通过蓝牙连接后立即发送/接收数据-Android

Question

这就是应该怎么做。

主机将使他/她的设备可被发现，然后选择将要加载的游戏板的类型。客户端将连接到主机设备，并且两个设备都将连接。主机先前选择的游戏板类型应同时在两个设备上加载。

这是我的代码，到目前为止，它仅会导致错误

BluetoothActivity.java

case MESSAGE_DEVICE_NAME:
    // save the connected device's name
    mConnectedDeviceName = msg.getData().getString(DEVICE_NAME);
    Toast.makeText(TwoPlayerActivityBluetooth.this, "Connected to " + mConnectedDeviceName, Toast.LENGTH_SHORT).show();

    /* If the device chose a game board, then send*/
    if (GBChoice != 0)
    {
        sendGamepiece(GBChoice);
    }

    /* If the device didn't choose a game board, then receive */
    else
    {
        byte[] readBuf2 = (byte[]) msg.obj;
        String readMessage2 = new String(readBuf2, 0, msg.arg1);

        /* Save the received data to a variable */
        ChosenGB = readMessage2;
    }


    /* If the sent game board choice and received game board choice is both 1, then load the game board1*/
    if (GBChoice == 1 && ChosenGB == 1)
    {
        loadGameBoard1();
    }
    break;

BluetoothService.java

        public void run()
        {
            readGamepiece();
            readLocation();
        }

        public void readGamepiece()
        {

            byte[] buffer2 = new byte[1024];
            int bytes;

        while(true)
        {
            try
            {
                bytes = mInStream.read(buffer2);
            mHandler.obtainMessage(BluetoothActivity.MESSAGE_DEVICE_NAME, bytes, -1, buffer2).sendToTarget();
            }
            catch(IOException e)
            {
                Log.e(TAG, "disconnected", e);
                connectionLost();
                break;
            }
        }

    }

    public void writeGamepiece(byte[] buffer2)
    {
        try
        {
            mOutStream.write(buffer2);
            mHandler.obtainMessage(BluetoothActivity.MESSAGE_DEVICE_NAME, -1 , -1 , buffer2).sendToTarget();

        }
        catch(IOException e)
        {
        Log.e(TAG, "Exception during write", e);
        }
    }


    public void readLocation()
    {

        byte[] buffer = new byte[1024];
        int bytes;

        while(true)
        {
            try
            {
                bytes = mInStream.read(buffer);
                mHandler.obtainMessage(BluetoothActivity.PLAYER_LOCATION_READ, bytes, -1, buffer).sendToTarget();
            }
            catch(IOException e)
            {
                Log.e(TAG, "disconnected", e);
                connectionLost();
                break;
            }
        }
    }


    public void writeLocation(byte[] buffer)
    {
        try
        {
            mOutStream.write(buffer);
            mHandler.obtainMessage(BluetoothActivity.PLAYER_LOCATION_WRITE, -1 , -1 , buffer).sendToTarget();
        }
        catch(IOException e)
        {
            Log.e(TAG, "Exception during write", e);
        }
    }

错误：

FATAL EXCEPTION: mainProcess: com.example.try34.midproject, PID: 3829
java.lang.NullPointerException: Attempt to invoke virtual method 'byte[] java.lang.String.getBytes()' on a null object reference
at com.example.try34.midproject.view.BluetoothActivity.sendGamepiece(BluetoothActivity.java:1024)
at com.example.try34.midproject.view.BluetoothActivity.access$1800(BluetoothActivity.java:44)
at com.example.try34.midproject.view.BluetoothActivity$9.handleMessage(BluetoothActivity.java:741)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7409)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)