Reverted to loading behavior of #7638 and improved it

The previous/reverted behavior caused unwanted data transmission:
* Removed loading via handleResults/loadMoreItems-callback because the RecyclerView is apparently not immediately updated in the UI when the data is set which causes one load of data to much.

Author: litetex

app/src/main/java/org/schabi/newpipe/fragments/list/BaseListFragment.java

@@ -312,14 +312,74 @@ public void selected(final CommentsInfoItem selectedItem) {
         });
 
         itemsList.clearOnScrollListeners();
-        itemsList.addOnScrollListener(new OnScrollBelowItemsListener() {
+
+        /*
+         * Add initial scroll listener - which tries to load more items when not enough
+         * are in the view (not scrollable) and more are available.
+         *
+         * Note: This method only works because "This callback will also be called if visible
+         * item range changes after a layout calculation. In that case, dx and dy will be 0."
+         * - which might be unexpected because no actual scrolling occurs...
+         *
+         * This listener will be replaced by DefaultItemListOnScrolledDownListener when
+         * * the view was actually scrolled
+         * * the view is scrollable
+         * * No more items can be loaded
+         */
+        itemsList.addOnScrollListener(new DefaultItemListOnScrolledDownListener() {
             @Override
-            public void onScrolledDown(final RecyclerView recyclerView) {
-                onScrollToBottom();
+            public void onScrolled(final RecyclerView recyclerView, final int dx, final int dy) {
+                super.onScrolled(recyclerView, dx, dy);
+
+                if (dy != 0) {
+                    log("Vertical scroll occurred");
+
+                    useNormalScrollListener();
+                    return;
+                }
+                if (isLoading.get()) {
+                    log("Still loading data -> Skipping");
+                    return;
+                }
+                if (!hasMoreItems()) {
+                    log("No more items to load");
+
+                    useNormalScrollListener();
+                    return;
+                }
+                if (itemsList.canScrollVertically(1)
+                        || itemsList.canScrollVertically(-1)) {
+                    log("View is scrollable");
+
+                    useNormalScrollListener();
+                    return;
+                }
+
+                log("Loading more data");
+                loadMoreItems();
+            }
+
+            private void useNormalScrollListener() {
+                log("Unregistering and using normal listener");
+                itemsList.removeOnScrollListener(this);
+                itemsList.addOnScrollListener(new DefaultItemListOnScrolledDownListener());
+            }
+
+            private void log(final String msg) {
+                if (DEBUG) {
+                    Log.d(TAG, "itemListInitScrollListener - " + msg);
+                }
             }
         });
     }
 
+    class DefaultItemListOnScrolledDownListener extends OnScrollBelowItemsListener {
+        @Override
+        public void onScrolledDown(final RecyclerView recyclerView) {
+            onScrollToBottom();
+        }
+    }
+
     private void onStreamSelected(final StreamInfoItem selectedItem) {
         onItemSelected(selectedItem);
         NavigationHelper.openVideoDetailFragment(requireContext(), getFM(),
@@ -407,66 +467,7 @@ public void onCreateOptionsMenu(@NonNull final Menu menu,
     // Load and handle
     //////////////////////////////////////////////////////////////////////////*/
 
