App crash when prinln accelerometer event value

Question

I develop an PC remote application that able to move cursor mouse using android accelerometer sensor. I use java.io.PrintWriter to read accelerometer event value from onSensorChanged and sent to server but the app crash. Please help. error log Code

Context context;
ToggleButton toggleButton2;
private ToggleButton toggleButton1;
Button nextButton;
Button previousButton;
TextView mousePad;
TextView returnedText;

TextView textViewX;
TextView textViewY;

private SensorManager mSensorManager;
private Sensor mAccelerometer;

private boolean isConnected=false;
private boolean mouseMoved=false;
private Socket socket;
private PrintWriter out;

private float initX =0;
private float initY =0;
private float disX =0;
private float disY =0;

private SpeechRecognizer speech = null;
private Intent recognizerIntent;
private String LOG_TAG = "VoiceRecognitionActivity";


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

    context = this;
    returnedText = (TextView) findViewById(R.id.returnedText);
    toggleButton1 = (ToggleButton) findViewById(R.id.toggleButton1);
    toggleButton2 = (ToggleButton) findViewById(R.id.toggleButton2);
    nextButton = (Button)findViewById(R.id.nextButton);
    previousButton = (Button)findViewById(R.id.previousButton);

    textViewX = (TextView) findViewById(R.id.textViewX);
    textViewY = (TextView) findViewById(R.id.textViewy);


    nextButton.setOnClickListener(this);
    previousButton.setOnClickListener(this);


    mousePad = (TextView)findViewById(R.id.mousePad);


    mousePad.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if(isConnected && out!=null){
                switch(event.getAction()){
                    case MotionEvent.ACTION_DOWN:
                        //save X and Y positions when user touches the TextView
                        initX =event.getX();
                        initY =event.getY();
                        mouseMoved=false;
                        break;
                    case MotionEvent.ACTION_MOVE:
                        disX = event.getX()- initX; //Mouse movement in x direction
                        disY = event.getY()- initY; //Mouse movement in y direction
                        /*set init to new position so that continuous mouse movement
                        is captured*/
                        initX = event.getX();
                        initY = event.getY();
                        if(disX !=0|| disY !=0){
                            out.println(disX +","+ disY); //send mouse movement to server
                        }
                        mouseMoved=true;
                        break;
                    case MotionEvent.ACTION_UP:
                        //consider a tap only if usr did not move mouse after ACTION_DOWN
                        if(!mouseMoved){
                            out.println(Constants.MOUSE_LEFT_CLICK);
                        }
                }
            }
            return true;
        }
    });



    speech = SpeechRecognizer.createSpeechRecognizer(this);
    speech.setRecognitionListener(this);
    recognizerIntent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    recognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_PREFERENCE,
            "en");
    recognizerIntent.putExtra(RecognizerIntent.EXTRA_CALLING_PACKAGE,
            this.getPackageName());
    recognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_WEB_SEARCH);
    recognizerIntent.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 1);

    toggleButton1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if (isChecked) {
                speech.startListening(recognizerIntent);
            } else {
                speech.stopListening();
            }
        }
    });
    mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    int id = item.getItemId();
    if(id == R.id.action_settings) {
        Intent i = new Intent(getApplicationContext(), SetIP.class);
        startActivity(i);
        finish();
    }

    //noinspection SimplifiableIfStatement
    if(id == R.id.action_connect) {

        Intent intent =  getIntent();
        String ipadd = intent.getStringExtra("ipaddress");
        ConnectPhoneTask connectPhoneTask = new ConnectPhoneTask();
        connectPhoneTask.execute(ipadd);
        return true;
    }

    return super.onOptionsItemSelected(item);
}


@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.playPauseButton:
            {
                out.println(Constants.MOUSE_RIGHT_CLICK);
            }
            break;
        case R.id.nextButton:
            if (isConnected && out!=null) {
                out.println(Constants.NEXT);
            }
            break;
        case R.id.previousButton:
            if (isConnected && out!=null) {
                out.println(Constants.PREVIOUS);
            }
            break;
    }

}

@Override
public void onDestroy()
{
    super.onDestroy();
    if(isConnected && out!=null) {
        try {
            out.println("exit");
            socket.close();
        } catch (IOException e) {
            Log.e("remotedroid", "Error in closing socket", e);
        }
    }
}

@Override
public void onResume() {
    super.onResume();
    mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}

@Override
protected void onPause() {
    super.onPause();
    if (speech != null) {
        speech.destroy();
        Log.i(LOG_TAG, "destroy");
    }
    mSensorManager.unregisterListener(this);
}

public void onStop() {
    super.onStop();
    mSensorManager.unregisterListener(this);
}

public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // can be safely ignored for this demo
}

public void onSensorChanged(SensorEvent event) {

    float x = event.values[0];
    float y = event.values[1];


    textViewX.setText(Float.toString(x));
    textViewY.setText(Float.toString(y));

