android 动画深入分析----属性动画（二）《android开发艺术与探索》
属性动画：
属性动画可以对任意对象的属性进行动画，不仅仅是View，动画默认时间300ms，默认帧率10ms/帧。可达到的效果：某个时间间隔内完成对象从一个属性值到另一个属性值的改变。属性动画从API11之后才有，这制约了属性动画的使用，可以采用nineoldandroids，可以在api11之前的版本使用。nineoldandroids的网址：http://nineoldandroids.com
比较常用的几个动画类：
ValueAnimator ObjectAnimator AnimatorSet
举例：
1.改变目标对象（target）的属性（propertyName）的值（values）
ObjectAnimator.ofFloat(target, propertyName, values).start();2.改变一个对象的背景颜色
ValueAnimator colorAnim = ObjectAnimator.ofInt(this, "backgroundColor", 0xffff8080,0xff8080ff);
colorAnim.setDuration(3000);
colorAnim.setEvaluator(new ArgbEvaluator());
colorAnim.setRepeatCount(ValueAnimator.INFINITE);
colorAnim.setRepeatMode(ValueAnimator.REVERSE);
colorAnim.start();3.动画集合
//View在5秒内旋转，平移，缩放，透明的改变
AnimatorSet set = new AnimatorSet();
set.playTogether(
ObjectAnimator.ofFloat(btn_anim, "rotationX", 0,360),
ObjectAnimator.ofFloat(btn_anim, "rotationY", 0,180),
ObjectAnimator.ofFloat(btn_anim, "rotation", 0,90),
ObjectAnimator.ofFloat(btn_anim, "tanslationX", 0,100),
ObjectAnimator.ofFloat(btn_anim, "tanslationY", 0,100),
ObjectAnimator.ofFloat(btn_anim, "scaleX",1,1.5f),
ObjectAnimator.ofFloat(btn_anim, "scaleY", 1,0.5f),
ObjectAnimator.ofFloat(btn_anim, "alpha", 1,0.25f,1)
);
set.setDuration(5000);
set.start();在res/animator也可以用xml
>
android:ordering对应的有2个值
together 表示动画集合中的子动画同时播放
sequentially 表示动画集合中的子动画按先后顺序播放
android:propertyName=""作用对象的属性名称
android:duration="" 动画时长
android:valueFrom="" 动画起始值
android:valueTo="" 动画结束值
android:startOffset="" 动画延迟时间（动画开始后多长时间开始播放动画）
android:repeatCount="" 动画的重复次数
android:repeatMode="" 动画的重复模式
android:valueType="" 属性的类型（intType/floatType）
举例：
代码调用上面的xml
AnimatorSet set = (AnimatorSet) AnimatorInflater.loadAnimator(this, R.animator.animator_xy);
set.setTarget(btn_anim);
set.start();理解插值器和估值器：
插值器（Interpolator）：
TimeInterpolator 时间插值器 根据时间的流逝的百分比来计算出当前属性值改变的百分比。
LinearInterpolator 线性插值器 ：匀速动画
AccelerateDecelerateInterpolator 加速减速插值器：动画两天慢中间快
DecelerateInterpolator 减速插值器：动画越来越慢
源码：
public class LinearInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
public LinearInterpolator() {
}
public LinearInterpolator(Context context, AttributeSet attrs) {
}
public float getInterpolation(float input) {
return input;
}
/** @hide */
@Override
public long createNativeInterpolator() {
return NativeInterpolatorFactoryHelper.createLinearInterpolator();
}
}这个线性值插器的返回值和输入值是一样的
估值器（TypeEvaluator）：
IntEvaluator：整型属性
FloatEvaluator：浮点型属性
ArgbEvaluator：Color型属性
源码：
public class IntEvaluator implements TypeEvaluator {
/**
* This function returns the result of linearly interpolating the start and end values, with
* fraction representing the proportion between the start and end values. The
* calculation is a simple parametric calculation: result = x0 + t * (v1 - v0),
* where x0 is startValue, x1 is endValue,
* and t is fraction.
*
* @param fraction The fraction from the starting to the ending values
* @param startValue The start value; should be of type int or
* Integer
* @param endValue The end value; should be of type int or Integer
* @return A linear interpolation between the start and end values, given the
* fraction parameter.
