ViewPager：重新创建活动后，一个片段保持空虚

Question

我有一个带有两个片段的ViewPager。两者都加载后，

• 我会更改语言或应用程序的黑暗模式，
• 因此重新创建了基础活动（我认为这是触发错误的原因），
• 然后我导航回ViewPager，
• 这是两个片段之一（然后是两个片段之一）（总是第一个）只是空。它没有加载，没有响应点击，也无能为力。重新创建另一个人，就像魅力一样。

---

包含ViewPager的片段：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    mBinding = MyFragmentBinding.inflate(inflater, container, false);
    View view = mBinding.getRoot();

    viewPager = mBinding.pageTabber;

    pageAdapter = new MyPageAdapter(getActivity(), getActivity(), this);
    viewPager.setAdapter(pageAdapter);

    new TabLayoutMediator(mBinding.tabLayout, viewPager,
            new TabLayoutMediator.TabConfigurationStrategy() {
                @Override
                public void onConfigureTab(@NonNull TabLayout.Tab tab, int position) {
                    if (getContext() == null) {
                        return;
                    }
                    switch (position) {
                        case 0:
                            tab.setText(...);
                            break;

                        case 1:
                            tab.setText(...);
                            break;

                        default:
                            break;
                    }
                }
            }
    ).attach();

    viewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
        public void onPageScrollStateChanged(int state) {}
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}

        public void onPageSelected(int position) {
            // ...
        }
    });
}

mypageadapter：

import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class MyPageAdapter extends FragmentStateAdapter {

    private int nr = -1;
    private Context context;

    private static final int FRAGMENT_COUNT = 2;

    public MyPageAdapter(@NonNull FragmentActivity fm, Context context) {
        super(fm);
        this.context = context;
    }

    public MyPageAdapter(@NonNull FragmentActivity fm, int nr, Context context) {
        super(fm);
        this.nr = nr;
        this.context = context;
    }

    @Override
    public long getItemId(int position) {
        return super.getItemId(position);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        if (position == 0) {
            return new Fragment1();

        } else {
            return new Fragment2();
        }
    }

    @Override
    public int getItemCount() {
        return FRAGMENT_COUNT;
    }
}

我已将日志添加到片段的生命周期中，以便理解它。 包装fragments是包含ViewPager的片段。

// navigating to the fragment that contains the ViewPager
2022-07-03 12:34:02.502 23112-23112/Log: WrappingFragment: onAttach
2022-07-03 12:34:02.502 23112-23112/Log: WrappingFragment: onCreateView
2022-07-03 12:34:02.624 23112-23112/Log: WrappingFragment: onResume
2022-07-03 12:34:02.675 23112-23112/Log: Fragment1: onAttach
2022-07-03 12:34:02.676 23112-23112/Log: Fragment1: onCreateView
2022-07-03 12:34:02.737 23112-23112/Log: Fragment1: onResume


// in the ViewPager: navigating to Fragment2
2022-07-03 12:34:32.114 23112-23112/Log: Fragment2: onAttach
2022-07-03 12:34:32.114 23112-23112/Log: Fragment2: onCreateView
2022-07-03 12:34:32.416 23112-23112/Log: Fragment1: onPause
2022-07-03 12:34:32.416 23112-23112/Log: Fragment2: onResume


// navigating to a different activity in order to change the dark mode setting
2022-07-03 12:34:53.209 23112-23112/Log: WrappingFragment: onPause
2022-07-03 12:34:54.594 23112-23112/Log: Fragment2: onPause
2022-07-03 12:34:55.368 23112-23112/Log: WrappingFragment: onStop
2022-07-03 12:34:55.368 23112-23112/Log: Fragment1: onStop
2022-07-03 12:34:55.368 23112-23112/Log: Fragment2: onStop


// Changing the dark mode setting
2022-07-03 12:35:09.957 23112-23112/Log: WrappingFragment: onDestroyView
2022-07-03 12:35:09.957 23112-23112/Log: WrappingFragment: onDestroy
2022-07-03 12:35:09.957 23112-23112/Log: WrappingFragment: onDetach
2022-07-03 12:35:09.958 23112-23112/Log: Fragment1: onDestroyView
2022-07-03 12:35:09.958 23112-23112/Log: Fragment1: onDestroy
2022-07-03 12:35:09.959 23112-23112/Log: Fragment1: onDetach
2022-07-03 12:35:09.959 23112-23112/Log: Fragment2: onCreateView
2022-07-03 12:35:09.959 23112-23112/Log: Fragment2: onCreateView
2022-07-03 12:35:09.960 23112-23112/Log: Fragment2: onDetach
2022-07-03 12:35:09.987 23112-23112/Log: WrappingFragment: onAttach
2022-07-03 12:35:09.987 23112-23112/Log: Fragment1: onAttach
2022-07-03 12:35:09.988 23112-23112/Log: Fragment2: onAttach
2022-07-03 12:35:10.165 23112-23112/Log: WrappingFragment: onCreateView
2022-07-03 12:35:10.226 23112-23112/Log: Fragment1: onCreateView
2022-07-03 12:35:10.246 23112-23112/Log: Fragment2: onCreateView
2022-07-03 12:35:10.360 23112-23112/Log: Fragment2: onResume
2022-07-03 12:35:10.378 23112-23112/Log: Fragment2: onPause
2022-07-03 12:35:10.389 23112-23112/Log: WrappingFragment: onStop
2022-07-03 12:35:10.389 23112-23112/Log: Fragment1: onStop
2022-07-03 12:35:10.390 23112-23112/Log: Fragment2: onStop


// navigating back to the other activity (where all the fragments are in)
2022-07-03 12:50:22.049 23112-23112/Log: Fragment2: onResume
2022-07-03 12:50:22.087 23112-23112/Log: WrappingFragment: onStop
2022-07-03 12:50:22.087 23112-23112/Log: WrappingFragment: onDestroyView
2022-07-03 12:50:22.088 23112-23112/Log: WrappingFragment: onDestroy
2022-07-03 12:50:22.088 23112-23112/Log: WrappingFragment: onDetach


// navigating to the Fragment that contains the ViewPager (the viewpager starts in fragment2 as when I navigated out of this, we were in fragment2)
2022-07-03 12:50:37.822 23112-23112/Log: WrappingFragment: onAttach
2022-07-03 12:50:37.822 23112-23112/Log: WrappingFragment: onCreateView
2022-07-03 12:50:37.880 23112-23112/Log: WrappingFragment: onResume


// in the ViewPager going to Fragment1
2022-07-03 12:50:47.322 23112-23112/Log: Fragment2: onPause
2022-07-03 12:50:47.323 23112-23112/Log: Fragment1: onResume

但是我只是找不到错误。