在官方文档中,node对象有一个_eventDispatcher成员变量,所以继承node的对象也有这个变量。
当我们需要去层等没有集成点击事件的节点监听点击事件时,需要这样,实例代码:
- 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);
- }
作为初学者,我刚看到这样的代码有点不懂,两个添加事件监听的方法,即:
addEventListenerWithFixedPriority和addEventListenerWithSceneGraphPriority。
于是官网上学习,发现后者可以实现当节点销毁时,同时销毁添加的事件监听。
前者官网上有相应的解释,但是不没有理解。后来学习了官网实例,才了解了addEventListenerWithFixedPriority的作用。所以学习还是要理论和实践相结合。
对于addEventListenerWithFixedPriority(EventListener* listener, int fixedPriority),需要传两个参数,一个是需要监听的事件,另一个是监听的事件等级,等级越小,事件越靠前。
这个是官方示例,当我点击黄色和红色区域时,先收到点击事件的是红色图片。如下图:
因为给上面各个图片的点击事件中,蓝色的fixedPriority为30, 红色的fixedPriority为35,黄色的fixedPriority为40,所以,如果点击蓝色和红色的共同区域,先收到事件的是蓝色;点击红色和黄色的共同区域,先收到事件的是红色。
下面是实例代码:
- // 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);
- }