HarmonyOS 文件下载saveas希望支持下绝对路径

pickerPhoto() { 
  try { 
    let options = new picker.PhotoSelectOptions(); 
    options.MIMEType = picker.PhotoViewMIMETypes.IMAGE_TYPE; 
    options.maxSelectNumber = 1; 
    let p = new picker.PhotoViewPicker(); 
    p.select(options).then((res:picker.PhotoSelectResult) => { 
      console.info("txy photo is uri" + res.photoUris[0]) 
      this.saveFile(res.photoUris[0]); 
    }) 
  } catch (e) { 
    console.error("txy select tailed..") 
  } 
} 
async saveFile(uri: string) { 
  // 将公共目录的文件，拷贝至沙箱路径 
  let destDist = getContext(this).cacheDir + "/test.png"; 
  let src = fs.openSync(uri, fs.OpenMode.READ_ONLY); 
  let dst = fs.openSync(destDist, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
  fs.copyFileSync(src.fd, dst.fd); 
}