今天来分析下属性动画的源码，首先从ObjectAnimator的ofFloat方法出发
ObjectAnimator oa = ObjectAnimator.ofFloat(iv, "translationY", 0f,1000f);
public static ObjectAnimator ofFloat(Object target, String propertyName, float... values) {
ObjectAnimator anim = new ObjectAnimator(target, propertyName);
anim.setFloatValues(values);
return anim;
}
发现new了一个ObjectAnimator ，把target和propertyName传入
private ObjectAnimator(Object target, String propertyName) {
setTarget(target);
setPropertyName(propertyName);
}
@Override
public void setTarget(@Nullable Object target) {
final Object oldTarget = getTarget();
if (oldTarget != target) {
if (isStarted()) {
cancel();
}
mTarget = target == null ? null : new WeakReference<Object>(target);
// New target should cause re-initialization prior to starting
mInitialized = false;
}
}
public void setPropertyName(@NonNull String propertyName) {
// mValues could be null if this is being constructed piecemeal. Just record the
// propertyName to be used later when setValues() is called if so.
if (mValues != null) {
PropertyValuesHolder valuesHolder = mValues[0];
String oldName = valuesHolder.getPropertyName();
valuesHolder.setPropertyName(propertyName);
mValuesMap.remove(oldName);
mValuesMap.put(propertyName, valuesHolder);
}
mPropertyName = propertyName;
// New property/values/target should cause re-initialization prior to starting
mInitialized = false;
}
setTarget方法使用了弱引用，setPropertyName方法是用于设置属性名用的并用PropertyValuesHolder存放，mValues 这时为null，所以仅仅将propertyName设置给mPropertyName，这段不是特别重要，了解下就行
ofFloat方法中接下来又调用了anim.setFloatValues(values);
@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);
}
}
显然这时候的mValues为null，mProperty 也为null，调用的setValues(PropertyValuesHolder.ofFloat(mPropertyName, values));该方法是父类ValueAnimator的方法
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;
}
其中将mValues 赋值，其他都不是很关键，到此代码就没有后续了，因此前面肯定还有别的操作，我们来到setValues方法传入参数时的PropertyValuesHolder.ofFloat(mPropertyName, values)方法
public static PropertyValuesHolder ofFloat(String propertyName, float... values) {
return new FloatPropertyValuesHolder(propertyName, values);
}
public void setFloatValues(float... values) {
mValueType = float.class;
mKeyframes = KeyframeSet.ofFloat(values);
}
static class FloatPropertyValuesHolder extends PropertyValuesHolder {
public FloatPropertyValuesHolder(String propertyName, float... values) {
super(propertyName);
setFloatValues(values);
}
@Override
public void setFloatValues(float... values) {
//调用父类的方法
super.setFloatValues(values);
mFloatKeyframes = (Keyframes.FloatKeyframes) mKeyframes;
}
}
FloatPropertyValuesHolder 的setFloatValues方法调用super.setFloatValues(values)，PropertyValuesHolder的setFloatValues方法调用KeyframeSet.ofFloat(values)为mKeyframes赋值,Keyframe是关键帧
(如：ObjectAnimator.ofFloat(iv, "translationY", 0f,1000f)，其中0f，和1000f就是关键帧)
该方法解析每一帧到KeyFrames集合
public static KeyframeSet ofFloat(float... values) {
boolean badValue = false;
int numKeyframes = values.length;
FloatKeyframe keyframes[] = new FloatKeyframe[Math.max(numKeyframes,2)];
if (numKeyframes == 1) {
keyframes[0] = (FloatKeyframe) Keyframe.ofFloat(0f);
keyframes[1] = (FloatKeyframe) Keyframe.ofFloat(1f, values[0]);
if (Float.isNaN(values[0])) {
badValue = true;
}
} else {
keyframes[0] = (FloatKeyframe) Keyframe.ofFloat(0f, values[0]);
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");
}
return new FloatKeyframeSet(keyframes);
}
属性动画的初始化就到这里，我们再来看ObjectAnimator到底是怎么运作的，来到它的start()方法
@Override
public void start() {
AnimationHandler.getInstance().autoCancelBasedOn(this);
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();
}
调用父类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;
mSelfPulse = !mSuppressSelfPulseRequested;
// 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;
mAnimationEndRequested = 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 = -1;
mFirstFrameTime = -1;
mStartTime = -1;
addAnimationCallback(0);
if (mStartDelay == 0 || mSeekFraction >= 0 || mReversing) {
// 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.
