React-native animated.event 自定义 onScroll 监听器

Question

在官方的 react-native 文档中有一节是关于 Animated.event 方法的。例如，他们使用以下代码：

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，我还想将 onScroll 回调参数映射到我自己的回调。基本上我想做这样的事情：

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

你能解释一下怎么做吗？

Answer 1

当你查看源代码时：

/**
   * 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,

我是这样工作的：

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

Answer 2

编写处理函数，如：

    handleScroll = (e) => {
        console.log(e.nativeEvent.contentOffset.y);
    }

您可以像这样添加 listener：

    Animated.event(
       [{ nativeEvent: { contentOffset: { y: this.state.scrollY } } }],
       { listener: (event) => this.handleScroll(event) }
    )

Answer 3

无法让 Michal 的解决方案为我工作。最终选择了这个

onScroll={({ nativeEvent }) => {
               animatedY.setValue(nativeEvent.contentOffset.y);
               // other actions to be performed on scroll
         }}

React-native animated.event 自定义 onScroll 监听器

React-native animated.event custom onScroll listener

destructuring

ecmascript-6

reactjs

react-native