React-Dropzone 图像预览未显示

IT技术 reactjs dropzone.js
2021-05-02 15:09:51

使用 react-dropzone ( https://www.npmjs.com/package/react-dropzone ) 并将文件记录到控制台，但无法获得图像预览以填充状态更改。知道我做错了什么吗？

export default class JoinForm extends Component {
    constructor(props) {
    super(props)
        this.state = {
            imageFiles: []
    }
}

onDrop(imageFiles) {
    this.setState({
        imageFiles: imageFiles
    })
    console.log(imageFiles)  
}

render() {

    return(
        <form className='join-form' ref='joinForm' autoComplete='off'>
            <Dropzone
                onDrop={this.onDrop}
                className='dropzone'
                activeClassName='active-dropzone'
                multiple={false}>
      <div>Drag and drop or click to select a 550x550px file to upload.</div>
    </Dropzone>

            {this.state.imageFiles.length > 0 ? <div>
    <h2>Uploading {this.state.imageFiles.length} files...</h2>
    <div>{this.state.imageFiles.map((file) => <img src={file.preview} /> )}</div>
    </div> : null}
        </form>
    )
}

};

3个回答

对此的正确答案：作为一个哑巴，忘记绑定它。

<Dropzone
  onDrop={this.onDrop.bind(this)} //<= Here
  className='dropzone'
  activeClassName='active-dropzone'
  multiple={false}
  style={imageUploadStyle}>
    <div>Drag and drop or click to select a 550x550px file to upload.</div>
</Dropzone>

https://toddmotto.com/react-create-class-versus-component/

您将文件存储在 中imageFiles，但在render方法中您正在映射this.state.files数组。

改变：

<div>{this.state.files.map((file) => <img src={file.preview} /> )}</div>

到： 

<div>{this.state.imageFiles.map((file) => <img src={file.preview} /> )}</div>

或者，因为您有这个常量const files = this.state.imageFiles，您可以将提到的语句更改为：

<div>{files.map((file) => <img src={file.preview} /> )}</div>

将渲染功能更改为 imageFiles

render() {
    const files = this.state.imageFiles

    return(
        <form className='join-form' ref='joinForm' autoComplete='off'>
            <Dropzone
                onDrop={this.onDrop}
                className='dropzone'
                activeClassName='active-dropzone'
                multiple={false}>
      <div>Drag and drop or click to select a 550x550px file to upload.</div>
    </Dropzone>

            {this.state.imageFiles.length > 0 ? <div>
    <h2>Uploading {this.state.imageFiles.length} files...</h2>
    <div>{this.state.imageFiles.map((file) => <img src={file.preview} /> )}</div>
    </div> : null}
        </form>
    )
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