AntDesign Upload组件上传图片

技术选型

前端技术选型： React Hook + typescript
antd版本：3.18

使用Upload上传图片

上传效果截图

预览效果截图

项目中完整写法：

import {Button, Form, Input, Modal, Upload, Icon} from 'antd';
const RegistrationForm = (props: IProps) => {const {form: { getFieldDecorator , validateFields},previewData} = props;const [filesList, setFilesList] = useState<UploadFile[]>([]);const [previewImage, setPreviewImage] = useState('');const [previewVisible, setPreviewVisible] = useState(false);const normFile = (e: any) => {if (Array.isArray(e)) {return e;}return e && e.fileList;};// 限制图片的格式，size，分辨率const handleBeforeUpload = (file: RcFile, FileList: RcFile[]): boolean | PromiseLike<void> => {const isJPG = file.type === 'image/jpeg';const isJPEG = file.type === 'image/jpeg';const isGIF = file.type === 'image/gif';const isPNG = file.type === 'image/png';if (!(isJPG || isJPEG || isGIF || isPNG)) {Modal.error({title: '只能上传JPG 、JPEG 、GIF、 PNG格式的图片~'});return false;}const isLt2M = file.size / 1024 / 1024 < 2;if (!isLt2M) {Modal.error({title: '超过2M限制，不允许上传~'});return false;}return (isJPG || isJPEG || isGIF || isPNG) && isLt2M && checkImageWH(file);};// 返回一个promise：通过检测则返回reslove；失败则返回reject，并阻止图片上传const checkImageWH = (file: RcFile): PromiseLike<void> => {const value: IFileProps =  file;return new Promise((resolve, reject) => {const filereader = new FileReader();filereader.onload = (e: any) => {const src = e.target.result;const image = new Image();image.onload = () => {value.width = image.width;value.height = image.height;resolve();};image.onerror = reject;image.src = src;};filereader.readAsDataURL(value);});};const handleChange = (info: UploadChangeParam) => {console.log(info.fileList);console.log(info.file);setFilesList(info.fileList);};const handleCancel = () => {setPreviewVisible(false);};const handlePreview = (file: UploadFile) => {const imageUrl = file.url || file.thumbUrl || '';setPreviewImage(imageUrl);setPreviewVisible(true);};return (<div><Form><FormItem label="截图" {...formItemLayout}>{getFieldDecorator('upload',{   valuePropName: 'fileList',getValueFromEvent: normFile})(<Uploadaction="/api/image/upload/"data={file => ({image_file: file})}listType="picture-card"fileList={filesList}onPreview={handlePreview}beforeUpload={handleBeforeUpload}onChange={handleChange}>{filesList.length >= 6 ? null : <Button><Icon type="upload"/> Click to upload</Button>}</Upload>)}</FormItem><Modal visible={previewVisible} footer={null} onCancel={handleCancel}><img alt="example" style={{ width: '100%' }} src={previewImage} /></Modal></Form></div>);
};
const ProductForms = Form.create<IProps>()(RegistrationForm);
export default ProductForms;

上传后，点击图片预览，浏览器卡死

依据上方的代码，通过 Antd 的 upload 组件将图片上传成功后，点击图片的缩略图，理应可以在当前页面弹出 Modal，预览图片。但实际的结果是，浏览器可能会卡死。

定位问题发现，原因是：图片上传成功后， upload 会将其转为 base64编码。base64这个字符串太大了，点击图片预览的时候，浏览器在解析一大串字符串，然后就卡死了。详细过程描述如下。

