属性动画（ObjectAnimator）源码分析
属性动画的集成关系
看一段属性动画的使用代码
上面我们看到 addAnimationFrameCallback（）中传递了一个this 说明ValueAnimator也实现了该接口 且是循环的不断调用该抽象回调方法
果然实现了该接口 我们去看看该接口有什么抽象方法
Paste_Image.png
ObjectAnimator animator=ObjectAnimator.ofFloat(image,"rotationX",0f,360f);
animator.setDuration(2000);//执行时间
animator.setInterpolator(new LinearInterpolator());//插值器
animator.setRepeatCount(-1);//-1 代表无限循环执行
animator.start();public static ObjectAnimator ofFloat(Object target, String propertyName, float... values) {
ObjectAnimator anim = new ObjectAnimator(target, propertyName);
anim.setFloatValues(values);
return anim;
}@Override
public void setFloatValues(float... 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.ofFloat(mProperty, values));
} else {
setValues(PropertyValuesHolder.ofFloat(mPropertyName, values));
}
} else {
super.setFloatValues(values);
}
}进入PropertyValuesHolder.ofFloat(mPropertyName, values)
public static PropertyValuesHolder ofFloat(String propertyName, float... values) {
return new FloatPropertyValuesHolder(propertyName, values);
}这里出现了 PropertyValuesHolder 那么这个类是干嘛的呢？
PropertyValuesHolder：顾名思义，就是属性值持有者，它保存了动画过程中所需要操作的属性和对应的值，我们通过ofFloat(Object target, String propertyName, float… values)构造的动画，ofFloat()的内部实现其实就是将传进来的参数封装成PropertyValuesHolder实例来保存动画状态。在封装成PropertyValuesHolder实例以后，后面的操作也是以PropertyValuesHolder为主的
我们看到返回一个new FloatPropertyValuesHolder(propertyName, values) 进入构造方法
public FloatPropertyValuesHolder(String propertyName, float... values) {
super(propertyName);
setFloatValues(values);
}//进入 super(propertyName) 看到只是跟PropertyValuesHolder的成员变量赋值
private PropertyValuesHolder(String propertyName) {
mPropertyName = propertyName;
}进入 setFloatValues(values)
@Override
public void setFloatValues(float... values) {
super.setFloatValues(values);
mFloatKeyframes = (Keyframes.FloatKeyframes) mKeyframes;
}//进入super.setFloatValues(values);
public void setFloatValues(float... values) {
mValueType = float.class;
mKeyframes = KeyframeSet.ofFloat(values);
}KeyframeSet.ofFloat(values);
Keyframe：意为关键帧，设置了关键帧后，动画就可以在各个关键帧之间平滑过渡的，一个关键帧必须包含两个原素，第一时间点，第二位置，即这个关键帧是表示的是某个物体在哪个时间点应该在哪个位置上。fraction表示当前进度，value表示当前位置。
我们进入KeyframeSet.ofFloat(values)
public static KeyframeSet ofFloat(float... values) {
//这里的values 参数就是我们所传递动画执行参数比如：
//ObjectAnimator.ofFloat(image,"rotationX",0f,360f);中的0f ,360f
boolean badValue = false;
int numKeyframes = values.length;
//生成最小2个长度大小的数组
FloatKeyframe keyframes[] = new FloatKeyframe[Math.max(numKeyframes,2)];
//单我们传递的参数只有一个的时候
if (numKeyframes == 1) {
//设置默认数组的元素的一个为0f
keyframes[0] = (FloatKeyframe) Keyframe.ofFloat(0f)；
keyframes[1] = (FloatKeyframe) Keyframe.ofFloat(1f, values[0]);
if (Float.isNaN(values[0])) {
badValue = true;
}
} else {
//如果不是一个参数
keyframes[0] = (FloatKeyframe) Keyframe.ofFloat(0f, values[0]);
//就遍历数组
for (int i = 1; i < numKeyframes; ++i) {
keyframes[i] =
(FloatKeyframe) Keyframe.ofFloat((float) i / (numKeyframes - 1), values[i]);
if (Float.isNaN(values[i])) {
badValue = true;
}
}
}
if (badValue) {
Log.w("Animator", "Bad value (NaN) in float animator");
}
//将生成的数组添加到List集合
return new FloatKeyframeSet(keyframes);
}接上一步进入new FloatKeyframeSet(keyframes);构造函数
public FloatKeyframeSet(FloatKeyframe... keyframes) {
super(keyframes);
}//在进入super(keyframes) 父类 KeyframeSet
class KeyframeSet implements Keyframes {
int mNumKeyframes;
Keyframe mFirstKeyframe;
Keyframe mLastKeyframe;
