ViewPager2 FragmentManager is already executing transactions

一、概述

　　双层Fragment+ViewPager2嵌套来回切换导致如下异常

ViewPager2 FragmentManager is already executing transactions

二、解决办法

　　FragmentStateAdapter的默认构造函数使用的是：

 public FragmentStateAdapter(@NonNull FragmentActivity fragmentActivity) {
        this(fragmentActivity.getSupportFragmentManager(), fragmentActivity.getLifecycle());
    }

　　改成下面的：

calendarAdapter = CalendarEventAdapter(childFragmentManager,requireActivity().lifecycle)

class CalendarEventAdapter(fragmentManager: FragmentManager, lifecycle: Lifecycle) :
    FragmentStateAdapter(fragmentManager, lifecycle) {

    private var fragments = ArrayList<Fragment>()
    override fun getItemCount(): Int {
        return fragments.size
    }

    override fun createFragment(position: Int): Fragment {
        return fragments[position]
    }

    fun addFragment(fragment: Fragment) {
        fragments.apply {
            fragments.add(fragment)
        }
    }
}