private void peekDrawerInvalidate() {
        if (mPeekScroller.computeScrollOffset()) {
            final int oldX = (int) mOffsetPixels;
            final int x = mPeekScroller.getCurrX();
            if (x != oldX) setOffsetPixels(x);

            if (!mPeekScroller.isFinished()) {
                postOnAnimation(mPeekRunnable);
                return;

            } else if (mPeekDelay > 0) {
                mPeekStartRunnable = new Runnable() {
                    @Override
                    public void run() {
                        startPeek();
                    }
                };
                postDelayed(mPeekStartRunnable, mPeekDelay);
            }
        }

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