实现效果图
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功能预览
- 【less】上传文件的input框样式的改造
- 获取图片列表
- 点击上传图片 + 转换成base64
- 上传中loading
- 上传失败
- 删除图片
- 查看大图
- 下载图片 + Blob URL
- useState 与 useEffect的使用
- 跨域
- 静态文件的查看
- 查询/删除/添加文件
- uuid
- 用同步的方式书写异步的操作（封装 async await promise集合体）
- axios
【前端】React
1.【less】上传文件的input框样式的改造
<div className="upload-container item">
<Icon type="plus" className="icon"/>
<div className="name">Upload</div>
<input id="upload-image"
type="file"
name="image"
accept="image/*"
onChange={()=>handleUploadImage(props)}/>
</div>
主要用到的是原生的input框：
type="file"弹出选择上传文件的框；
accept="image/*"来限制你选择上传的文件只能是图片类型的；
当你弹出选择文件的框之后，无论是选择还是取消都会触发onChange事件。
原生input上传文件的样式很丑，于是换样式成了重中之重！
思路：
1.把input框给隐藏掉
2.并且要设置一个与最终样式同样大小的宽高，通过子绝父相让input框覆盖在最上层，这样才能够命中点击事件
.upload-container{
margin: 5px;
padding: 3px;
float: left;
border-style: dashed;
background-color: #f5f5f5;
position: relative; //父相
flex-direction: column;
.icon{
color: #e1e1e1;
margin-top: 10px;
font-size: 40px;
font-weight: bolder;
}
.name{
color: #a3a3a3;
}
input{
width: 100%;
height: 100%; // 与父样式等宽高
cursor: pointer;
position: absolute; // 子绝
top: 0;
opacity: 0; // 全透明
}
}
2. 用同步的方式书写异步的操作（封装 async await promise集合体）+ 获取图片列表 + useState
const baseUrl = 'http://localhost:8080/image';
const getImageListUrl = `${baseUrl}/list`;
const [list, setList] = useState([]);
const ajax = (url, data={}, type='GET') =>{
return new Promise((resolve)=>{
const promise = type === 'GET' ? axios.get(url, {params: data}) : axios.post(url, data)
promise.then(res=>{
const data = res.data;
data.status !== 0 ? message.error(data.msg) : resolve(data);
}).catch(err => {
message.error('Network request Error: '+err);
})
})
};
const getAndUpdateImageList = async(setList) => {
const data = await ajax(getImageListUrl);
setList(data.data);
};
3. 点击上传图片 + 转换成base
出现上传文件的框，无论是选择还是取消，都会触发onChange事件，所以要判断你选择的targetFile是否存在。
通过FileReder将图片转成base64，用同步的方式将最终结果抛出去:
const getBase64 = (file) => {
const fileReader = new FileReader();
fileReader.readAsDataURL(file);
return new Promise((resolve)=>{
fileReader.onload = (data) => {
resolve(data.target.result)
}
})
};
获取到了base64之后再发送axios请求到后端：
const handleUploadImage= async ({list,action,uploadImage,setUploadLoading, setUploadErrorFileName})=>{
const input = document.getElementById('upload-image');
const targetFile = input.files[0];
if (targetFile){
setUploadLoading(true);
const { name } = targetFile;
const imageBase64 = await getBase64(targetFile);
await axios.post(action, {imageBase64, name})
.then(()=>{
uploadImage(action + "/" + name);
}).catch(() => {
setUploadErrorFileName(name);
});
setUploadLoading(false);
}
};
4. 上传中loading
当我们开始上传图片的时候，会将uploadLoading设置成true，上传成功之后会将uploadLoading再设置成false！
const handleUploadImage= async ({list,action,uploadImage,setUploadLoading, setUploadErrorFileName})=>{
const input = document.getElementById('upload-image');
const targetFile = input.files[0];
if (targetFile){
setUploadLoading(true);
...
setUploadLoading(false);
}
};
const [uploadLoading, setUploadLoading] = useState(false);
{uploadLoading && renderUploading()}
const renderUploading =()=> (
<div className="uploading item">
<Icon className="icon" type='loading' />
<span>Uploading...</span>
</div>
);
5. 上传失败
与loading其实同理, 其次，上传失败之后设置uploadErrorFileName来渲染失败的样式。
await axios.post(action, {imageBase64, name})
.then(()=>{
...
