HarmonyOS 签名是一个unit8Array,我怎么获得如下字符串

得到unit8arry后需要使用base64进行编码，base64Helper.encodeToStringSync(signData.data)，可以参考下面的demo：

async function signMessagePromise(priKey: cryptoFramework.PriKey) {
  let base64Helper = new util.Base64Helper();
  let signAlg = "RSA1024|PKCS1|MD5";
  let signer = cryptoFramework.createSign(signAlg);
  await signer.init(priKey);
  await signer.update(input1); // 如果明文较短，可以直接调用sign接口一次性传入
  let signData = await signer.sign(input2);
  let str = base64Helper.encodeToStringSync(signData.data)
  let unitdata = base64Helper.decodeSync(str)
  let signBlob: cryptoFramework.DataBlob = { data: unitdata }
  return signBlob;
}