Question

不能通过引用使用子级的功能。

export class Home extends React.Component {
constructor() {
    this.imageReference = React.createRef();
}

state = {
    fadeAnim: new Animated.Value(0),
}

componentDidMount() {
    Animated.timing(
        this.state.fadeAnim,
        {
            toValue: 1,
            duration: 2400,
            useNativeDriver: true
        }
    ).start(() => this.imageReference.current.initImageAnimation());
}

render() {
    let { fadeAnim } = this.state;

    return (
        <View style={{ flex: 1 }}>
            <Animated.View style={{
                opacity: fadeAnim,
                flex: 1,
                backgroundColor: '#7eb3e0',
                justifyContent: 'center',
                alignItems: 'center'
            }}>
                <Logo ref={this.imageReference} />
            </Animated.View>
        </View>
    )
}

发生错误：TypeError：未定义不是对象（正在评估 '_this.imageReference = _react.default.createRef（）'）

Answer 1

我相信您在构造函数中缺少super（）才能使实例属性正常工作：

constructor() {
    super()
    this.imageReference = React.createRef();
}

此SO答案详细说明了原因： How to extend a class without having to using super in ES6?

如何在React Native中调用函数

1 个答案: