Fix scrolling in main screen grid

GridLayoutManager is buggy - https://issuetracker.google.com/issues/37067220:
it randomly loses or incorrectly assigns focus when being scrolled via
direction-based navigation. This commit reimplements onFocusSearchFailed()
on top of scrollBy() to work around that problem.

Ordinary touch-based navigation should not be affected.

app/src/main/java/org/schabi/newpipe/views/FixedGridLayoutManager.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) Eltex ltd 2019 <eltex@eltex-co.ru>
+ * FixedGridLayoutManager.java is part of NewPipe.
+ *
+ * NewPipe is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * NewPipe is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with NewPipe.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.schabi.newpipe.views;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.FocusFinder;
+import android.view.View;
+import android.view.ViewGroup;
+
+import androidx.recyclerview.widget.GridLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+// Version of GridLayoutManager that works around https://issuetracker.google.com/issues/37067220
+public class FixedGridLayoutManager extends GridLayoutManager {
+    public FixedGridLayoutManager(Context context, int spanCount) {
+        super(context, spanCount);
+    }
+
+    public FixedGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+    }
+
+    public FixedGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {
+        super(context, spanCount, orientation, reverseLayout);
+    }
+
+    @Override
+    public View onFocusSearchFailed(View focused, int focusDirection, RecyclerView.Recycler recycler, RecyclerView.State state) {
+        FocusFinder ff = FocusFinder.getInstance();
+
+        View result = ff.findNextFocus((ViewGroup) focused.getParent(), focused, focusDirection);
+        if (result != null) {
+            return super.onFocusSearchFailed(focused, focusDirection, recycler, state);
+        }
+
+        if (focusDirection == View.FOCUS_DOWN) {
+            scrollVerticallyBy(10, recycler, state);
+            return null;
+        }
+
+        return super.onFocusSearchFailed(focused, focusDirection, recycler, state);
+    }
+}

app/src/main/java/org/schabi/newpipe/views/NewPipeRecyclerView.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) Eltex ltd 2019 <eltex@eltex-co.ru>
+ * NewPipeRecyclerView.java is part of NewPipe.
+ *
+ * NewPipe is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * NewPipe is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with NewPipe.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.schabi.newpipe.views;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.View;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.recyclerview.widget.RecyclerView;
+
+public class NewPipeRecyclerView extends RecyclerView {
+    private static final String TAG = "FixedRecyclerView";
+
+    public NewPipeRecyclerView(@NonNull Context context) {
+        super(context);
+    }
+
+    public NewPipeRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public NewPipeRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyle) {
+        super(context, attrs, defStyle);
+    }
+
+    @Override
+    public View focusSearch(int direction) {
+        return null;
+    }
+
+    @Override
+    public View focusSearch(View focused, int direction) {
+        return null;
+    }
+
+    @Override
+    public boolean dispatchUnhandledMove(View focused, int direction) {
+        View found = super.focusSearch(focused, direction);
+        if (found != null) {
+            found.requestFocus(direction);
+            return true;
+        }
+
+        if (direction == View.FOCUS_UP) {
+            if (canScrollVertically(-1)) {
+                scrollBy(0, -10);
+                return true;
+            }
+
+            return false;
+        }
+
+        return super.dispatchUnhandledMove(focused, direction);
+    }
+}