HarmonyOS 鸿蒙Next下载与文件管理按钮实现方案 HarmonyOS 鸿蒙Next中如何设计一个下载按钮下载文件到本地及一个文件管理按钮调用系统文件管理系统找到刚下载的文件的具体方案

参考下载文档：

https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/app-file-upload-download-V5#下载网络资源文件至应用文件目录

使用request.downloadFile，

下载到沙箱位置：filePath: filesDir + '/xxxx.png'（/data/app/el2/100/base/com.example.myapplication/haps/entry/files/xxx.jpg）

文件管理是指的手机自带的文件管理器么？是的话，需要将沙箱目录下的图片复制到手机管理器，再使用DocumentViewPicker拉起弹窗查看

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-file-picker-V5#documentviewpicker

```
import common from ‘@ohos.app.ability.common’;
import fs from ‘@ohos.file.fs’;
import { picker } from ‘@kit.CoreFileKit’;
import { image } from ‘@kit.ImageKit’;
import { resourceManager } from ‘@kit.LocalizationKit’;
import { BusinessError } from ‘@kit.BasicServicesKit’;
let context = getContext(this) as common.UIAbilityContext;
let fileNameArr = [‘food.png’]//将原图片放在rawfile下
@Entry
@Component
struct Page10 {
  @State message: string = ‘Hello World’;
  build() {
    Column() {
      Button(‘1、图片写入沙箱’)//将源文件放在rawfile目录下，改成下载功能
        .onClick(() => {
          this.rawToFile(fileNameArr[0])
        })
      Button(‘2、沙箱word文件保存到手机文件管理’)
        .onClick(() => {
          this.save()//保存后请打开文件管理，保存的文档就在刚刚选中的目录下
        })
      Button(‘3、拉起文件，返回uri’)
        .onClick(() => {
          this.findPngUri()//拉起查看，返回地址
        })
    }
  }
  rawToFile(fileName: string) {
    context.resourceManager.getRawFileContent(fileName, (_err, value) => {
      let myBuffer: ArrayBufferLike = value.buffer
      let filePath = context.filesDir + ‘/’ + fileName
      console.log(“rawToFile中filePath:” + filePath);
      let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
      let writeLen = fs.writeSync(file.fd, myBuffer);
      console.info(“写入数据和文件成功：” + writeLen);
      console.info(“沙箱名称是：” + fileName);
      fs.closeSync(file);
    });
  }
  save() {
    console.log(‘fileNameArr:’ + fileNameArr)
    const documentSaveOptions = new picker.DocumentSaveOptions(); // 创建文件管理器保存选项实例
    documentSaveOptions.newFileNames = fileNameArr; // 保存文件名（可选）
    const documentViewPicker = new picker.DocumentViewPicker;
    documentViewPicker.save(documentSaveOptions)
      .then((documentSaveResult) => {
        // 获取到到图片或者视频文件的URI后进行文件读取等操作
        console.info('documentSaveResult.save successfully, audioSaveResult uri: ’ + JSON.stringify(documentSaveResult))
        let filePath = ‘’
        let uri = ‘’
        for (let index = 0; index < documentSaveResult.length; index++) {
          uri = documentSaveResult[index]
          console.log(uri${index}:${uri})
          filePath = context.filesDir + ‘/’ + fileNameArr[index]
          console.log(‘循环filePath：’ + filePath)
          // 沙箱路径文件
          let sanFile = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
          let pubFile = fs.openSync(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
          // 将文件从沙箱路拷贝到公共路径
          fs.copyFileSync(sanFile.fd, pubFile.fd)
          fs.closeSync(sanFile)
          fs.closeSync(pubFile)
        }
      })
      .catch((err: Error) => {
        console.error(Invoke documentPicker.select failed, message is ${err.message});
      })
  }
  findPngUri() {
    try {
      let documentSelectOptions = new picker.DocumentSelectOptions();
      let documentPicker = new picker.DocumentViewPicker(context);
      documentPicker.select(documentSelectOptions).then((documentSelectResult: Array<string>) => {
        console.info('DocumentViewPicker.select successfully, documentSelectResult uri: ’ +
        JSON.stringify(documentSelectResult));
        let uri = documentSelectResult[0]
        console.log(‘图片的uri地址是:’ + uri)
      }).catch((err: BusinessError) => {
        console.error('DocumentViewPicker.select failed with err: ’ + JSON.stringify(err));
      });
    } catch (error) {
      let err: BusinessError = error as BusinessError;
      console.error('DocumentViewPicker failed with err: ’ + JSON.stringify(err));
    }
  }
}