423 lines
13 KiB
Java
423 lines
13 KiB
Java
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/*
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* Copyright (C) 2006 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.widget;
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import android.content.Context;
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import android.hardware.SensorManager;
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import android.view.ViewConfiguration;
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import android.view.animation.AnimationUtils;
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import android.view.animation.Interpolator;
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/**
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* This class encapsulates scrolling. The duration of the scroll
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* can be passed in the constructor and specifies the maximum time that
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* the scrolling animation should take. Past this time, the scrolling is
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* automatically moved to its final stage and computeScrollOffset()
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* will always return false to indicate that scrolling is over.
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*/
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public class Scroller {
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private int mMode;
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private int mStartX;
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private int mStartY;
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private int mFinalX;
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private int mFinalY;
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private int mMinX;
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private int mMaxX;
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private int mMinY;
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private int mMaxY;
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private int mCurrX;
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private int mCurrY;
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private long mStartTime;
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private int mDuration;
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private float mDurationReciprocal;
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private float mDeltaX;
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private float mDeltaY;
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private boolean mFinished;
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private Interpolator mInterpolator;
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private float mCoeffX = 0.0f;
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private float mCoeffY = 1.0f;
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private float mVelocity;
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private static final int DEFAULT_DURATION = 250;
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private static final int SCROLL_MODE = 0;
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private static final int FLING_MODE = 1;
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private final float mDeceleration;
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private static float sViscousFluidScale;
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private static float sViscousFluidNormalize;
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static {
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// This controls the viscous fluid effect (how much of it)
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sViscousFluidScale = 8.0f;
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// must be set to 1.0 (used in viscousFluid())
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sViscousFluidNormalize = 1.0f;
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sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);
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}
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/**
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* Create a Scroller with the default duration and interpolator.
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*/
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public Scroller(Context context) {
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this(context, null);
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}
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/**
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* Create a Scroller with the specified interpolator. If the interpolator is
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* null, the default (viscous) interpolator will be used.
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*/
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public Scroller(Context context, Interpolator interpolator) {
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mFinished = true;
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mInterpolator = interpolator;
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float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
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mDeceleration = SensorManager.GRAVITY_EARTH // g (m/s^2)
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* 39.37f // inch/meter
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* ppi // pixels per inch
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* ViewConfiguration.getScrollFriction();
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}
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/**
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*
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* Returns whether the scroller has finished scrolling.
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*
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* @return True if the scroller has finished scrolling, false otherwise.
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*/
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public final boolean isFinished() {
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return mFinished;
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}
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/**
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* Force the finished field to a particular value.
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*
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* @param finished The new finished value.
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*/
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public final void forceFinished(boolean finished) {
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mFinished = finished;
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}
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/**
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* Returns how long the scroll event will take, in milliseconds.
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*
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* @return The duration of the scroll in milliseconds.
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*/
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public final int getDuration() {
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return mDuration;
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}
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/**
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* Returns the current X offset in the scroll.
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*
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* @return The new X offset as an absolute distance from the origin.
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*/
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public final int getCurrX() {
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return mCurrX;
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}
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/**
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* Returns the current Y offset in the scroll.
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*
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* @return The new Y offset as an absolute distance from the origin.
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*/
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public final int getCurrY() {
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return mCurrY;
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}
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/**
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* @hide
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* Returns the current velocity.
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*
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* @return The original velocity less the deceleration. Result may be
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* negative.
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*/
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public float getCurrVelocity() {
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return mVelocity - mDeceleration * timePassed() / 2000.0f;
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}
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/**
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* Returns the start X offset in the scroll.
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*
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* @return The start X offset as an absolute distance from the origin.
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*/
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public final int getStartX() {
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return mStartX;
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}
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/**
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* Returns the start Y offset in the scroll.
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*
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* @return The start Y offset as an absolute distance from the origin.
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*/
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public final int getStartY() {
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return mStartY;
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}
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/**
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* Returns where the scroll will end. Valid only for "fling" scrolls.
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*
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* @return The final X offset as an absolute distance from the origin.
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*/
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public final int getFinalX() {
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return mFinalX;
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}
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/**
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* Returns where the scroll will end. Valid only for "fling" scrolls.
