在android

Question

为什么在尝试通过蓝牙发送byte []时会出现NullPointerException？它发生在mConnectedThread.write（mOutput）;在内部ConnectThread类之前的底层附近的主类中调用。我一直在向控制台写日志，他们都说这个字节不是空的，但它仍然拒绝发送。这是我的主要课程：

public class bluetoothMusicListener extends AppCompatActivity {

BluetoothAdapter mBluetoothAdapter;
Context          mContext;
ConnectedThread  mConnectedThread;
ConnectThread    mConnectThread;
Handler          mHandler;
View             mConnectToDevices;
View             mSendText;
BluetoothDevice  mDevice;
ParcelUuid       list[];

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.bluetooth_listener);

    mConnectToDevices = findViewById(R.id.connectToDevices);
    mSendText = findViewById(R.id.sendText);

    mContext = getApplicationContext();

    mBluetoothAdapter = mBluetoothAdapter.getDefaultAdapter();
    if (mBluetoothAdapter == null) {
        Toast.makeText(mContext, "No bluetooth adapter found", Toast.LENGTH_SHORT).show();
    }

    if (!mBluetoothAdapter.isEnabled()) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, 1);
    }

    mConnectToDevices.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
            //BluetoothDevice mDevice[] = (BluetoothDevice)pairedDevices.toArray();

            if (pairedDevices.size() > 0) {
                for (BluetoothDevice device : pairedDevices) {
                    mDevice = device;
                    list = device.getUuids();
                }
            }

            mHandler = new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    byte[] writeBuf = (byte[]) msg.obj;
                    int begin = (int)msg.arg1;
                    int end = (int)msg.arg2;

                    switch(msg.what) {
                        case 1:
                            String writeMessage = new String(writeBuf);
                            TextView fromDevice = (TextView) findViewById(R.id.fromDevice);
                            fromDevice.setText(writeMessage);
                            break;
                    }
                }
            };

            mConnectThread = new ConnectThread(mDevice, mHandler);
            mConnectThread.start();
        }
    });

    mSendText.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            EditText input = (EditText)findViewById(R.id.editText);

            if (input.getText() != null) {
                //for(int i = 0; i < mConnectedThread.length || i < 5; i++) {
                    String stringOutput = input.getText().toString();
                    byte[] mOutput = (byte[])stringOutput.getBytes();
                    Log.v("input", "input is: " + input);
                    Log.v("input", "input getText is: " + input.getText());
                    Log.v("input", "input getText toString is: " + input.getText().toString());
                    Log.v("input", "output is: " + mOutput.toString());
                    mConnectedThread.write(mOutput);
                //}
            }
        }
    });
}
private class ConnectThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final BluetoothDevice mmDevice;
    private final Handler mHandler;
    private final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb");

    public ConnectThread(BluetoothDevice device, Handler handler) {
        BluetoothSocket tmp = null;
        mHandler = handler;
        mmDevice = device;
        try {
            tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
        } catch (IOException e) {
            e.printStackTrace();
        }
        mmSocket = tmp;
    }

    public void run() {
        mBluetoothAdapter.cancelDiscovery();
        try {
            mmSocket.connect();
        } catch (IOException connectException) {
            try {
                mmSocket.close();
            } catch (IOException closeException) {
                closeException.printStackTrace();
            }
            return;
        }

        mConnectedThread = new ConnectedThread(mmSocket, mHandler);
        mConnectedThread.start();
    }

    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
}

这是我的ConnectedThread类：

class ConnectedThread extends Thread {
private       BluetoothSocket mmSocket;
private       Handler         mHandler;
private       InputStream     mmInStream;
private       OutputStream    mmOutStream;

public ConnectedThread(BluetoothSocket socket, Handler handler) {
    mmSocket = socket;
    mHandler = handler;
    InputStream tmpIn = null;
    OutputStream tmpOut = null;
    try {
        tmpIn = socket.getInputStream();
        tmpOut = socket.getOutputStream();
    } catch (IOException e) {
        e.printStackTrace();
    }
    mmInStream = tmpIn;
    mmOutStream = tmpOut;
}

public void run() {
    byte[] buffer = new byte[1024];
    int begin = 0;
    int bytes = 0;
    while (true) {
        try {
            bytes += mmInStream.read(buffer, bytes, buffer.length - bytes);
            for(int i = begin; i < bytes; i++) {
                if(buffer[i] == "#".getBytes()[0]) {
                    mHandler.obtainMessage(1, begin, i, buffer).sendToTarget();
                    begin = i + 1;
                    if(i == bytes - 1) {
                        bytes = 0;
                        begin = 0;
                    }
                }
            }
        } catch (IOException e) {
            break;
        }
    }
}

public void write(byte[] bytes) {
    try {
        mmOutStream.write(bytes);
    } catch(IOException e ){
        e.printStackTrace();
    }
}

public void cancel() {
    try {
        mmSocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

谢谢！