Tried to implement the feature

app/src/main/java/org/schabi/newpipe/database/playlist/model/PlaylistEntity.java

@@ -15,7 +15,7 @@ public class PlaylistEntity {
     public static final String PLAYLIST_ID = "uid";
     public static final String PLAYLIST_NAME = "name";
     public static final String PLAYLIST_THUMBNAIL_URL = "thumbnail_url";
-    //TODO: add field
+    public static final String PLAYLIST_THUMBNAIL_SET = "isThumbnailSet";
 
     @PrimaryKey(autoGenerate = true)
     @ColumnInfo(name = PLAYLIST_ID)
@@ -27,9 +27,14 @@ public class PlaylistEntity {
     @ColumnInfo(name = PLAYLIST_THUMBNAIL_URL)
     private String thumbnailUrl;
 
-    public PlaylistEntity(final String name, final String thumbnailUrl) {
+    @ColumnInfo(name = PLAYLIST_THUMBNAIL_SET)
+    private boolean isThumbnailSet;
+
+    public PlaylistEntity(final String name, final String thumbnailUrl,
+                          final boolean isThumbnailSet) {
         this.name = name;
         this.thumbnailUrl = thumbnailUrl;
+        this.isThumbnailSet = isThumbnailSet;
     }
 
     public long getUid() {
@@ -55,4 +60,13 @@ public class PlaylistEntity {
     public void setThumbnailUrl(final String thumbnailUrl) {
         this.thumbnailUrl = thumbnailUrl;
     }
+
+    public boolean getIsThumbnailSet() {
+        return isThumbnailSet;
+    }
+
+    public void setIsThumbnailSet(final boolean isThumbnailSet) {
+        this.isThumbnailSet = isThumbnailSet;
+    }
+
 }

app/src/main/java/org/schabi/newpipe/local/bookmark/BookmarkFragment.java

@@ -8,6 +8,8 @@ import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.ArrayAdapter;
+import android.widget.TextView;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -24,7 +26,6 @@ import org.schabi.newpipe.database.playlist.PlaylistLocalItem;
 import org.schabi.newpipe.database.playlist.PlaylistMetadataEntry;
 import org.schabi.newpipe.database.playlist.model.PlaylistRemoteEntity;
 import org.schabi.newpipe.databinding.DialogEditTextBinding;
-import org.schabi.newpipe.databinding.DialogTitleBinding;
 import org.schabi.newpipe.error.ErrorInfo;
 import org.schabi.newpipe.error.UserAction;
 import org.schabi.newpipe.local.BaseLocalListFragment;
@@ -258,32 +259,51 @@ public final class BookmarkFragment extends BaseLocalListFragment<List<PlaylistL
     }
 
     private void showLocalDialog(final PlaylistMetadataEntry selectedItem) {
+        final boolean isPlaylistThumbnailSet = localPlaylistManager
+                .getIsPlaylistThumbnailSet(selectedItem.uid);
+        final AlertDialog.Builder builder = new AlertDialog.Builder(activity);
 
-        //TODO
+        final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(getContext(),
+                android.R.layout.simple_list_item_1) {
+            @Override
+            public View getView(final int position, final View convertView,
+                                final ViewGroup parent) {
+                final View v = super.getView(position, convertView, parent);
+                final TextView textView = v.findViewById(android.R.id.text1);
 
-        final DialogTitleBinding dialogBinding =
+                if (!isPlaylistThumbnailSet && position == 2) {
-                DialogTitleBinding.inflate(LayoutInflater.from(requireContext()));
+                    textView.setEnabled(false);
+                    return v;
+                }
 
-        dialogBinding.itemRoot.setVisibility(View.GONE);
+                textView.setEnabled(true);
-        dialogBinding.itemTitleView.setVisibility(View.GONE);
+                return v;
-        dialogBinding.itemAdditionalDetails.setVisibility(View.GONE);
+            }
-        final String[] items = new String[]{"Delete", "Rename", "Thumbnail"};
+        };
-        final DialogInterface.OnClickListener action = (d, index) -> {
+        arrayAdapter.addAll(getString(R.string.rename), getString(R.string.delete),
+                getString(R.string.unset_playlist_thumbnail));
+
+        // Rename = 0; Delete = 1; Unset Thumbnail = 2
+        final DialogInterface.OnClickListener action = (dialog, index) -> {
             switch (index) {
                 case 0: showRenameDialog(selectedItem);
                     break;
                 case 1:
+                    showDeleteDialog(selectedItem.name,
+                            localPlaylistManager.deletePlaylist(selectedItem.uid));
+                    dialog.dismiss();
                     break;
                 case 2:
+                    if (isPlaylistThumbnailSet) {
+                        final String ur = "drawable://" + R.drawable.placeholder_thumbnail_playlist;
+                        localPlaylistManager.changePlaylistThumbnail(selectedItem.uid, ur,
+                            false).observeOn(AndroidSchedulers.mainThread()).subscribe();
+                    }
                     break;
             }
         };
 
