[英]React component doesn't re-render after the state was updated
我遇到了 React class 組件的問題。 該組件是一個表單,它存儲用戶的輸入,並在單擊按鈕時將收集到的信息提交給主組件。 當向上推 state 后,我嘗試將組件的 state 更新為具有默認輸入值(submitForm 中的 this.setState(this.baseState))時,會出現此問題。 我正在使用 react chrome 擴展,可以看到 state 已更新,因為無法在頁面上看到它呈現。 img1:調用 submitForm 之前img2:調用 submitForm 之后,state 已更新但在頁面上看不到更改
感謝您對此的想法!
class AttendeeForm extends React.Component {
constructor(props) {
super(props);
this.state = {
firstName: '',
lastName: '',
email: '',
shirt: 'XS', // default
skillLevel: 'beginner', // default
};
this.handleChange = this.handleChange.bind(this);
this.submitForm = this.submitForm.bind(this);
}
handleChange(event) {
this.setState({
[event.target.id]: event.target.value,
});
}
submitForm() {
this.props.addAttendee(this.state);
this.setState({
firstName: '',
lastName: '',
email: '',
shirt: 'XS', // default
skillLevel: 'beginner', // default
})
}
render() {
return (
<div className="attendee-form">
<h2>Register Attendee</h2>
<label>First Name: </label>
<input type="text" id="firstName" onChange={this.handleChange}></input>
<label>Last Name: </label>
<input type="text" id="lastName" onChange={this.handleChange}></input>
<label>Email: </label>
<input type="email" id="email" onChange={this.handleChange}></input>
<label>Shirt Size:</label>
<select onChange={this.handleChange} id="shirt" >
<option value="XS">XS</option>
<option value="S">S</option>
<option value="M">M</option>
<option value="L">L</option>
<option value="XL">XL</option>
<option value="XXL">XXL</option>
</select>
<label>Skill Level:</label>
<select onChange={this.handleChange} id="skillLevel" >
<option value="beginner">beginner</option>
<option value="intermediate">intermediate</option>
<option value="expert">expert</option>
</select>
<button onClick={this.submitForm}>REGISTER</button>
</div>
);
}
}
為所有輸入字段提供默認值
<input type="text" id="lastName" value={this.state.lastName} onChange={this.handleChange}></input>
每個字段都需要來自 state 的當前值,例如 firstName 和 lastName 來自 state
class AttendeeForm extends React.Component { constructor(props) { super(props); this.state = { firstName: '', lastName: '', email: '', shirt: 'XS', // default skillLevel: 'beginner', // default }; this.handleChange = this.handleChange.bind(this); this.submitForm = this.submitForm.bind(this); } handleChange(event) { this.setState({ [event.target.id]: event.target.value, }); } submitForm() { this.setState({ firstName: '', lastName: '', email: '', shirt: 'XS', // default skillLevel: 'beginner', // default }) } render() { return ( <div className="attendee-form"> <h2>Register Attendee</h2> <label>First Name: </label> <input type="text" id="firstName" onChange={this.handleChange} value={this.state.firstName}></input> <label>Last Name: </label> <input type="text" id="lastName" onChange={this.handleChange} value={this.state.lastName}></input> <label>Email: </label> <input type="email" id="email" onChange={this.handleChange}></input> <label>Shirt Size:</label> <select onChange={this.handleChange} id="shirt" > <option value="XS">XS</option> <option value="S">S</option> <option value="M">M</option> <option value="L">L</option> <option value="XL">XL</option> <option value="XXL">XXL</option> </select> <label>Skill Level:</label> <select onChange={this.handleChange} id="skillLevel" > <option value="beginner">beginner</option> <option value="intermediate">intermediate</option> <option value="expert">expert</option> </select> <button onClick={this.submitForm}>REGISTER</button> </div> ); } } ReactDOM.render( <AttendeeForm />, document.getElementById("root") );
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script> <div id="root"></div>
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