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).
