一、需求背景

1、需要实现小程序下载最大500M视频
2、同时需支持图片下载
3、退到其他页面再次回到当前页面时，下载进度也需要展示

二、实现步骤

1、在app.ts文件定义一个全局变量globalDownLoadData

2、写一个独立的下载hooks，代码如下（hooks/useDownLoad.ts文件）

import Taro, { useDidShow } from '@tarojs/taro';
import { useState, useCallback, useEffect, useRef } from 'react';
import { tips } from '@/modules/utils/log';
import { GET_ENV } from '@/modules/core/env';// 下载选项接口
interface DownloadOptions {/** 下载文件的URL */url: string;// 下载的是图片还是视频,默认是视频isImg?: boolean;// 下载成功后的回调successFn?: () => void;
}// 请注意_taskId格式应该为：`material_${routerParams.id}`
// material为页面标志，请注意唯一性，避免不同页面的id重复
export const useDownLoad = _taskId => {const taskId = `${GET_ENV()}_${_taskId}`;const globalDownLoadData = useRef(Taro.getApp().globalDownLoadData);const [progress, setProgress] = useState(0);useDidShow(() => {// 恢复目标页面下载进度setProgress(globalDownLoadData.current[taskId]?.progress || 0);});useEffect(() => {globalDownLoadData.current[taskId] = {progress,downloadTask: globalDownLoadData.current[taskId]?.downloadTask};}, [progress]);// 赋值数据给全局useEffect(() => {Taro.getApp().globalDownLoadData = globalDownLoadData.current;}, [globalDownLoadData]);useEffect(() => {// 再次进入页面时，将监听加上addProgressUpdate();}, []);/*** 执行文件下载* @param options 下载选项*/const downloadFn = useCallback(async (options: DownloadOptions) => {try {setProgress(0);// 创建下载任务globalDownLoadData.current[taskId].downloadTask = Taro.downloadFile({url: options.url,success: async res => {if (res.statusCode === 200) {// 下载成功，保存到相册Taro.getSetting({success(settingRes) {// 是否相册授权，已授权直接保存图片if (settingRes.authSetting['scope.writePhotosAlbum']) {const Api = options.isImg ? 'saveImageToPhotosAlbum' : 'saveVideoToPhotosAlbum';Taro[Api]({filePath: res.tempFilePath,success() {tips('下载完成');options.successFn?.();// 下载完成后清除进度setProgress(0);},fail(err) {console.log('saveImageToPhotosAlbum err', err);setProgress(0);}});// 未授权，则先授权} else {Taro.authorize({scope: 'scope.writePhotosAlbum',fail() {tips('下载失败，请先点击右上角获取授权');setProgress(0);}});}},fail(err) {setProgress(0);tips('下载失败，请稍后再试');console.log('getSetting err', err);}});} else {// 下载失败setProgress(0);tips('下载失败，请稍后再试');console.log('downloadFile下载出错了：', res);}},fail: error => {// 下载出错setProgress(0);globalDownLoadData.current[taskId] = {progress: 0,downloadTask: null};console.log('下载出错了：', error);Taro.showModal({title: '下载异常',content: '下载异常或文件大小超过小程序限制，请通过浏览器下载！',confirmColor: '#3f57ff',success: modalRes => {if (modalRes.confirm) {Taro.setClipboardData({data: options.url,success() {tips('资源链接已复制');}});}}});}});addProgressUpdate();} catch (error) {// 捕获其他异常tips('下载失败，请稍后再试');console.log('downloadFn下载失败======>', error);setProgress(0);}}, []);// 监听下载进度变化const addProgressUpdate = () => {const downloadTask = globalDownLoadData.current[taskId]?.downloadTask;if (!downloadTask) {setProgress(0);return;}downloadTask.onProgressUpdate(res => {if (res.progress >= 100) {// 下载完成时，延迟2秒后清除进度setTimeout(() => {setProgress(0);downloadTask.abort();delete globalDownLoadData.current[taskId];}, 2000);} else {setProgress(res.progress);}});};return {downloadFn,progress};
};

3、页面使用

import { useDownLoad } from '@/subPages/hooks/useDownLoad';const { downloadFn, progress } = useDownLoad(`material_${routerParams.id}`);const onDownload = () => {if (!curUrl) {tips('下载资源不存在');return;}Taro.showModal({title: '提示',confirmColor: '#3f57ff',content: '确定要下载该素材吗？',success: async res => {if (res.confirm) {downloadFn({url: curUrl,isImg: false});}}});};

四、参考文档：

https://developers.weixin.qq.com/miniprogram/dev/api/network/download/wx.downloadFile.html
https://developers.weixin.qq.com/miniprogram/dev/api/media/image/wx.saveImageToPhotosAlbum.html
https://developers.weixin.qq.com/miniprogram/dev/api/media/video/wx.saveVideoToPhotosAlbum.html