-    /**
-     * If more items are loadable and the itemList is not scrollable -> load more data.
-     * <br/>
-     * Should be called once the initial items inside {@link #startLoading(boolean)}
-     * has been loaded and added to the {@link #itemsList}.
-     * <br/>
-     * Otherwise the loading indicator is always shown but no data can be loaded
-     * because the view is not scrollable; see also #1974.
-     */
-    protected void ifMoreItemsLoadableLoadUntilScrollable() {
-        ifMoreItemsLoadableLoadUntilScrollable(0);
-    }
-
-    /**
-     * If more items are loadable and the itemList is not scrollable -> load more data.
-     *
-     * @param recursiveCallCount Amount of recursive calls that occurred
-     * @see #ifMoreItemsLoadableLoadUntilScrollable()
-     */
-    protected void ifMoreItemsLoadableLoadUntilScrollable(final int recursiveCallCount) {
-        // Try to prevent malfunction / stackoverflow
-        if (recursiveCallCount > 100) {
-            Log.w(TAG, "loadEnoughInitialData - Too many recursive calls - Aborting");
-            return;
-        }
-        if (!hasMoreItems()) {
-            if (DEBUG) {
-                Log.d(TAG, "loadEnoughInitialData - OK: No more items to load");
-            }
-            return;
-        }
-        if (itemsList.canScrollVertically(1)
-                || itemsList.canScrollVertically(-1)) {
-            if (DEBUG) {
-                Log.d(TAG, "loadEnoughInitialData - OK: itemList is scrollable");
-            }
-            return;
-        }
-        if (DEBUG) {
-            Log.d(TAG, "loadEnoughInitialData - View is not scrollable "
-                    + "but it could load more items -> Loading more");
-        }
-        loadMoreItems(() ->
-                ifMoreItemsLoadableLoadUntilScrollable(recursiveCallCount + 1));
-    }
-
-    /**
-     * Loads more items.
-     * @param initialDataLoadCallback
-     *          Callback used in {@link #ifMoreItemsLoadableLoadUntilScrollable()}.
-     *          <br/>
-     *          Execute it once the data was loaded and added to the {@link #itemsList}.
-     *          <br/>
-     *          Might be <code>null</code>.
-     */
-    protected abstract void loadMoreItems(@Nullable Runnable initialDataLoadCallback);
-
-    protected void loadMoreItems() {
-        loadMoreItems(null);
-    }
+    protected abstract void loadMoreItems();
 
     protected abstract boolean hasMoreItems();
 

app/src/main/java/org/schabi/newpipe/fragments/list/BaseListInfoFragment.java

@@ -6,7 +6,6 @@
 import android.view.View;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 
 import org.schabi.newpipe.error.ErrorInfo;
 import org.schabi.newpipe.error.UserAction;
@@ -146,7 +145,6 @@ public void startLoading(final boolean forceLoad) {
                     currentInfo = result;
                     currentNextPage = result.getNextPage();
                     handleResult(result);
-                    ifMoreItemsLoadableLoadUntilScrollable();
                 }, throwable ->
                         showError(new ErrorInfo(throwable, errorUserAction,
                                 "Start loading: " + url, serviceId)));
@@ -162,7 +160,7 @@ public void startLoading(final boolean forceLoad) {
     protected abstract Single<ListExtractor.InfoItemsPage> loadMoreItemsLogic();
 
     @Override
-    protected void loadMoreItems(@Nullable final Runnable initialDataLoadCallback) {
+    protected void loadMoreItems() {
         isLoading.set(true);
 
         if (currentWorker != null) {
@@ -178,9 +176,6 @@ protected void loadMoreItems(@Nullable final Runnable initialDataLoadCallback) {
                 .subscribe(infoItemsPage -> {
                     isLoading.set(false);
                     handleNextItems(infoItemsPage);
-                    if (initialDataLoadCallback != null) {
-                        initialDataLoadCallback.run();
-                    }
                 }, (@NonNull Throwable throwable) ->
                         dynamicallyShowErrorPanelOrSnackbar(new ErrorInfo(throwable,
                                 errorUserAction, "Loading more items: " + url, serviceId)));

app/src/main/java/org/schabi/newpipe/fragments/list/search/SearchFragment.java

@@ -868,15 +868,12 @@ public void startLoading(final boolean forceLoad) {
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .doOnEvent((searchResult, throwable) -> isLoading.set(false))
-                .subscribe(result -> {
-                    handleResult(result);
-                    ifMoreItemsLoadableLoadUntilScrollable();
-                }, this::onItemError);
+                .subscribe(this::handleResult, this::onItemError);
 
     }
 
     @Override
-    protected void loadMoreItems(@Nullable final Runnable initialDataLoadCallback) {
+    protected void loadMoreItems() {
         if (!Page.isValid(nextPage)) {
             return;
         }
@@ -894,12 +891,7 @@ protected void loadMoreItems(@Nullable final Runnable initialDataLoadCallback) {
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .doOnEvent((nextItemsResult, throwable) -> isLoading.set(false))
-                .subscribe(itemsPage -> {
-                    handleNextItems(itemsPage);
-                    if (initialDataLoadCallback != null) {
-                        initialDataLoadCallback.run();
-                    }
-                }, this::onItemError);
+                .subscribe(this::handleNextItems, this::onItemError);
     }
 
     @Override