//正常情况下调用了这个方法
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);
}
}
}
再来到startAnimation方法
private void startAnimation() {
if (Trace.isTagEnabled(Trace.TRACE_TAG_VIEW)) {
Trace.asyncTraceBegin(Trace.TRACE_TAG_VIEW, getNameForTrace(),
System.identityHashCode(this));
}
mAnimationEndRequested = false;
//注意，这里很关键，ObjectAnimator也实现了initAnimation方法
initAnimation();
mRunning = true;
if (mSeekFraction >= 0) {
mOverallFraction = mSeekFraction;
} else {
mOverallFraction = 0f;
}
if (mListeners != null) {
notifyStartListeners();
}
}
我们来到ObjectAnimator的initAnimation方法
@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();
}
}
mValues是一个PropertyValuesHolder数组，所以调用的是PropertyValuesHolder的setupSetterAndGetter方法，并把target传入
/**
* Internal function (called from ObjectAnimator) to set up the setter and getter
* prior to running the animation. If the setter has not been manually set for this
* object, it will be derived automatically given the property name, target object, and
* types of values supplied. If no getter has been set, it will be supplied iff any of the
* supplied values was null. If there is a null value, then the getter (supplied or derived)
* will be called to set those null values to the current value of the property
* on the target object.
* @param target The object on which the setter (and possibly getter) exist.
*/
void setupSetterAndGetter(Object target) {
//这时mProperty为null
if (mProperty != null) {
// check to make sure that mProperty is on the class of target
try {
Object testValue = null;
List<Keyframe> 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) {
//获取了class
Class targetClass = target.getClass();
if (mSetter == null) {//进入判断
setupSetter(targetClass);
}
List<Keyframe> 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());
}
}
}
}
}
我们再看setupSetter(targetClass)方法
/**
* Utility function to get the setter from targetClass
* @param targetClass The Class on which the requested method should exist.
*/
void setupSetter(Class targetClass) {
Class<?> propertyType = mConverter == null ? mValueType : mConverter.getTargetType();
//将前缀"set"传入
mSetter = setupSetterOrGetter(targetClass, sSetterPropertyMap, "set", propertyType);
}
/**
* Returns the setter or getter requested. This utility function checks whether the
* requested method exists in the propertyMapMap cache. If not, it calls another
* utility function to request the Method from the targetClass directly.
* @param targetClass The Class on which the requested method should exist.
* @param propertyMapMap The cache of setters/getters derived so far.
* @param prefix "set" or "get", for the setter or getter.
* @param valueType The type of parameter passed into the method (null for getter).
* @return Method the method associated with mPropertyName.
*/
private Method setupSetterOrGetter(Class targetClass,
HashMap<Class, HashMap<String, Method>> 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<String, Method> propertyMap = propertyMapMap.get(targetClass);
boolean wasInMap = false;
if (propertyMap != null) {
wasInMap = propertyMap.containsKey(mPropertyName);
if (wasInMap) {
setterOrGetter = propertyMap.get(mPropertyName);
}
}
if (!wasInMap) {
//拼接
setterOrGetter = getPropertyFunction(targetClass, prefix, valueType);
if (propertyMap == null) {
propertyMap = new HashMap<String, Method>();
propertyMapMap.put(targetClass, propertyMap);
}
//setterOrGetter是Method，将它存入propertyMapMap方便利用反射
propertyMap.put(mPropertyName, setterOrGetter);
}
}
return setterOrGetter;
}
我们再看下getPropertyFunction方法
/**
* Determine the setter or getter function using the JavaBeans convention of setFoo or
* getFoo for a property named 'foo'. This function figures out what the name of the
* function should be and uses reflection to find the Method with that name on the
* target object.
*
* @param targetClass The class to search for the method
* @param prefix "set" or "get", depending on whether we need a setter or getter.
* @param valueType The type of the parameter (in the case of a setter). This type
* is derived from the values set on this PropertyValuesHolder. This type is used as
* a first guess at the parameter type, but we check for methods with several different
* types to avoid problems with slight mis-matches between supplied values and actual
* value types used on the setter.
* @return Method the method associated with mPropertyName.
*/
private Method getPropertyFunction(Class targetClass, String prefix, Class valueType) {
// TODO: faster implementation...
Method returnVal = null;
//拼接
String methodName = getMethodName(prefix, mPropertyName);
Class args[] = null;
if (valueType == null) {
try {
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;
}
/**
* Utility method to derive a setter/getter method name from a property name, where the
* prefix is typically "set" or "get" and the first letter of the property name is
* capitalized.
*
* @param prefix The precursor to the method name, before the property name begins, typically
* "set" or "get".
* @param propertyName The name of the property that represents the bulk of the method name
* after the prefix. The first letter of this word will be capitalized in the resulting
* method name.
* @return String the property name converted to a method name according to the conventions
* specified above.
