Fix scrolling to correct comment after closing replies

app/src/main/java/org/schabi/newpipe/MainActivity.java

@@ -44,6 +44,7 @@ import android.widget.FrameLayout;
 import android.widget.Spinner;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.app.AppCompatActivity;
@@ -51,6 +52,7 @@ import androidx.core.app.ActivityCompat;
 import androidx.core.view.GravityCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentContainerView;
 import androidx.fragment.app.FragmentManager;
 import androidx.preference.PreferenceManager;
 
@@ -64,6 +66,7 @@ import org.schabi.newpipe.databinding.ToolbarLayoutBinding;
 import org.schabi.newpipe.error.ErrorUtil;
 import org.schabi.newpipe.extractor.NewPipe;
 import org.schabi.newpipe.extractor.StreamingService;
+import org.schabi.newpipe.extractor.comments.CommentsInfoItem;
 import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.services.peertube.PeertubeInstance;
 import org.schabi.newpipe.fragments.BackPressable;
@@ -561,9 +564,7 @@ public class MainActivity extends AppCompatActivity {
                 // Expand DetailsFragment if CommentRepliesFragment was opened
                 // and no other CommentRepliesFragments are on top of the back stack
                 // to show the top level comments again.
-                final FragmentManager.BackStackEntry bse = fm.getBackStackEntryAt(
+                openDetailFragmentFromCommentReplies(fm, false);
-                        fm.getBackStackEntryCount() - 2); // current fragment is at the top
-                openDetailFragmentFromCommentReplies(fm, bse);
             }
 
         } else {
@@ -646,10 +647,7 @@ public class MainActivity extends AppCompatActivity {
             // Expand DetailsFragment if CommentRepliesFragment was opened
             // and no other CommentRepliesFragments are on top of the back stack
             // to show the top level comments again.
-            fm.popBackStackImmediate();
+            openDetailFragmentFromCommentReplies(fm, true);
-            final FragmentManager.BackStackEntry bse = fm.getBackStackEntryAt(
-                    fm.getBackStackEntryCount() - 1);
-            openDetailFragmentFromCommentReplies(fm, bse);
         } else if (!NavigationHelper.tryGotoSearchFragment(fm)) {
             // If search fragment wasn't found in the backstack go to the main fragment
             NavigationHelper.gotoMainFragment(fm);
@@ -850,38 +848,64 @@ public class MainActivity extends AppCompatActivity {
 
