How to synchronize two scrollview in Android?

Question

I have two horizontal scrollview, and want to keep them always at the same position / distance. If user scrolls one, need to scroll programmatically the other. The challenge is, that an infinite loop will occur. One will raise the other, other will raise first. How can I set a state, indicate that a user initiated scroll is still in progress? So other scrollview should not execute the programmatic scroll.

One of them is a HorizontalScrollView other is a RecyclerView.

Tried solutions like below, without any success:

    horizontalScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {

        @Override
        public void onScrollChanged() {

            if (programmaticScrollEnable) {
                programmaticScrollEnable = false;
                // do programmatic scrolling here
                programmaticScrollEnable = true;
            }
        }
    });

Tried to change state in onScrollStateChanged method:

            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);

                /*if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    MainActivity.programmaticScrollEnable = true;
                }*/
            }

Answer 1

Try this...

horizontalScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {

    @Override
    public void onScrollChanged() {

   recyclerView.scrollTo(horizontalScrollView.scrollTo(horizontalScrollView.getScrollX(), 0);

    }
});