cocos2d-x 基础系列 (01) 创建一个只有退出程序按钮的demo

在之前的文章中已经熟悉了coco2d-x的基本用法，这个系列主要分析它的一些类，结合官网提供coco2d-x Programmers Guide v3.12.pdf

pdf下载地址
https://pan.baidu.com/s/1bp3UDP1
看完了一大半左右，感觉没有实际写代码好，所以只是走马观花匆匆地扫过去。另外在github上提供更适合新手学习的代码，programmers-guide-samples-3.10.zip，操作性比coco2d-x源文件自带的CppTest强一点，因为都是一些基本操作的。看它的名字应该是基于version 3.12的。

里面的内容分成十几个章节，这个系列就是学习这些小代码的，可能会分得更细一些，一下子给太多容易掌握不住，每次进步一点点，累积起来就是巨大的进步。

很多的地方会加上自己的注释，或者查看官网提供的API手册，不懂的地方还希望见谅，毕竟在游戏上我也是新手。

源码demo下载地址
https://pan.baidu.com/s/1pKWwjcJ
第一篇创建只有一个退出按钮的demo，代替原来提供的HelloWorldScene.cpp类。

先把那四个类的源码粘贴出来

AppDelegate.h

Delegate的字面的意思就是代表的意思，现在我们需要知道的大概是applicationDidFinishLaunching, applicationDidEnterBackground, applicationWillEnterForeground

根据字面意思就可以推断出来，第一个表示程序需要完成的内容，第二个表示程序进入后台，第三个表示程序讲进入前台。

这几个大概意思知道就可以了，写coco2d-x engine的人都替我们写好了。

#ifndef  _APP_DELEGATE_H_
#define  _APP_DELEGATE_H_

#include "cocos2d.h"

/**
@brief    The cocos2d Application.

Private inheritance here hides part of interface from Director.
*/
class  AppDelegate : private cocos2d::Application
{
public:
AppDelegate();
virtual ~AppDelegate();

virtual void initGLContextAttrs();

/**
@brief    Implement Director and Scene init code here.
@return true    Initialize success, app continue.
@return false   Initialize failed, app terminate.
*/
virtual bool applicationDidFinishLaunching();

/**
@brief  Called when the application moves to the background
@param  the pointer of the application
*/
virtual void applicationDidEnterBackground();

/**
@brief  Called when the application reenters the foreground
@param  the pointer of the application
*/
virtual void applicationWillEnterForeground();
};

#endif // _APP_DELEGATE_H_

AppDelegate.cpp

这里对新手来说比较疑惑的是GL是什么，就是一组图像渲染的接口，还没到学习OpenGL的地步，有兴趣可以自己查阅资料。

需要弄清楚几个尺寸，这里选用的是mediumResolutionSize 1024 × 768

4000

后面还有对象的尺寸，基点等，对我们计算物体的位置十分重要。

真正需要关注的是auto scene = MainScene::createScene(); 创建一个场景，大概可以翻译成场景，

编程手册上打了一个比方说Driector类似于拍电影的导演，Scene类似于场景。

Animation就是动画吧，英语都比较直白，比较好理解。

#include "AppDelegate.h"
#include "MainScene.h"

USING_NS_CC;

static cocos2d::Size designResolutionSize = cocos2d::Size(480, 320);
static cocos2d::Size smallResolutionSize = cocos2d::Size(480, 320);
static cocos2d::Size mediumResolutionSize = cocos2d::Size(1024, 768);
static cocos2d::Size largeResolutionSize = cocos2d::Size(2048, 1536);

AppDelegate::AppDelegate()
{
}

AppDelegate::~AppDelegate()
{
}

// if you want a different context, modify the value of glContextAttrs
// it will affect all platforms
void AppDelegate::initGLContextAttrs()
{
/* GLContextAttrs Struct
* set OpenGL context attributes:
* redBits, greenBits, blueBits, alphaBits, depthBits, stencilBits
* /SourceCode/cocos/platform/CCLView.h
*/
GLContextAttrs glContextAttrs = {8, 8, 8, 8, 24, 8};

GLView::setGLContextAttrs(glContextAttrs);
}

// if you want to use the package manager to install more packages,
// don't modify or remove this function
static int register_all_packages()
{
return 0; //flag for packages manager
}

bool AppDelegate::applicationDidFinishLaunching() {
// initialize director
auto director = Director::getInstance();
auto glview = director->getOpenGLView();
if(!glview) {
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32) || (CC_TARGET_PLATFORM == CC_PLATFORM_MAC) || (CC_TARGET_PLATFORM == CC_PLATFORM_LINUX)
glview = GLViewImpl::createWithRect("GameDemo", cocos2d::Rect(0, 0, mediumResolutionSize.width, mediumResolutionSize.height));
#else
glview = GLViewImpl::create("GameDemo");
#endif
director->setOpenGLView(glview);
}

