Android - Getting MotionSensor fails (NullPointer)

Question

I am currently trying to implement a ScrollView whereby I want the included ImageView to be scrolled through a RotationVectorSensor and a SensorEventListener.

This is my code so far:

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.util.Log;
import android.view.Menu;
import android.widget.HorizontalScrollView;
import android.widget.Toast;


public class MainActivity extends Activity implements SensorEventListener {

private SensorManager sensorManager;
private Sensor sensor;
private HorizontalScrollView scrollView;

private String TAG = MainActivity.class.getSimpleName();

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

    sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    sensor = sensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);

    if (sensor != null) {
        sensorManager.registerListener(this, sensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        Log.d(TAG, "Sensor found.");
    } else {
        Log.e(TAG, "Sensor NOT found.");
        Toast.makeText(this, "ROTATION_VECTOR Sensor not found",
                Toast.LENGTH_LONG).show();
        finish();
    }
    scrollView = (HorizontalScrollView) findViewById(R.id.panoramaScrollView);
    Log.d(TAG, "Panorama Scroll View found.");
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // TODO Auto-generated method stub

}

@Override
public void onSensorChanged(SensorEvent event) {
    Toast.makeText(this, "rotating Yippi!", Toast.LENGTH_LONG).show();
    if (event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR) {
        final float angle = event.values[2];
        scrollView.post(new Runnable() { 
            public void run() {
                if (scrollView != null) {
                    scrollView.scrollTo((int)angle, scrollView.getBottom());
                    Log.d(TAG, "scrollTo executed.");
                }
            } 
        });
    }

}


@Override
public void onResume() {
    super.onResume();
    sensorManager.registerListener(this,  sensor, SensorManager.SENSOR_DELAY_NORMAL);
    Log.d(TAG, "SensorListener registered");
}


@Override
public void onPause() {
    super.onPause();
    if (sensor != null) {
        sensorManager.unregisterListener(this);
        Log.d(TAG, "SensorListener unregistered");
    }
}

}

The Nullpointer occurs directly after the sensor is initialized:

sensor = sensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);

Therefor the app exits and prints: "Sensor NOT found"...

Is there anything I've forgotten?
Thanks in advance!

Answer 1

I found the solution. The following lines were missing in the android manifest:

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_MOCK_LOCATION"/>