*/
static String getMethodName(String prefix, String propertyName) {
if (propertyName == null || propertyName.length() == 0) {
// shouldn't get here
return prefix;
}
//将第一个字母转为大写
char firstLetter = Character.toUpperCase(propertyName.charAt(0));
String theRest = propertyName.substring(1);
return prefix + firstLetter + theRest;
}
getMethodName方法将前缀和我们传入的属性名拼接，最终变成setXXX方法
我们回到ObjectAnimator的initAnimation方法，它又调用了super.initAnimation()
void initAnimation() {
if (!mInitialized) {
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
mValues[i].init();
}
mInitialized = true;
}
}
void init() {
if (mEvaluator == null) {
// We already handle int and float automatically, but not their Object
// equivalents
mEvaluator = (mValueType == Integer.class) ? sIntEvaluator :
(mValueType == Float.class) ? sFloatEvaluator :
null;
}
if (mEvaluator != null) {
// KeyframeSet knows how to evaluate the common types - only give it a custom
// evaluator if one has been set on this class
mKeyframes.setEvaluator(mEvaluator);
}
}
PropertyValuesHolder的init方法将估值器Evaluator和关键帧集合绑定
回到ValueAnimator的start方法
private void start(boolean playBackwards) {
if (Looper.myLooper() == null) {
throw new AndroidRuntimeException("Animators may only be run on Looper threads");
}
mReversing = playBackwards;
mSelfPulse = !mSuppressSelfPulseRequested;
// 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;
mAnimationEndRequested = 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 = -1;
mFirstFrameTime = -1;
mStartTime = -1;
//回调
addAnimationCallback(0);
if (mStartDelay == 0 || mSeekFraction >= 0 || mReversing) {
// 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);
}
}
}
之前分析了startAnimation方法，我们再看addAnimationCallback方法
private void addAnimationCallback(long delay) {
if (!mSelfPulse) {
return;
}
getAnimationHandler().addAnimationFrameCallback(this, delay);
}
来到AnimationHandler类
//之后会调用
private final Choreographer.FrameCallback mFrameCallback = new Choreographer.FrameCallback() {
@Override
public void doFrame(long frameTimeNanos) {
doAnimationFrame(getProvider().getFrameTime());
if (mAnimationCallbacks.size() > 0) {
getProvider().postFrameCallback(this);
}
}
};
/**
* Register to get a callback on the next frame after the delay.
*/
public void addAnimationFrameCallback(final AnimationFrameCallback callback, long delay) {
//mAnimationCallbacks一开始为空
if (mAnimationCallbacks.size() == 0) {
getProvider().postFrameCallback(mFrameCallback);
}
if (!mAnimationCallbacks.contains(callback)) {
mAnimationCallbacks.add(callback);
}
if (delay > 0) {
mDelayedCallbackStartTime.put(callback, (SystemClock.uptimeMillis() + delay));
}
}
再看getProvider().postFrameCallback(mFrameCallback)方法
private AnimationFrameCallbackProvider getProvider() {
if (mProvider == null) {
mProvider = new MyFrameCallbackProvider();
}
return mProvider;
}
/**
* Default provider of timing pulse that uses Choreographer for frame callbacks.
*/
private class MyFrameCallbackProvider implements AnimationFrameCallbackProvider {
final Choreographer mChoreographer = Choreographer.getInstance();
@Override
public void postFrameCallback(Choreographer.FrameCallback callback) {
mChoreographer.postFrameCallback(callback);
}
@Override
public void postCommitCallback(Runnable runnable) {
//关键代码
mChoreographer.postCallback(Choreographer.CALLBACK_COMMIT, runnable, null);
}
@Override
public long getFrameTime() {
return mChoreographer.getFrameTime();
}
@Override
public long getFrameDelay() {
return Choreographer.getFrameDelay();
}
@Override
public void setFrameDelay(long delay) {
Choreographer.setFrameDelay(delay);
}
}
Choreographer类是一个垂直同步类---用于控制每隔16ms刷新的控制器，可以通过这个定时控制器不断调用上面的runnable线程，源码比较多，只要了解下就行了，我们发现先调用mChoreographer.postFrameCallback(callback)，callback就是AnimationHandler中定义的mFrameCallback ，其中又会调用 doAnimationFrame(getProvider().getFrameTime());
来到doAnimationFrame方法
private void doAnimationFrame(long frameTime) {
long currentTime = SystemClock.uptimeMillis();
final int size = mAnimationCallbacks.size();
for (int i = 0; i < size; i++) {
final AnimationFrameCallback callback = mAnimationCallbacks.get(i);
if (callback == null) {
continue;
}
if (isCallbackDue(callback, currentTime)) {
//调用
callback.doAnimationFrame(frameTime);
if (mCommitCallbacks.contains(callback)) {
getProvider().postCommitCallback(new Runnable() {
@Override
public void run() {
commitAnimationFrame(callback, getProvider().getFrameTime());
}
});
}
}
}
cleanUpList();
}
调用callback.doAnimationFrame(frameTime)，callback就是AnimationFrameCallback接口实例化，我们又发现ValueAnimator实现了AnimationFrameCallback，所以这里调用的是ValueAnimator的doAnimationFrame方法
/**
* 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
*/
public final boolean doAnimationFrame(long frameTime) {
if (mStartTime < 0) {
// First frame. If there is start delay, start delay count down will happen *after* this
// frame.
