分析版本api 24
首先我们要找一个入口，就从ObjectAnimator.ofInt(this, "width", 0, -20).start()开始吧，其他动画都是类似的。
先看参数构造
ObjectAnimator.ofInt(this, "currentProgress", 0, progress)
/ *
* @param target The object whose property is to be animated.
* @param property The property being animated.
* @param values A set of values that the animation will animate between over time.
* @return An ObjectAnimator object that is set up to animate between the given values.
*/
public static <T> ObjectAnimator ofInt(T target, Property<T, Integer> property, int... values) {
ObjectAnimator anim = new ObjectAnimator(target, property);
anim.setIntValues(values);
return anim;
}
通过target, property构造了ObjectAnimator，并设置了可变int数组values ，继续看 anim.setIntValues(values);
@Override
public void setIntValues(int... values) {
if (mValues == null || mValues.length == 0) {
// No values yet - this animator is being constructed piecemeal. Init the values with
// whatever the current propertyName is
if (mProperty != null) {
setValues(PropertyValuesHolder.ofInt(mProperty, values));
} else {
setValues(PropertyValuesHolder.ofInt(mPropertyName, values));
}
} else {
super.setIntValues(values);
}
}
a 继续数组为空时，调用自身的setIntValues(values)，
public void setValues(PropertyValuesHolder... values) {
int numValues = values.length;
mValues = values;
mValuesMap = new HashMap<String, PropertyValuesHolder>(numValues);
for (int i = 0; i < numValues; ++i) {
PropertyValuesHolder valuesHolder = values[i];
mValuesMap.put(valuesHolder.getPropertyName(), valuesHolder);
}
// New property/values/target should cause re-initialization prior to starting
mInitialized = false;
}
b 否则父类的ValueAnimator的public void setValues(PropertyValuesHolder... values)
public void setIntValues(int... values) {
if (values == null || values.length == 0) {
return;
}
if (mValues == null || mValues.length == 0) {
setValues(PropertyValuesHolder.ofInt("", values));
} else {
PropertyValuesHolder valuesHolder = mValues[0];
valuesHolder.setIntValues(values);
}
// New property/values/target should cause re-initialization prior to starting
mInitialized = false;
}
还是走上一个函数a public void setValues(PropertyValuesHolder... values)最终将数据塞给mValuesMap保存下来
正式start()
public void start() {
// See if any of the current active/pending animators need to be canceled
AnimationHandler handler = sAnimationHandler.get();
if (handler != null) {
int numAnims = handler.mAnimations.size();
for (int i = numAnims - 1; i >= 0; i--) {
if (handler.mAnimations.get(i) instanceof ObjectAnimator) {
ObjectAnimator anim = (ObjectAnimator) handler.mAnimations.get(i);
if (anim.mAutoCancel && hasSameTargetAndProperties(anim)) {
anim.cancel();
}
}
}
numAnims = handler.mPendingAnimations.size();
for (int i = numAnims - 1; i >= 0; i--) {
if (handler.mPendingAnimations.get(i) instanceof ObjectAnimator) {
ObjectAnimator anim = (ObjectAnimator) handler.mPendingAnimations.get(i);
if (anim.mAutoCancel && hasSameTargetAndProperties(anim)) {
anim.cancel();
}
}
}
numAnims = handler.mDelayedAnims.size();
for (int i = numAnims - 1; i >= 0; i--) {
if (handler.mDelayedAnims.get(i) instanceof ObjectAnimator) {
ObjectAnimator anim = (ObjectAnimator) handler.mDelayedAnims.get(i);
if (anim.mAutoCancel && hasSameTargetAndProperties(anim)) {
anim.cancel();
}
}
}
}
if (DBG) {
Log.d(LOG_TAG, "Anim target, duration: " + getTarget() + ", " + getDuration());
for (int i = 0; i < mValues.length; ++i) {
PropertyValuesHolder pvh = mValues[i];
Log.d(LOG_TAG, " Values[" + i + "]: " +
pvh.getPropertyName() + ", " + pvh.mKeyframes.getValue(0) + ", " +
pvh.mKeyframes.getValue(1));
}
}
super.start();
}
这段代码逻辑还是比较清楚的，在比较与mAnimations，mPendingAnimations，mDelayedAnims数组中找出是否存在当前动画，先cancel掉。
接着log，然后 super.start();
@Override
public void start() {
start(false);
}
private void start(boolean playBackwards) {
if (Looper.myLooper() == null) {
throw new AndroidRuntimeException("Animators may only be run on Looper threads");
}
mReversing = playBackwards;
mPlayingBackwards = playBackwards;
if (playBackwards && mSeekFraction != -1) {
if (mSeekFraction == 0 && mCurrentIteration == 0) {
// special case: reversing from seek-to-0 should act as if not seeked at all
mSeekFraction = 0;
} else if (mRepeatCount == INFINITE) {
mSeekFraction = 1 - (mSeekFraction % 1);
} else {
mSeekFraction = 1 + mRepeatCount - (mCurrentIteration + mSeekFraction);
}
mCurrentIteration = (int) mSeekFraction;
mSeekFraction = mSeekFraction % 1;
}
if (mCurrentIteration > 0 && mRepeatMode == REVERSE &&
