How are sensors used in Android games?

Question

How do people create games which make the object move when we turn or rotate our phone in different directions (accelerating a car, for example)? Do they use readings from the accelerometer and gyroscope or do they use OpenGL in Android?

Answer 1

They are likely using the accelerometer, because it is widely available on a large variety of devices.

You might want to take a look at this tutorial: http://blog.androgames.net/85/android-accelerometer-tutorial/

And here's a demo of the accelerometer feature from Google: http://developer.android.com/resources/samples/AccelerometerPlay/src/com/example/android/accelerometerplay/AccelerometerPlayActivity.html

Answer 2

This example shows a simple calculation for the 3 directions value
pitch, orientation and azimuth.

if(SensorManager.getRotationMatrix(R, null, AccelerometerValues_last, MagneticFieldValues_last))
{
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_Y, SensorManager.AXIS_MINUS_X, remapR);
SensorManager.getOrientation(remapR, orientationValues);

Matrix.multiplyMV(orientationVector, 0, remapR, 0, sZVector, 0);
pitch = (float) (-Math.atan2(orientationVector[1], orientationVector[2]) * RADIANS_TO_DEGREES);

Matrix.multiplyMV(orientationVector, 0, remapR, 0, sZVector, 0);
orientation = (float) (-Math.atan2(orientationVector[0], orientationVector[1]) * RADIANS_TO_DEGREES);

Matrix.invertM(remapR_inv, 0, remapR, 0);
Matrix.multiplyMV(azimuthVector, 0, remapR_inv, 0, sZVector, 0);
azimuth = (float) (180 + Math.atan2(azimuthVector[0], azimuthVector[1]) * RADIANS_TO_DEGREES);
}     

The complete code in the article How to use Android sensors?. FYI.