ValueAnimator API 介绍

public class ValueAnimator 
extends Animator 继承Animator

java.lang.Object
↳	android.animation.Animator
	↳	android.animation.ValueAnimator

Known direct subclasses   直接子类 ObjectAnimator,  TimeAnimator

这个类为正在运行的动画提供了简单的计时引擎，正在运行的动画计算动画的值并且将它设置在目标对象。

所有动画都使用一个计时脉冲，它运行在自定义的handler去确保属性的改变放生在UI线程。

默认情况下，ValueAnimator 使用非线性时间插入器，通过AccelerateDecelerateInterpolator类，此类加速进入动画并且减速退出动画，这个行为通过调用setInterpolator(TimeInterpolator)来改变。

Animators can be created from either code or resource files. Here is an example of a ValueAnimator resource file:

动画可以通过代码或者资源文件创建。一下是一个ValueAnimator 资源文件的例子。

从API23开始，同样可以用PropertyValuesHolder 和Keyframe 资源标签去创建多步动画。注意你可以定义明确的小数值（从0到1）为每一个 keyframe 去决定何时动画应该到达那个值。当然，你可以停止小数而keyframes 会被均匀地分配在整个过程。

Summary  总结

Nested classes        嵌套的类
interface	ValueAnimator.AnimatorUpdateListener Implementors of this interface can add themselves as update listeners to an ValueAnimatorinstance to receive callbacks on every animation frame, after the current frame's values have been calculated for that ValueAnimator.  实现这个接口可以将它们自己添加为对ValueAnimator实例更新监听，去接收在每一动画帧的回调，这是发生在当前ValueAnimator帧的值被计算之后。

Constants
int	INFINITE This value used used with the setRepeatCount(int) property to repeat the animation indefinitely. 这个值用在setRepeatCount(int) 属性去无限重复动画。
int	RESTART When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation restarts from the beginning. 当动画结束并且repeatCount  是INFINITE   或者一个正值时，动画重头开始。
int	REVERSE When the animation reaches the end and repeatCount is INFINITE or a positive value, the animation reverses direction on every iteration. 当动画结束并且repeatCount  是INFINITE   或者一个正值时，动画在每个迭代取反方向

Inherited constants  继承类
From class android.animation.Animator

Public constructors   公共构造器
ValueAnimator() Creates a new ValueAnimator object. 创建一个新ValueAnimator 对象

