Animated.Value

驱动动画的一维标量值. 一个Animated.Value可以同步地驱动多个属性，但每次只能以一种动画机制变化。如果改用了其他动画机制（例如开始一个新的动画或是调用setValue），则会停止先前的动画。

一般这样来初始化new Animated.Value(0);

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文档

方法

setValue()

setValue(value);

直接赋值。注意这会导致正在运行的动画中断而直接更新到新值。

参数：

名称	类型	必需	说明
value	number	是	新的动画值

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setOffset()

setOffset(offset);

Sets an offset that is applied on top of whatever value is set, whether via setValue, an animation, or Animated.event. Useful for compensating things like the start of a pan gesture.

参数：

名称	类型	必需	说明
offset	number	是	Offset value

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flattenOffset()

flattenOffset();

Merges the offset value into the base value and resets the offset to zero. The final output of the value is unchanged.

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extractOffset()

extractOffset();

Sets the offset value to the base value, and resets the base value to zero. The final output of the value is unchanged.

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addListener()

addListener(callback);

Adds an asynchronous listener to the value so you can observe updates from animations. This is useful because there is no way to synchronously read the value because it might be driven natively.

Returns a string that serves as an identifier for the listener.

参数：

名称	类型	必需	说明
callback	function	是	The callback function which will receive an object with a value key set to the new value.

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removeListener()

removeListener(id);

移除一个监听函数。 The id param shall match the identifier previously returned by addListener().

参数：

名称	类型	必需	说明
id	string	是	Id for the listener being removed.

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removeAllListeners()

removeAllListeners();

移除所有监听函数。

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stopAnimation()

stopAnimation([callback]);

Stops any running animation or tracking. callback is invoked with the final value after stopping the animation, which is useful for updating state to match the animation position with layout.

参数：

名称	类型	必需	说明
callback	function	否	A function that will receive the final value.

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resetAnimation()

resetAnimation([callback]);

Stops any animation and resets the value to its original.

参数：

名称	类型	必需	说明
callback	function	否	A function that will receive the original value.

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interpolate()

interpolate(config);

Interpolates the value before updating the property, e.g. mapping 0-1 to 0-10.

See AnimatedInterpolation.js

参数：

名称	类型	必需	说明
config	object	是	看下面的说明

The config object is composed of the following keys:

• inputRange: an array of numbers
• outputRange: an array of numbers or strings
• easing (optional): a function that returns a number, given an input number
• extrapolate (optional): a string such as 'extend', 'identity', or 'clamp'
• extrapolateLeft (optional): a string such as 'extend', 'identity', or 'clamp'
• extrapolateRight (optional): a string such as 'extend', 'identity', or 'clamp'

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animate()

animate(animation, callback);

Typically only used internally, but could be used by a custom Animation class.

参数：

名称	类型	必需	说明
animation	Animation	是	See Animation.js.
callback	function	是	Callback function.

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stopTracking()

stopTracking();

Typically only used internally.

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track()

track(tracking);

Typically only used internally.

参数：

名称	类型	必需	说明
tracking	AnimatedNode	是	See AnimatedNode.js