[英]“undefined is not an object” when trying to access TextInput of the sibling component using references
在Parent
组件中,我试图在第一Child
组件的TextInput
中按下“提交”按钮时将第二Child
组件的TextInput
聚焦,但出现此错误: 错误消息
Child.js
import React from "react";
import { View, TextInput} from "react-native";
export default class Child extends React.Component {
focus = ref => {
ref.input.focus();
};
render() {
return (
<View>
<TextInput
placeholder='enter text'
onSubmitEditing={() => {
this.focus(this.props.destinationRef);
}}
ref={input => {
this.input = input;
}}
/>
</View>
);
}
}
Parent.js
import React from "react";
import Child from "./Child";
import { View, StyleSheet } from "react-native";
export default class Parent extends React.Component {
// componentDidMount() {
// setTimeout(() => {
// this.two.input.focus();
// }, 3000);
// }
render() {
return (
<View style={styles.container}>
<Child
destinationRef={() => {
if (!this.two) return this.two;
}}
ref={input => {
this.one = input;
}}
/>
<Child ref={input => (this.two = input)} />
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: "#fff",
alignItems: "center",
justifyContent: "center"
}
});
请注意,当我取消注释componendDidMount
,第二个TextInput
在安装后三秒钟成功聚焦。
我认为渲染更新中的问题。 在第一个渲染时间中, destinationRef
未定义,父状态未更新或强制更新,因此道具也未更新。
我尝试一点优化您的代码。 您可以使用箭头功能this
进行绑定:
import React from "react";
import Child from "./Child";
import { View, StyleSheet } from "react-native";
export default class Parent extends React.Component {
_makeFocus(){
this.two.input.focus();
}
handleOnSubmit(){
this._makeFocus();
}
render() {
return (
<View style={styles.container}>
<Child
onSubmit={this.handleOnSubmit.bind(this)}
ref={input => {
this.one = input;
}}
/>
<Child ref={input => (this.two = input)} />
</View>
);
}
}
我会稍微改变一下逻辑,因为我认为裁判给您带来了麻烦。
上级:
<View style={styles.container}>
<Child next={this.two} ref={comp => this.one = comp}/>
<Child next={this.one} ref={comp => this.two = comp}/>
</View>
儿童:
<TextInput
placeholder='enter text'
onSubmitEditing={() => {
if (this.props.next)
this.props.next.focus();
}}
/>
编辑:
我相信您的方法是正确的,我只会将父级更新为:
export default class Parent extends React.Component {
constructor(props){
super(props);
this.references = {};
}
onFocus = (ref) => {
this.references[ref].focus();
}
render() {
return (
<View style={styles.container}>
<Child
destinationRef={'two'}
onFocus={this.onFocus}
ref={input => this.references['one'] = input}
/>
<Child ref={input => this.references['two'] = input} />
</View>
);
}
}
和您的孩子:
export default class Child extends React.Component {
render() {
return (
<View>
<TextInput
placeholder='enter text'
onSubmitEditing={() => {
this.props.onFocus(this.props.destinationRef);
}}
/>
</View>
);
}
}
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