     private void openDetailFragmentFromCommentReplies(
             @NonNull final FragmentManager fm,
-            @NonNull final FragmentManager.BackStackEntry bse) {
+            final boolean popBackStack
-        if (!CommentRepliesFragment.TAG.equals(bse.getName())) {
+    ) {
-            final CommentRepliesFragment commentRepliesFragment =
+        // obtain the name of the fragment under the replies fragment that's going to be popped
-                    (CommentRepliesFragment) fm.findFragmentByTag(
+        @Nullable final String fragmentUnderEntryName;
-                            CommentRepliesFragment.TAG);
+        if (fm.getBackStackEntryCount() < 2) {
-            final BottomSheetBehavior bsb = BottomSheetBehavior
+            fragmentUnderEntryName = null;
-                    .from(mainBinding.fragmentPlayerHolder);
+        } else {
-            bsb.addBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
+            fragmentUnderEntryName = fm.getBackStackEntryAt(fm.getBackStackEntryCount() - 2)
-                @Override
+                    .getName();
-                public void onStateChanged(@NonNull final View bottomSheet,
-                                           final int newState) {
-                    if (newState == BottomSheetBehavior.STATE_EXPANDED) {
-                        final Fragment detailFragment = fm.findFragmentById(
-                                R.id.fragment_player_holder);
-                        if (detailFragment instanceof VideoDetailFragment
-                                && commentRepliesFragment != null) {
-                            // should always be the case
-                            ((VideoDetailFragment) detailFragment).scrollToComment(
-                                    commentRepliesFragment.getCommentsInfoItem());
-                        }
-                        bsb.removeBottomSheetCallback(this);
-                    }
-                }
-
-                @Override
-                public void onSlide(@NonNull final View bottomSheet,
-                                    final float slideOffset) {
-                    // not needed, listener is removed once the sheet is expanded
-                }
-            });
-            bsb.setState(BottomSheetBehavior.STATE_EXPANDED);
         }
+
+        // the root comment is the comment for which the user opened the replies page
+        @Nullable final CommentRepliesFragment repliesFragment =
+                (CommentRepliesFragment) fm.findFragmentByTag(CommentRepliesFragment.TAG);
+        @Nullable final CommentsInfoItem rootComment =
+                repliesFragment == null ? null : repliesFragment.getCommentsInfoItem();
+
+        // sometimes this function pops the backstack, other times it's handled by the system
+        if (popBackStack) {
+            fm.popBackStackImmediate();
+        }
+
+        // only expand the bottom sheet back if there are no more nested comment replies fragments
+        // stacked under the one that is currently being popped
+        if (CommentRepliesFragment.TAG.equals(fragmentUnderEntryName)) {
+            return;
+        }
+
+        final BottomSheetBehavior<FragmentContainerView> behavior = BottomSheetBehavior
+                .from(mainBinding.fragmentPlayerHolder);
+        // do not return to the comment if the details fragment was closed
+        if (behavior.getState() == BottomSheetBehavior.STATE_HIDDEN) {
+            return;
+        }
+
+        // scroll to the root comment once the bottom sheet expansion animation is finished
+        behavior.addBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
+            @Override
+            public void onStateChanged(@NonNull final View bottomSheet,
+                                       final int newState) {
+                if (newState == BottomSheetBehavior.STATE_EXPANDED) {
+                    final Fragment detailFragment = fm.findFragmentById(
+                            R.id.fragment_player_holder);
+                    if (detailFragment instanceof VideoDetailFragment && rootComment != null) {
+                        // should always be the case
+                        ((VideoDetailFragment) detailFragment).scrollToComment(rootComment);
+                    }
+                    behavior.removeBottomSheetCallback(this);
+                }
+            }
+
+            @Override
+            public void onSlide(@NonNull final View bottomSheet, final float slideOffset) {
+                // not needed, listener is removed once the sheet is expanded
+            }
+        });
+
+        behavior.setState(BottomSheetBehavior.STATE_EXPANDED);
     }
 
     private boolean bottomSheetHiddenOrCollapsed() {

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

@@ -1014,10 +1014,16 @@ public final class VideoDetailFragment
     }
 
     public void scrollToComment(final CommentsInfoItem comment) {
-        final Fragment fragment = pageAdapter.getItem(
+        final int commentsTabPos = pageAdapter.getItemPositionByTitle(COMMENTS_TAB_TAG);
-                pageAdapter.getItemPositionByTitle(COMMENTS_TAB_TAG));
+        final Fragment fragment = pageAdapter.getItem(commentsTabPos);
-        if (fragment instanceof CommentsFragment) {
+        if (!(fragment instanceof CommentsFragment)) {
-            ((CommentsFragment) fragment).scrollToComment(comment);
+            return;
+        }
+
+        // unexpand the app bar only if scrolling to the comment succeeded
+        if (((CommentsFragment) fragment).scrollToComment(comment)) {
+            binding.appBarLayout.setExpanded(false, false);
+            binding.viewPager.setCurrentItem(commentsTabPos, false);
         }
     }
 

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

@@ -111,7 +111,13 @@ public class CommentsFragment extends BaseListInfoFragment<CommentsInfoItem, Com
         return ItemViewMode.LIST;
     }
 
-    public void scrollToComment(final CommentsInfoItem comment) {
+    public boolean scrollToComment(final CommentsInfoItem comment) {
-        itemsList.scrollToPosition(infoListAdapter.getItemsList().indexOf(comment));
+        final int position = infoListAdapter.getItemsList().indexOf(comment);
+        if (position < 0) {
+            return false;
+        }
+
+        itemsList.scrollToPosition(position);
+        return true;
     }
 }