React-native animation.event自定义onScroll侦听器 [英] React-native animated.event custom onScroll listener

问题描述

在本地本机文档中，有关于Animated.event方法的部分.例如，他们使用以下代码:

In official react-native documentation there is a section about Animated.event method. As example they use following code:

onScroll={Animated.event(
   // scrollX = e.nativeEvent.contentOffset.x
   [{ nativeEvent: {
        contentOffset: {
          x: scrollX
        }
      }
    }]
 )}

我想将正确的值映射到Animated.event方法，并且我还要映射onScroll回调参数到我自己的回调.基本上我想做这样的事情:

I would like to map correct values to Animated.event method and I would also like to map onScroll callback parameters to my own callback. Basically I would like to do something like this:

onScroll={(event) => {
  myOwnCallback(event.nativeEvent.contentOffset.x)
  Animated.event(
    // scrollX = e.nativeEvent.contentOffset.x
    [{nativeEvent: {
        contentOffset: {
          x: scrollX
        }
      }
    }]
  )
}}

您能解释一下该怎么做吗?

Could you please explain how to do that?

推荐答案

当您查看源代码时:

/**
   * Takes an array of mappings and extracts values from each arg accordingly,
   * then calls `setValue` on the mapped outputs.  e.g.
   *
   *```javascript
   *  onScroll={Animated.event(
   *    [{nativeEvent: {contentOffset: {x: this._scrollX}}}]
   *    {listener},          // Optional async listener
   *  )
   *  ...
   *  onPanResponderMove: Animated.event([
   *    null,                // raw event arg ignored
   *    {dx: this._panX},    // gestureState arg
   *  ]),
   *```
   *
   * Config is an object that may have the following options:
   *
   *   - `listener`: Optional async listener.
   *   - `useNativeDriver`: Uses the native driver when true. Default false.
   */
  event,

这就是我的工作方式:

onScroll={Animated.event(
            [{ nativeEvent: { contentOffset: { y: this.state.scrollY } } }],
  {
    useNativeDriver: true,
    listener: event => {
      const offsetY = event.nativeEvent.contentOffset.y
      // do something special
    },
  },
)}

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