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*
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* @return The final Y offset as an absolute distance from the origin.
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*/
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public final int getFinalY() {
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return mFinalY;
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}
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/**
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* Call this when you want to know the new location. If it returns true,
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* the animation is not yet finished. loc will be altered to provide the
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* new location.
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*/
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public boolean computeScrollOffset() {
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if (mFinished) {
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return false;
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}
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int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
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if (timePassed < mDuration) {
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switch (mMode) {
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case SCROLL_MODE:
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float x = (float)timePassed * mDurationReciprocal;
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if (mInterpolator == null)
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x = viscousFluid(x);
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else
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x = mInterpolator.getInterpolation(x);
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mCurrX = mStartX + Math.round(x * mDeltaX);
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mCurrY = mStartY + Math.round(x * mDeltaY);
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break;
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case FLING_MODE:
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float timePassedSeconds = timePassed / 1000.0f;
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float distance = (mVelocity * timePassedSeconds)
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- (mDeceleration * timePassedSeconds * timePassedSeconds / 2.0f);
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mCurrX = mStartX + Math.round(distance * mCoeffX);
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// Pin to mMinX <= mCurrX <= mMaxX
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mCurrX = Math.min(mCurrX, mMaxX);
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mCurrX = Math.max(mCurrX, mMinX);
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mCurrY = mStartY + Math.round(distance * mCoeffY);
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// Pin to mMinY <= mCurrY <= mMaxY
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mCurrY = Math.min(mCurrY, mMaxY);
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mCurrY = Math.max(mCurrY, mMinY);
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if (mCurrX == mFinalX && mCurrY == mFinalY) {
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mFinished = true;
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}
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break;
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}
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}
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else {
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mCurrX = mFinalX;
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mCurrY = mFinalY;
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mFinished = true;
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}
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return true;
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}
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/**
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* Start scrolling by providing a starting point and the distance to travel.
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* The scroll will use the default value of 250 milliseconds for the
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* duration.
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*
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* @param startX Starting horizontal scroll offset in pixels. Positive
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* numbers will scroll the content to the left.
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* @param startY Starting vertical scroll offset in pixels. Positive numbers
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* will scroll the content up.
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* @param dx Horizontal distance to travel. Positive numbers will scroll the
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* content to the left.
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* @param dy Vertical distance to travel. Positive numbers will scroll the
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* content up.
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*/
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public void startScroll(int startX, int startY, int dx, int dy) {
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startScroll(startX, startY, dx, dy, DEFAULT_DURATION);
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}
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/**
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* Start scrolling by providing a starting point and the distance to travel.
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*
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* @param startX Starting horizontal scroll offset in pixels. Positive
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* numbers will scroll the content to the left.
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* @param startY Starting vertical scroll offset in pixels. Positive numbers
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* will scroll the content up.
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* @param dx Horizontal distance to travel. Positive numbers will scroll the
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* content to the left.
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* @param dy Vertical distance to travel. Positive numbers will scroll the
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* content up.
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* @param duration Duration of the scroll in milliseconds.
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*/
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public void startScroll(int startX, int startY, int dx, int dy, int duration) {
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mMode = SCROLL_MODE;
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mFinished = false;
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mDuration = duration;
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mStartTime = AnimationUtils.currentAnimationTimeMillis();
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mStartX = startX;
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mStartY = startY;
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mFinalX = startX + dx;
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mFinalY = startY + dy;
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mDeltaX = dx;
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mDeltaY = dy;
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mDurationReciprocal = 1.0f / (float) mDuration;
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}
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/**
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* Start scrolling based on a fling gesture. The distance travelled will
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* depend on the initial velocity of the fling.
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*
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* @param startX Starting point of the scroll (X)
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* @param startY Starting point of the scroll (Y)
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* @param velocityX Initial velocity of the fling (X) measured in pixels per
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* second.
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* @param velocityY Initial velocity of the fling (Y) measured in pixels per
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* second
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* @param minX Minimum X value. The scroller will not scroll past this
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* point.
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* @param maxX Maximum X value. The scroller will not scroll past this
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* point.