TimeInterpolator mInterpolator; // only used in the 2-keyframe case
List mKeyframes; // only used when there are not 2 keyframes
TypeEvaluator mEvaluator;
public KeyframeSet(Keyframe... keyframes) {
mNumKeyframes = keyframes.length;
// 将数组添加mKeyframes集合中 里面保存的是动画每的一帧
mKeyframes = Arrays.asList(keyframes);
mFirstKeyframe = keyframes[0];
mLastKeyframe = keyframes[mNumKeyframes - 1];
mInterpolator = mLastKeyframe.getInterpolator();
} 由上可以看出：
PropertyValuesHolder 它保存了动画过程中所需要操作的属性和对应的值 同时持有KeyframeSet.ofFloat(values）得到动画每一帧的集合
我去再去属性动画的其他属性设置看看
//设置执行时间
@Override
@NonNull
public ObjectAnimator setDuration(long duration) {
super.setDuration(duration);
return this;
}
//进入super.setDuration(duration);
@Override
public ValueAnimator setDuration(long duration) {
if (duration < 0) {
throw new IllegalArgumentException("Animators cannot have negative duration: " +
duration);
}
mUnscaledDuration = duration;
updateScaledDuration();
return this;
}
//设置执行时间 函数 sDurationScale=1.0f
private void updateScaledDuration() {
mDuration = (long)(mUnscaledDuration * sDurationScale);
}//设置插值器
@Override
public void setInterpolator(TimeInterpolator value) {
if (value != null) {
mInterpolator = value;
} else {
//如果为空 就使用默认的插值器 线性
mInterpolator = new LinearInterpolator();
}
}最后我们来关注重点 start（）方法
@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();
}**super.start();**调用父类的start()方法
@Override
public void start() {
start(false);
}//在接着跟进
private void start(boolean playBackwards) {
if (Looper.myLooper() == null) {
throw new AndroidRuntimeException("Animators may only be run on Looper threads");
}
mReversing = playBackwards;
// Special case: reversing from seek-to-0 should act as if not seeked at all.
if (playBackwards && mSeekFraction != -1 && mSeekFraction != 0) {
if (mRepeatCount == INFINITE) {
// Calculate the fraction of the current iteration.
float fraction = (float) (mSeekFraction - Math.floor(mSeekFraction));
mSeekFraction = 1 - fraction;
} else {
mSeekFraction = 1 + mRepeatCount - mSeekFraction;
}
}
mStarted = true;
mPaused = false;
mRunning = false;
// Resets mLastFrameTime when start() is called, so that if the animation was running,
// calling start() would put the animation in the
// started-but-not-yet-reached-the-first-frame phase.
mLastFrameTime = 0;
AnimationHandler animationHandler = AnimationHandler.getInstance();
//这里每隔16毫秒会回调一次该回调方法 这里有一个this
animationHandler.addAnimationFrameCallback(this, (long) (mStartDelay * sDurationScale));
if (mStartDelay == 0 || mSeekFraction >= 0) {
// If there's no start delay, init the animation and notify start listeners right away
// to be consistent with the previous behavior. Otherwise, postpone this until the first
// frame after the start delay.
startAnimation();
if (mSeekFraction == -1) {
// No seek, start at play time 0. Note that the reason we are not using fraction 0
// is because for animations with 0 duration, we want to be consistent with pre-N
// behavior: skip to the final value immediately.
setCurrentPlayTime(0);
} else {
setCurrentFraction(mSeekFraction);
}
}
}
Paste_Image.png
Paste_Image.png
果然实现了该接口 我们去看看该接口有什么抽象方法
//该抽象方法有2个
interface AnimationFrameCallback {
void doAnimationFrame(long frameTime);
void commitAnimationFrame(long frameTime);
}//抽象方法的实现
* Processes a frame of the animation, adjusting the start time if needed.
*
* @param frameTime The frame time.
* @return true if the animation has ended.