(mCurrentIteration < (mRepeatCount + 1) || mRepeatCount == INFINITE)) {
// if we were seeked to some other iteration in a reversing animator,
// figure out the correct direction to start playing based on the iteration
if (playBackwards) {
mPlayingBackwards = (mCurrentIteration % 2) == 0;
} else {
mPlayingBackwards = (mCurrentIteration % 2) != 0;
}
}
int prevPlayingState = mPlayingState;
mPlayingState = STOPPED;
mStarted = true;
mStartedDelay = false;
mPaused = false;
updateScaledDuration(); // in case the scale factor has changed since creation time
AnimationHandler animationHandler = getOrCreateAnimationHandler();
animationHandler.mPendingAnimations.add(this);
if (mStartDelay == 0) {
// This sets the initial value of the animation, prior to actually starting it running
if (prevPlayingState != SEEKED) {
setCurrentPlayTime(0);
}
mPlayingState = STOPPED;
mRunning = true;
notifyStartListeners();
}
animationHandler.start();
}
AnimationHandler是一个单例对象，getOrCreateAnimationHandler()获取。 不同属性动画版本，这里有所区别。 animationHandler.start();
public void start() {
scheduleAnimation();
}
继续看
private void scheduleAnimation() {
if (!mAnimationScheduled) {
mChoreographer.postCallback(Choreographer.CALLBACK_ANIMATION, mAnimate, null);
mAnimationScheduled = true;
}
}
原来是在这里mChoreographer.postCallback(Choreographer.CALLBACK_ANIMATION, mAnimate, null); Choreographer机制，用于同Vsync机制配合，实现统一调度界面绘图
最终调用
private void postCallbackDelayedInternal(int callbackType,
Object action, Object token, long delayMillis) {
if (DEBUG_FRAMES) {
Log.d(TAG, "PostCallback: type=" + callbackType
+ ", action=" + action + ", token=" + token
+ ", delayMillis=" + delayMillis);
}
synchronized (mLock) {
final long now = SystemClock.uptimeMillis();
final long dueTime = now + delayMillis;
mCallbackQueues[callbackType].addCallbackLocked(dueTime, action, token);
if (dueTime <= now) {
scheduleFrameLocked(now);
} else {
Message msg = mHandler.obtainMessage(MSG_DO_SCHEDULE_CALLBACK, action);
msg.arg1 = callbackType;
msg.setAsynchronous(true);
mHandler.sendMessageAtTime(msg, dueTime);
}
}
}
mCallbackQueues[callbackType].addCallbackLocked(dueTime, action, token);根据类型加入不同的队列
Android系统Choreographer机制实现过程
当VSYNC信号到达时，Choreographer doFrame()函数被调用。代码较多，中间省略掉
void doFrame(long frameTimeNanos, int frame) {
...
try {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "Choreographer#doFrame");
mFrameInfo.markInputHandlingStart();
doCallbacks(Choreographer.CALLBACK_INPUT, frameTimeNanos);
mFrameInfo.markAnimationsStart();
doCallbacks(Choreographer.CALLBACK_ANIMATION, frameTimeNanos);
mFrameInfo.markPerformTraversalsStart();
doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameTimeNanos);
doCallbacks(Choreographer.CALLBACK_COMMIT, frameTimeNanos);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
if (DEBUG_FRAMES) {
final long endNanos = System.nanoTime();
Log.d(TAG, "Frame " + frame + ": Finished, took "
+ (endNanos - startNanos) * 0.000001f + " ms, latency "
+ (startNanos - frameTimeNanos) * 0.000001f + " ms.");
}
}
于是
void doCallbacks(int callbackType, long frameTimeNanos) {
CallbackRecord callbacks;
synchronized (mLock) {
final long now = SystemClock.uptimeMillis();
//从指定类型的CallbackQueue队列中查找执行时间到的CallbackRecord
callbacks = mCallbackQueues[callbackType].extractDueCallbacksLocked(now);
if (callbacks == null) {
return;
}
mCallbacksRunning = true;
}
try {
//由于CallbackQueues是按时间先后顺序排序的，因此遍历执行所有时间到的CallbackRecord 。 这个record是CallbackQueues post的时候加入的。
for (CallbackRecord c = callbacks; c != null; c = c.next) {
c.run(frameTimeNanos);
}
} finally {
synchronized (mLock) {
mCallbacksRunning = false;
do {
final CallbackRecord next = callbacks.next;
recycleCallbackLocked(callbacks);
callbacks = next;
} while (callbacks != null);
}
}
}
for (CallbackRecord c = callbacks; c != null; c = c.next) {
c.run(frameTimeNanos);
}
这句即调用mAnimate的run方法
final Runnable mAnimate = new Runnable() {
@Override
public void run() {
mAnimationScheduled = false;
doAnimationFrame(mChoreographer.getFrameTime());
}
};
继续走doAnimationFrame(mChoreographer.getFrameTime());
void doAnimationFrame(long frameTime) {
mLastFrameTime = frameTime;
// mPendingAnimations holds any animations that have requested to be started
// We're going to clear mPendingAnimations, but starting animation may
// cause more to be added to the pending list (for example, if one animation
// starting triggers another starting). So we loop until mPendingAnimations
// is empty.
