HarmonyOS 鸿蒙Next中download下载直接走到了fail

download下载直接走到了fail,具体报了什么错嘛，或者可以参考下面示例request.downloadFile下载文件是可以成功下载的

【背景知识】

request.downloadFile接口用于下载任务，支持配置后台下载（后台任务下载成功或者失败界面都会有弹窗提示，前台任务没有任何提示信息），支持暂停恢复下载，用on(‘complete’)成功回调之后可以做一些业务操作，比如将图片保存到相册、进行页面展示等。

request接口中的filePath参数配置只支持沙箱路径，不支持用户uri地址

常用设置文件下载路径有两种方式：

filesDir获取应用的文件路径：

context = this.getUIContext().getHostContext() as common.UIAbilityContext; //context需在组件内获取
...
filePath = this.context.filesDir + '/' + fileName // /data/storage/el2/base/haps/entry/files/1751420076162987800.png

cacheDir获取应用的文件路径：

context = this.getUIContext().getHostContext() as common.UIAbilityContext; 
...
filePath = this.context.cacheDir + '/' + fileName // /data/storage/el2/base/haps/entry/cache/1751420076162987800.png

【解决方案】

完整示例

import { request, systemDateTime } from '@kit.BasicServicesKit';
import { common } from '@kit.AbilityKit';
import { promptAction } from '@kit.ArkUI';

interface DownloadResult {
  isSuccess: boolean,
  msg: string
}

@Entry
@Component
struct Index {
  context = this.getUIContext().getHostContext() as common.UIAbilityContext;
  @State downloadUrl: string ='https://www.example.com' // 需要手动将url替换为真实服务器的HTTP协议地址
  @State filePath: string = ''
  @State current: number = 0
  @State total: number = 0
  @State downloadTask: request.DownloadTask = {} as request.DownloadTask
  @State downloadImage: string = ''

  DownloadFile(url: string):Promise<DownloadResult>{
    return new Promise(async(resolve,reject)=>{
      const fileName = `${systemDateTime.getTime(true)}.png`
      this.filePath = this.context.filesDir + '/' + fileName
      this.downloadTask = await request.downloadFile(this.context, { url, filePath: this.filePath })
      // 监听下载进度
      this.downloadTask.on('progress', (receivedSize: number, totalSize: number) => {
        this.current = receivedSize
        this.total = totalSize
      })

      // 监听下载是否失败
      this.downloadTask.on('fail', (err) => {
        if (err){
          return reject({ isSuccess: false, msg: "下载失败" });
        }
      })

      // 监听下载是否完成
      this.downloadTask.on('complete', () => {
        this.downloadImage = "file://" + this.filePath
        return resolve({ isSuccess: true, msg: 'Download task completed.' });
      })
    })
  }

  build() {
    Column({ space: 10 }) {
      Row({ space: 20 }) {
        Progress({ value: this.current, total: this.total, type: ProgressType.ScaleRing }).width(100).height(100)
          .backgroundColor(Color.Black)
          .style({ strokeWidth: 15, scaleCount: 20, scaleWidth: 5 })
        Row() {
          Image(this.downloadImage)
        }.width(100).height(100)
      }

      Button('download下载').onClick(() => {
        this.DownloadFile(this.downloadUrl).then((result)=>{
          if (result.isSuccess) {
           console.log('下载成功');
          } else {
            console.error(`失败: ${result.msg}`);
            console.log('下载失败');
          }
        })
      })
    }
    .height('100%')
    .width('100%')
  }
}