Make scrollbars flash from code (like iOS flashScrollIndicators)

Question

In iOS there is the flashScrollIndicators method on the UIScrollView class that allows you to make the scrollbars flash briefly like they do when the view is first displayed.

I can't find in the documentation the Android equivalent to this, to make the scrollbars flash briefly on scrollable views (ScrollView, ListView, WebView, etc). I tried issuing a requestLayout() on the view, but that didn't work.

The reason I'm asking this, is because my views are contained in a ViewPager and when the user swipes to a different page, that page has often already been drawn and doesn't flash the scrollbars.

answering my own question here

The method is called awakenScrollBars and is defined in the View class. Unfortunately the method is protected so you will have to subclass the ScrollView, ListView or whatever view you want to have its scrollbars flashed.

Alternatively, the public methods scrollTo and scrollBy also flash the scrollbars but only if the scroll position has actually changed. So f.e. listView.scrollBy(0,0) won't work and listView.scrollTo(0,0) only works if the view wasn't already at the top.

If are unable to subclass the view, the following seems to work, although admittedly it's kind of a hack:

view.setVisibility(View.INVISIBLE);
view.setVisibility(View.VISIBLE);

Setting the view to invisible and then immediately to visible again doesn't seem to cause any redraws, but it has the side-effect of triggering the scrollbar flashing.

Answer 1

I solved a similar problem by forcing it to scroll up and down directly after each other.

scrollView.scrollBy(0, 1);
scrollView.scrollBy(0, -1);

This causes the scroll view to show the vertical scrollbar, unless there is nothing to scroll.