while (mPendingAnimations.size() > 0) {
ArrayList<ValueAnimator> pendingCopy =
(ArrayList<ValueAnimator>) mPendingAnimations.clone();
mPendingAnimations.clear();
int count = pendingCopy.size();
for (int i = 0; i < count; ++i) {
ValueAnimator anim = pendingCopy.get(i);
// If the animation has a startDelay, place it on the delayed list
if (anim.mStartDelay == 0) {
anim.startAnimation(this);
} else {
mDelayedAnims.add(anim);
}
}
}
// Next, process animations currently sitting on the delayed queue, adding
// them to the active animations if they are ready
int numDelayedAnims = mDelayedAnims.size();
for (int i = 0; i < numDelayedAnims; ++i) {
ValueAnimator anim = mDelayedAnims.get(i);
if (anim.delayedAnimationFrame(frameTime)) {
mReadyAnims.add(anim);
}
}
int numReadyAnims = mReadyAnims.size();
if (numReadyAnims > 0) {
for (int i = 0; i < numReadyAnims; ++i) {
ValueAnimator anim = mReadyAnims.get(i);
anim.startAnimation(this);
anim.mRunning = true;
mDelayedAnims.remove(anim);
}
mReadyAnims.clear();
}
// Now process all active animations. The return value from animationFrame()
// tells the handler whether it should now be ended
int numAnims = mAnimations.size();
for (int i = 0; i < numAnims; ++i) {
mTmpAnimations.add(mAnimations.get(i));
}
for (int i = 0; i < numAnims; ++i) {
ValueAnimator anim = mTmpAnimations.get(i);
if (mAnimations.contains(anim) && anim.doAnimationFrame(frameTime)) {
mEndingAnims.add(anim);
}
}
mTmpAnimations.clear();
if (mEndingAnims.size() > 0) {
for (int i = 0; i < mEndingAnims.size(); ++i) {
mEndingAnims.get(i).endAnimation(this);
}
mEndingAnims.clear();
}
// Schedule final commit for the frame.
mChoreographer.postCallback(Choreographer.CALLBACK_COMMIT, mCommit, null);
// If there are still active or delayed animations, schedule a future call to
// onAnimate to process the next frame of the animations.
if (!mAnimations.isEmpty() || !mDelayedAnims.isEmpty()) {
scheduleAnimation();
}
}
这里有好几个重要的逻辑，其实处理的主要调度在这里发出：
1 首先遍历mPendingAnimations队列 ：
a 要延迟启动，加入mDelayedAnims队列
b 如果不是延迟则调用startAnimation(AnimationHandler handler)方法
2 接着处理mDelayedAnims延迟队列，经过delayedAnimationFrame判断是否唤醒当前的动画
如果唤醒的话将ValueAnimator对象添加到mReadyAnims准备列表中；
3 接下来处理mReadyAnims列表，遍历该列表取出ValueAnimator对象并调用startAnimation(AnimationHandler handler)方法
4 下一步将处理mAnimations动画列表，通过遍历将当前要启动的动画倒装在临时列表mTmpAnimations，遍历临时列表调用anim.doAnimationFrame(frameTime)方法，通过该方法的返回值判断是否为动画的最后一帧，若是，则将ValueAnimator对象添加到mEndingAnims结束动画列表。遍历结束后清除临时列表mTmpAnimations；
5 最后遍历mEndingAnims结束列表调用endAnimation()方法，遍历结束后清除mEndingAnims列表。
6 mAnimations和mDelayedAnims两个列表，只要任何一个不为空还会调用scheduleAnimation方法，形成了循环。
参考 http://icedcap.github.io/2016/06/21/Android%E5%8A%A8%E7%94%BB%E5%AE%8C%E5%85%A8%E6%80%BB%E7%BB%93/
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先看ValueAnimator的startAnimation(AnimationHandler handler)，好吧，一系列初始化
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这里先initAnimation之后就notifyStartListeners
先看listener
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原来是这里回调listener开始动画。
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接着继续看，动画执行：
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final boolean doAnimationFrame(long frameTime) {
if (mPlayingState == STOPPED) {
mPlayingState = RUNNING;
if (mSeekFraction < 0) {
mStartTime = frameTime;
} else {
long seekTime = (long) (mDuration * mSeekFraction);
mStartTime = frameTime - seekTime;
mSeekFraction = -1;
}
mStartTimeCommitted = false; // allow start time to be compensated for jank
}
if (mPaused) {
if (mPauseTime < 0) {
mPauseTime = frameTime;
}
return false;
} else if (mResumed) {
mResumed = false;
if (mPauseTime > 0) {
// Offset by the duration that the animation was paused
mStartTime += (frameTime - mPauseTime);
mStartTimeCommitted = false; // allow start time to be compensated for jank
}
}
// The frame time might be before the start time during the first frame of
// an animation. The "current time" must always be on or after the start
// time to avoid animating frames at negative time intervals. In practice, this
// is very rare and only happens when seeking backwards.
