Modify NestedScrollableHost to suit our need

Now manages nested child scrolling when the orientation is perpendicular

app/src/main/java/de/danoeh/antennapod/view/NestedScrollableHost.java

@@ -14,6 +14,7 @@
  * limitations under the License.
  *
  * Source: https://github.com/android/views-widgets-samples/blob/87e58d1/ViewPager2/app/src/main/java/androidx/viewpager2/integration/testapp/NestedScrollableHost.kt
+ * And modified for our need
  */
 
 package de.danoeh.antennapod.view;
@@ -23,21 +24,23 @@
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewConfiguration;
+import android.view.ViewParent;
 import android.widget.FrameLayout;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.viewpager2.widget.ViewPager2;
 
 import static androidx.viewpager2.widget.ViewPager2.ORIENTATION_HORIZONTAL;
+import static androidx.viewpager2.widget.ViewPager2.ORIENTATION_VERTICAL;
 
 /**
  * Layout to wrap a scrollable component inside a ViewPager2. Provided as a solution to the problem
  * where pages of ViewPager2 have nested scrollable elements that scroll in the same direction as
  * ViewPager2. The scrollable element needs to be the immediate and only child of this host layout.
  *
  * <p>This solution has limitations when using multiple levels of nested scrollable elements
- * (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).</p>
+ * (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).
  */
 class NestedScrollableHost extends FrameLayout {
 
@@ -63,47 +66,19 @@ private ViewPager2 getParentViewPager() {
         return v == null ? null : (ViewPager2) v;
     }
 
-    private View getChild() {
-        return getChildCount() > 0 ? getChildAt(0) : null;
-    }
-
-    private boolean canChildScroll(int orientation, float delta) {
-        int direction = (int) -Math.copySign(1, delta);
-        View child = getChild();
-        if (child == null) {
-            return false;
-        }
-        switch (orientation) {
-            case 0:
-                return child.canScrollHorizontally(direction);
-            case 1:
-                return child.canScrollVertically(direction);
-            default:
-                return false;
-        }
-    }
-
     public boolean onInterceptTouchEvent(MotionEvent e) {
-        handleInterceptTouchEvent(e);
-        return super.onInterceptTouchEvent(e);
-    }
-
-    private void handleInterceptTouchEvent(MotionEvent e) {
         ViewPager2 parentViewPager = getParentViewPager();
         if (parentViewPager == null) {
-            return;
+            return super.onInterceptTouchEvent(e);
         }
-        int orientation = parentViewPager.getOrientation();
 
-        // Early return if child can't scroll in same direction as parent
-        if (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f)) {
-            return;
-        }
+        ViewParent parent = getParent();
+        int orientation = parentViewPager.getOrientation();
 
         if (e.getAction() == MotionEvent.ACTION_DOWN) {
             initialX = e.getX();
             initialY = e.getY();
-            getParent().requestDisallowInterceptTouchEvent(true);
+            parent.requestDisallowInterceptTouchEvent(true);
         } else if (e.getAction() == MotionEvent.ACTION_MOVE) {
             int dx = (int) (e.getX() - initialX);
             int dy = (int) (e.getY() - initialY);
@@ -112,22 +87,25 @@ private void handleInterceptTouchEvent(MotionEvent e) {
             // assuming ViewPager2 touch-slop is 2x touch-slop of child
             float scaledDx = Math.abs(dx) * (isVpHorizontal ? .5f : 1f);
             float scaledDy = Math.abs(dy) * (isVpHorizontal ? 1f : .5f);
-
             if (scaledDx > touchSlop || scaledDy > touchSlop) {
+                int value = isVpHorizontal ? dy : dx;
                 if (isVpHorizontal == (scaledDy > scaledDx)) {
-                    // Gesture is perpendicular, allow all parents to intercept
-                    getParent().requestDisallowInterceptTouchEvent(false);
-                } else {
-                    // Gesture is parallel, query child if movement in that direction is possible
-                    if (canChildScroll(orientation, isVpHorizontal ? dx : dy)) {
-                        // Child can scroll, disallow all parents to intercept
-                        getParent().requestDisallowInterceptTouchEvent(true);
-                    } else {
-                        // Child cannot scroll, allow all parents to intercept
-                        getParent().requestDisallowInterceptTouchEvent(false);
-                    }
+                    // Gesture is perpendicular
+                    orientation = orientation == ORIENTATION_VERTICAL
+                            ? ORIENTATION_HORIZONTAL : ORIENTATION_VERTICAL;
+                    value = isVpHorizontal ? dy : dx;
+                }
+
+                int direction = (int) -Math.copySign(1, value);
+                View child = getChildAt(0);
+                if (orientation == ORIENTATION_HORIZONTAL)
+                    parent.requestDisallowInterceptTouchEvent(child.canScrollHorizontally(direction));
+                else {
+                    parent.requestDisallowInterceptTouchEvent(child.canScrollVertically(direction));
                 }
             }
         }
+
+        return super.onInterceptTouchEvent(e);
     }
 }