This Android application demonstrates that setting the ViewPager2.offscreenPageLimit property to a value which is not the default OFFSCREEN_PAGE_LIMIT_DEFAULT value does not work as expected. It seems that more pages are created and retained than requested.
The application consists of an Activity class (MainActivity), a FragmentStateAdapter implementation (ViewPagerAdapter) and a Fragment class (PageFragment).
The ViewPager2.offscreenPageLimit property is set in MainActivity to 1 with the intention that only one page is retained either side of the currently visible page.
When the application is run, the ViewPager2 instance, which has an item count of ten, is initialised and only pages 1 and 2 are created, as expected. On tapping the second tab, only page 3 is created, as expected. However, on scrolling to a tab further away – e.g. the tenth tab – and tapping on it, pages 6, 7, 8, 9 and 10 are created.
The expectation was that only pages 9 and 10 would be created.
Another observation is that when page 3 is navigated to, the expectation is that only pages 2 to 4 will be retained and all other pages will be removed from the view hierarchy.
However, it seems that three pages either side of the currently visible page are retained at any given time despite the value of 1 which was passed into the ViewPager2.offscreenPageLimit property.
- See here for the associated bug report in IssueTracker.