c++ - Cocos2d-x : How can I draw a resizing rectangle?

Question

我正在使用 Cocos2d-x 3.4(出色的框架 BTW :))开发一个项目。我想知道如何绘制一个简单的半透明选区，您可以在 Windows 上看到相同的选区？

http://cdn.maximumpcguides.com/windows-7/wp-content/uploads/2010/11/use-translucent-select-rectangle-2.png

我尝试使用 DrawNode 类，但未能实现这一点:'(我希望有人能告诉我正确的方法，请:-)

Answer 1

使用 DrawNode 绘制非常简单。

在 onTouchBegan 事件上设置起点，在 onTouchMoved 事件上设置终点。

// HelloWorld.h
class HelloWorld : public Layer{
public:
    ...
    bool onTouchBegan(const Touch *touch, Event *event);
    void onTouchMoved(const Touch *touch, Event *event);
    void onTouchEnded(const Touch *touch, Event *event);

protected:
    Vec2 _originPoint;
    Vec2 _destinationPoint;
    DrawNode *_drawNode;
};


// HelloWorld.cpp 
bool HelloWorld::init()
{
    if ( !Layer::init() ) return false;

    // Add touch listener
    auto listener = EventListenerTouchOneByOne::create();
    listener->setSwallowTouches(true);
    listener->onTouchBegan = CC_CALLBACK_2(HelloWorld::onTouchBegan, this);
    listener->onTouchMoved = CC_CALLBACK_2(HelloWorld::onTouchMoved, this);
    listener->onTouchEnded = CC_CALLBACK_2(HelloWorld::onTouchEnded, this);
    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);

    // Create the draw node
    _drawNode = DrawNode::create();
    addChild(_drawNode);

    return true;
}

bool HelloWorld::onTouchBegan(const cocos2d::Touch *touch, cocos2d::Event *event)
{
    _originPoint = touch->getLocation();
    _destinationPoint = _originPoint;

    return true;
}

void HelloWorld::onTouchMoved(const cocos2d::Touch *touch, cocos2d::Event *event)
{
    _destinationPoint = touch->getLocation();

    _drawNode->clear();
    _drawNode->drawSolidRect(_originPoint, _destinationPoint, Color4F(0,0,1,0.2));
    _drawNode->drawRect(_originPoint, _destinationPoint, Color4F::BLUE);
}

void HelloWorld::onTouchEnded(const cocos2d::Touch *touch, cocos2d::Event *event)
{
    _drawNode->clear();
}