HarmonyOS string怎么与Uint8Array互转？

//string转Uint8Array 
 stringToUint8Array(str: string): Uint8Array { 
    try { 
      let textEncoder = new util.TextEncoder("utf-8"); 
      let array: Uint8Array = textEncoder.encodeInto(str); 
      return array 
    } catch (err) { 
      QDLogUtils.error(`stringToUint8Array = ${err}`) 
      return new Uint8Array() 
    } 
  } 
//Uint8Array转string 
  uint8ArrayToString(arr: Uint8Array): string { 
    let str = '' 
    if (arr && arr.length > 0) { 
      try { 
        let textDecode = util.TextDecoder.create('utf-8') 
        str = textDecode.decodeWithStream(arr) 
      } catch (err) { 
      } 
    } 
    return str 
  }