Public methods
void	addUpdateListener(ValueAnimator.AnimatorUpdateListener listener) Adds a listener to the set of listeners that are sent update events through the life of an animation. 添加一个监听器到监听器的集合，这个集合在整个动画生命周期被发送更新时间
static boolean	areAnimatorsEnabled() Returns whether animators are currently enabled, system-wide. 返回是否动画当前可操作的
void	cancel() Cancels the animation. 取消动画
ValueAnimator	clone() Creates and returns a copy of this object. 创建并返回这个对象的副本
void	end() Ends the animation. 结束动画
float	getAnimatedFraction() Returns the current animation fraction, which is the elapsed/interpolated fraction used in the most recent frame update on the animation.
Object	getAnimatedValue() The most recent value calculated by this ValueAnimator when there is just one property being animated. ValueAnimator 计算的最近值 当只有一个属性被执行
Object	getAnimatedValue(String propertyName) The most recent value calculated by this ValueAnimator for propertyName. 获取propertyName 对应的ValueAnimator 计算的最近的值
long	getCurrentPlayTime() Gets the current position of the animation in time, which is equal to the current time minus the time that the animation started. 及时获取当前动画的位置，相当于当前时间减去开始时间
long	getDuration() Gets the length of the animation. 获取动画的时长
static long	getFrameDelay() The amount of time, in milliseconds, between each frame of the animation. 动画的帧与帧之间时间的总量，毫秒
TimeInterpolator	getInterpolator() Returns the timing interpolator that this ValueAnimator uses. 返回ValueAnimator使用的时间差之器
int	getRepeatCount() Defines how many times the animation should repeat. 返回动画应该重复的次数
int	getRepeatMode() Defines what this animation should do when it reaches the end. 返回动画结束时动画应该做什么
long	getStartDelay() The amount of time, in milliseconds, to delay starting the animation after start() is called.  start()调用之后 延时的时间总量
long	getTotalDuration() Gets the total duration of the animation, accounting for animation sequences, start delay, and repeating. 获取动画持续的时间总量，包括顺序，开始延时和重复
PropertyValuesHolder[]	getValues() Returns the values that this ValueAnimator animates between. 返回ValueAnimator 所执行在值。
boolean	isRunning() Returns whether this Animator is currently running (having been started and gone past any initial startDelay period and not yet ended). 返回动画是否在执行。
boolean	isStarted() Returns whether this Animator has been started and not yet ended. 返回是否动画开始并且还没结束
static ValueAnimator	ofArgb(int... values) Constructs and returns a ValueAnimator that animates between color values. 构造并返回一个执行在颜色之间的ValueAnimator
static ValueAnimator	ofFloat(float... values) Constructs and returns a ValueAnimator that animates between float values. 构造并返回一个执行在floate值之间的ValueAnimator
static ValueAnimator	ofInt(int... values) Constructs and returns a ValueAnimator that animates between int values. 构造并返回一个执行在int值之间的ValueAnimator
static ValueAnimator	ofObject(TypeEvaluator evaluator, Object... values) Constructs and returns a ValueAnimator that animates between Object values. 构造并返回一个执行在Object 值之间的ValueAnimator
static ValueAnimator	ofPropertyValuesHolder(PropertyValuesHolder... values) Constructs and returns a ValueAnimator that animates between the values specified in the PropertyValuesHolder objects. 构造并返回一个执行在定义在PropertyValuesHolder值之间的ValueAnimator
void	pause() Pauses a running animation. 暂停动画
void	removeAllUpdateListeners() Removes all listeners from the set listening to frame updates for this animation. 清除所有更新监听
void	removeUpdateListener(ValueAnimator.AnimatorUpdateListener listener) Removes a listener from the set listening to frame updates for this animation. 清除集合中的指定监听
void	resume() Resumes a paused animation, causing the animator to pick up where it left off when it was paused. 使暂停的动画获取焦点
void	reverse() Plays the ValueAnimator in reverse. 反向执行动画
void	setCurrentFraction(float fraction) Sets the position of the animation to the specified fraction. 设置动画的位置到指定的小数值
void	setCurrentPlayTime(long playTime) Sets the position of the animation to the specified point in time. 设置动画的位置到指定的时间点
ValueAnimator	setDuration(long duration) Sets the length of the animation. 设置动画执行的时长
void	setEvaluator(TypeEvaluator value) The type evaluator to be used when calculating the animated values of this animation. 类型估值器用在计算动画执行值时
void	setFloatValues(float... values) Sets float values that will be animated between. 设置动画执行的值
static void	setFrameDelay(long frameDelay) The amount of time, in milliseconds, between each frame of the animation. 帧与帧之间的时长
void	setIntValues(int... values) Sets int values that will be animated between. 设置动画执行的值
void	setInterpolator(TimeInterpolator value) The time interpolator used in calculating the elapsed fraction of this animation. 设置时间差值器
void	setObjectValues(Object... values) Sets the values to animate between for this animation.
void	setRepeatCount(int value) Sets how many times the animation should be repeated. 设置重复次数
void	setRepeatMode(int value) Defines what this animation should do when it reaches the end. 设置动画结束时的动作
void	setStartDelay(long startDelay) The amount of time, in milliseconds, to delay starting the animation after start() is called. 设置开始延时
void	setValues(PropertyValuesHolder... values) Sets the values, per property, being animated between.
void	start() Starts this animation.
String	toString() Returns a string representation of the object.

Inherited methods
From class android.animation.Animator
From class java.lang.Object