1 files changed, 127 insertions, 38 deletions

diff --git a/app/src/main/java/de/danoeh/antennapod/view/NestedScrollableHost.java b/app/src/main/java/de/danoeh/antennapod/view/NestedScrollableHost.java
index 0e1846f1c..ff52df71f 100644
--- a/app/src/main/java/de/danoeh/antennapod/view/NestedScrollableHost.java
+++ b/app/src/main/java/de/danoeh/antennapod/view/NestedScrollableHost.java
@@ -20,92 +20,181 @@
 package de.danoeh.antennapod.view;
 
 import android.content.Context;
+import android.content.res.TypedArray;
+import android.os.Build;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewConfiguration;
-import android.view.ViewParent;
+import android.view.ViewTreeObserver;
 import android.widget.FrameLayout;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
 import androidx.viewpager2.widget.ViewPager2;
 
+import de.danoeh.antennapod.R;
+
 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
+ * 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).
- */
-class NestedScrollableHost extends FrameLayout {
+ */ // KhaledAlharthi/NestedScrollableHost.java
+public class NestedScrollableHost extends FrameLayout {
+
+    private ViewPager2 parentViewPager;
+    private int touchSlop = 0;
+    private float initialX = 0f;
+    private float initialY = 0f;
+    private int preferVertical = 1;
+    private int preferHorizontal = 1;
+    private int scrollDirection = 0;
 
     public NestedScrollableHost(@NonNull Context context) {
         super(context);
-        touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
+        init(context);
     }
 
     public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs) {
         super(context, attrs);
+        init(context);
+        setAttributes(context, attrs);
+    }
+
+    public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        init(context);
+        setAttributes(context, attrs);
+    }
+
+    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
+    public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs,
+                                int defStyleAttr, int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+        init(context);
+        setAttributes(context, attrs);
+    }
+
+    private void setAttributes(@NonNull Context context, @Nullable AttributeSet attrs) {
+        TypedArray a = context.getTheme().obtainStyledAttributes(
+                attrs,
+                R.styleable.NestedScrollableHost,
+                0, 0);
+
+        try {
+            preferHorizontal = a.getInteger(R.styleable.NestedScrollableHost_preferHorizontal, 1);
+            preferVertical = a.getInteger(R.styleable.NestedScrollableHost_preferVertical, 1);
+            scrollDirection = a.getInteger(R.styleable.NestedScrollableHost_scrollDirection, 0);
+        } finally {
+            a.recycle();
+        }
+
+    }
+
+    private void init(Context context) {
         touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
+
+
+        getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
+            @Override
+            public boolean onPreDraw() {
+                View v = (View) getParent();
+                while (v != null && !(v instanceof ViewPager2) || isntSameDirection(v)) {
+                    v = (View) v.getParent();
+                }
+                parentViewPager = (ViewPager2) v;
+
+                getViewTreeObserver().removeOnPreDrawListener(this);
+                return false;
+            }
+        });
     }
 
-    private int touchSlop;
-    private float initialX = 0f;
-    private float initialY = 0f;
+    private Boolean isntSameDirection(View v) {
+        int orientation = 0;
+        switch (scrollDirection) {
+            default:
+            case 0:
+                return false;
+            case 1:
+                orientation = ORIENTATION_VERTICAL;
+                break;
+            case 2:
+                orientation = ORIENTATION_HORIZONTAL;
+                break;
+        }
+        return ((v instanceof ViewPager2) && ((ViewPager2) v).getOrientation() != orientation);
+    }
+
+
+    @Override
+    public boolean onInterceptTouchEvent(MotionEvent ev) {
+        handleInterceptTouchEvent(ev);
+        return super.onInterceptTouchEvent(ev);
+    }
 
-    private ViewPager2 getParentViewPager() {
-        View v = (View) getParent();
-        while (v != null && !(v instanceof ViewPager2)) {
-            v = (View) v.getParent();
+
+    private boolean canChildScroll(int orientation, float delta) {
+        int direction = (int) -delta;
+        View child = getChildAt(0);
+        if (orientation == 0) {
+            return child.canScrollHorizontally(direction);
+        } else if (orientation == 1) {
+            return child.canScrollVertically(direction);
+        } else {
+            throw new IllegalArgumentException();
         }
-        return v == null ? null : (ViewPager2) v;
     }
 
-    public boolean onInterceptTouchEvent(MotionEvent e) {
-        ViewPager2 parentViewPager = getParentViewPager();
+    private void handleInterceptTouchEvent(MotionEvent e) {
         if (parentViewPager == null) {
-            return super.onInterceptTouchEvent(e);
+            return;
         }
-
-        ViewParent parent = getParent();
         int orientation = parentViewPager.getOrientation();
+        boolean preferedDirection = preferHorizontal + preferVertical > 2;
+
+        // Early return if child can't scroll in same direction as parent and theres no prefered scroll direction
+        if (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f) && !preferedDirection) {
+            return;
+        }
+
 
         if (e.getAction() == MotionEvent.ACTION_DOWN) {
             initialX = e.getX();
             initialY = e.getY();
-            parent.requestDisallowInterceptTouchEvent(true);
+            getParent().requestDisallowInterceptTouchEvent(true);
         } else if (e.getAction() == MotionEvent.ACTION_MOVE) {
-            int dx = (int) (e.getX() - initialX);
-            int dy = (int) (e.getY() - initialY);
-            boolean isVpHorizontal = orientation == ORIENTATION_HORIZONTAL;
+            float dx = e.getX() - initialX;
+            float dy = e.getY() - initialY;
+            boolean isVpHorizontal = orientation == ViewPager2.ORIENTATION_HORIZONTAL;
 
             // 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);
+            float scaledDx = Math.abs(dx) * (isVpHorizontal ? 1f : 0.5f) * preferHorizontal;
+            float scaledDy = Math.abs(dy) * (isVpHorizontal ? 0.5f : 1f) * preferVertical;
             if (scaledDx > touchSlop || scaledDy > touchSlop) {
-                int value = isVpHorizontal ? dy : dx;
                 if (isVpHorizontal == (scaledDy > scaledDx)) {
-                    // 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));
+                    // Gesture is perpendicular, allow all parents to intercept
+                    getParent().requestDisallowInterceptTouchEvent(preferedDirection);
                 } else {
-                    parent.requestDisallowInterceptTouchEvent(child.canScrollVertically(direction));
+                    // 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);
+                    }
                 }
             }
-        }
 
-        return super.onInterceptTouchEvent(e);
+        }
     }
 }