-        //TODO add rename dialog
+        builder.setAdapter(arrayAdapter, action)
-
-        final AlertDialog.Builder builder = new AlertDialog.Builder(activity);
-
-        builder.setItems(items, action)
                 .create()
                 .show();
     }
@@ -302,11 +322,6 @@ public final class BookmarkFragment extends BaseLocalListFragment<List<PlaylistL
                                 selectedItem.uid,
                                 dialogBinding.dialogEditText.getText().toString()))
                 .setNegativeButton(R.string.cancel, null)
-                .setNeutralButton(R.string.delete, (dialog, which) -> {
-                    showDeleteDialog(selectedItem.name,
-                            localPlaylistManager.deletePlaylist(selectedItem.uid));
-                    dialog.dismiss();
-                })
                 .create()
                 .show();
     }

app/src/main/java/org/schabi/newpipe/local/dialog/PlaylistAppendDialog.java

@@ -134,7 +134,7 @@ public final class PlaylistAppendDialog extends PlaylistDialog {
         if (playlist.thumbnailUrl
                 .equals("drawable://" + R.drawable.placeholder_thumbnail_playlist)) {
             playlistDisposables.add(manager
-                    .changePlaylistThumbnail(playlist.uid, streams.get(0).getThumbnailUrl())
+                    .changePlaylistThumbnail(playlist.uid, streams.get(0).getThumbnailUrl(), false)
                     .observeOn(AndroidSchedulers.mainThread())
                     .subscribe(ignored -> successToast.show()));
         }

app/src/main/java/org/schabi/newpipe/local/playlist/LocalPlaylistFragment.java

@@ -405,8 +405,9 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
                 .zipWith(historyIdsMaybe, (playlist, historyStreamIds) -> {
                     // Remove Watched, Functionality data
                     final List<PlaylistStreamEntry> notWatchedItems = new ArrayList<>();
+                    final boolean isThumbnailSet = playlistManager
+                            .getIsPlaylistThumbnailSet(playlistId);
                     boolean thumbnailVideoRemoved = false;
-                    //TODO: add blocker here
 
                     if (removePartiallyWatched) {
                         for (final var playlistItem : playlist) {
@@ -415,7 +416,7 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
 
                             if (indexInHistory < 0) {
                                 notWatchedItems.add(playlistItem);
-                            } else if (!thumbnailVideoRemoved
+                            } else if (!isThumbnailSet && !thumbnailVideoRemoved
                                     && playlistManager.getPlaylistThumbnail(playlistId)
                                     .equals(playlistItem.getStreamEntity().getThumbnailUrl())) {
                                 thumbnailVideoRemoved = true;
@@ -436,7 +437,7 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
                             if (indexInHistory < 0 || (streamStateEntity != null
                                     && !streamStateEntity.isFinished(duration))) {
                                 notWatchedItems.add(playlistItem);
-                            } else if (!thumbnailVideoRemoved
+                            } else if (!isThumbnailSet && !thumbnailVideoRemoved
                                     && playlistManager.getPlaylistThumbnail(playlistId)
                                     .equals(playlistItem.getStreamEntity().getThumbnailUrl())) {
                                 thumbnailVideoRemoved = true;
@@ -586,13 +587,12 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
         disposables.add(disposable);
     }
 
-    private void changeThumbnailUrl(final String thumbnailUrl) {
+    private void changeThumbnailUrl(final String thumbnailUrl, final boolean isPermanent) {
-        if (playlistManager == null) {
+        if (playlistManager == null || (!isPermanent && playlistManager
+                .getIsPlaylistThumbnailSet(playlistId))) {
             return;
         }
 
-        //TODO add blocker here
-
         final Toast successToast = Toast.makeText(getActivity(),
                 R.string.playlist_thumbnail_change_success,
                 Toast.LENGTH_SHORT);
@@ -603,7 +603,7 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
         }
 
         final Disposable disposable = playlistManager
-                .changePlaylistThumbnail(playlistId, thumbnailUrl)
+                .changePlaylistThumbnail(playlistId, thumbnailUrl, isPermanent)
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe(ignore -> successToast.show(), throwable ->
                         showError(new ErrorInfo(throwable, UserAction.REQUESTED_BOOKMARK,
@@ -612,8 +612,11 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
     }
 
     private void updateThumbnailUrl() {
+        if (playlistManager.getIsPlaylistThumbnailSet(playlistId)) {
+            return;
+        }
+
         final String newThumbnailUrl;
-        //TODO: add blocker here
         if (!itemListAdapter.getItemsList().isEmpty()) {
             newThumbnailUrl = ((PlaylistStreamEntry) itemListAdapter.getItemsList().get(0))
                     .getStreamEntity().getThumbnailUrl();
@@ -621,7 +624,7 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
             newThumbnailUrl = "drawable://" + R.drawable.placeholder_thumbnail_playlist;
         }
 
