Load enough initial data into BaseListFragment

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

@@ -271,7 +271,7 @@ public abstract class BaseListFragment<I, N> extends BaseStateFragment<I>
     @Override
     protected void initListeners() {
         super.initListeners();
-        infoListAdapter.setOnStreamSelectedListener(new OnClickGesture<StreamInfoItem>() {
+        infoListAdapter.setOnStreamSelectedListener(new OnClickGesture<>() {
             @Override
             public void selected(final StreamInfoItem selectedItem) {
                 onStreamSelected(selectedItem);
@@ -418,7 +418,66 @@ public abstract class BaseListFragment<I, N> extends BaseStateFragment<I>
     // Load and handle
     //////////////////////////////////////////////////////////////////////////*/
 
-    protected abstract void loadMoreItems();
+    /**
+     * 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, "loadEnoughInitial - 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 boolean hasMoreItems();
 

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

@@ -6,6 +6,7 @@ import android.util.Log;
 import android.view.View;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 import org.schabi.newpipe.error.ErrorInfo;
 import org.schabi.newpipe.error.UserAction;
@@ -65,7 +66,7 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
         super.onResume();
         // Check if it was loading when the fragment was stopped/paused,
         if (wasLoading.getAndSet(false)) {
-            if (hasMoreItems() && infoListAdapter.getItemsList().size() > 0) {
+            if (hasMoreItems() && !infoListAdapter.getItemsList().isEmpty()) {
                 loadMoreItems();
             } else {
                 doInitialLoadLogic();
@@ -105,6 +106,7 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
     // Load and handle
     //////////////////////////////////////////////////////////////////////////*/
 
+    @Override
     protected void doInitialLoadLogic() {
         if (DEBUG) {
             Log.d(TAG, "doInitialLoadLogic() called");
@@ -144,6 +146,7 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
                     currentInfo = result;
                     currentNextPage = result.getNextPage();
                     handleResult(result);
+                    ifMoreItemsLoadableLoadUntilScrollable();
                 }, throwable ->
                         showError(new ErrorInfo(throwable, errorUserAction,
                                 "Start loading: " + url, serviceId)));
@@ -158,7 +161,8 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
      */
     protected abstract Single<ListExtractor.InfoItemsPage> loadMoreItemsLogic();
 
-    protected void loadMoreItems() {
+    @Override
+    protected void loadMoreItems(@Nullable final Runnable initialDataLoadCallback) {
         isLoading.set(true);
 
         if (currentWorker != null) {
@@ -171,9 +175,12 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .doFinally(this::allowDownwardFocusScroll)
-                .subscribe((@NonNull ListExtractor.InfoItemsPage InfoItemsPage) -> {
+                .subscribe(infoItemsPage -> {
                     isLoading.set(false);
-                    handleNextItems(InfoItemsPage);
+                    handleNextItems(infoItemsPage);
+                    if (initialDataLoadCallback != null) {
+                        initialDataLoadCallback.run();
+                    }
                 }, (@NonNull Throwable throwable) ->
                         dynamicallyShowErrorPanelOrSnackbar(new ErrorInfo(throwable,
                                 errorUserAction, "Loading more items: " + url, serviceId)));
@@ -223,7 +230,7 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
         setTitle(name);
 
         if (infoListAdapter.getItemsList().isEmpty()) {
-            if (result.getRelatedItems().size() > 0) {
+            if (!result.getRelatedItems().isEmpty()) {
                 infoListAdapter.addInfoItemList(result.getRelatedItems());
                 showListFooter(hasMoreItems());
             } else {
@@ -240,7 +247,7 @@ public abstract class BaseListInfoFragment<I extends ListInfo>
             final List<Throwable> errors = new ArrayList<>(result.getErrors());
             // handling ContentNotSupportedException not to show the error but an appropriate string
             // so that crashes won't be sent uselessly and the user will understand what happened
-            errors.removeIf(throwable -> throwable instanceof ContentNotSupportedException);
+            errors.removeIf(ContentNotSupportedException.class::isInstance);
 
             if (!errors.isEmpty()) {
                 dynamicallyShowErrorPanelOrSnackbar(new ErrorInfo(result.getErrors(),

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

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