cocos2d-x 3.0 触摸机制的使用

http://blog.csdn.net/decajes/article/details/38233645cocos2d-x 3.0版本的事件分发的机制较之之前的版本进行了修改，把事件处理的逻辑分离出来，并通过不同的事件监听器来监听不同的事件。当一个节点收到了事件,就会指派一个事件分发器_eventDispatcher专门来分发这些事件。对于触摸来说，大概的过程就是我们先创建一个对应触摸事件的监听器，然后覆盖触摸事件的函数，并把它们绑定到监听器，然后可以设置一下这个监听器的属性，最后把监听器添加到分发器之中，系统就会自动进行触摸事件的处理。我们先看看单点触摸的使用，下面是源代码中关于单点触摸监听器的类，可以看到[cpp] view
plaincopyclass EventListenerTouchOneByOne: public EventListener{public:static const std::string LISTENER_ID;static EventListenerTouchOneByOne* create();virtual~EventListenerTouchOneByOne();void setSwallowTouches(bool needSwallow);bool isSwallowTouches();///Overridesvirtual EventListenerTouchOneByOne* clone() override;virtual bool checkAvailable() override;//public:std::function<bool(Touch*, Event*)>onTouchBegan;std::function<void(Touch*, Event*)>onTouchMoved;std::function<void(Touch*, Event*)>onTouchEnded;std::function<void(Touch*, Event*)> onTouchCancelled;private:EventListener TouchOneByOne();bool init();std::vector<Touch*>_claimedTouches;bool _needSwallow;friend class EventDispatcher;};</span>这个类看上去比较容易理解，下面我们用代码来演示一下怎么使用。在HelloWorld的init函数中注册监听器并添加到事件分发器中去。[cpp] view
plaincopy//添加一个测试的精灵autoonion = Sprite::create("onion.png");onion->setPosition(Point(visibleSize.width/2, visibleSize.height/2));onion->setScale(0.2);this->addChild(onion);//创建一个触摸监听器，这里使用单点触摸事件autoTouchListenr = EventListenerTouchOneByOne::create();//设置吞噬为true，不让触摸往下传递TouchListenr->setSwallowTouches(true);//和回调函数绑定TouchListenr->onTouchBegan= CC_CALLBACK_2(HelloWorld::onTouchBegan,this);TouchListenr->onTouchMoved= CC_CALLBACK_2(HelloWorld::onTouchMoved,this);TouchListenr->onTouchEnded= CC_CALLBACK_2(HelloWorld::onTouchEnded,this);//添加监听器到事件分发器中_eventDispatcher->addEventListenerWithSceneGraphPriority(TouchListenr,onion);下面我们覆盖单点触摸中提供的触摸函数：[cpp] view
plaincopybool HelloWorld::onTouchBegan(Touch* touch, Event* event){//获取精灵对象并取得精灵的矩阵autosprite = static_cast<Sprite*>(event->getCurrentTarget());Rect rect = sprite->getBoundingBox();//获取触摸点的坐标Point point = touch->getLocation();//判断触摸点是否在精灵的矩阵范围内if(rect.containsPoint(point)){return true;}return false;}void HelloWorld::onTouchMoved(Touch* touch, Event* event){//获取精灵对象autosprite = static_cast<Sprite*>(event->getCurrentTarget());//改变精灵的位置sprite->setPosition(sprite->getPosition()+ touch->getDelta());}void HelloWorld::onTouchEnded(Touch* touch, Event* event){CCLog("touch end!");}点击调试运行，可以在屏幕中拉动所测试的精灵，如下图：在上面的例子中我们看到了，传递过来的参数主要有Touch* touch和Event* event，我们可以进入源代码中查看他们的作用。Touch类是继承了REF，查看源代码中的主要成员如下：[cpp] view
plaincopy/**returns the current touch location in OpenGL coordinates */Point getLocation() const;/**returns the previous touch location in OpenGL coordinates */Point getPreviousLocation() const;/**returns the start touch location in OpenGL coordinates */Point getStartLocation() const;/**returns the delta of 2 current touches locations in screen coordinates */Point getDelta() const;/**returns the current touch location in screen coordinates */Point getLocationInView() const;/**returns the previous touch location in screen coordinates */Point getPreviousLocationInView() const;/**returns the start touch location in screen coordinates */Point getStartLocationInView() const;也就是Touch传入的是触摸点的坐标位置，并且Touch类为我们提供一些坐标的写法，那么我们就方便很多了。譬如上面例子中的触摸移动时，Touch就为我提供一个getDelta()来计算点的位移。而对于Event类，主要是传入处理的对象，看源代码有以下主要成员：[cpp] view
