Proximity Sensor

<uses-feature android:name="android.hardware.sesor.proximity"    android:required="true" />

public class MainActivity extends AppCompatActivity {

    private SensorManager sensorManager;
    private Sensor proximitySensor;
    private SensorEventListener proximitySensorListener;

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
        proximitySensor = sensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);

        if (proximitySensor == null) {
            Toast.makeText(this, "Proximity sensor is not available !", Toast.LENGTH_LONG).show();
            finish();
        }

        proximitySensorListener = new SensorEventListener() {
            @Override            public void onSensorChanged(SensorEvent sensorEvent) {
                if (sensorEvent.values[0] < proximitySensor.getMaximumRange()) {
                    getWindow().getDecorView().setBackgroundColor(Color.RED);
                } else {
                   // setContentView();                   // getWindow().getDecorView().setBackgroundColor(Color.GREEN);                }
            }

            @Override            public void onAccuracyChanged(Sensor sensor, int i) {

            }
        };

        sensorManager.registerListener(proximitySensorListener, proximitySensor,
                2*1000*1000);
    }

    @Override    protected void onPause() {
        super.onPause();
        sensorManager.unregisterListener(proximitySensorListener);
    }
}