javascript - readAsDataURL 多图像上传 ReactJS

Question

美好的一天，我如何更改我的代码，以便它接受带有预览的多个图像上传，并且用户可以删除和设置主图像。

顺便说一句，我的代码只允许上传一张图片。

这是我到目前为止所得到的:

_handleImageChange(e) {
    e.preventDefault();

    let reader = new FileReader();
    let file = e.target.files;

    console.log('file', file);
    console.log('reader', reader);

    reader.onloadend = () => {
    
      this.setState({
        file: file,
        imagePreviewUrl: reader.result
      });
      this.props.onImageChange(this.state);
    }
    reader.readAsDataURL(file);
  }

  render(){
    let { imagePreviewUrl } = this.state;
    let $imagePreview = null;
    let path = Config.PROJECT_PATH + '' + Config.IMAGE.PATH + '' + this.props.imageModule + '/thumb/' + this.props.image;

    if (imagePreviewUrl) {
      $imagePreview = (<ThumbImage image={imagePreviewUrl} ref='myImage'/>);
    }
    else{
      if (this.props.image) {
        $imagePreview = (<ThumbImage image={path} />);
      }
      else{
        $imagePreview = (<ThumbImage image={defaultImage} />);
      }
    }
    return(
      <div>
        <div className="modal-image-preview">
          { $imagePreview }
        </div>
        <div className="modal-image-button">
          <form onSubmit={(e)=>this._handleSubmit(e)}>
            <RaisedButton style= {{ backgroundColor: '#000' }} containerElement='image' label="Choose an Image" labelPosition="before" onChange={(e)=>this._handleImageChange(e)}>
              <input type="file" style={styles.imageInput} multiple/>
            </RaisedButton>
          </form>
        </div>
      </div>
    );
  }

非常感谢您的帮助。

Answer 1

要在 React 代码中上传图像，您需要将 state 中的每个路径转换为 ​​Array

然后适当改变setstate，在渲染组件时使用map函数循环遍历state。

这是我上传多个图像的代码，希望它能让您更好地了解它:

    constructor(props) {
    super(props);
    this.state = {
      files: [],
      imagesPreviewUrls: []
    };
    this._handleImageChange = this._handleImageChange.bind(this);
    this._handleSubmit = this._handleSubmit.bind(this);
  }

  _handleSubmit(e) {
    //Sumbit handler
    e.preventDefault();
    const formData = new FormData();
    formData.append('image', this.state.file);
    axios.get('/api/upload', formData) 
    .then(response => { console.log(response) });
  }

  _handleImageChange(e) {
    e.preventDefault();

    let files = Array.from(e.target.files);

    files.forEach((file) => {
        let reader = new FileReader();
        reader.onloadend = () => {
            this.setState({    
                 files: [...this.state.files, file],
                 imagesPreviewUrls: [...this.state.imagesPreviewUrls, reader.result]
            });
        }
        reader.readAsDataURL(file);
    });
  }

  render() { 
    return (
      <div>
        <form onSubmit={this._handleSubmit}>
        <input className="upload" type="file" accept='image/*' onChange={this._handleImageChange} multiple/>
        <button type="submit" onClick={this._handleSubmit}>Upload Image</button>
        {this.state.imagesPreviewUrls.map((imagePreviewUrl) => {
            return <img key={imagePreviewUrl} alt='previewImg' src={imagePreviewUrl} />
        })}
        </form>
      </div>
    )
  }