final long currentTime = Math.max(frameTime, mStartTime);
return animationFrame(currentTime);
}
boolean animationFrame(long currentTime) {
boolean done = false;
switch (mPlayingState) {
case RUNNING:
case SEEKED:
float fraction = mDuration > 0 ? (float)(currentTime - mStartTime) / mDuration : 1f;
if (mDuration == 0 && mRepeatCount != INFINITE) {
// Skip to the end
mCurrentIteration = mRepeatCount;
if (!mReversing) {
mPlayingBackwards = false;
}
}
if (fraction >= 1f) {
if (mCurrentIteration < mRepeatCount || mRepeatCount == INFINITE) {
// Time to repeat
if (mListeners != null) {
int numListeners = mListeners.size();
for (int i = 0; i < numListeners; ++i) {
mListeners.get(i).onAnimationRepeat(this);
}
}
if (mRepeatMode == REVERSE) {
mPlayingBackwards = !mPlayingBackwards;
}
mCurrentIteration += (int) fraction;
fraction = fraction % 1f;
mStartTime += mDuration;
// Note: We do not need to update the value of mStartTimeCommitted here
// since we just added a duration offset.
} else {
done = true;
fraction = Math.min(fraction, 1.0f);
}
}
if (mPlayingBackwards) {
fraction = 1f - fraction;
}
animateValue(fraction);
break;
}
return done;
}
mCurrentIteration < mRepeatCount || mRepeatCount == INFINITE 条件内回调了onAnimationRepeat(this)。 而改函数继续调用了 animateValue(fraction); fraction 动画进度。然后先调用子类ObjectAnimator的animateValue
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注意到先调用了ValueAnimator super.animateValue(fraction);
void animateValue(float fraction) {
fraction = mInterpolator.getInterpolation(fraction);
mCurrentFraction = fraction;
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
mValues[i].calculateValue(fraction);
}
if (mUpdateListeners != null) {
int numListeners = mUpdateListeners.size();
for (int i = 0; i < numListeners; ++i) {
mUpdateListeners.get(i).onAnimationUpdate(this);
}
}
}
calculateValue将根据Keyframes获取到的值塞给mAnimatedValue
void calculateValue(float fraction) {
Object value = mKeyframes.getValue(fraction);
mAnimatedValue = mConverter == null ? value : mConverter.convert(value);
}
这里回调了动画的进度mUpdateListeners.get(i).onAnimationUpdate(this)，很多时候可以根据这个回调来完成我们想要的一些效果，如贝塞尔曲线运动等。animateValue然后回到子类ObjectAnimator的void animateValue(float fraction) 方法
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此时调用PropertyValuesHolder的 void setAnimatedValue(Object target)
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可见是使用反射方式给对应属性值设置了value值。
里面的逻辑比较清晰，但是调用太多了，读起来还是比较费劲的。最后给出一下整个的时序：
Animator#start() --> ValueAnimator#start() --> ValueAnimator# start(false) --> AnimationHandler#start()--> scheduleAnimation() -->
--> Choreographer#postCallback(Choreographer.CALLBACK_ANIMATION ....(省略) -->
AnimationHandler # void doAnimationFrame(long frameTime)--> ValueAnimator # startAnimation(AnimationHandler) -->ValueAnimator # notifyStartListeners --> AnimatorListener#onAnimationStart() -->ValueAnimator # doAnimationFrame() -->
ValueAnimator # animationFrame(currentTime) --> ObjectAnimator#animateValue(fraction) --> ValueAnimator # animateValue(fraction) --> AnimatorListener#onAnimationUpdate(this) -->PropertyValuesHolder # setAnimatedValue(target)
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