《Cocos2d-x3.x游戏开发之旅》学习

1.addEventListenerWidthSceneGraphPriority函数，这个函数的两个参数作用如下:

EventListener *listener:事件监听对象，当触摸事件发生时通过它来回调;
Node *node:绑定的对象，当node对象被释放时，监听事件的注册也会被取消，同时，有多个触摸事件发生时(比如几个按钮叠加在一起),会根据node层次优先回调(越在上面的对象越先回调);

addEventListenerWithFixedPriority,也是用于注册监听事件，但这个函数需要手动指定触摸事件回调的优先级，并且需要手动取消监听事件。一帮情况下，我们使用addEventListenerWidthSceneGraphPriority就可以了。

bool HelloWorld::init() {
    if (!Layer::init()) { return false; }
    
    Size visibleSize = Director::getInstance()->getVisibleSize();

    /* 创建两个精灵，相互有重叠的部分 */
    
    Sprite *sp1 = Sprite::create("sprite1.png");
    sp1->setPosition(Point(visibleSize.width * 0.5f, visibleSize.height * 0.5f));
    this->addChild(sp1);

    Sprite *sp2 = Sprite::create("sprite2.png");
    sp2->setPosition(Point(visibleSize.width * 0.5f, visibleSize.height * 0.5f));
    this->addChild(sp2);

    auto listener = EventListenerTouchOneByOne::create();
    listener->onTouchBegan = [](Touch *touch, Event *event) {
        /* 注册监听事件时绑定了一个Node对象，在这里就可以取出这个对象 */
        auto target = static_cast<Sprite *>(event->getCurrentTarget());
        Point pos = Director::getInstance()->convertToGL(touch->getLocationInView());

        /* 判断单击的坐标是否在精灵的范围内 */
        if (target->getBoundingBox().containsPoint(pos)) {
            /* 设置精灵的透明度为100 */
            target->setOpacity(100);
            return true;
        }

        return false;
    };
    listener->onTouchEnded = [](Touch *touch, Event *event) {
        /* 恢复精灵的透明度 */
        auto target = static_cast<Sprite *>(event->getCurrentTarget());
        target->setOpacity(255);
    };
    /* 注册监听事件，绑定精灵1 */
    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, sp1);

    /*注册监听事件，绑定精灵2，这里要注意，listener对象复制了一份*/
    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener->clone(), sp2);
    return true;
}

分步骤来讲解:

a) 创建两个精灵，让这两个精灵刚好有部分位置是重叠的;

b) 创建EventListenerTouchOneByOne监听事件;

c) 在onTouchBegan函数里获取事件绑定的精灵对象，判断单击的坐标是否在精灵的范围内，是的话，则修改精灵的透明度为100;

d) 调用addEventListenerWithSceneGraphPriority函数分别添加两个精灵的监听事件;

通常我们要求在单击重叠部位的时候，只有上面的按钮能获得响应。要实现这个效果，很简单，我们给listener调用一个函数即可:

.listener->setSwallowTouches(true);

setSwallowTouches函数用于设置是否吞没事件。

2.多点触控

bool HelloWorld::init() {
    if (!Layer::init()) { return false; }
    auto listener = EventListenerTouchAllAtOnce::create();
    listener->onTouchesBegan = [](const std::vector<Touch *>& touches, Event *event) {};
    listener->onTouchesMoved = [](const std::vector<Touch *>& touches, Event *event) {};
    listener->onTouchesEnded = [](const std::vector<Touch *>& touches, Event *event) {};
    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);
    return true;
}

bool HelloWorld::init() {
    if (!Layer::init()) { return false; }
    Label *logText1 = Label::create("", "Arial", 24);
    logText1->setPosition(Point(400, 280));
    this->addChild(logText1, 1, 1);

    Label *logText2 = Label::create("", "Arial", 24);
    logText3->setPosition(Point(400, 100));
    this->addChild(logText3, 1, 3);
    auto listener = EventListenerTouchAllAtOnce::create();

    listener->onTouchesBegan = [&](const std::vector<Touch *>& touches, Event *event) {
        auto logText = (Label *)this->getChildByTag(1);
        int num = touches.size();
        logText->setString(Value(num).asString() + " Touches:");
    };

    listener->onTouchesMoved = [&](const std::vector<Touch *>& touches, Event *event) {
        auto logText = (Label *)this->getChildByTag(2);
        int num = touches.size();
        std::string text = Value(num).asString() + " Touches:";
        for (auto &touch : touches) {
            auto location = touch->getLocation();
            text += "[touchID" + Value(touch->getID()).asString() + "],";
        }
        logText->setString(text);
    };

    listener->onTouchesEnded = [&](const std::vector<Touch *>& touches, Event *event) {
        auto logText = (Label *)this->getChildByTag(3);
        int num = touches.size();
        logText->setString(Value(num).asString() + " Touches:");
    };

    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);
    return true;
}

《Cocos2d-x3.x游戏开发之旅》学习

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