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, TransitionSplitCols, TransitionTurnOffTiles, TransitionCrossFade, Sprite, LayerColor, Label, RenderTexture,SpriteBatchNode, PhysicsSprite, ProgressTimer, ParticleSystemQuad, ParticleBatchNode, TransitionScene, DrawNode, MotionStreak,VideoPlayer, TransitionPageTurn, AtlasNode ,
以及 PhysicsDebugNode 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, 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, 0, 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, 0, sprite->getContentSize().width, sprite->getContentSize().height);
if (rect.containsPoint(poi