Android ScrollView jumps up after changing child element visibility

I have a ScrollView that contains elements with visibility set to View.GONE by default. The problem is that whenever this visibility changes from View.GONE to View.VISIBLE, scroll jumps up as it is shown on second picture: https://i.imgur.com/WmRc4M2.png

The red box represents current scroll position, blue rectangle is an element which visibility is changed, and green rectangle is some element (for example button) that I can refer to. I want my ScrollView to work as it is shown on third picture. If green button is on the screen, it should also be visible on screen after displaying new element (the blue one) above it. Any ideas how can I achieve it?

Answer

well, it behaves exacly as it should – scroll position is on e.g. 200px from top and this doesn’t change when new item changes its visibility

you should scroll by yourself to proper (new) point, use scrollTo method – measure height of this new View and call scrollView.scrollTo(0, currentScrollY + heightOfNewView)

be aware that when you change visibility then you can’t call above scrollTo just one line below, you have to wait for this View being measured and drawn. so you should call scrollTo in e.g.

visibilityChangedView.setVisibility(View.VISIBLE);
visibilityChangedView.post(new Runnable() {

        // this will be called when visibilityChangedView won't have
        // any pending tasks to do, but we just changed visibility,
        // so at first view will be measured and drawn, after that
        // below run() method will be called

        @Override
        public void run() {
            int heightOfNewView = visibilityChangedView.getMeasuredHeight();
            int currentScrollY = scrollView.getScrollY();
            scrollView.scrollTo(0, currentScrollY + heightOfNewView);
        }
);

there is a chance that this automatic scroll will be visible to user as quick jump – at first whole view will be drawn as #2 and after split second/one frame it will redraw at new position like #3. I don’t know how your content is built (rest of childs in Scrollview), but I suspect that this should be RecyclerView or at least ListView with proper Adapter, not ScrollView with fixed layout