    Log.i(LOG_TAG, x+","+y);

    if ((x = null) && (y = null))
     try{
    out.println(String.valueOf(x)+","+String.valueOf(y));

}catch (IOException e) {
Log.e("remotedroid", "huhuhu", e);}}

@Override
public void onBeginningOfSpeech() {
    Log.i(LOG_TAG, "onBeginningOfSpeech");
}

@Override
public void onBufferReceived(byte[] buffer) {
    Log.i(LOG_TAG, "onBufferReceived: " + buffer);
}

@Override
public void onEndOfSpeech() {
    Log.i(LOG_TAG, "onEndOfSpeech");
    toggleButton1.setChecked(false);
}

@Override
public void onError(int errorCode) {
    String errorMessage = getErrorText(errorCode);
    Log.d(LOG_TAG, "FAILED " + errorMessage);
    toggleButton1.setChecked(false);
}

@Override
public void onEvent(int arg0, Bundle arg1) {
    Log.i(LOG_TAG, "onEvent");
}

@Override
public void onPartialResults(Bundle arg0) {
    Log.i(LOG_TAG, "onPartialResults");
}

@Override
public void onReadyForSpeech(Bundle arg0) {
    Log.i(LOG_TAG, "onReadyForSpeech");
}

@Override
public void onResults(Bundle results) {
    Log.i(LOG_TAG, "onResults");
    ArrayList<String> matches = results
            .getStringArrayList(SpeechRecognizer.RESULTS_RECOGNITION);
    String text = "";
    for (String result : matches) {
        text = result;
    }

    out.println(text);
    returnedText.setText(text);

}

@Override
public void onRmsChanged(float rmsdB) {
    Log.i(LOG_TAG, "onRmsChanged: " + rmsdB);

}

public static String getErrorText(int errorCode) {
    String message;
    switch (errorCode) {
        case SpeechRecognizer.ERROR_AUDIO:
            message = "Audio recording error";
            break;
        case SpeechRecognizer.ERROR_CLIENT:
            message = "Client side error";
            break;
        case SpeechRecognizer.ERROR_INSUFFICIENT_PERMISSIONS:
            message = "Insufficient permissions";
            break;
        case SpeechRecognizer.ERROR_NETWORK:
            message = "Network error";
            break;
        case SpeechRecognizer.ERROR_NETWORK_TIMEOUT:
            message = "Network timeout";
            break;
        case SpeechRecognizer.ERROR_NO_MATCH:
            message = "No match";
            break;
        case SpeechRecognizer.ERROR_RECOGNIZER_BUSY:
            message = "RecognitionService busy";
            break;
        case SpeechRecognizer.ERROR_SERVER:
            message = "error from server";
            break;
        case SpeechRecognizer.ERROR_SPEECH_TIMEOUT:
            message = "No speech input";
            break;
        default:
            message = "Didn't understand, please try again.";
            break;
    }
    return message;
}

public class ConnectPhoneTask extends AsyncTask<String,Void,Boolean> {

    @Override
    protected Boolean doInBackground(String... params) {
        boolean result = true;
        try {
            InetAddress serverAddr = InetAddress.getByName(params[0]);
            socket = new Socket(serverAddr, Constants.SERVER_PORT);//Open socket on server IP and port
        } catch (IOException e) {
            Log.e("remotedroid", "Error while connecting", e);
            result = false;
        }
        return result;
    }

    @Override
    protected void onPostExecute(Boolean result)
    {
        isConnected = result;
        Toast.makeText(context,isConnected?"Connected to server!":"Error while connecting",Toast.LENGTH_LONG).show();
        try {
            if(isConnected) {
                out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket
                        .getOutputStream())), true);

            }
        }catch (IOException e){
            Log.e("remotedroid", "Error while creating OutWriter", e);
            Toast.makeText(context,"Error while connecting",Toast.LENGTH_LONG).show();
        }
    }
}

}

Answer 1

Ensure that the out variable is initiated before it is being used. Looking at your code, use

if(isConnected && out!=null) {
    // Your code to use out
    // out.println(.......);
}

The above if condition will check that the variable is not null and also that the connection is already made.

In the class ConnectPhoneTask, onPostExecuted method is where the out variable is initiated, ensure that the connection is made with the phone.

//This is where the variable is initiated already in your code
out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket
                        .getOutputStream())), true);

So the out variable should only be used once after the connection is made.

See example below,

public void onSensorChanged(SensorEvent event) {
    float x = event.values[0];
    float y = event.values[1];

    textViewX.setText(Float.toString(x));
    textViewY.setText(Float.toString(y));

    Log.i(LOG_TAG, x+","+y);

    if(isConnected && out!=null)
        out.println(String.valueOf(x) + "," + String.valueOf(y));
}