ListView - Add APIs which return the closest item in specific position in current view.

cocos/ui/UIListView.cpp

@@ -529,6 +529,118 @@ void ListView::interceptTouchEvent(TouchEventType event, Widget *sender, Touch*
     }
 }
     
+static Vec2 calculateItemPositionWithAnchor(Widget* item, const Vec2& itemAnchorPoint)
+{
+    Vec2 origin(item->getLeftBoundary(), item->getBottomBoundary());
+    Size size = item->getContentSize();
+    return origin + Vec2(size.width * itemAnchorPoint.x, size.height * itemAnchorPoint.y);
+}
+    
+static Widget* findClosestItem(const Vec2& targetPosition, const Vector<Widget*>& items, const Vec2& itemAnchorPoint, ssize_t firstIndex, float distanceFromFirst, ssize_t lastIndex, float distanceFromLast)
+{
+    CCASSERT(firstIndex >= 0 && lastIndex < items.size() && firstIndex <= lastIndex, "");
+    if (firstIndex == lastIndex)
+    {
+        return items.at(firstIndex);
+    }
+    if (lastIndex - firstIndex == 1)
+    {
+        if (distanceFromFirst <= distanceFromLast)
+        {
+            return items.at(firstIndex);
+        }
+        else
+        {
+            return items.at(lastIndex);
+        }
+    }
+    
+    // Binary search
+    ssize_t midIndex = (firstIndex + lastIndex) / 2;
+    Vec2 itemPosition = calculateItemPositionWithAnchor(items.at(midIndex), itemAnchorPoint);
+    float distanceFromMid = (targetPosition - itemPosition).length();
+    if (distanceFromFirst <= distanceFromLast)
+    {
+        // Left half
+        return findClosestItem(targetPosition, items, itemAnchorPoint, firstIndex, distanceFromFirst, midIndex, distanceFromMid);
+    }
+    else
+    {
+        // Right half
+        return findClosestItem(targetPosition, items, itemAnchorPoint, midIndex, distanceFromMid, lastIndex, distanceFromLast);
+    }
+}
+
+Widget* ListView::getClosestItemToPosition(const Vec2& targetPosition, const Vec2& itemAnchorPoint) const
+{
+    if (_items.empty())
+    {
+        return nullptr;
+    }
+    
+    // Find the closest item through binary search
+    ssize_t firstIndex = 0;
+    Vec2 firstPosition = calculateItemPositionWithAnchor(_items.at(firstIndex), itemAnchorPoint);
+    float distanceFromFirst = (targetPosition - firstPosition).length();
+    
+    ssize_t lastIndex = _items.size() - 1;
+    Vec2 lastPosition = calculateItemPositionWithAnchor(_items.at(lastIndex), itemAnchorPoint);
+    float distanceFromLast = (targetPosition - lastPosition).length();
+    
+    return findClosestItem(targetPosition, _items, itemAnchorPoint, firstIndex, distanceFromFirst, lastIndex, distanceFromLast);
+}
+
+Widget* ListView::getClosestItemToPositionInCurrentView(const Vec2& positionRatioInView, const Vec2& itemAnchorPoint) const
+{
+    // Calculate the target position
+    Size contentSize = getContentSize();
+    Vec2 targetPosition = -_innerContainer->getPosition();
+    targetPosition.x += contentSize.width * positionRatioInView.x;
+    targetPosition.y += contentSize.height * positionRatioInView.y;
+    return getClosestItemToPosition(targetPosition, itemAnchorPoint);
+}
+
+Widget* ListView::getCenterItemInCurrentView() const
+{
+    return getClosestItemToPositionInCurrentView(Vec2::ANCHOR_MIDDLE);
+}
+
+Widget* ListView::getLeftmostItemInCurrentView() const
+{
+    if (_direction == Direction::HORIZONTAL)
+    {
+        return getClosestItemToPositionInCurrentView(Vec2::ANCHOR_MIDDLE_LEFT);
+    }
+    return nullptr;
+}
+
+Widget* ListView::getRightmostItemInCurrentView() const
+{
+    if (_direction == Direction::HORIZONTAL)
+    {
+        return getClosestItemToPositionInCurrentView(Vec2::ANCHOR_MIDDLE_RIGHT);
+    }
+    return nullptr;
+}
+
+Widget* ListView::getTopmostItemInCurrentView() const
+{
+    if (_direction == Direction::VERTICAL)
+    {
+        return getClosestItemToPositionInCurrentView(Vec2::ANCHOR_MIDDLE_TOP);
+    }
+    return nullptr;
+}
+
+Widget* ListView::getBottommostItemInCurrentView() const
+{
+    if (_direction == Direction::VERTICAL)
+    {
+        return getClosestItemToPositionInCurrentView(Vec2::ANCHOR_MIDDLE_BOTTOM);
+    }
+    return nullptr;
+}
+
 ssize_t ListView::getCurSelectedIndex() const
 {
     return _curSelectedIndex;

cocos/ui/UIListView.h

@@ -220,7 +220,54 @@ public:
     virtual void removeAllChildrenWithCleanup(bool cleanup) override;
     virtual void removeChild(Node* child, bool cleaup = true) override;
     
