异步调用问题，封装调用系统hash方法时，由于异步处理，在hash处理前返回了结果。

/** 
 
 获取 hash 调用入口 
 */ 
public async getHash() { 
  // then 方案 
  this.hashByPromise("11111111", "???") 
  .then((data) => { 
    AlertDialog.show({ message: "hash: " + baseUtil.base64Encode(data) }); 
    console.log("hash: " + baseUtil.uint8ArrayToHexStr(data)); 
  }); 
  // await 方案 
  let data: Uint8Array = await this.hashByPromise("11111111", "???"); 
  console.log("hash: " + baseUtil.uint8ArrayToHexStr(data)); 
} 
// callback 方案 
public async hashByCallback(strPlain: string, strHashAlg: string): Promise<Uint8Array> { 
  let reHash: Uint8Array = new Uint8Array(); 
  if (strPlain.length != 0) { 
  let plain: Uint8Array = baseUtil.stringToUint8Array(strPlain); 
  Logger.verbose("index", "#######finalChallenge2"); 
  reHash = await this.doHashByCallback(plain, "SHA256", (reHash: Uint8Array) => { 
  Logger.verbose("index", "#######finalChallenge5"); 
  return reHash; 
}); 
} 
return reHash; 
} 
 
//promise 用法与 callback 相差不大： 
// Promise 方案 
public async hashByPromise(strPlain: string, strHashAlg: string): Promise<Uint8Array> { 
  let reHash: Uint8Array = new Uint8Array(); 
  if (strPlain.length != 0) { 
  let plain: Uint8Array = baseUtil.stringToUint8Array(strPlain); 
  Logger.verbose("index", "#######finalChallenge2"); 
  reHash = await this.doHashByPromise(plain, "SHA256") 
  .then((reHash: Uint8Array) => { 
  Logger.verbose("index", "#######finalChallenge5"); 
  return reHash; 
}); 
} 
return reHash; 
} 
 
public async doHashByPromise(strPlain: Uint8Array, hashAlg: string): Promise<Uint8Array> { 
  Logger.verbose("index", "#######finalChallenge3"); 
  let reHash: Uint8Array = new Uint8Array([]); 
  try { 
  let md: cryptoFramework.Md = cryptoFramework.createMd(hashAlg); 
  let digestPlain: cryptoFramework.DataBlob = { data: strPlain }; 
  // 数据量较少时，可以只做一次update，将数据全部传入，接口未对入参长度做限制 
  let promiseMdUpdate = md.update(digestPlain); 
  reHash = await promiseMdUpdate.then(() => { 
    let promiseMdDigest = md.digest(); 
    return promiseMdDigest; 
  }).then(mdOutput => { 
    Logger.verbose("index", "#######finalChallenge4"); 
    // 返回计算结果 
    return mdOutput.data; 
    Logger.verbose("index", "[Promise]: MD result mdOutput: " + mdOutput.data); 
  }).catch((error: BusinessError) => { 
    Logger.error("index", "[Promise]: error: " + error.message); 
    // 返回空结果 
    return new Uint8Array([]); 
  }); 
} catch (error) { 
  let e = error as BusinessError; 
  Logger.verbose("index", "[Callback]: error code: " + e.code + ", message is: " + e.message); 
} 
return reHash; 
}
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