*/
public Integer evaluate(float fraction, Integer startValue, Integer endValue) {
int startInt = startValue;
return (int)(startInt + fraction * (endValue - startInt));
}
} 上面三个参数分别表示 估值小数 开始值 结束值
自定义估值算法需要实现TypeEvaluator
属性动画的监听器：
AnimatorListener和AnimatorUpdateListener
public static interface AnimatorListener {
void onAnimationStart(Animator animation);
void onAnimationEnd(Animator animation);
void onAnimationCancel(Animator animation);
void onAnimationRepeat(Animator animation);
}
public static interface AnimatorUpdateListener {
void onAnimationUpdate(ValueAnimator animation);
}
对任意属性做动画：
分析属性动画原理：属性动画要求作用的对象是提供该属性的get和set方法，属性动画根据外界传递的该属性的初始值和最终值，以动画的效果多次去调用set方法，每次传递给set方法的值不一样，确切的说是随着时间的推移，所传递的值越来越接近最终值。
如果要多object的abc属性做动画必须同时满足下面两个条件：
1.object必须提供setabc的方法，如果动画的时候没有传递初始值，还需提供getabc方法，系统要去取abc属性的初始值。（如果条件不满足会Crash）
2.object的setabc对abc所做的改变必须通过某种方法反映出来，比如会带来UI改变。（这个条件不满足，动画无效，不会Crash）
属性动画的工作原理：
ObjectAnimator.ofInt(this, "backgroundColor", 0xffff8080,0xff8080ff).start();调用了start（）；
@Override
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();
}首先判断当前的动画，等待的动画（Pending）和延迟的动画（Delayed）中有和当前动画相同的动画，那么就把相同的动画取消调，接下来是log，再接着就是调用父类 super.start();接着看ValueAnimator的start方法：
@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();
}
可以看出属性动画是需要运行在Looper的线程中，会调用animationHandler.start();
@SuppressWarnings("unchecked")
protected static class AnimationHandler implements Runnable {
// The per-thread list of all active animations
/** @hide */
protected final ArrayList mAnimations = new ArrayList();
// Used in doAnimationFrame() to avoid concurrent modifications of mAnimations
private final ArrayList mTmpAnimations = new ArrayList();
// The per-thread set of animations to be started on the next animation frame
/** @hide */
protected final ArrayList mPendingAnimations = new ArrayList();
/**
* Internal per-thread collections used to avoid set collisions as animations start and end
* while being processed.
* @hide
*/
protected final ArrayList mDelayedAnims = new ArrayList();
private final ArrayList mEndingAnims = new ArrayList();
private final ArrayList mReadyAnims = new ArrayList();
private final Choreographer mChoreographer;
private boolean mAnimationScheduled;
private AnimationHandler() {
mChoreographer = Choreographer.getInstance();
}
/**
* Start animating on the next frame.
*/
public void start() {
scheduleAnimation();
}
private void doAnimationFrame(long 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 pendingCopy =
(ArrayList) 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();
}
// 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();
}
}
// Called by the Choreographer.
@Override
public void run() {
mAnimationScheduled = false;
doAnimationFrame(mChoreographer.getFrameTime());
}
private void scheduleAnimation() {
if (!mAnimationScheduled) {
mChoreographer.postCallback(Choreographer.CALLBACK_ANIMATION, this, null);
mAnimationScheduled = true;
}
}
} 看出animationHandler并不是Handler 而是实现了Runable接口 run方法调用了doAnimationFrame
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;
}
}
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);
}
}
// 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);
}doAnimationFrame最后调用了animationFrame
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;
} else {
done = true;
fraction = Math.min(fraction, 1.0f);
}
}
if (mPlayingBackwards) {
fraction = 1f - fraction;
}
animateValue(fraction);
break;
}
return done;
}animationFrame内部调用了 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);
}
}
}PropertyValuesHolder[] oldValues = mValues;可以发现get方法反射调用的来看set方法：
private void setupValue(Object target, Keyframe kf) {
if (mProperty != null) {
Object value = convertBack(mProperty.get(target));
kf.setValue(value);
}
try {
if (mGetter == null) {
Class targetClass = target.getClass();
setupGetter(targetClass);
if (mGetter == null) {
// Already logged the error - just return to avoid NPE
return;
}
}
Object value = convertBack(mGetter.invoke(target));
kf.setValue(value);
} catch (InvocationTargetException e) {
Log.e("PropertyValuesHolder", e.toString());
} catch (IllegalAccessException e) {
Log.e("PropertyValuesHolder", e.toString());
}
}setAnimatedValue将新的属性值设置给对象可以看出Set也是反射的
void setAnimatedValue(Object target) {
if (mProperty != null) {
mProperty.set(target, getAnimatedValue());
}
if (mSetter != null) {
try {
mTmpValueArray[0] = getAnimatedValue();
mSetter.invoke(target, mTmpValueArray);
} catch (InvocationTargetException e) {
Log.e("PropertyValuesHolder", e.toString());
} catch (IllegalAccessException e) {
Log.e("PropertyValuesHolder", e.toString());
}
}
}使用动画注意的事项：
OOM（帧动画）
内存泄露（有一类无限循环的动画，在Activity提出时及时停止）
View动画问题：View是影像动画不是改变View的状态，有时候出现View无法隐藏，即setVisibility（View.Gonew）失效
这个时候用view.clearAnimation()清除动画。
尽量使用pd 不使用px
交互：3.0之前 View动画和属性动画，无法触发单击事件，老位置可以触发单击事件。3.0之后属性动画的单击事件是移动后的位置，但view动画还是在以前的位置。
使用动画时使用硬件加速。