// turn on display FPS
// director->setDisplayStats(true);

// set FPS. the default value is 1.0/60 if you don't call this
// director->setAnimationInterval(1.0f / 60);

// Set the design resolution
glview->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, ResolutionPolicy::NO_BORDER);
auto frameSize = glview->getFrameSize();
// if the frame's height is larger than the height of medium size.
if (frameSize.height > mediumResolutionSize.height)
{
director->setContentScaleFactor(MIN(largeResolutionSize.height/designResolutionSize.height, largeResolutionSize.width/designResolutionSize.width));
}
// if the frame's height is larger than the height of small size.
else if (frameSize.height > smallResolutionSize.height)
{
director->setContentScaleFactor(MIN(mediumResolutionSize.height/designResolutionSize.height, mediumResolutionSize.width/designResolutionSize.width));
}
// if the frame's height is smaller than the height of medium size.
else
{
director->setContentScaleFactor(MIN(smallResolutionSize.height/designResolutionSize.height, smallResolutionSize.width/designResolutionSize.width));
}

register_all_packages();

// create a scene. it's an autorelease object
auto scene = MainScene::createScene();

// run
director->runWithScene(scene);

return true;
}

// This function will be called when the app is inactive. Note, when receiving a phone call it is invoked.
void AppDelegate::applicationDidEnterBackground() {
Director::getInstance()->stopAnimation();

// if you use SimpleAudioEngine, it must be paused
// SimpleAudioEngine::getInstance()->pauseBackgroundMusic();
}

// this function will be called when the app is active again
void AppDelegate::applicationWillEnterForeground() {
Director::getInstance()->startAnimation();

// if you use SimpleAudioEngine, it must resume here
// SimpleAudioEngine::getInstance()->resumeBackgroundMusic();
}

开始创建我们自己的场景，命名为

MainScene.h

英文注释已经说的很清楚了，CREATE_FUNC是一个宏，我觉得没有必要在现在就进行深入理解，除非你的C++功底特别深厚。

我猜大概的意思是向系统注册这个MainScene.

#ifndef MAINSCENE_H
#define MAINSCENE_H

#include "cocos2d.h"

class MainScene : public cocos2d::Node {
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 return bool,
// instead of returning 'id' in cocos2d-iphone
virtual bool init();

// a selector callback
void onMenuCloseCallback(cocos2d::Ref *sender);
CREATE_FUNC(MainScene);
};
#endif

MainScene.cpp

MenuItemImage和Menu是应该是被包含的关系，一个Menu中可以创建好多的Item，最后以NULL结尾，C++11是用nullptr,不过表达的意思是一样的。

origin.x指的是可见尺寸的原点，在坐下角，visibleSize.width是指屏幕的宽度，closeItem->getContentSize（）是指物体的尺寸。

Item的原点是在图片的正中间(0.5, 0.5),那么根据这么计算就可以得出是把Item放在右下角了。

点按钮回调相应的函数安卓中很多，知道怎么注册怎么用就可以了。

MenuItemImage的继承关系图

#include "MainScene.h"

USING_NS_CC;

Scene *MainScene::createScene() {
// 'scene' is an autorelease object

auto scene = Scene::create();

// 'layer' is an autorelease object
auto layer = MainScene::create();

// add layer as a child to scene
scene->addChild(layer);

// return the scene
return scene;
}

// On "init" you need to initialize your instance
bool MainScene::init()
{
// Super init first
if (!Node::init())
return false;

Size visibleSize = Director::getInstance()->getVisibleSize();
// Return visible origin coordinate of the OpenGL view in points
Vec2 origin = Director::getInstance()->getVisibleOrigin();

// Add a menu item with "X" image, which is clicked to quit the program
// Add a "close" icon to exit the progress, it's an autorelease object
auto closeItem = MenuItemImage::create("CloseNormal.png",
"CloseSelected.png", CC_CALLBACK_1(MainScene::onMenuCloseCallback, this));

// getContentsSize()
// Returns the untransoformed size of the node

// default value (0.5, 0.5)
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 closeMenu = Menu::create(closeItem, NULL);
closeMenu->setPosition(Vec2::ZERO);
this->addChild(closeMenu, 1);

return true;
}

void MainScene::onMenuCloseCallback(Ref *sender) {
Director::getInstance()->end();
}

差不多就可以编译运行。



手机上运行也是相同的效果，点击按钮会退出。