* @hide
*/
//参数为绘制一帧的时间(每隔16毫秒调用一次) 监听手机发出的Vsync信号
public final void doAnimationFrame(long frameTime) {
AnimationHandler handler = AnimationHandler.getInstance();
if (mLastFrameTime == 0) {
// First frame
handler.addOneShotCommitCallback(this);
if (mStartDelay > 0) {
startAnimation();
}
if (mSeekFraction < 0) {
mStartTime = frameTime;
} else {
long seekTime = (long) (getScaledDuration() * mSeekFraction);
mStartTime = frameTime - seekTime;
mSeekFraction = -1;
}
mStartTimeCommitted = false; // allow start time to be compensated for jank
}
mLastFrameTime = frameTime;
if (mPaused) {
mPauseTime = frameTime;
handler.removeCallback(this);
return;
} 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
}
handler.addOneShotCommitCallback(this);
}
final long currentTime = Math.max(frameTime, mStartTime);
boolean finished = animateBasedOnTime(currentTime);
if (finished) {
endAnimation();
}
}boolean animateBasedOnTime(long currentTime) {
boolean done = false;
if (mRunning) {
final long scaledDuration = getScaledDuration();
//（总时间-开始时间）/运行的时间 得出运行百分比
final float fraction = scaledDuration > 0 ?
(float)(currentTime - mStartTime) / scaledDuration : 1f;
final float lastFraction = mOverallFraction;
final boolean newIteration = (int) fraction > (int) lastFraction;
final boolean lastIterationFinished = (fraction >= mRepeatCount + 1) &&
(mRepeatCount != INFINITE);
if (scaledDuration == 0) {
// 0 duration animator, ignore the repeat count and skip to the end
done = true;
} else if (newIteration && !lastIterationFinished) {
// Time to repeat
if (mListeners != null) {
//mListeners监听集合
int numListeners = mListeners.size();
for (int i = 0; i < numListeners; ++i) {
//观察者模式 监听回调 动画重复执行
mListeners.get(i).onAnimationRepeat(this);
}
}
} else if (lastIterationFinished) {
done = true;
}
mOverallFraction = clampFraction(fraction);
float currentIterationFraction = getCurrentIterationFraction(mOverallFraction);
//这里调用ObjectAnimator子类的animateValue（）函数
animateValue(currentIterationFraction);
}
return done;
}进入ObjectAnimator子类的animateValue（）
@CallSuper
@Override
//参数执行百分比（0-1）
void animateValue(float fraction) {
final Object target = getTarget();
if (mTarget != null && target == null) {
// We lost the target reference, cancel and clean up.
cancel();
return;
}
//调用父类animateValue（）方法
super.animateValue(fraction);
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
//这里设置View的宽高 target代表动画控件
mValues[i].setAnimatedValue(target);
}
}//进入父类的animateValue（）；
@CallSuper
void animateValue(float fraction) {
//调用插值器的方法 （策略模式） 得到插值器运行百分比
fraction = mInterpolator.getInterpolation(fraction);
//赋值成员变量
mCurrentFraction = fraction;
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
//调用PropertyValuesHolder 的calculateValue（）；
mValues[i].calculateValue(fraction);
}
if (mUpdateListeners != null) {
int numListeners = mUpdateListeners.size();
for (int i = 0; i < numListeners; ++i) {
//动画更新监听回调回调
mUpdateListeners.get(i).onAnimationUpdate(this);
}
}
}//抽象插值器
public interface TimeInterpolator {
float getInterpolation(float input);
}//PropertyValuesHolder 的calculateValue
void calculateValue(float fraction) {
Object value = mKeyframes.getValue(fraction);
//返回执行动画的百分比
mAnimatedValue = mConverter == null ? value : mConverter.convert(value);
}//接上面mAnimatedValue返回后回到 ObjectAnimator的 animateValue（）继续执行来到
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
//这里设置View的宽高 target代表动画控件
mValues[i].setAnimatedValue(target);
}//进入 mValues[i].setAnimatedValue(target);
void setAnimatedValue(Object target) {
if (mProperty != null) {
mProperty.set(target, getAnimatedValue());
}
if (mSetter != null) {
try {
mTmpValueArray[0] = getAnimatedValue();
//mSetter是在startAnimator()初始化的时候通过反射赋值
//invoke 重绘 动画view
mSetter.invoke(target, mTmpValueArray);
} catch (InvocationTargetException e) {
Log.e("PropertyValuesHolder", e.toString());
} catch (IllegalAccessException e) {
Log.e("PropertyValuesHolder", e.toString());
}
}
}//其中mSetter 是在动画初始化的时候赋值ObjectAnimator
@CallSuper
@Override
void initAnimation() {
if (!mInitialized) {
// mValueType may change due to setter/getter setup; do this before calling super.init(),
// which uses mValueType to set up the default type evaluator.
