HarmonyOS 鸿蒙Next 下载并保存DPF到本地

import { request } from '@kit.BasicServicesKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { picker } from '@kit.CoreFileKit';
import { fileIo as fs } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';
import { JSON } from '@kit.ArkTS';

@Component
export struct FileDemo {
  @State pdfUri: string = ''
  @State downLoadFileSavePath: string = ''

  requestPdf() {
    let context = getContext(this) as common.UIAbilityContext;
    let fileName = Date.now().toString() + '.pdf'
    let filePath = context.filesDir + `/${fileName}`;
    
    try {
      request.downloadFile(getContext(), {
        url: 'https://xxx/xxx.pdf',
        filePath: filePath
      }).then((data: request.DownloadTask) => {
        let downloadTask: request.DownloadTask = data;
        downloadTask.on('complete', () => {
          let documentSaveOptions = new picker.DocumentSaveOptions();
          documentSaveOptions.newFileNames = [fileName];
          let documentViewPicker = new picker.DocumentViewPicker();
          documentViewPicker.save(documentSaveOptions).then((documentSaveResult: Array<string>) => {
            try {
              this.downLoadFileSavePath = documentSaveResult[0];
              let sanFile = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
              let pubFile = fs.openSync(this.downLoadFileSavePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
              fs.copyFileSync(sanFile.fd, pubFile.fd)
              fs.closeSync(sanFile.fd)
              fs.closeSync(pubFile.fd)
            } catch (e) {
              console.log(`Failed to copy file ${JSON.stringify(e)}`)
            }
          })
        })
      }).catch((err: BusinessError) => {
        console.error(`Failed to request the download. Code: ${err.code}, message: ${err.message}`);
      })
    } catch (err) {
      console.error(`Failed to request the download. err: ${JSON.stringify(err)}`);
    }
  }

  build() {
    Column() {
      Button('request PDF')
        .onClick(() => {
          this.requestPdf()
        })
    }
    .width('100%')
    .height('100%')
  }
}