android app blocks device from going into sleep/stand by mode

gistfile1.java

public class MyActivity extends Activity { 

	// define the wakeLock as attribute
	PowerManager.WakeLock wakeLock ;
	@Override
	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
		wakeLock = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, "tag");
		wakeLock.acquire();
	}
	@Override
	protected void onDestroy() {

		super.onDestroy();
		wakeLock.release();
	}
	@Override
	public void onResume() {

		super.onResume();
		wakeLock.acquire();
	}
	@Override
	public void onPause() {

		super.onResume();
		wakeLock.release();
	}
}