在官方文檔中,node對象有一個_eventDispatcher成員變量,所以繼承node的對象也有這個變量。
當我們需要去層等沒有集成點擊事件的節點監聽點擊事件時,需要這樣,實例代碼:
- listener->onTouchBegan = [=](Touch* touch, Event* event){
- Vec2 locationInNode = this->convertToNodeSpace(touch->getLocation());
- Size s = this->getContentSize();
- Rect rect = Rect(0, 0, s.width, s.height);
- if (rect.containsPoint(locationInNode))
- {
- this->setColor(Color3B::RED);
- return true;
- }
- return false;
- };
- listener->onTouchEnded = [=](Touch* touch, Event* event){
- this->setColor(Color3B::WHITE);
- if (_removeListenerOnTouchEnded)
- {
- _eventDispatcher->removeEventListener(listener);
- }
- };
- if (_fixedPriority != 0)
- {
- _eventDispatcher->addEventListenerWithFixedPriority(listener, _fixedPriority);
- }
- else
- {
- _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);
- }
作爲初學者,我剛看到這樣的代碼有點不懂,兩個添加事件監聽的方法,即:
addEventListenerWithFixedPriority和addEventListenerWithSceneGraphPriority。
於是官網上學習,發現後者可以實現當節點銷燬時,同時銷燬添加的事件監聽。
前者官網上有相應的解釋,但是不沒有理解。後來學習了官網實例,才瞭解了addEventListenerWithFixedPriority的作用。所以學習還是要理論和實踐相結合。
對於addEventListenerWithFixedPriority(EventListener* listener, int fixedPriority),需要傳兩個參數,一個是需要監聽的事件,另一個是監聽的事件等級,等級越小,事件越靠前。
這個是官方示例,當我點擊黃色和紅色區域時,先收到點擊事件的是紅色圖片。如下圖:
因爲給上面各個圖片的點擊事件中,藍色的fixedPriority爲30, 紅色的fixedPriority爲35,黃色的fixedPriority爲40,所以,如果點擊藍色和紅色的共同區域,先收到事件的是藍色;點擊紅色和黃色的共同區域,先收到事件的是紅色。
下面是實例代碼:
- // FixedPriorityChangedTest
- class TouchableSprite : public Sprite
- {
- public:
- static TouchableSprite* create(int priority = 0)
- {
- auto ret = new (std::nothrow) TouchableSprite(priority);
- if (ret && ret->init())
- {
- ret->autorelease();
- }
- else
- {
- CC_SAFE_DELETE(ret);
- }
- return ret;
- }
- protected:
- TouchableSprite(int priority)
- : _listener(nullptr)
- , _fixedPriority(priority)
- , _removeListenerOnTouchEnded(false)
- {
- }
- public:
- void onEnter() override
- {
- Sprite::onEnter();
- auto listener = EventListenerTouchOneByOne::create();
- listener->setSwallowTouches(true);
- listener->onTouchBegan = [=](Touch* touch, Event* event){
- Vec2 locationInNode = this->convertToNodeSpace(touch->getLocation());
- Size s = this->getContentSize();
- Rect rect = Rect(0, 0, s.width, s.height);
- if (rect.containsPoint(locationInNode))
- {
- this->setColor(Color3B::RED);
- return true;
- }
- return false;
- };
- listener->onTouchEnded = [=](Touch* touch, Event* event){
- this->setColor(Color3B::WHITE);
- if (_removeListenerOnTouchEnded)
- {
- _eventDispatcher->removeEventListener(listener);
- }
- };
- if (_fixedPriority != 0)
- {
- _eventDispatcher->addEventListenerWithFixedPriority(listener, _fixedPriority);
- }
- else
- {
- _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);
- }
- _listener = listener;
- }
- void onExit() override
- {
- _eventDispatcher->removeEventListener(_listener);
- Sprite::onExit();
- }
- void removeListenerOnTouchEnded(bool toRemove) { _removeListenerOnTouchEnded = toRemove; };
- inline EventListener* getListener() { return _listener; };
- private:
- EventListener* _listener;
- int _fixedPriority;
- bool _removeListenerOnTouchEnded;
- };
- void FixedPriorityTest::onEnter()
- {
- EventDispatcherTestDemo::onEnter();
- Vec2 origin = Director::getInstance()->getVisibleOrigin();
- Size size = Director::getInstance()->getVisibleSize();
- auto sprite1 = TouchableSprite::create(30);
- sprite1->setTexture("Images/CyanSquare.png");
- sprite1->setPosition(origin+Vec2(size.width/2, size.height/2) + Vec2(-80, 40));
- addChild(sprite1, 10);
- auto sprite2 = TouchableSprite::create(35);
- sprite2->setTexture("Images/MagentaSquare.png");
- sprite2->setPosition(origin+Vec2(size.width/2, size.height/2));
- addChild(sprite2, 20);
- auto sprite3 = TouchableSprite::create(40);
- sprite3->setTexture("Images/YellowSquare.png");
- sprite3->setPosition(Vec2(0, 0));
- sprite2->addChild(sprite3, 1);
- }