HarmonyOS 怎样使用savebutton下载项目里的图片

可以参考开发文档：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-security-components-savebutton-V5

参考代码：

import photoAccessHelper from '@ohos.file.photoAccessHelper';
import fs from '@ohos.file.fs';
@Entry
@Component
struct Page {
  build() {
    Column() {
      Image($r('app.media.background'))
        .height(300)
        .width(300)
      SaveButton().onClick(async (event: ClickEvent, result: SaveButtonOnClickResult) => {
        if (result == SaveButtonOnClickResult.SUCCESS) {
          try {
            const context = getContext(this);
            let helper = photoAccessHelper.getPhotoAccessHelper(context);
            let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'jpg');
            // 使用uri打开文件，可以持续写入内容，写入过程不受时间限制
            let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
            try {
              context.resourceManager.getMediaContent($r('app.media.background').id, 0)
                .then(async value => {
                  let media = value.buffer;
                  // 写到媒体库文件中
                  await fs.write(file.fd, media);
                  await fs.close(file.fd);
                  AlertDialog.show({message:'已保存至相册!'});
                });
            }
            catch (err) {
              console.error("error is "+ JSON.stringify(err))
            }
          } catch (error) {
            console.error("error is "+ JSON.stringify(error));
          }
        }
        else {
          AlertDialog.show({ message: "设置权限失败" })
        }
      })
    }
  }
}