ViewPager2 setCurrentItem bug workaround?

Question

This reported bug is causing me problems; https://issuetracker.google.com/issues/183847283

When combined with FragmentStateAdapter, ViewPager2.setCurrentItem doesn't always work. The TabLayout correctly changes (if you have one), but the ViewPager2 itself doesn't show the correct page.

Has anyone found a workaround?

Answer 1

I had a similar problem, if not the same. The solution was to change fragments/tabs/pages in a specific order.

1. The FragmentStateAdapter should be notified first of the change to the fragment.
2. The TabLayout should then call selectTab under a post
3. The ViewPager should then call setCurrentItem under a post, inside the TabLayouts post to selectTab.

This may be overkill but it worked for me.

Example

//or some other notify depending on your use case.
fragmentStateAdapter.notifyItemInserted(position);

tabLayout.post(()->{
     tabLayout.selectTab(tabLayout.getTabAt(position));
     viewPager2.post(()->{
          viewPager2.setCurrentItem(position);
          //I noticed on older devices like API 19
          //the viewPager wouldn't complete transformations
          //so we call this.
          viewPager2.requestTransform();
     });
});