@Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
    }
Sentinel value for no current active pointer.
Used by {@link #mActivePointerId}.
app/src/main/java/home/smart/fly/animations/widget/NestedScrollView.java