private void postAnimationInvalidate() {
        if (mScroller.computeScrollOffset()) {
            final int oldX = (int) mOffsetPixels;
            final int x = mScroller.getCurrX();

            if (x != oldX) setOffsetPixels(x);
            if (x != mScroller.getFinalX()) {
                postOnAnimation(mDragRunnable);
                return;
            }
        }

        completeAnimation();
    }
Callback when each frame in the drawer animation should be drawn.
menudrawer/src/net/simonvt/menudrawer/DraggableDrawer.java