cocos2dx-v3.0-图形绘制-draw()函数

cocos2dx已经封装了很多关于opengl的函数，可以方便的使用，在3.0v以前，是在draw编写绘制代码，3.0v以后，还是在draw函数里，但发生了点变化。

先来看一下Node类关于draw函数的申明

     virtual void draw(Renderer *renderer,const Mat4& transform,uint32_t flags);
        virtual void draw() final;

第二函数已经被声明为final，也就是不能重载（C++11规定，final函数必需要加关键词virtual).所以不能再像老版本一样使用。

重写第一个方法来绘制你自己的节点。

被TransitionFadeTR,TransitionSplitColsTransitionTurnOffTilesTransitionCrossFadeSpriteLayerColorLabelRenderTextureSpriteBatchNodePhysicsSpriteProgressTimerParticleSystemQuadParticleBatchNodeTransitionSceneDrawNodeMotionStreakVideoPlayerTransitionPageTurnAtlasNodePhysicsDebugNode重载.

下面给出一个例子，先看结果图

可以拖动四个结点改变曲线

声明代码

#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__

#include "cocos2d.h"

class HelloWorld : public cocos2d::Layer
{
public:
    // there's no 'id' in cpp,so we recommend returning the class instance pointer
    static cocos2d::Scene* createScene();

    // Here's a difference. Method 'init' in cocos2d-x returns bool,instead of returning 'id' in cocos2d-iphone
    virtual bool init();  
    
    // a selector callback
    void menuCloseCallback(cocos2d::Ref* pSender);
	
	virtual void draw(cocos2d::Renderer *renderer,const cocos2d::Mat4 &transform,uint32_t flags) override;

    // implement the "static create()" method manually
    CREATE_FUNC(HelloWorld);
private:
	cocos2d::Sprite *yellow,*bule,*orange,*red;
	bool onTouchBegan(cocos2d::Touch *touch,cocos2d::Event *event);
	void  onTouchMoved(cocos2d::Touch*touch,cocos2d::Event *event);

};

#endif // __HELLOWORLD_SCENE_H__

实现代码

// on "init" you need to initialize your instance
bool HelloWorld::init()
{
    //////////////////////////////
    // 1. super init first
    if ( !Layer::init() )
    {
        return false;
    }
    
    Size visibleSize = Director::getInstance()->getVisibleSize();
    Vec2 origin = Director::getInstance()->getVisibleOrigin();

    /////////////////////////////
    // 2. add a menu item with "X" image,which is clicked to quit the program
    //    you may modify it.

    // add a "close" icon to exit the progress. it's an autorelease object
    auto closeItem = MenuItemImage::create(
                                           "CloseNormal.png","CloseSelected.png",CC_CALLBACK_1(HelloWorld::menuCloseCallback,this));
    
	closeItem->setPosition(Vec2(origin.x + visibleSize.width - closeItem->getContentSize().width/2,origin.y + closeItem->getContentSize().height/2));

    // create menu,it's an autorelease object
    auto menu = Menu::create(closeItem,NULL);
    menu->setPosition(Vec2::ZERO);
    this->addChild(menu,1);

    /////////////////////////////
    // 3. add your codes below...

    // add a label shows "Hello World"
    // create and initialize a label
    
    auto label = LabelTTF::create("Hello World","Arial",24);
    
    // position the label on the center of the screen
    label->setPosition(Vec2(origin.x + visibleSize.width/2,origin.y + visibleSize.height - label->getContentSize().height));

    // add the label as a child to this layer
    this->addChild(label,1);

    // add "HelloWorld" splash screen"
    auto sprite = Sprite::create("HelloWorld.png");

    // position the sprite on the center of the screen
    sprite->setPosition(Vec2(visibleSize.width/2 + origin.x,visibleSize.height/2 + origin.y));

    // add the sprite as a child to this layer
  //  this->addChild(sprite,0);


	red = Sprite::create("red.png");
	red->setPosition(10,10);
	this->addChild(red,3);
    
	yellow = Sprite::create("yellow.png");
	yellow->setPosition(200,200);
	this->addChild(yellow,3);

	bule = Sprite::create("bule.png");
	bule->setPosition(400,400);
	this->addChild(bule,3);

	orange = Sprite::create("orang.png");
	orange->setPosition(500,500);
	this->addChild(orange,4);

	auto listener = EventListenerTouchOneByOne::create();
	listener->onTouchBegan = CC_CALLBACK_2( HelloWorld::onTouchBegan,this);
	listener->onTouchMoved = CC_CALLBACK_2(HelloWorld::onTouchMoved,this);
	this->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listener,bule);
	this->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listener->clone(),orange);
	this->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listener->clone(),yellow);
	this->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listener->clone(),red);

	
    return true;
}


void HelloWorld::menuCloseCallback(Ref* pSender)
{
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WP8) || (CC_TARGET_PLATFORM == CC_PLATFORM_WINRT)
	MessageBox("You pressed the close button. Windows Store Apps do not implement a close button.","Alert");
    return;
#endif

    Director::getInstance()->end();

#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
    exit(0);
#endif
}

void  HelloWorld::draw(Renderer* renderer,const Mat4 &transform,uint32_t flags){
	
	auto array = PointArray::create(10);
	ccDrawLine(Vec2(100,100),Vec2(900,100));
	ccDrawLine(Vec2(100,Vec2(100,600));
	array->addControlPoint(Vec2(100,100));
	array->addControlPoint(red->getPosition());
	array->addControlPoint(bule->getPosition());
	array->addControlPoint(yellow->getPosition());
	array->addControlPoint(orange->getPosition());
	ccDrawCardinalSpline(array,100);

}	

bool HelloWorld::onTouchBegan(cocos2d::Touch *touch,cocos2d::Event *event){
	auto sprite = static_cast<Sprite*>(event->getCurrentTarget());
	auto point = sprite->convertToNodeSpace(touch->getLocation());
	auto rect = Rect(0,sprite->getContentSize().width,sprite->getContentSize().height);
	if (rect.containsPoint(poi