plaincopy/**Gets the event type */inline Type getType() const { return_type; };/**Stops propagation for current event */inline void stopPropagation() { _isStopped = true; };/**Checks whether the event has been stopped */inline bool isStopped() const { return_isStopped; };/**@brief Gets current target of the event* @return The target with which the eventassociates.* @note It onlys be available when the eventlistener is associated with node.* It returns 0 when the listener isassociated with fixed priority.*/inline Node* getCurrentTarget() { return_currentTarget; };那么我们在处理触摸对象的时候和例子那样通过getCurrentTarget()来获取对象并处理即可。另一方面，我们在把监听器添加到事件分发器的时候，会看到代码提示两种方法，一个为：addEventListenerWithSceneGraphPriority，另一个为addEventListenerWithFixedPriority。同样可以查看源代码如下：[cpp] view
plaincopy/**Adds a event listener for a specified event with the priority of scene graph.* @param listener The listener of a specifiedevent.* @param node The priority of the listener isbased on the draw order of this node.* @note The priority of scene graph will be fixed value 0. So the order oflistener item* in the vector will be ' <0, scenegraph (0 priority), >0'.*/voidaddEventListenerWithSceneGraphPriority(EventListener*listener, Node* node);/**Adds a event listener for a specified event with the fixed priority.* @param listener The listener of a specifiedevent.* @param fixedPriority The fixed priority ofthe listener.* @note A lower priority will be called beforethe ones that have a higher value.* 0 priority is forbidden for fixedpriority since it's used for scene graph based priority.*/voidaddEventListenerWithFixedPriority(EventListener*listener, int fixedPriority);根据注释可以知道，前者的触发优先级是按照第二个参数中的node的显示顺序来确定的，而且默认的fixedPriority为0，也就是如果精灵位置靠前，则会优先响应触摸。而后者按照第二个参数的整形变量值的大小来确定的，而且不能为0，值越小那么优先响应触摸。两者除了优先级不一样，移除的过程也有差异。前者会在触摸对象对应的node析构之后系统会帮我们调用移除触摸，但是后者就需要我们手动移除，这一点要注意。下面我们可以修改上述例子的代码，添加多两个精灵，然后在分发事件代码中添加：[cpp] view
plaincopy_eventDispatcher->addEventListenerWithSceneGraphPriority(TouchListenr->clone(),onion2);_eventDispatcher->addEventListenerWithSceneGraphPriority(TouchListenr->clone(),onion3);点击运行可以测试一下，没有问题。要是想使用addEventListenerWithFixedPriority的方式的话，虽然可以自定义优先级，但是由于没有绑定node对象，所以还需要在触摸函数中引入需要控制的对象才行。但是最后别忘了使用_eventDispatcher->removeEventListener(listerName);来实现监听器的移除。多点触摸和单点触摸类似，看下面多点触摸监听器的源码。[cpp] view
plaincopyclass EventListenerTouchAllAtOnce: public EventListener{public:static const std::string LISTENER_ID;static EventListenerTouchAllAtOnce* create();virtual ~EventListenerTouchAllAtOnce();///Overridesvirtua lEventListenerTouchAllAtOnce* clone() override;virtual bool checkAvailable() override;//public:std::function<void(conststd::vector<Touch*>&,Event*)> onTouchesBegan;std::function<void(conststd::vector<Touch*>&,Event*)> onTouchesMoved;std::function<void(conststd::vector<Touch*>&,Event*)> onTouchesEnded;std::function<void(conststd::vector<Touch*>&,Event*)> onTouchesCancelled;private:EventListener TouchAllAtOnce();bool init();private:friend class EventDispatcher;};

可以发现多点触摸就是传入多个Touch对象而已，然后处理的时候可以遍历vector<Touch*>来逐个处理每一个点，例子可以参考源码自带的例子MutiTouchTest。

文章写到这里为止，如有理解不当，请不吝赐教，谢谢。