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* @param minY Minimum Y value. The scroller will not scroll past this
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* point.
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* @param maxY Maximum Y value. The scroller will not scroll past this
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* point.
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*/
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public void fling(int startX, int startY, int velocityX, int velocityY,
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int minX, int maxX, int minY, int maxY) {
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mMode = FLING_MODE;
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mFinished = false;
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float velocity = (float)Math.hypot(velocityX, velocityY);
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mVelocity = velocity;
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mDuration = (int) (1000 * velocity / mDeceleration); // Duration is in
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// milliseconds
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mStartTime = AnimationUtils.currentAnimationTimeMillis();
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mStartX = startX;
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mStartY = startY;
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mCoeffX = velocity == 0 ? 1.0f : velocityX / velocity;
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mCoeffY = velocity == 0 ? 1.0f : velocityY / velocity;
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int totalDistance = (int) ((velocity * velocity) / (2 * mDeceleration));
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mMinX = minX;
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mMaxX = maxX;
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mMinY = minY;
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mMaxY = maxY;
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mFinalX = startX + Math.round(totalDistance * mCoeffX);
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// Pin to mMinX <= mFinalX <= mMaxX
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mFinalX = Math.min(mFinalX, mMaxX);
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mFinalX = Math.max(mFinalX, mMinX);
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mFinalY = startY + Math.round(totalDistance * mCoeffY);
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// Pin to mMinY <= mFinalY <= mMaxY
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mFinalY = Math.min(mFinalY, mMaxY);
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mFinalY = Math.max(mFinalY, mMinY);
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}
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static float viscousFluid(float x)
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{
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x *= sViscousFluidScale;
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if (x < 1.0f) {
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x -= (1.0f - (float)Math.exp(-x));
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} else {
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float start = 0.36787944117f; // 1/e == exp(-1)
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x = 1.0f - (float)Math.exp(1.0f - x);
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x = start + x * (1.0f - start);
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}
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x *= sViscousFluidNormalize;
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return x;
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}
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/**
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* Stops the animation. Contrary to {@link #forceFinished(boolean)},
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* aborting the animating cause the scroller to move to the final x and y
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* position
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*
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* @see #forceFinished(boolean)
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*/
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public void abortAnimation() {
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mCurrX = mFinalX;
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mCurrY = mFinalY;
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mFinished = true;
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}
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/**
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* Extend the scroll animation. This allows a running animation to scroll
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* further and longer, when used with {@link #setFinalX(int)} or {@link #setFinalY(int)}.
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*
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* @param extend Additional time to scroll in milliseconds.
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* @see #setFinalX(int)
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* @see #setFinalY(int)
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*/
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public void extendDuration(int extend) {
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int passed = timePassed();
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mDuration = passed + extend;
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mDurationReciprocal = 1.0f / (float)mDuration;
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mFinished = false;
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}
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/**
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|
|
* Returns the time elapsed since the beginning of the scrolling.
|
||
|
|
*
|
||
|
|
* @return The elapsed time in milliseconds.
|
||
|
|
*/
|
||
|
|
public int timePassed() {
|
||
|
|
return (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Sets the final position (X) for this scroller.
|
||
|
|
*
|
||
|
|
* @param newX The new X offset as an absolute distance from the origin.
|
||
|
|
* @see #extendDuration(int)
|
||
|
|
* @see #setFinalY(int)
|
||
|
|
*/
|
||
|
|
public void setFinalX(int newX) {
|
||
|
|
mFinalX = newX;
|
||
|
|
mDeltaX = mFinalX - mStartX;
|
||
|
|
mFinished = false;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Sets the final position (Y) for this scroller.
|
||
|
|
*
|
||
|
|
* @param newY The new Y offset as an absolute distance from the origin.
|
||
|
|
* @see #extendDuration(int)
|
||
|
|
* @see #setFinalX(int)
|
||
|
|
*/
|
||
|
|
public void setFinalY(int newY) {
|
||
|
|
mFinalY = newY;
|
||
|
|
mDeltaY = mFinalY - mStartY;
|
||
|
|
mFinished = false;
|
||
|
|
}
|
||
|
|
}
|