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I have main fragment with ViewPager2 that contains other fragments. Each child fragment can open another detail fragment (main fragment replaced with details fragment). When I go back to from detail fragment, ViewPager2 recreate all child fragments.

If I try to reuse the adapter (FragmentStateAdapter):

if (pagerAdapter == null) {
        pagerAdapter = Adapter(this)
        binding.viewPager.adapter = pagerAdapter
    }else{
        binding.viewPager.adapter = pagerAdapter
    }

I got crash:

java.lang.IllegalArgumentException at androidx.core.util.Preconditions.checkArgument(Preconditions.java:38) at androidx.viewpager2.adapter.FragmentStateAdapter.onAttachedToRecyclerView(FragmentStateAdapter.java:132) at androidx.recyclerview.widget.RecyclerView.setAdapterInternal(RecyclerView.java:1209) at androidx.recyclerview.widget.RecyclerView.setAdapter(RecyclerView.java:1161) at androidx.viewpager2.widget.ViewPager2.setAdapter(ViewPager2.java:461)

How to avoid creating new fragment every time?

Pavel Poley
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1 Answers1

1

I solved the problem. I init adapter every time in onCreate, before I used lazy for init adapter.

logVP2.adapter = SummaryDetailsPageAdapter(childFragmentManager, lifecycle).apply { setData(args?.list) }

Volodymyr Zakharov
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  • this should be marked as the right answer. but why this happen really? what is the problem with lazy? – Mr.A2 Jun 08 '22 at 19:15