如何使ScrollView仅在React Native中的子级较大时滚动

可以基于某些条件呈现普通视图或滚动视图,请考虑以下示例:

class MyComponent extends React.Component {
  constructor(props){
    super(props)
    this.state = {
      childHeight: 0,
      screenHeight: Dimensions.get('window').height
    }
  }
  render(){
    const wrapper = this.state.childHeight > this.state.screenHeight ? ScrollView : View 
    return (
      <Wrapper>
        //onLayout passes a an object with a synthetic event that has a nativeEvent prop
        //I pull off the nativeEvent prop using deconstruction so I can get the height
        <View onLayout={
          ({ nativeEvent }) => {
            this.setState({ childHeight: nativeEvent.layout.height })
          }}>
        {children}
        </View>
      </Wrapper>
    )
  }
}

这只是一个实现,您可以随心所欲地执行它。以下是关于 onLayout 支柱。

如果您不能或不想使用视图,那么您必须进行其他类型的布局计算。一种方法是通过操纵您的样式和子属性:

const myStyle = StyleSheet.create({
  childStyle: {
    height: 180 
  }
})

class MyComponent extends React.Component {
  constructor(props){
    super(props)
    this.state = {
      childHeight: React.Children.count(props.children) * 180, 
      //get the count of how many children have been passed to your component
      //and multiple it by whatever height your children have set in their styles
      screenHeight: Dimensions.get('window').height 
  }
  render(){
    const wrapper = this.state.childHeight > this.state.screenHeight ? ScrollView : View
    return (
      <Wrapper>
        {children}
      </Wrapper>
    )
  }
}

如果在多个渲染中孩子的数量可以改变,那么我建议学习 FlatList component