-        changeThumbnailUrl(newThumbnailUrl);
+        changeThumbnailUrl(newThumbnailUrl, false);
     }
 
     private void deleteItem(final PlaylistStreamEntry item) {
@@ -789,7 +792,8 @@ public class LocalPlaylistFragment extends BaseLocalListFragment<List<PlaylistSt
                     .setAction(
                             StreamDialogDefaultEntry.SET_AS_PLAYLIST_THUMBNAIL,
                             (f, i) ->
-                                    changeThumbnailUrl(item.getStreamEntity().getThumbnailUrl()))
+                                    changeThumbnailUrl(item.getStreamEntity().getThumbnailUrl(),
+                                            true))
                     .setAction(
                             StreamDialogDefaultEntry.DELETE,
                             (f, i) -> deleteItem(item))

app/src/main/java/org/schabi/newpipe/local/playlist/LocalPlaylistManager.java

@@ -41,7 +41,7 @@ public class LocalPlaylistManager {
         }
         final StreamEntity defaultStream = streams.get(0);
         final PlaylistEntity newPlaylist =
-                new PlaylistEntity(name, defaultStream.getThumbnailUrl());
+                new PlaylistEntity(name, defaultStream.getThumbnailUrl(), false);
 
         return Maybe.fromCallable(() -> database.runInTransaction(() ->
                 upsertStreams(playlistTable.insert(newPlaylist), streams, 0))
@@ -96,24 +96,29 @@ public class LocalPlaylistManager {
     }
 
     public Maybe<Integer> renamePlaylist(final long playlistId, final String name) {
-        return modifyPlaylist(playlistId, name, null);
+        return modifyPlaylist(playlistId, name, null, false);
     }
 
     public Maybe<Integer> changePlaylistThumbnail(final long playlistId,
-                                                  final String thumbnailUrl) {
+                                                  final String thumbnailUrl,
-        return modifyPlaylist(playlistId, null, thumbnailUrl);
+                                                  final boolean isPermanent) {
+        return modifyPlaylist(playlistId, null, thumbnailUrl, isPermanent);
     }
 
     public String getPlaylistThumbnail(final long playlistId) {
         return playlistTable.getPlaylist(playlistId).blockingFirst().get(0).getThumbnailUrl();
     }
 
+    public boolean getIsPlaylistThumbnailSet(final long playlistId) {
+        return playlistTable.getPlaylist(playlistId).blockingFirst().get(0).getIsThumbnailSet();
+    }
+
     private Maybe<Integer> modifyPlaylist(final long playlistId,
                                           @Nullable final String name,
-                                          @Nullable final String thumbnailUrl) {
+                                          @Nullable final String thumbnailUrl,
+                                          final boolean isPermanent) {
         return playlistTable.getPlaylist(playlistId)
                 .firstElement()
-                .filter(playlistEntities -> !playlistEntities.isEmpty())
                 .map(playlistEntities -> {
                     final PlaylistEntity playlist = playlistEntities.get(0);
                     if (name != null) {
@@ -121,6 +126,7 @@ public class LocalPlaylistManager {
                     }
                     if (thumbnailUrl != null) {
                         playlist.setThumbnailUrl(thumbnailUrl);
+                        playlist.setIsThumbnailSet(isPermanent);
                     }
                     return playlistTable.update(playlist);
                 }).subscribeOn(Schedulers.io());

app/src/main/res/values/strings.xml

@@ -7,6 +7,7 @@
     <string name="install">Install</string>
     <string name="cancel">Cancel</string>
     <string name="ok">OK</string>
+    <string name="yes">Yes</string>
     <string name="open_in_browser">Open in browser</string>
     <string name="mark_as_watched">Mark as watched</string>
     <string name="open_in_popup_mode">Open in popup mode</string>
@@ -438,6 +439,7 @@
     <string name="mute">Mute</string>
     <string name="unmute">Unmute</string>
     <string name="set_as_playlist_thumbnail">Set as playlist thumbnail</string>
+    <string name="unset_playlist_thumbnail">Unset thumbnail</string>
     <string name="bookmark_playlist">Bookmark Playlist</string>
     <string name="unbookmark_playlist">Remove Bookmark</string>
     <string name="delete_playlist_prompt">Delete this playlist\?</string>