如何将文件转换成字符串

getContext().resourceManager.getRawFileContent('MyStr.txt').then((value: Uint8Array) => { 
  let textDecoder: util.TextDecoder = util.TextDecoder.create(); // 调用util模块的TextDecoder类 
  let retStr: string = textDecoder.decodeWithStream(value); // 对Uint8Array解码 
  let strBase64 = new util.Base64Helper().encodeToStringSync(value); 
  console.info(retStr); 
  console.info(strBase64); 
}).catch((error: BusinessError) => { 
  console.info('getRawFileContent promise error is ' + error); 
});