HarmonyOS 如何将文件管理器中的文件保存到应用沙箱

参考示例如下：

async function picture() {
  let documentSelectOptions = new picker.DocumentSelectOptions();
  let documentPicker = new picker.DocumentViewPicker();
  documentPicker.select(documentSelectOptions).then((documentSelectResult: Array<string>) => {
    console.info('DocumentViewPicker.select successfully, documentSelectResult uri: ' + JSON.stringify(documentSelectResult));
    let file = fs.openSync(documentSelectResult[0], fs.OpenMode.READ_ONLY)
    let file2 = fs.openSync(pathDir+'/test333.txt', fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
    console.info('DocumentViewPicker  file.fd, file2.fd: ' + JSON.stringify(file.fd),JSON.stringify(file2.fd));
    fs.copyFileSync(file.fd, file2.fd)
    fs.closeSync(file);
    fs.closeSync(file2);
  }).catch((err: BusinessError) => {
    console.error('DocumentViewPicker.select failed with err: ' + JSON.stringify(err));
  });
}