React 组件没有在 setState 上重新渲染

Question

我有以下代码。我正在使用 setState 方法 (this.setState({ country: "", offset: "" });) 设置状态，它不会导致 render() 方法自行重新呈现。

  state = { country: "", offset: "" };
  onClicked = () => {
    console.log("Fine Click away");
    // Get the call back from props
    let country = this.state.country;
    let offset = this.state.offset;
    this.setState({ country: "", offset: "" });
    const callback = this.props.onpress;

    if (callback) {
      callback(country, offset);
    }
  };
getTheCountryName = event => {
    this.setState({ country: event.target.value });
  };
  getTheOffSet = e => {
    this.setState({ offset: e.target.value });
  };
render() {

    const Caption = this.props.caption;
    return (
      <div>
        <br></br>
        <br></br>
        <div>Please enter the name of country and offset:</div>
        <input
          placeholder="Name of Country"
          onChange={this.getTheCountryName}
        />
        <input placeholder="offset" onChange={this.getTheOffSet} />
        <br></br>
        <br></br>
        <button className="rectangular-button" onClick={this.onClicked}>
          <div className="caption">{Caption}</div>
        </button>
      </div>
    );
  }
}```

Answer 1

以任何方式重置状态都不会触发输入值的更新，因为您实际上并没有在返回的 JSX 中使用您的状态。下面的代码会将值提供给输入，以便在您的状态更改时更新它们。你可以阅读 React here 中的表单和受控输入：

class App extends React.Component {
   state = { country: "", offset: "" };
  onClicked = () => {
    console.log("Fine Click away");
    // Get the call back from props
    let country = this.state.country;
    let offset = this.state.offset;
    this.setState({ country: "", offset: "" });
    const callback = this.props.onpress;

    if (callback) {
      callback(country, offset);
    }
  };
getTheCountryName = event => {
    this.setState({ country: event.target.value });
  };
  getTheOffSet = e => {
    this.setState({ offset: e.target.value });
  };
render() {

    const Caption = this.props.caption;
    return (
      <div>
        <br></br>
        <br></br>
        <div>Please enter the name of country and offset:</div>
        <input
          placeholder="Name of Country"
          onChange={this.getTheCountryName}
          value={this.state.country}
        />
        <input value={this.state.offset} placeholder="offset" onChange={this.getTheOffSet} />
        <br></br>
        <br></br>
        <button className="rectangular-button" onClick={this.onClicked}>
          <div className="caption">Reset</div>
        </button>
      </div>
    );
  }
}