Revert to deprecated BEHAVIOR_SET_USER_VISIBLE_HINT in TabAdapter

Also added comment explaining why

app/src/main/java/org/schabi/newpipe/fragments/detail/TabAdapter.java

@@ -2,6 +2,7 @@ package org.schabi.newpipe.fragments.detail;
 
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
@@ -10,16 +11,20 @@ import androidx.fragment.app.FragmentPagerAdapter;
 import java.util.ArrayList;
 import java.util.List;
 
-public class TabAdaptor extends FragmentPagerAdapter {
+public class TabAdapter extends FragmentPagerAdapter {
     private final List<Fragment> mFragmentList = new ArrayList<>();
     private final List<String> mFragmentTitleList = new ArrayList<>();
     private final FragmentManager fragmentManager;
 
-    public TabAdaptor(final FragmentManager fm) {
-        super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
+    public TabAdapter(final FragmentManager fm) {
+        // if changed to BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT => crash if enqueueing stream in
+        // the background and then clicking on it to open VideoDetailFragment:
+        // "Cannot setMaxLifecycle for Fragment not attached to FragmentManager"
+        super(fm, BEHAVIOR_SET_USER_VISIBLE_HINT);
         this.fragmentManager = fm;
     }
 
+    @NonNull
     @Override
     public Fragment getItem(final int position) {
         return mFragmentList.get(position);
@@ -57,7 +62,7 @@ public class TabAdaptor extends FragmentPagerAdapter {
     }
 
     @Override
-    public int getItemPosition(final Object object) {
+    public int getItemPosition(@NonNull final Object object) {
         if (mFragmentList.contains(object)) {
             return mFragmentList.indexOf(object);
         } else {
@@ -82,7 +87,9 @@ public class TabAdaptor extends FragmentPagerAdapter {
     }
 
     @Override
-    public void destroyItem(final ViewGroup container, final int position, final Object object) {
+    public void destroyItem(@NonNull final ViewGroup container,
+                            final int position,
+                            @NonNull final Object object) {
         fragmentManager.beginTransaction().remove((Fragment) object).commitNowAllowingStateLoss();
     }
 

app/src/main/java/org/schabi/newpipe/fragments/detail/VideoDetailFragment.java

@@ -244,7 +244,7 @@ public class VideoDetailFragment
 
     private AppBarLayout appBarLayout;
     private ViewPager viewPager;
-    private TabAdaptor pageAdapter;
+    private TabAdapter pageAdapter;
     private TabLayout tabLayout;
     private FrameLayout relatedStreamsLayout;
 
@@ -752,7 +752,7 @@ public class VideoDetailFragment
 
         appBarLayout = rootView.findViewById(R.id.appbarlayout);
         viewPager = rootView.findViewById(R.id.viewpager);
-        pageAdapter = new TabAdaptor(getChildFragmentManager());
+        pageAdapter = new TabAdapter(getChildFragmentManager());
         viewPager.setAdapter(pageAdapter);
         tabLayout = rootView.findViewById(R.id.tablayout);
         tabLayout.setupWithViewPager(viewPager);

app/src/main/java/org/schabi/newpipe/fragments/list/comments/CommentsFragment.java

@@ -26,8 +26,6 @@ import io.reactivex.disposables.CompositeDisposable;
 public class CommentsFragment extends BaseListInfoFragment<CommentsInfo> {
     private CompositeDisposable disposables = new CompositeDisposable();
 
-    private boolean mIsVisibleToUser = false;
-
     public static CommentsFragment getInstance(final int serviceId, final  String url,
                                                final String name) {
         final CommentsFragment instance = new CommentsFragment();
@@ -39,12 +37,6 @@ public class CommentsFragment extends BaseListInfoFragment<CommentsInfo> {
     // LifeCycle
     //////////////////////////////////////////////////////////////////////////*/
 
-    @Override
-    public void setUserVisibleHint(final boolean isVisibleToUser) {
-        super.setUserVisibleHint(isVisibleToUser);
-        mIsVisibleToUser = isVisibleToUser;
-    }
-
     @Override
     public void onAttach(final Context context) {
         super.onAttach(context);
@@ -92,7 +84,7 @@ public class CommentsFragment extends BaseListInfoFragment<CommentsInfo> {
     public void handleResult(@NonNull final CommentsInfo result) {
         super.handleResult(result);
 
-        AnimationUtils.slideUp(getView(), 120, 150, 0.06f);
+        AnimationUtils.slideUp(requireView(), 120, 150, 0.06f);
 
         if (!result.getErrors().isEmpty()) {
             showSnackBarError(result.getErrors(), UserAction.REQUESTED_COMMENTS,