Question

在官方反应原生文档中，有一节关于Animated.event方法。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
        }
      }
    }]
  )
}}

请你解释一下如何做到这一点？

Answer 1

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
    },
  },
)}

Answer 2

写处理程序函数

handleSctoll = (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.handleSctoll(event) }
)

React-native animated.event自定义onScroll侦听器

2 个答案: