ViewPager2拍照/授权返回后自动跳页问题求助

我正在开发一个基于ViewPager2的项目，其中一个TakePictureFragment需要申请相机权限并拍摄照片，拍摄完成后本应在该Fragment中显示照片，但返回该Fragment时会自动跳转到下一页且无任何报错，请问如何实现仅在用户点击按钮时才执行页面跳转？

ViewActivity 代码 #

class ViewActivity : BaseActivity() {

   private lateinit var binding: ActivityView
   private lateinit var adapter: PagerAdapter

   override fun onCreate(savedInstanceState: Bundle?){ 
      super.onCreate(savedInstanceState)

      adapterViewPager()
      goToNextPage()
      goToBackPage()
   }

   private fun adapterViewPager(){
      adapter = ViewAdapter(supportFragmentManager, lifecycle)

      adapter.addFragment(HelloWordFragment())
      adapter.addFragment(TakePictureFragment())
      adapter.addFragment(LoginFragment())
      adapter.addFragment(ConfirmEmailFragment())

      binding.viewPager.adapter = adapter
   }

   private fun goToNextPage(){
      binding.viewPager.setCurrentItem(binding.viewPager.currentItem + 1)
   }
 
   private fun goToBackPage(){
      binding.viewPager.setCurrentItem(binding.viewPager.currentItem - 1)
   }
}

PagerAdapter（Java）代码 #

public final class PagerAdapter extends FragmentStateAdapter {

   private final List<Fragment> fragList = new ArrayList<>() 

   ViewAdapter(FragmentManager fm, Lifecycle lf){
      super(fm, lf)
   }

   public Fragment createViewPager(int position){
      return fragList.get(position)
   }

   public void addFragment(Fragment fragment){
      fragList.add(fragment)
   }
}

TakePictureFragment 代码 #

class TakePictureFragment : Fragment() {
   
   private lateinit var binding : FragmentTakePicture

   override fun onCreateView(
      inflater: LayoutInflater, container: ViewGroup?,
      savedInstanceState: Bundle?
   ): View {
      binding = FragmentTakePicture.inflate(layoutInflater, container, false)
      return binding.root
   }

   override fun onViewCreated(view: View, savedInstanceState: Bundle?){ 
      super.onViewCreated(view, savedInstanceState)

      next()
   }

   override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
      super.onActivityResult(requestCode, resultCode, data)
      if (resultCode == RESULT_OK) {
            when (requestCode) {
                REQUEST_IMAGE_CAPTURE -> {...}
                REQUEST_GALLERY_IMAGE -> {...}
            }
      }
   }

   private fun next(){
      binding.buttonNext.setOnClickListener {
         parent.goToNextPage()
      }
   }
}

问题根源 #

1. ViewActivity的onCreate方法中直接调用了goToNextPage()和goToBackPage()，这会导致Activity启动时自动执行页面跳转；当从相机返回时，若Activity发生重建，onCreate会再次执行，触发自动跳页。
2. Java版PagerAdapter未正确重写FragmentStateAdapter的必要方法，自定义的createViewPager无法被ViewPager2识别，可能引发Fragment生命周期异常，间接导致页面跳转问题。

修复步骤 #

1. 移除自动跳转的初始化代码
   在ViewActivity的onCreate中删除直接调用goToNextPage()和goToBackPage()的语句，仅保留ViewPager初始化逻辑：

   override fun onCreate(savedInstanceState: Bundle?){ 
      super.onCreate(savedInstanceState)
   
      adapterViewPager()
      // 移除 goToNextPage() 和 goToBackPage() 调用
   }
   

2. 修正PagerAdapter的核心方法
   重写FragmentStateAdapter要求的createFragment和getItemCount方法，并添加数据更新通知：

   public final class PagerAdapter extends FragmentStateAdapter {
   
      private final List<Fragment> fragList = new ArrayList<>();
   
      public PagerAdapter(FragmentManager fm, Lifecycle lf){
         super(fm, lf);
      }
   
      @NonNull
      @Override
      public Fragment createFragment(int position){
         return fragList.get(position);
      }
   
      @Override
      public int getItemCount() {
         return fragList.size();
      }
   
      public void addFragment(Fragment fragment){
         fragList.add(fragment);
         notifyDataSetChanged(); // 通知适配器更新数据
      }
   }
   

3. 确保跳转逻辑仅绑定按钮点击
   优化TakePictureFragment中获取Activity的方式，避免空指针，确保只有点击按钮时才触发跳转：

   private fun next(){
      binding.buttonNext.setOnClickListener {
         (activity as? ViewActivity)?.goToNextPage()
      }
   }
   

4. 保存并恢复ViewPager页面状态
   在ViewActivity中保存当前页面位置，避免Activity重建后页面重置：

   override fun onSaveInstanceState(outState: Bundle) {
      super.onSaveInstanceState(outState)
      outState.putInt("current_page", binding.viewPager.currentItem)
   }
   
   override fun onCreate(savedInstanceState: Bundle?){ 
      super.onCreate(savedInstanceState)
   
      adapterViewPager()
      // 恢复之前的页面位置
      savedInstanceState?.let {
         binding.viewPager.setCurrentItem(it.getInt("current_page"), false)
      }
   }
   

内容的提问来源于stack exchange，提问作者ShawDD