如何聚焦位于子组件中的输入字段

Question

我在父组件中有一个按钮。我想通过单击该按钮来聚焦位于子组件中的输入字段。我怎么能这样做。

Answer 1

您可以使用refs来获得结果

class Parent extends React.Component {
  
  handleClick = () => {
    this.refs.child.refs.myInput.focus();
  }
  render() {
    return (
      <div>
        <Child ref="child"/>
        <button onClick={this.handleClick.bind(this)}>focus</button>
      </div>
    )
  }
}

class Child extends React.Component {
  render() {
    return (
      <input type="text" ref="myInput"/>
    )
  }
}

ReactDOM.render(<Parent/>, document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

更新：

React docs建议使用ref callback而不是string refs

class Parent extends React.Component {
  
  handleClick = () => {
    this.child.myInput.focus();
  }
  render() {
    return (
      <div>
        <Child ref={(ch) => this.child = ch}/>
        <button onClick={this.handleClick.bind(this)}>focus</button>
      </div>
    )
  }
}

class Child extends React.Component {
  render() {
    return (
      <input type="text" ref={(ip)=> this.myInput= ip}/>
    )
  }
}

ReactDOM.render(<Parent/>, document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

Answer 2

不是从父级访问子组件的输入元素，而是公开如下方法，

class Parent extends React.Component {

  handleClick = () => {
    this.refs.child.setFocus();
  };

  render() {
    return (
      <div>
        <Child ref="child"/>
        <button onClick={this.handleClick.bind(this)}>focus</button>
      </div>
    )
  }
}

class Child extends React.Component {

  setFocus() {
    this.refs.myInput.focus();
  }

  render() {
    return (
      <input type="text" ref="myInput"/>
    )
  }
}

ReactDOM.render(<Parent/>, document.getElementById('app'));

Answer 3

您可以简单地在子组件中使用componentDidMount（），如下所示

class Child extends React.Component {
  componentDidMount() {
   this.myInput.focus()
  }

  render() {
    return (
      <input type="text" ref={(input)=> this.myInput= input}/>
    )
  }
}