I have no experience with OpenGL nor accelerometer, but swipe (called fling in Android's API) is not hard to achieve. First thing you need when making such a custom View, is implementing a GestureDetector and call its onTouchEvent() in your view's onTouchEvent()
GestureDetector mGD = new GestureDetector(getContext(),
new SimpleOnGestureListener() {
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
// beware, it can scroll to infinity
scrollBy((int)distanceX, (int)distanceY);
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float vX, float vY) {
mScroller.fling(getScrollX(), getScrollY(),
-(int)vX, -(int)vY, 0, (int)mMaxScrollX, 0, (int)mMaxScrollY);
invalidate(); // don't remember if it's needed
return true;
}
@Override
public boolean onDown(MotionEvent e) {
if(!mScroller.isFinished() ) { // is flinging
mScroller.forceFinished(true); // to stop flinging on touch
}
return true; // else won't work
}
});
@Override
public boolean onTouchEvent(MotionEvent event) {
return mGD.onTouchEvent(event);
}
While OnGestureListener.onScroll() calls directly View.scrollBy(), for the onFling() method you'll need a Scroller.
Scroller is a simple object that, as reference says, encapsulates scrolling. It can be used for continuous scrolling or to react to flings. Scroller.fling() begin a "simulation" of fling scroll inside itself, and by watching it you can copy its smoothness with a continuous redrawing animation:
@Override
protected void onDraw(Canvas canvas) {
// ....your drawings....
// scrollTo invalidates, so until animation won't finish it will be called
// (used after a Scroller.fling() )
if(mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
}
}
that is, until animation is running, calculate the point we reached and scroll there.
As a last note: remember to return true in your OnGestureListener.onDown(), even if you don't want to do anything on down, or it won't work.
And be careful, because Scroller in Android 2.2 has a bug for which the fling animation will not actually end even if it reaches the limits you passed as arguments (yet computed offset respects them, so it won't actually move).
