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cocos2dx-3.X中对事件处理分析(2),
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- 上一篇中,我们大致分析了一下事件处理的整个概括,这一篇,我们来针对EventDispatcher这个核心的事件处理类中的一些函数进行分析,主要涉及到事件的添加,处理, 移除。
- 1、
- 添加事件:
- 1.1.
- /** Adds a event listener for a specified event with the priority of scene graph.
- * @param listener The listener of a specified event.
- * @param node The priority of the listener is based on the draw order of this node.
- * @note The priority of scene graph will be fixed value 0. So the order of listener item
- * in the vector will be ' <0,scene graph (0 priority),>0'.
- */
- //注释部分说的很明确,用这个函数,优先级固定为0
- void addEventListenerWithSceneGraPHPriority(EventListener* listener,Node* node);
- -------》》》
- void EventDispatcher::addEventListenerWithSceneGraPHPriority(EventListener* listener,Node* node)
- {
- CCASSERT(listener && node,"Invalid parameters.");
- CCASSERT(!listener->isRegistered(),"The listener has been registered.");
-
- if (!listener->checkAvailable())
- return;
-
- listener->setAssociatedNode(node);
- listener->setFixedPriority(0); //这里就是对应上面的注释,优先级为0
- listener->setRegistered(true);
-
- addEventListener(listener); //添加监听器
- }
- 1.2.
- 我们再来看另外一个添加函数:
- /** Adds a event listener for a specified event with the fixed priority.
- * @param listener The listener of a specified event.
- * @param fixedPriority The fixed priority of the listener.
- * @note A lower priority will be called before the ones that have a higher value.
- * 0 priority is forbidden for fixed priority since it's used for scene graph based priority.
- */
- //这个添加函数需要传入一个优先级,但是最终调用的也是addEventListener函数
- void addEventListenerWithFixedPriority(EventListener* listener,int fixedPriority);
- 1.3.添加Custom事件的函数
- /** Adds a Custom event listener.
- It will use a fixed priority of 1.
- * @param eventName A given name of the event.
- * @param callback A given callback method that associated the event name.
- * @return the generated event. Needed in order to remove the event from the dispather
- */
- EventListenerCustom* addCustomEventListener(const std::string &eventName,const std::function<void(EventCustom*)>& callback);
- -→>>>
- EventListenerCustom* EventDispatcher::addCustomEventListener(const std::string &eventName,const std::function<void(EventCustom*)>& callback)
- {
- EventListenerCustom *listener = EventListenerCustom::create(eventName,callback);
- addEventListenerWithFixedPriority(listener,1); //最终还是调用addEventListener(listener);方法,下面我们就来看下这个方法:
- return listener;
- }
- 1.4、
- 既然所有的添加事件,最终都会调用addEventListener函数,我们就去这个函数中看一下:
- /** Adds an event listener with item
- * @note if it is dispatching event,the added operation will be delayed to the end of current dispatch
- * @see forceAddEventListener
- */
- void addEventListener(EventListener* listener);
- ----→>>>
- void EventDispatcher::addEventListener(EventListener* listener)
- {
- if (_inDispatch == 0)
- {
- forceAddEventListener(listener); //主要是这个函数
- }
- else
- {
- _toAddedListeners.push_back(listener); //这个是个临时存储
- }
-
- listener->retain();
- }
-
- --→>>>我们进入这个函数中去看下:
- void EventDispatcher::forceAddEventListener(EventListener* listener)
- {
- EventListenerVector* listeners = nullptr;
- //每一种事件都有一个特定的listenerID,其实就是一个字符串标记,如
- const std::string EventListenerTouchOneByOne::LISTENER_ID = "__cc_touch_one_by_one";,根据这个标记,即可以对所有的事件进行分类,
- 每一种分类都会记录在下面这个map中。
- /** Listeners map */
- std::unordered_map<EventListener::ListenerID,EventListenerVector*> _listenerMap;
- EventListener::ListenerID listenerID = listener->getListenerID();
- auto itr = _listenerMap.find(listenerID);
- if (itr == _listenerMap.end())
- {
-
- listeners = new (std::nothrow) EventListenerVector();
- _listenerMap.insert(std::make_pair(listenerID,listeners));
- }
- else
- {
- listeners = itr->second;
- }
-
- listeners->push_back(listener); //假如到分类的列表中
- //这里对优先级为0的进行了特殊处理,刚才在上面有个添加函数,优先级固定为0,这里对他要进行一些特殊处理
- if (listener->getFixedPriority() == 0)
- {
- setDirty(listenerID,DirtyFlag::SCENE_GRAPH_PRIORITY);
-
- auto node = listener->getAssociatedNode();
- CCASSERT(node != nullptr,"Invalid scene graph priority!");
-
- associateNodeAndEventListener(node,listener);
-
- if (node->isRunning())
- {
- resumeEventListenersForTarget(node);
- }
- }
- else
- {
- setDirty(listenerID,DirtyFlag::FIXED_PRIORITY);
- }
- }
-
- 注意:
- EventListenerCustom* addCustomEventListener(const std::string &eventName,const std::function<void(EventCustom*)>& callback);
- 在使用上面这个函数添加Custom事件时,Custom事件的ListenerID就是传进来的eventName函数。