Merge pull request #26 from FastComments/nested-view-pager

Improved support for nested view pagers

Author: winrid

libraries/sdk/src/main/java/com/fastcomments/sdk/NestedScrollableHost.java

@@ -0,0 +1,147 @@
+package com.fastcomments.sdk;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.ViewConfiguration;
+import android.widget.FrameLayout;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.viewpager2.widget.ViewPager2;
+
+/**
+ * Layout that prevents horizontal touch event conflicts when nesting a horizontal ViewPager2
+ * inside another horizontal ViewPager2. This specifically handles the case where image galleries
+ * need to work properly when the feed is embedded in a parent ViewPager2.
+ * 
+ * Key behaviors:
+ * - Only handles horizontal scroll conflicts (preserves vertical scrolling)
+ * - Allows child ViewPager2 to consume horizontal swipes when it can scroll
+ * - Delegates to parent when child reaches horizontal bounds
+ * - Never interferes with vertical scrolling of the feed
+ * 
+ * Based on Google's NestedScrollableHost but optimized for horizontal-only conflicts.
+ */
+public class NestedScrollableHost extends FrameLayout {
+    private int touchSlop;
+    private float initialX = 0f;
+    private float initialY = 0f;
+
+    public NestedScrollableHost(@NonNull Context context) {
+        super(context);
+        init();
+    }
+
+    public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs);
+        init();
+    }
+
+    public NestedScrollableHost(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+        init();
+    }
+
+    private void init() {
+        touchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
+    }
+
+    @Override
+    public boolean onInterceptTouchEvent(MotionEvent ev) {
+        handleInterceptTouchEvent(ev);
+        return super.onInterceptTouchEvent(ev);
+    }
+
+    private void handleInterceptTouchEvent(MotionEvent ev) {
+        switch (ev.getAction()) {
+            case MotionEvent.ACTION_DOWN:
+                initialX = ev.getX();
+                initialY = ev.getY();
+                // Don't block parent initially - let them know we might want to handle horizontals
+                break;
+
+            case MotionEvent.ACTION_MOVE:
+                float deltaX = Math.abs(ev.getX() - initialX);
+                float deltaY = Math.abs(ev.getY() - initialY);
+                
+                // Only handle horizontal scroll conflicts when parent is horizontal ViewPager2
+                if (isParentHorizontalViewPager() && deltaX > touchSlop && deltaX > deltaY) {
+                    // This is primarily a horizontal swipe
+                    boolean swipeLeft = (ev.getX() - initialX) < 0;
+                    
+                    // Check if our child ViewPager2 can scroll in the swipe direction
+                    if (canChildScrollHorizontally(swipeLeft)) {
+                        // Child can handle this horizontal scroll, block parent
+                        getParent().requestDisallowInterceptTouchEvent(true);
+                    } else {
+                        // Child can't scroll further horizontally, let parent handle
+                        getParent().requestDisallowInterceptTouchEvent(false);
+                    }
+                } else if (deltaY > touchSlop && deltaY > deltaX) {
+                    // This is primarily a vertical swipe - always let parent handle
+                    // (for feed scrolling)
+                    getParent().requestDisallowInterceptTouchEvent(false);
+                }
+                break;
+                
+            case MotionEvent.ACTION_UP:
+            case MotionEvent.ACTION_CANCEL:
+                // Reset state
+                getParent().requestDisallowInterceptTouchEvent(false);
+                break;
+        }
+    }
+
+    /**
+     * Check if the child view can scroll horizontally in the specified direction
+     * @param swipeLeft true if swiping left, false if swiping right
+     * @return true if the child can scroll in the specified direction
+     */
+    private boolean canChildScrollHorizontally(boolean swipeLeft) {
+        View child = getChildAt(0);
+        if (child == null) {
+            return false;
+        }
+
+        if (swipeLeft) {
+            // Swiping left means scrolling to show next item (positive direction)
+            return child.canScrollHorizontally(1);
+        } else {
+            // Swiping right means scrolling to show previous item (negative direction)
+            return child.canScrollHorizontally(-1);
+        }
+    }
+
+    /**
+     * Check if there's a parent ViewPager2 that's oriented horizontally
+     * We only need to handle conflicts with horizontal parent ViewPagers
+     */
+    private boolean isParentHorizontalViewPager() {
+        ViewPager2 parentVp = findParentViewPager2();
+        if (parentVp != null) {
+            return parentVp.getOrientation() == ViewPager2.ORIENTATION_HORIZONTAL;
+        }
+        // If no parent ViewPager2, no conflict to handle
+        return false;
+    }
+
+    /**
+     * Find the parent ViewPager2 in the view hierarchy
+     */
+    private ViewPager2 findParentViewPager2() {
+        View parent = (View) getParent();
+        while (parent != null) {
+            if (parent instanceof ViewPager2) {
+                return (ViewPager2) parent;
+            }
+            if (parent.getParent() instanceof View) {
+                parent = (View) parent.getParent();
+            } else {
+                break;
+            }
+        }
+        return null;
+    }
+}

libraries/sdk/src/main/res/layout/feed_post_item_multi_image.xml

@@ -152,11 +152,17 @@
                 </LinearLayout>
             </LinearLayout>
 
-            <!-- ViewPager for 4+ images -->
-            <androidx.viewpager2.widget.ViewPager2
-                android:id="@+id/imageViewPager"
+            <!-- ViewPager for 2+ images wrapped in NestedScrollableHost -->
+            <com.fastcomments.sdk.NestedScrollableHost
                 android:layout_width="match_parent"
-                android:layout_height="300dp" />
+                android:layout_height="300dp">
+                
+                <androidx.viewpager2.widget.ViewPager2
+                    android:id="@+id/imageViewPager"
+                    android:layout_width="match_parent"
+                    android:layout_height="match_parent" />
+                    
+            </com.fastcomments.sdk.NestedScrollableHost>
 
             <!-- Image Counter (smaller size) -->
             <TextView