-        
+	/**
+	 * @brief Query the closest item to a specific position in inner container.
+	 *
+	 * @param targetPosition Specifies the target position in inner container's coordinates.
+	 * @param itemAnchorPoint Specifies an anchor point of each item for position to calculate distance.
+	 * @return A item instance if list view is not empty. Otherwise, returns null.
+	 */
+	Widget* getClosestItemToPosition(const Vec2& targetPosition, const Vec2& itemAnchorPoint = Vec2::ANCHOR_MIDDLE) const;
+	
+	/**
+	 * @brief Query the closest item to a specific position in current view.
+	 *
+	 * @param positionRatioInView Specifies the target position with ratio in list view's content size.
+	 * @param itemAnchorPoint Specifies an anchor point of each item for position to calculate distance.
+	 * @return A item instance if list view is not empty. Otherwise, returns null.
+	 */
+	Widget* getClosestItemToPositionInCurrentView(const Vec2& positionRatioInView, const Vec2& itemAnchorPoint = Vec2::ANCHOR_MIDDLE) const;
+	
+    /**
+     * @brief Query the center item
+     * @return A item instance.
+     */
+    Widget* getCenterItemInCurrentView() const;
+    
+    /**
+     * @brief Query the leftmost item in horizontal list
+     * @return A item instance.
+     */
+    Widget* getLeftmostItemInCurrentView() const;
+    
+    /**
+     * @brief Query the rightmost item in horizontal list
+     * @return A item instance.
+     */
+    Widget* getRightmostItemInCurrentView() const;
+    
+    /**
+     * @brief Query the topmost item in horizontal list
+     * @return A item instance.
+     */
+    Widget* getTopmostItemInCurrentView() const;
+    
+    /**
+     * @brief Query the bottommost item in horizontal list
+     * @return A item instance.
+     */
+    Widget* getBottommostItemInCurrentView() const;
+    
     /**
      * @brief Query current selected widget's idnex.
      *

tests/cpp-tests/Classes/UITest/CocoStudioGUITest/UIListViewTest/UIListViewTest.cpp

@@ -67,10 +67,7 @@ bool UIListViewTest_Vertical::init()
         listView->setBackGroundImage("cocosui/green_edit.png");
         listView->setBackGroundImageScale9Enabled(true);
         listView->setContentSize(Size(240, 130));
-        listView->setPosition(Vec2((widgetSize.width - backgroundSize.width) / 2.0f +
+		listView->setPosition(Vec2((widgetSize - listView->getContentSize()) / 2.0f));
-                                    (backgroundSize.width - listView->getContentSize().width) / 2.0f,
-                                    (widgetSize.height - backgroundSize.height) / 2.0f +
-                                    (backgroundSize.height - listView->getContentSize().height) / 2.0f));
         listView->addEventListener((ui::ListView::ccListViewCallback)CC_CALLBACK_2(UIListViewTest_Vertical::selectedItemEvent, this));
         listView->addEventListener((ui::ListView::ccScrollViewCallback)CC_CALLBACK_2(UIListViewTest_Vertical::selectedItemEventScrollView,this));
 		listView->setScrollBarPositionFromCorner(Vec2(7, 7));
@@ -84,8 +81,7 @@ bool UIListViewTest_Vertical::init()
         Layout* default_item = Layout::create();
         default_item->setTouchEnabled(true);
         default_item->setContentSize(default_button->getContentSize());
-        default_button->setPosition(Vec2(default_item->getContentSize().width / 2.0f,
+		default_button->setPosition(Vec2(default_item->getContentSize() / 2.0f));
-                                          default_item->getContentSize().height / 2.0f));
         default_item->addChild(default_button);
         
         // set model
@@ -166,6 +162,41 @@ bool UIListViewTest_Vertical::init()
         // set items margin
         listView->setItemsMargin(2.0f);
         
+        // Show the indexes of items on each boundary.
+        {
+            float position = 75;
+            // Labels
+            Text* labels[3];
+            labels[0] = Text::create(" ", "fonts/Marker Felt.ttf", 12);
+            labels[0]->setAnchorPoint(Vec2::ANCHOR_MIDDLE);
+            labels[0]->setPosition(_uiLayer->getContentSize() / 2 + Size(0, position));
+            _uiLayer->addChild(labels[0]);
+            labels[1] = Text::create("  ", "fonts/Marker Felt.ttf", 12);
+            labels[1]->setAnchorPoint(Vec2::ANCHOR_MIDDLE);
+            labels[1]->setPosition(_uiLayer->getContentSize() / 2 + Size(140, 0));
+            _uiLayer->addChild(labels[1]);
+            labels[2] = Text::create(" ", "fonts/Marker Felt.ttf", 12);
+            labels[2]->setAnchorPoint(Vec2::ANCHOR_MIDDLE);
+            labels[2]->setPosition(_uiLayer->getContentSize() / 2 + Size(0, -position));
+            _uiLayer->addChild(labels[2]);
+            
+            // Callback
+            listView->ScrollView::addEventListener([labels](Ref* ref, ScrollView::EventType eventType) {
+                ListView* listView = dynamic_cast<ListView*>(ref);
+                if(listView == nullptr || eventType != ScrollView::EventType::CONTAINER_MOVED)
+                {
+                    return;
+                }
+                auto bottom = listView->getBottommostItemInCurrentView();
+                auto center = listView->getCenterItemInCurrentView();
+                auto top = listView->getTopmostItemInCurrentView();
+                
+                labels[0]->setString(StringUtils::format("Top index=%zd", listView->getIndex(top)));
+                labels[1]->setString(StringUtils::format("Center\nindex=%zd", listView->getIndex(center)));
+                labels[2]->setString(StringUtils::format("Bottom index=%zd", listView->getIndex(bottom)));
+            });
+        }
+        
         return true;
     }