}).catch(() => {
setUploadErrorFileName(name);
});
const [uploadErrorFileName, setUploadErrorFileName] = useState(null);
{uploadErrorFileName && renderUploadError(uploadErrorFileName,setUploadErrorFileName)}
const renderUploadError =(uploadErrorFileName, setUploadErrorFileName)=> (
<div className="uploading item error">
<Icon className="icon" type='close-circle' />
<div className="error-message">Error!</div>
<div className="name">{uploadErrorFileName}</div>
<div className="config item">
<Icon className="delete-icon" type="delete" onClick={()=> setUploadErrorFileName(null)}/>
</div>
</div>
);
6. 删除图片
const deleteImage = async ({name}, setList)=>{
await ajax(deleteImageUrl,{name});
getAndUpdateImageList(setList);
};
7. 查看大图
用到了Antd的上传图片一样，用到的Modal框去显示大图， 用previewSrc保存选择的结果
const [previewSrc, setPreviewSrc] = useState(null);
<Modal
width={800}
className="preview-modal"
visible={previewSrc !== null}
title={null}
footer={null}
onCancel={()=>setPreviewSrc(null)} >
<img src={previewSrc} alt=""/>
</Modal>
8. 下载图片 + blob
思路：
1.用a标签的download属性来实现下载效果，因为下载按钮是Icon，所以点击download Icon之后触发a标签的download
2.使用Blob: 使用URL.createObjectURL()函数可以创建一个Blob URL
<Icon type="download" className="icon" onClick={()=>downloadImage(item, onDownload)}/>
<a id="download-image" download={item.name}/>
const downloadImage=(item, onDownload)=>{
const target = document.getElementById('download-image');
const blob = new Blob([item.src]);
target.href = URL.createObjectURL(blob);
target.click();
onDownload(item);
};
【后端】Nest
1.跨域
app.enableCors();
2.静态文件暴露
const app = await NestFactory.create<NestExpressApplication>(AppModule);
app.useStaticAssets(join(__dirname, '..', 'data/images'), {
prefix: '/images/',
});
3.写文件
- 解析base64,生成buffer
- fs.writeFile(buffer)
@Post('/image/add')
getImage(@Req() req, @Res() res): void {
const {imageBase64, name} = req.body;
const base64Data = imageBase64.replace(/^data:image\/\w+;base64,/, '');
const dataBuffer = new Buffer(base64Data, 'base64');
fs.writeFile(`data/images/${name}`, dataBuffer, (err) => {
if (err) {
res.send(err);
} else {
res.send({status: 0 });
}
});
}
4.读文件
fs.readdirSync(文件名)
@Get('/image/list')
getProductList(@Res() res): void {
const data = fs.readdirSync('data/images');
const url = 'http://localhost:8080/images/';
res.send({
data: data.map(item => ({
name: item,
id: uuid(),
src: url + item,
})),
status: 0,
});
}
5.删文件
fs.unlinkSync(文件名)
@Get('/image/delete')
deleteImage(@Query() query, @Res() res): void {
const files = fs.readdirSync('data/images');
const target = files.filter(item => item === query.name);
if (target) {
fs.unlinkSync('data/images/' + target);
res.send({status: 0 });
}
res.send({status: 1 });
}
案例
用useEffect代替了didMount请求图片列表
const [list, setList] = useState([]);
useEffect(() => {
getAndUpdateImageList(setList);
},[]);
import React,{useState, useEffect} from 'react';
import UploadImage from "./component/upload-image/upload-image";
import axios from "axios";
import {message} from "antd";
const baseUrl = 'http://localhost:8080/image';
const getImageListUrl = `${baseUrl}/list`;
const addImageUrl = `${baseUrl}/add`;
const deleteImageUrl = `${baseUrl}/delete`;
const ajax = (url, data={}, type='GET') =>{
return new Promise((resolve)=>{
const promise = type === 'GET' ? axios.get(url, {params: data}) : axios.post(url, data)
promise.then(res=>{
const data = res.data;
data.status !== 0 ? message.error(data.msg) : resolve(data);
}).catch(err => {
message.error('Network request Error: '+err);
})
})
};
const getAndUpdateImageList = async(setList) => {
const data = await ajax(getImageListUrl);
setList(data.data);
};
const deleteImage = async ({name}, setList)=>{
await ajax(deleteImageUrl,{name});
getAndUpdateImageList(setList);
};
const uploadImage = (item, setList) => {
getAndUpdateImageList(setList);
};
const downloadImage = (item) => {
console.log('downloadImage', item)
};
function App() {
const [list, setList] = useState([]);
useEffect(() => {
getAndUpdateImageList(setList);
},[]);
return (
<div className="App">
<UploadImage
action={addImageUrl}
list={list}
onUpload={(item)=>uploadImage(item, setList)}
onDelete={(item)=>deleteImage(item, setList)}
onDownload={(item)=>downloadImage(item)}
/>
</div>
);
}
export default App;
