java - 如何按原样发送字节数，而不是将它们作为 Android 蓝牙输出流中的单独数字发送？

Question

我想通过我的蓝牙输出流发送，例如:239 作为 239，但目前，我的蓝牙代码将其发送为“2”，然后是“3”，然后是“9”；总共 3 个字节，而不是 1 个字节，接收也是以 3 个字节进行。

Tx 端代码 (Java):使用计时器每 10 秒发送一次数据。

打包数据为:

    private void startTimer() {
        TimerTask mTimerTask = new TimerTask() {
            @RequiresApi(api = Build.VERSION_CODES.KITKAT)
            @Override
            public void run() {
                byte[] mByte = new byte[1];

                mTimeStamp += mPeriod;  //mPeriod = 10000; initial mTimeStamp = 0
                mData += 2; //initial mData = 0

                String s = "239";
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mTimeStamp & 0xFF000000) >> 24));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mTimeStamp & 0x00FF0000) >> 16));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mTimeStamp & 0x0000FF00) >> 8));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mTimeStamp & 0x000000FF) >> 0));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = "0";
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = "0";
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mData & 0x0000FF00) >> 8));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
                s = Integer.toString(((mData & 0x000000FF) >> 0));
                mByte = s.getBytes(StandardCharsets.UTF_8);
                mBluetoothConnection.write(mByte);
            }
        };
        Timer timer = new Timer("schedule", true);

        timer.scheduleAtFixedRate(mTimerTask, 10, mPeriod);
    }

以及写入函数:

//Call this from the main activity to send data to the remote device
        public void write(byte[] bytes) {
            String text = new String(bytes, Charset.defaultCharset());
            Log.d(TAG, "write: Writing to outputstream: " + text);
            try {
                Log.d(TAG, "write: bytes length: " + bytes.length);
                mmOutStream.write(bytes);
            } catch (IOException e) {
                Log.e(TAG, "write: Error writing to output stream. " + e.getMessage() );
            }
        }

记录相同的 cat 输出:

01-06 23:33:32.012 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 239
01-06 23:33:32.012 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 3
01-06 23:33:32.018 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.018 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 0
01-06 23:33:32.018 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 1
01-06 23:33:32.020 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.020 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 4
01-06 23:33:32.020 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 1
01-06 23:33:32.021 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.021 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 147
01-06 23:33:32.021 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 3
01-06 23:33:32.022 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.022 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 224
01-06 23:33:32.022 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 3
01-06 23:33:32.024 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.024 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 0
01-06 23:33:32.024 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 1
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 0
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 1
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 0
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 1
01-06 23:33:32.033 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Write Called.
01-06 23:33:32.034 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: Writing to outputstream: 60
01-06 23:33:32.034 19455-19682/com.example.user.bluetooth_communication D/BluetoothConnectionServ: write: bytes length: 2

Rx 端代码 (Kotlin):

// Keep listening to the InputStream until an exception occurs
            Log.d("ConnectionActivity", "Inside ListeningThread")
            while (true) { // Read from the InputStream
                if(mBluetoothSocket != null)
                {
                    try {
                        bytes = mBluetoothSocket!!.inputStream.read(buffer)
                        val incomingMessage = String(buffer, 0, bytes)
                        Log.d("ConnectionActivity", "No of bytes: $bytes, " + "InputStream: $incomingMessage")
                        var intentIncomingMessage = Intent("incomingMessage")
                        intentIncomingMessage.putExtra("theMessage", incomingMessage)
                        LocalBroadcastManager.getInstance(mContext).sendBroadcast(intentIncomingMessage)

                    } catch (e: IOException) {
                        Log.e(TAG, "write: Error reading Input Stream. " + e.message)
                        break
                    }
                }
            }

示例 logcat 输出:

2020-01-12 16:12:10.817 13707-13937 D/ConnectionActivity: No of bytes: 3, InputStream: 239
2020-01-12 16:12:10.848 13707-13937 D/ConnectionActivity: No of bytes: 12, InputStream: 074324000094
2020-01-12 16:12:20.817 13707-13937 D/ConnectionActivity: No of bytes: 3, InputStream: 239
2020-01-12 16:12:20.842 13707-13937 D/ConnectionActivity: No of bytes: 10, InputStream: 0783000096
2020-01-12 16:12:30.817 13707-13937 D/ConnectionActivity: No of bytes: 3, InputStream: 239
2020-01-12 16:12:30.845 13707-13937 D/ConnectionActivity: No of bytes: 12, InputStream: 071221600098

在上面的输出中，我需要的是:第一两行数据应该是

D/ConnectionActivity: No of bytes: 1, InputStream: 239
D/ConnectionActivity: No of bytes: 1, InputStream: 0
D/ConnectionActivity: No of bytes: 1, InputStream: 74
D/ConnectionActivity: No of bytes: 1, InputStream: 32
D/ConnectionActivity: No of bytes: 1, InputStream: 40
D/ConnectionActivity: No of bytes: 1, InputStream: 0
D/ConnectionActivity: No of bytes: 1, InputStream: 0
D/ConnectionActivity: No of bytes: 1, InputStream: 0
D/ConnectionActivity: No of bytes: 1, InputStream: 94

我认为这个问题部分(如果不是全部)与我传输数据的方式有关。在 Tx 端 logcat 输出中，可以看到 239 的字节长度被打印为 3，而不是 1。

Answer 1

一些java流基础知识:

final byte number1 = 89;
final byte number2 = 45;
final byte number3 = 75;
final ByteArrayOutputStream byteOutput = new ByteArrayOutputStream();
final DataOutputStream o = new DataOutputStream(byteOutput);
o.writeByte(number1);
o.writeByte(number2);
o.writeByte(number3);
//for other types you can do:
//        o.writeBoolean();
//        o.writeUTF();
//etc.
final byte[] bytes = byteOutput.toByteArray();
o.close();
//now you can send this array.
// to read the data sent simply take your input stream:
// or alternatively: val inputStream = DataInputStream(mBluetoothSocket!!.inputStream)
final ByteArrayInputStream byteInputStream = new ByteArrayInputStream(bytes);
final DataInputStream inputStream = new DataInputStream(byteInputStream);
System.out.println(inputStream.readByte()); //prints number 1 aka 89
System.out.println(inputStream.readByte()); //prints number 2 aka 45
System.out.println(inputStream.readByte()); //prints number 3 aka 75

这应该允许您发送原始字节，而无需在字符串之间进行转换。

在 Kotlin 中，如果需要无符号字节，您可以将 .toUByte() 添加到 inputStream.readByte()。