[cocos2d-x]关于3.x的触摸机制

触摸机制的概念

通过对要监听触摸的节点进行注册，然后自定义相应的触摸函数，由事件监听器实现对触摸的监听并且实现相应的响应动作。

触摸的分类

单点触摸
下面是实现单点触摸监听的步骤：

//第一步：先创建一个要进行触摸检测的精灵
auto spr=Sprite::create("helloworld.png");
//第二步：创建一个事件监听器
auto touchListener= EventListenerTouchOneByOne::create();
//第三步：设置不让触摸检测传递到下一层
touchListener->setSwallowTouches(true);

//******重点*****
//第四步（第一种方法）：设置相应的触摸函数
//先在头文件中声明四个回调函数：
std::function<bool(Touch*t, Event*)>onTouchBegan;
std::function<void(Touch*, Event*)>onTouchMoved;  
std::function<void(Touch*, Event*)>onTouchEnded;  
std::function<void(Touch*, Event*)> onTouchCancelled;
//然后在设置对应函数：
listner>onTouchBegan=CC_CALLBACK_2(GameTest::onTouchBegan,this);
listner->onTouchMoved=CC_CALLBACK_2(GameTest::onTouchMoved, this);
listner->onTouchEnded=CC_CALLBACK_2(GameTest::onTouchEnded, this);
//将监听器添加带事件派发器中
_eventDispatcher->addEventListenerWithSceneGraphPriority(listner, spr);
//给监听器设置优先级，越高越先响应
listner->setFixedPriority(1);

//第四步（第二种方法）：使用lambda表达式，这种更加方便
listner->onTouchBegan = [](Touch*t, Event*e) {  return true; };
listner->onTouchMoved = [](Touch*t, Event*e) {};
listner->onTouchEnded = [](Touch*t, Event*e) {};

多点触摸
多点触摸和单点触摸类似，不过使用的参数使用vector数组来存储了多个touch触摸点的坐标位置，下面是不同的地方

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;

触摸函数的两个参数的含义

Touch*的作用：传入触摸点的坐标位置，下面是Touch类中提供的一些方法。

    Vec2 getLocation() const;
    /** Returns the previous touch location in OpenGL coordinates.
     *
     * @return The previous touch location in OpenGL coordinates.
     */
    Vec2 getPreviousLocation() const;
    /** Returns the start touch location in OpenGL coordinates.
     *
     * @return The start touch location in OpenGL coordinates.
     */
    Vec2 getStartLocation() const;
    /** Returns the delta of 2 current touches locations in screen coordinates.
     *
     * @return The delta of 2 current touches locations in screen coordinates.
     */
    Vec2 getDelta() const;
    /** Returns the current touch location in screen coordinates.
     *
     * @return The current touch location in screen coordinates.
     */
    Vec2 getLocationInView() const;
    /** Returns the previous touch location in screen coordinates. 
     *
     * @return The previous touch location in screen coordinates.
     */
    Vec2 getPreviousLocationInView() const;
    /** Returns the start touch location in screen coordinates.
     *
     * @return The start touch location in screen coordinates.
     */
    Vec2 getStartLocationInView() const;

    /** Set the touch information. It always used to monitor touch event.
     *
     * @param id A given id
     * @param x A given x coordinate.
     * @param y A given y coordinate.
     */

Event*作用：主要是传入要进行操作的对象比如：键盘，鼠标，游戏手柄等等，下面是它提供的一些函数。

    Type getType() const { return _type; }

    /** Stops propagation for current event.
     */
    void stopPropagation() { _isStopped = true; }

    /** Checks whether the event has been stopped.
     *
     * @return True if the event has been stopped.
     */
    bool isStopped() const { return _isStopped; }

    /** Gets current target of the event.
     * @return The target with which the event associates.
     * @note It's only available when the event listener is associated with node.
     *        It returns 0 when the listener is associated with fixed priority.
     */
    Node* getCurrentTarget() { return _currentTarget; }

其他注意事项

virtual bool onTouchBegan( Touch *Touch, Event *Event);

①如果返回false，则本层的onTouchMoved(),onTouchEnded()不会再接收到消息，但是本层之下的其它层会接收到消息

②如果返回true，则本层的onTouchMoved(),onTouchEnded()可以接收到消息，但是本层之下的其它层不能再接收到消息