final Object target = getTarget();
if (target != null) {
final int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
mValues[i].setupSetterAndGetter(target);
}
}
super.initAnimation();
}
}//其中mValues[i].setupSetterAndGetter(target); PropertyValuesHolder
void setupSetterAndGetter(Object target) {
mKeyframes.invalidateCache();
if (mProperty != null) {
// check to make sure that mProperty is on the class of target
try {
Object testValue = null;
List keyframes = mKeyframes.getKeyframes();
int keyframeCount = keyframes == null ? 0 : keyframes.size();
for (int i = 0; i < keyframeCount; i++) {
Keyframe kf = keyframes.get(i);
if (!kf.hasValue() || kf.valueWasSetOnStart()) {
if (testValue == null) {
testValue = convertBack(mProperty.get(target));
}
kf.setValue(testValue);
kf.setValueWasSetOnStart(true);
}
}
return;
} catch (ClassCastException e) {
Log.w("PropertyValuesHolder","No such property (" + mProperty.getName() +
") on target object " + target + ". Trying reflection instead");
mProperty = null;
}
}
// We can't just say 'else' here because the catch statement sets mProperty to null.
if (mProperty == null) {
Class targetClass = target.getClass();
if (mSetter == null) {
setupSetter(targetClass);
}
List keyframes = mKeyframes.getKeyframes();
int keyframeCount = keyframes == null ? 0 : keyframes.size();
for (int i = 0; i < keyframeCount; i++) {
Keyframe kf = keyframes.get(i);
if (!kf.hasValue() || kf.valueWasSetOnStart()) {
if (mGetter == null) {
setupGetter(targetClass);
if (mGetter == null) {
// Already logged the error - just return to avoid NPE
return;
}
}
try {
Object value = convertBack(mGetter.invoke(target));
kf.setValue(value);
kf.setValueWasSetOnStart(true);
} catch (InvocationTargetException e) {
Log.e("PropertyValuesHolder", e.toString());
} catch (IllegalAccessException e) {
Log.e("PropertyValuesHolder", e.toString());
}
}
}
}
} 其中： if (mSetter == null) {setupSetter(targetClass);}
private void setupGetter(Class targetClass) {
mGetter = setupSetterOrGetter(targetClass, sGetterPropertyMap, "get", null);
}
//继续深入
private Method setupSetterOrGetter(Class targetClass,
HashMap> propertyMapMap,
String prefix, Class valueType) {
Method setterOrGetter = null;
synchronized(propertyMapMap) {
// Have to lock property map prior to reading it, to guard against
// another thread putting something in there after we've checked it
// but before we've added an entry to it
HashMap propertyMap = propertyMapMap.get(targetClass);
boolean wasInMap = false;
if (propertyMap != null) {
wasInMap = propertyMap.containsKey(mPropertyName);
if (wasInMap) {
setterOrGetter = propertyMap.get(mPropertyName);
}
}
if (!wasInMap) {
setterOrGetter = getPropertyFunction(targetClass, prefix, valueType);
if (propertyMap == null) {
propertyMap = new HashMap();
propertyMapMap.put(targetClass, propertyMap);
}
propertyMap.put(mPropertyName, setterOrGetter);
}
}
return setterOrGetter;
} //其中： setterOrGetter = getPropertyFunction(targetClass, prefix, valueType);
private Method getPropertyFunction(Class targetClass, String prefix, Class valueType) {
// TODO: faster implementation...
Method returnVal = null;
String methodName = getMethodName(prefix, mPropertyName);
Class args[] = null;
if (valueType == null) {
try {
//这里通过反射获取动画方法
returnVal = targetClass.getMethod(methodName, args);
} catch (NoSuchMethodException e) {
// Swallow the error, log it later
}
} else {
args = new Class[1];
Class typeVariants[];
if (valueType.equals(Float.class)) {
typeVariants = FLOAT_VARIANTS;
} else if (valueType.equals(Integer.class)) {
typeVariants = INTEGER_VARIANTS;
} else if (valueType.equals(Double.class)) {
typeVariants = DOUBLE_VARIANTS;
} else {
typeVariants = new Class[1];
typeVariants[0] = valueType;
}
for (Class typeVariant : typeVariants) {
args[0] = typeVariant;
try {
returnVal = targetClass.getMethod(methodName, args);
if (mConverter == null) {
// change the value type to suit
mValueType = typeVariant;
}
return returnVal;
} catch (NoSuchMethodException e) {
// Swallow the error and keep trying other variants
}
}
// If we got here, then no appropriate function was found
}
if (returnVal == null) {
Log.w("PropertyValuesHolder", "Method " +
getMethodName(prefix, mPropertyName) + "() with type " + valueType +
" not found on target class " + targetClass);
}
return returnVal;
}属性动画的原理就是不断调用view.setScrollX() view.setScrollY()