如何修复 View Pager 2 FragmentManager 已经在执行事务？

问题描述

ViewPager2 由 IllegalStateException 引起 FragmentManager 已经在执行事务

复制崩溃：旋转屏幕时

如何修复 Viewpager2 FragmentManager 已经在执行事务？

完整源代码： https://github.com/stevdza-san/ViewPager2-with-Navigation-Component-TestApp

ViewPagerFragment.kt

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import com.test.zigmaster.databinding.FragmentViewPagerBinding


class ViewPagerFragment : Fragment() {
    var binding : FragmentViewPagerBinding?= null

    override fun onCreateView(
        inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?
    ): View {
        // Inflate the layout for this fragment
       // val view = inflater.inflate(R.layout.fragment_view_pager,container,false)

        binding = FragmentViewPagerBinding.inflate(inflater)


        val fragmentList = arraylistof<Fragment>(
            FirstScreen(),SecondScreen(),ThirdScreen()
        )

        val adapter = ViewPagerAdapter(
            fragmentList,requireActivity().supportFragmentManager,lifecycle
        )

        binding!!.viewPager.adapter = adapter

        return binding!!.root
    }

    override fun onDestroyView() {
        super.onDestroyView()
        binding=null
    }

}

ViewPagerAdapter.kt

import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager
import androidx.lifecycle.Lifecycle
import androidx.viewpager2.adapter.FragmentStateAdapter

class ViewPagerAdapter(
    list: ArrayList<Fragment>,fm: FragmentManager,lifecycle: Lifecycle
) : FragmentStateAdapter(fm,lifecycle) {

    private val fragmentList = list

    override fun getItemCount(): Int {
        return fragmentList.size
    }

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

fragment_view_pager.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.app_intro.ViewPagerFragment">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

FirstScreen.kt

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.viewpager2.widget.ViewPager2
import com.test.zigmaster.R
import com.test.zigmaster.databinding.FragmentFirstScreenBinding

class FirstScreen : Fragment() {

   private var binding : FragmentFirstScreenBinding?= null

    override fun onCreateView(
        inflater: LayoutInflater,savedInstanceState: Bundle?
    ): View {
        // Inflate the layout for this fragment
        binding = FragmentFirstScreenBinding.inflate(inflater)

        val viewPager =  activity?.findViewById<ViewPager2>(R.id.viewPager)

        binding!!.next.setonClickListener {
            viewPager?.currentItem = 1
        }

        return binding!!.root
    }

    override fun onDestroyView() {
        super.onDestroyView()
        binding=null
    }

解决方法

将 view.viewPager.adapter = adapter 更改为

 Handler(Looper.getMainLooper()).post {
        view.viewPager.adapter = adapter
    }

在https://github.com/stevdza-san/ViewPager2-with-Navigation-Component-TestApp/blob/master/app/src/main/java/com/jovanovic/stefan/mytestapp/onboarding/ViewPagerFragment.kt