反应事件句柄OnChange

Question

我正在尝试通过在app.js中执行onchange事件来更新标题组件的标题，但似乎无法正确绑定它们。 因此，当用户输入内容时，它将在标题组件中显示文本。

APP.JS

 import React, { Component } from 'react';

    import './App.css';
    import Header from './Header';

    class App extends Component {

      constructor(props) {
        super(props);
       this.state = {name: "Michael"}

      }

       handleChange(e) {
         const name = e.target.value;
         this.changeTitle(name);
       }

      render() {
        return (
          <div className="App">
            <Header changeTitle={this.changeTitle.bind(this)} title={this.state.name}/>
            <p className="App-intro">
              Type here to change name.
            <input type="text" onChange={this.handleChange.bind(this)}/>
            </p>
          </div>
        );
      }
    }

    export default App;

HEADER.JS

import React, { Component } from 'react';
import logo from './logo.svg';

class Header extends Component {
  changeTitle(name) {
     this.setState({name});
   }
    render() {
        return (
            <div>
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>Welcome to React {this.props.name}</h2>
                </div>
            </div>
        );
    }
}

export default Header;

Answer 1

changeTitle函数应在App组件中定义，而不应在Header组件中定义。 实际上，您可以直接调用changeTitle组件，而不是从handleChange调用它，并且在Header组件中，以this.props.title而不是this.props.name身份访问prop。

import React, { Component } from 'react';

import './App.css';
import Header from './Header';

class App extends Component {

  constructor(props) {
    super(props);
   this.state = {name: "Michael"}

  }
   changeTitle = (e) =>{
      this.setState({name: e.target.value});
    }

  render() {
    return (
      <div className="App">
        <Header title={this.state.name}/>
        <p className="App-intro">
          Type here to change name.
        <input type="text" onChange={this.changeTitle}/>
        </p>
      </div>
    );
  }
}

export default App;

并将其用作标题

import React, { Component } from 'react';
import logo from './logo.svg';

class Header extends Component {

    render() {
        return (
            <div>
                <div className="App-header">
                    <img src={logo} className="App-logo" alt="logo" />
                    <h2>Welcome to React {this.props.title}</h2>
                </div>
            </div>
        );
    }
}

export default Header;

工作片段：

  class App extends React.Component { constructor(props) { super(props); this.state = {name: "Michael"} } changeTitle = (e) =>{ this.setState({name: e.target.value}); } render() { return ( <div className="App"> <Header title={this.state.name}/> <p className="App-intro"> Type here to change name. <input type="text" onChange={this.changeTitle}/> </p> </div> ); } } class Header extends React.Component { render() { var logo = 'https://processing.org/tutorials/pixels/imgs/tint1.jpg'; return ( <div> <div className="App-header"> <img src={logo} className="App-logo" alt="logo" /> <h2>Welcome to React {this.props.title}</h2> </div> </div> ); } } ReactDOM.render(<App/>, 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

您无需将change事件传递给Header组件，只需传递数据并在App组件中执行setState 。

原因是您仅使用Header组件显示标题名称，因此状态应由父组件App管理。

检查工作片段：

 class App extends React.Component { constructor(props) { super(props); this.state = {name: "Michael"} } handleChange(e) { const name = e.target.value; this.setState({name}); //do the setState here } render() { return ( <div className="App"> <Header title={this.state.name}/> <p className="App-intro"> Type here to change name. <input type="text" onChange={this.handleChange.bind(this)}/> </p> </div> ); } } class Header extends React.Component { render() { return ( <div> <div className="App-header"> <img src={''} className="App-logo" alt="logo" /> <h2>Welcome to React {this.props.title}</h2> </div> </div> ); } } ReactDOM.render(<App/>, 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'/>