SystemClock.elapsedRealtime();
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onTick(millisLeft);
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// take into account user's onTick taking time to execute
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long delay = lastTickStart + mCountdownInterval - SystemClock.elapsedRealtime();
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// special case: user's onTick took more than interval to
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// complete, skip to next interval
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while (delay < 0) delay += mCountdownInterval;
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sendMessageDelayed(obtainMessage(MSG), delay);
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}
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}
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}
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};
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}
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