mStartTime = mReversing
? frameTime
: frameTime + (long) (mStartDelay * resolveDurationScale());
}
// Handle pause/resume
if (mPaused) {
mPauseTime = frameTime;
removeAnimationCallback();
return false;
} else if (mResumed) {
mResumed = false;
if (mPauseTime > 0) {
// Offset by the duration that the animation was paused
mStartTime += (frameTime - mPauseTime);
}
}
if (!mRunning) {
// If not running, that means the animation is in the start delay phase of a forward
// running animation. In the case of reversing, we want to run start delay in the end.
if (mStartTime > frameTime && mSeekFraction == -1) {
// This is when no seek fraction is set during start delay. If developers change the
// seek fraction during the delay, animation will start from the seeked position
// right away.
return false;
} else {
// If mRunning is not set by now, that means non-zero start delay,
// no seeking, not reversing. At this point, start delay has passed.
mRunning = true;
startAnimation();
}
}
if (mLastFrameTime < 0) {
if (mSeekFraction >= 0) {
long seekTime = (long) (getScaledDuration() * mSeekFraction);
mStartTime = frameTime - seekTime;
mSeekFraction = -1;
}
mStartTimeCommitted = false; // allow start time to be compensated for jank
}
mLastFrameTime = frameTime;
// 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);
//关键代码
boolean finished = animateBasedOnTime(currentTime);
if (finished) {
endAnimation();
}
return finished;
}
关键代码是：boolean finished = animateBasedOnTime(currentTime);
/**
* This internal function processes a single animation frame for a given animation. The
* currentTime parameter is the timing pulse sent by the handler, used to calculate the
* elapsed duration, and therefore
* the elapsed fraction, of the animation. The return value indicates whether the animation
* should be ended (which happens when the elapsed time of the animation exceeds the
* animation's duration, including the repeatCount).
*
* @param currentTime The current time, as tracked by the static timing handler
* @return true if the animation's duration, including any repetitions due to
* <code>repeatCount</code> has been exceeded and the animation should be ended.
*/
boolean animateBasedOnTime(long currentTime) {
boolean done = false;
if (mRunning) {
final long scaledDuration = getScaledDuration();
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) {
int numListeners = mListeners.size();
for (int i = 0; i < numListeners; ++i) {
mListeners.get(i).onAnimationRepeat(this);
}
}
} else if (lastIterationFinished) {
done = true;
}
mOverallFraction = clampFraction(fraction);
float currentIterationFraction = getCurrentIterationFraction(
mOverallFraction, mReversing);
animateValue(currentIterationFraction);
}
return done;
}
发现其中计算出了动画执行进度，并再最后调用animateValue方法，注意我们现在再ValueAnimator类中，animateValue方法也在ObjectAnimator中实现了，我们看ObjectAnimator的animateValue方法
void animateValue(float fraction) {
final Object target = getTarget();
if (mTarget != null && target == null) {
// We lost the target reference, cancel and clean up. Note: we allow null target if the
/// target has never been set.
cancel();
return;
}
super.animateValue(fraction);
int numValues = mValues.length;
for (int i = 0; i < numValues; ++i) {
//关键代码
mValues[i].setAnimatedValue(target);
}
}
我们在看FloatPropertyValuesHolder（我们一开始用的是ofFloat）的setAnimatedValue方法
/**
* Internal function to set the value on the target object, using the setter set up
* earlier on this PropertyValuesHolder object. This function is called by ObjectAnimator
* to handle turning the value calculated by ValueAnimator into a value set on the object
* according to the name of the property.
* @param target The target object on which the value is set
*/
@Override
void setAnimatedValue(Object target) {
if (mFloatProperty != null) {
mFloatProperty.setValue(target, mFloatAnimatedValue);
return;
}
if (mProperty != null) {
mProperty.set(target, mFloatAnimatedValue);
return;
}
if (mJniSetter != 0) {
nCallFloatMethod(target, mJniSetter, mFloatAnimatedValue);
return;
}
if (mSetter != null) {
try {
mTmpValueArray[0] = mFloatAnimatedValue;
mSetter.invoke(target, mTmpValueArray);
} catch (InvocationTargetException e) {
Log.e("PropertyValuesHolder", e.toString());
} catch (IllegalAccessException e) {
Log.e("PropertyValuesHolder", e.toString());
}
}
}
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