上方代码中，我们可以把 handleChange(file, fileList)方法中的 file、以及 fileList打印出来看看。 file指的是当前正在上传的单个 img，fileList是已上传的全部 img 列表。当我上传完两张图片后，打印结果如下：

file的打印的结果如下：

    {"uid": "rc-upload-1551084269812-5","width": 600,"height": 354,"lastModified": 1546701318000,"lastModifiedDate": "2019-01-05T15:15:18.000Z","name": "e30e7b9680634b2c888c8bb513cc595d.jpg","size": 31731,"type": "image/jpeg","percent": 100,"originFileObj": {"uid": "rc-upload-1551084269812-5","width": 600,"height": 354},"status": "done","thumbUrl": "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAHQ9qKKlbimcXrIH9o2vH/AC2T+ddPj98v+9RRWsuhnHdk0ar9qb5R0Pb6VPB/qh9aKKiRr0Irnt/vUDr+NFFJCRqWxJik5Pb+dLJ938aKK06mYSdKKKKBH//Z","response": {"retCode": 0,"imgUrl": "http://qianguyihao.com/opfewfwj098902kpkpkkj976fe.jpg","photoid": 271850}}

fileList 的打印结果：

[{"uid": "rc-upload-1551084269812-3","width": 1000,"height": 667,"lastModified": 1501414799000,"lastModifiedDate": "2017-07-30T11:39:59.000Z","name": "29381f30e924b89914e91b33.jpg","size": 135204,"type": "image/jpeg","percent": 100,"originFileObj": {"uid": "rc-upload-1551084269812-3","width": 1000,"height": 667},"status": "done","thumbUrl": "data:image/jpeg;base64,/E3ju1tlaK1fzJOnHQU3LsLV7HO6Zrk11MZJ7luT0A4FZuRagi9quvzQQ4iuEJ7ZpqTG4djDsPFl2Lg733f8C4q+YhQ8zoYfGSqoMmfwo5huLL0HjiyPDSYPvxRdC1XQvxeLrB8fvl/OnoLmL9vrdvvYS3NGFVe2YsASOh71JfQyrqV2mXLHOcccVSIYEnDyZO9XXB9KYH//Z","response": {"retCode": 0,"msg": "success","imgUrl": "http://qianguyihao.com/hfwpjouiurewnmbhepr689.jpg",}},{"uid": "rc-upload-1551084269812-5","width": 600,"height": 354,"lastModified": 1546701318000,"lastModifiedDate": "2019-01-05T15:15:18.000Z","name": "e30e7b9680634b2c888c8bb513cc595d.jpg","size": 31731,"type": "image/jpeg","percent": 100,"originFileObj": {"uid": "rc-upload-1551084269812-5","width": 600,"height": 354},"status": "done","thumbUrl": "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAHQ9qKKlbimcXrIH9o2vH/AC2T+ddPj98v+9RRWsuhnHdk0ar9qb5R0Pb6VPB/qh9aKKiRr0Irnt/vUDr+NFFJCRqWxJik5Pb+dLJ938aKK06mYSdKKKKBH//Z","response": {"retCode": 0,"imgUrl": "http://qianguyihao.com/opfewfwj098902kpkpkkj976fe.jpg","photoid": 271850}}
]

上方的json数据中，需要做的几点解释：

response字段里面的数据，请求后端接口后，后台返回给前端数据，包含了图片中的url链接
status字段里存放的是图片上传的实时状态，包括上传中、上传完成、上传失败。
thumbUrl字段里面存放的是图片的base64编码。

这个base64编码非常非常长。当点击图片预览的时候，其实就是加载的 thumbUrl 这个字段里的资源，难怪浏览器会卡死。

解决办法：在 handleChange方法里，图片上传成功后，将 thumbUrl 字段里面的 base64 编码改为真实的图片url。代码实现如下：

  handleChange = ({ file, fileList }) => {console.log(JSON.stringify(file)); // file 是当前正在上传的 单个 imgconsole.log(JSON.stringify(fileList)); // fileList 是已上传的全部 img 列表// 【重要】将 图片的base64替换为图片的url。 这一行一定不会能少。// 图片上传成功后，fileList数组中的 thumbUrl 中保存的是图片的base64字符串，这种情况，导致的问题是：图片上传成功后，点击图片缩略图，浏览器会会卡死。而下面这行代码，可以解决该bug。fileList.forEach(imgItem => {if (imgItem && imgItem.status == 'done' && imgItem.response && imgItem.response.imgUrl) {imgItem.thumbUrl = imgItem.response.imgUrl;}});setFilesList(ifilList);};