React Native Animated singleValue.stopTracking 不是函数

问题描述

我有以下代码可以在 React Native 中制作动画

I have the following code to animate in React Native

Animated.timing(
    this.state.absoluteChangeX,
    {toValue: 0},
).start(function() {
    this.lastX = 0;
    this.lastY = 0;
}); 

很简单，但每当触发时，我都会收到错误消息:singleValue.stopTracking 不是函数

Pretty simple, but whenever it's triggered, I receive the error:singleValue.stopTracking is not a function

这里是错误的来源:

/react-native/Libraries/Animates/src/AnimtaedImplementation.js

/react-native/Libraries/Animates/src/AnimtaedImplementation.js

var timing = function(
  value: AnimatedValue | AnimatedValueXY,
  config: TimingAnimationConfig,
): CompositeAnimation {
  return maybeVectorAnim(value, config, timing) || {
    start: function(callback?: ?EndCallback): void {
      var singleValue: any = value;
      var singleConfig: any = config;
      singleValue.stopTracking(); // <--------------- HERE!!!
      if (config.toValue instanceof Animated) {
        singleValue.track(new AnimatedTracking(
          singleValue,
          config.toValue,
          TimingAnimation,
          singleConfig,
          callback
        ));
      } else {
        singleValue.animate(new TimingAnimation(singleConfig), callback);
      }
    },

    stop: function(): void {
      value.stopAnimation();
    },
  };
};

我不是很精通 typeScript，但是 var singleValue: any 意味着singleValue"可以是任何类型.就我而言，它是一个数字.由于数字没有方法，所以这会出错是有道理的.

I'm not extremely versed in typeScript, but var singleValue: any means that "singleValue" could be any type. In my case, it's a number. Since numbers don't have methods, it would make sense that this would error.

我做错了什么吗?

推荐答案

您希望设置动画的值必须是 Animated.Value 的实例，或其子类型之一.当你初始化你的状态时，它应该看起来像这样:

The value you wish to animate must be an instance of Animated.Value, or one of its subtypes. When you initialize your state, it should look something like this:

getInitialState() {
  return { absoluteChangeX: new Animated.Value(0) };
}

框架方法中类型声明为any的事实只是缺乏约束，而不是明确邀请将任何值传递给它.

The fact that the type declaration in the framework method is any is just a lack of constraint, not an explicit invitation to pass any value into it.

有关更多示例，请参阅动画文档.

See the Animated docs for more examples.

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