如何在React Native中使用Animated.diffClamp

问题描述

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关于如何实现Animated.diffClamp的任何代码示例？

Any code example of how to implement Animated.diffClamp?

我正在尝试创建类似于Google Play应用中的标题滚动动画。当您开始向下滚动时，我已经隐藏了标题，但是问题是我想在开始向上滚动时再次显示标题，它仅在您到达视图顶部时显示。

I'm trying to create a header scroll animation like the one featured in the google play app. I already hide the header when you start scrolling down, but the problem is that I want to show the header again as soon as you start scrolling up, it shows only when you reach the top of the view.

class Services extends Component {
  constructor(props){
  super(props);
  this.state = {
    scrollY : new Animated.Value(0),
  }
}

renderScrollViewContent(){
  return (
    <View style={styles.scrollViewContent}>
    </View>
  )
}

render() {
  const headerHeight = this.state.scrollY.interpolate({
    inputRange: [0, 60],
    outputRange: [0, -60],
    extrapolate: 'clamp'
  });

  return (
    <View style={styles.container}>
      <ScrollView style={styles.container}
        scrollEventThrottle={16}
        onScroll={Animated.event(
          [{nativeEvent: {contentOffset: {y: this.state.scrollY}}}]
        )}
      >
        {this.renderScrollViewContent()}
      </ScrollView>
      <Animated.View style={[styles.header, {top: headerHeight}]}>
        <View style={styles.bar}>
          <Text style={styles.title}>Title</Text>
        </View>
      </Animated.View>
    </View>
  );
 }
}

推荐答案

我们正是为此用例添加了此内容。这是文档页面

We added this exactly for this use case. Here's the doc page https://facebook.github.io/react-native/docs/animated.html#diffclamp

我还建议将其与翻译转换配合使用（更好的性能，可与本机驱动程序一起使用）。这是您使用它的示例渲染：

I also recommend using it with a translate transform (better perf and can be used with native driver). Here's your example render using it:

const headerTranslate = Animated.diffClamp(this.state.scrollY, 0, 60)
  .interpolate({
    inputRange: [0, 1],
    outputRange: [0, -1],
  });

return (
 <View style={styles.container}>
   <ScrollView style={styles.container}
     scrollEventThrottle={16}
     onScroll={Animated.event(
       [{nativeEvent: {contentOffset: {y: this.state.scrollY}}}]
     )}
   >
     {this.renderScrollViewContent()}
   </ScrollView>
   <Animated.View style={[styles.header, {transform: [{translateY: headerTranslate}]}]}>
     <View style={styles.bar}>
       <Text style={styles.title}>Title</Text>
     </View>
   </Animated.View>
 </View>
);

它的工作原理是将滚动位置传递给diffClamp，以便在之后将其固定在0到60之间我们使用插值法将值设为负（我们希望它向上转换）。

How it works is we pass the scroll position to diffClamp so it is clamped between 0 and 60, after we use interpolate to make the value negative (we want it to translate up).

这篇关于如何在React Native中使用Animated.diffClamp的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

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