use custom view to improve performance for nested scroll views

app/src/main/java/com/dkanada/gramophone/ui/activities/details/ArtistDetailActivity.java

@@ -123,6 +123,8 @@ public class ArtistDetailActivity extends AbsSlidingMusicPanelActivity implement
 
         binding.songs.setLayoutManager(new GridLayoutManager(this, 1));
         binding.songs.setAdapter(songAdapter);
+
+        binding.scrollView.setRecyclerView(binding.songs);
     }
 
     private void setUpAlbumRecyclerView() {

app/src/main/java/com/dkanada/gramophone/views/InceptionScrollView.java

@@ -0,0 +1,84 @@
+package com.dkanada.gramophone.views;
+
+import android.content.Context;
+import android.graphics.Rect;
+import android.util.AttributeSet;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.ViewTreeObserver;
+
+import androidx.annotation.NonNull;
+import androidx.core.widget.NestedScrollView;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+public class InceptionScrollView extends NestedScrollView {
+    private RecyclerView recyclerView;
+
+    public InceptionScrollView(@NonNull Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @Override
+    public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed, int type) {
+        // if scrolling down and scroll view not at bottom and recycler view fills screen but scroll view doesn't fill the screen
+        if (dy > 0 && !isSvScrolledToBottom(this) && !isRvFillParent(this, recyclerView) && isSvFillParent(this)) {
+            scrollBy(0, dy);
+            consumed[1] = dy;
+            return;
+        }
+
+        // send to normal scroll view method
+        super.onNestedPreScroll(target, dx, dy, consumed, type);
+    }
+
+    public void setRecyclerView(RecyclerView recyclerView) {
+        this.recyclerView = recyclerView;
+
+        InceptionScrollView scrollView = this;
+        this.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
+            @Override
+            public void onGlobalLayout() {
+                Rect scrollBounds = new Rect();
+                getDrawingRect(scrollBounds);
+
+                ViewGroup.LayoutParams params = recyclerView.getLayoutParams();
+                params.height = scrollBounds.bottom;
+
+                recyclerView.setLayoutParams(params);
+                scrollView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
+            }
+        });
+    }
+
+    private static boolean isSvScrolledToBottom(NestedScrollView sv) {
+        return !sv.canScrollVertically(1);
+    }
+
+    // might be useful in the future
+    private static boolean isRvScrolledToTop(RecyclerView rv) {
+        final LinearLayoutManager lm = (LinearLayoutManager) rv.getLayoutManager();
+        return lm != null && lm.findFirstCompletelyVisibleItemPosition() == 0;
+    }
+
+    private static boolean isRvFillParent(NestedScrollView sv, RecyclerView rv) {
+        Rect scrollLocationInParent = new Rect();
+        sv.getHitRect(scrollLocationInParent);
+
+        Rect viewLocationVisible = new Rect();
+        rv.getDrawingRect(viewLocationVisible);
+
+        return viewLocationVisible == scrollLocationInParent;
+    }
+
+    // this would probably need changes to do exactly what it says in the name
+    private static boolean isSvFillParent(NestedScrollView sv) {
+        Rect scrollBounds = new Rect();
+        sv.getHitRect(scrollBounds);
+
+        Rect viewBounds = new Rect();
+        sv.getDrawingRect(viewBounds);
+
+        return viewBounds.top >= scrollBounds.top;
+    }
+}

app/src/main/res/layout/activity_artist_detail.xml

@@ -146,7 +146,8 @@
 
         </com.google.android.material.appbar.AppBarLayout>
 
-        <androidx.core.widget.NestedScrollView
+        <com.dkanada.gramophone.views.InceptionScrollView
+            android:id="@+id/scroll_view"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             app:layout_behavior="@string/appbar_scrolling_view_behavior">
@@ -179,7 +180,7 @@
 
             </LinearLayout>
 
-        </androidx.core.widget.NestedScrollView>
+        </com.dkanada.gramophone.views.InceptionScrollView>
 
     </androidx.coordinatorlayout.widget.CoordinatorLayout>