Efficient Graphics and Portability with OpenGL ES - Pro Android Games - page 131

Figure 4-6. Icosahedron in action
Next, you simply check the number of active fingers. A value of 1 indicates a swipe,
2 indicates a pinch. If swiping, you call the setRotationSpeed(DX1) function with the delta
coordinates for the first finger in the X axis. If pinching, you call setPinch(DX1, DX2) with the
deltas for both fingers in the X coordinate.
When swiping to the left, the delta X value is negative; it is positive when swiping to
the right. In either case, you decrease or increase the rotation speed and call the view's
setRotationSpeed function, which invokes doSetRotation in C++.
if (DX < 0) {
speed -= 20;
} else {
speed += 20;
}
// clamp 0-100
if (speed < 0)
speed = 0;
if (speed > 100)
speed = 100;
view.setRotationSpeed(speed);