@Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        if (mDragViewResId != -1) {
            setDragView(findViewById(mDragViewResId));
        }
        if (mScrollableViewResId != -1) {
            setScrollableView(findViewById(mScrollableViewResId));
        }
    }
Set the Drag View after the view is inflated
app/src/main/java/home/smart/fly/animations/widget/slidepanel/SlidingUpPanelLayout.java