三、添加一个精灵
我们先用个简单的方式，把player, projectile, target三个PNG文件拷贝到 D:\Work7\NEWPLUS\TDA_DATA\UserData 目录下，这使其可以在模拟器上直接通过文件路径访问到。Uphone有其资源打包的方式，图片和音乐都可以打包到动态库文件内，这个另外会有教程描述，我们这里先让事情简单化。
关于cocos2d坐标系统的规则，简而言之就是左下角为原点，向上向右按像素递增，这在Wenderlich的原文中有详细描述，我们这里就不再赘述了。直接切入代码
现在我们在HelloWorldScene.cpp里面，找到bool HelloWorld::init()函数，把它替换成下面代码
bool HelloWorld::init()
{
//////////////////////////////
// 1. super init first
if ( !CCLayer::init() )
{
return false;
}
/////////////////////////////
// 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
CCMenuItemImage *pCloseItem = CCMenuItemImage::itemFromNormalImage( "CloseNormal.png",
"CloseSelected.png",
this,
menu_selector(HelloWorld::menuCloseCallback) );
pCloseItem->setPosition( ccp(CCDirector::getSharedDirector()->getWinSize().width - 20, 20) );
// create menu, it's an autorelease object
CCMenu* pMenu = CCMenu::menuWithItems(pCloseItem, NULL);
pMenu->setPosition( CGPointZero );
this->addChild(pMenu);
/////////////////////////////
// 3. add your codes below...
CGSize winSize = CCDirector::getSharedDirector()->getWinSize();
CCSprite *player = CCSprite::spriteWithFile("Player.png",
CGRectMake(0, 0, 27, 40) );
player->setPosition( ccp(player->getContentSize().width/2, winSize.height/2) );
this->addChild(player);
return true;
}
其实我们只修改了 // 3. add your codes below 这段。
cocos2d-x和cocos2d-iphone的接口有细微的差别，不过你一旦习惯了这个差别，写起代码来就会很顺手。
我们抛开添加"X"退出按钮的一段，单纯地看一下这两段init函数的差异.
// cpp with cocos2d-x
bool HelloWorld::init()
{
if ( CCLayer::init() )
{
CGSize winSize = CCDirector::getSharedDirector()->getWinSize();
CCSprite *player = CCSprite::spriteWithFile("Player.png",
CGRectMake(0, 0, 27, 40) );
player->setPosition( ccp(player->getContentSize().width/2,
winSize.height/2) );
this->addChild(player);
}
return true;
}
|
// objc with cocos2d-iphone
-(id) init
{
if( (self=[super init] ))
{
CGSize winSize = [[CCDirector sharedDirector] winSize];
CCSprite *player = [CCSprite spriteWithFile:@"Player.png"
rect:CGRectMake(0, 0, 27, 40) ];
player.position = ccp(player.contentSize.width/2,
winSize.height/2);
[self addChild:player];
}
return self;
}
|
好了，我们编译运行一下，可以看到带头大哥一袭黑衣，很猥琐地躲在黑色背景上，只露出一双杀红了的眼睛。为了游戏性，我们需要把背景颜色改成白的。只要简单地修改，使HelloWorld不是继承CCLayer,而是继承CCColorLayer就行了。
在HelloWorldScene.h中，修改HelloWorld类声明如下。
（左边为cpp代码，也就是读者现在应该使用的，右边为Cocos2dSimpleGame原来使用cocos2d-iphone的objc代码，用以对比参考。本系列后面的行文也都如此）
// cpp with cocos2d-x
class HelloWorld : public cocos2d::CCColorLayer
|
// objc with cocos2d-iphone
@interface HelloWorld : CCColorLayer
|
然后在HelloWorld::init()函数实现中，修改刚开始的
if ( !CCLayer::init() )
{
return false;
}
变成
if ( !CCColorLayer::initWithColor( ccc4(255,255,255,255) ) )
{
return false;
}
这里小改了一下逻辑，原版objc里是如果super init成功，就BALA-BALA做后面的工作；我喜欢防御性编程，如果失败则先做出错处理、跳出，然后才继续写正确流程。这么做有两个好处，一是不会写到后面漏掉了错误处理，二是不用做太多层的if嵌套。这个是题外话了。抛开if的逻辑，我们来对比一下这句super init在cpp和objc的区别
// cpp with cocos2d-x
if ( CCColorLayer::initWithColor( ccc4(255,255,255,255) )
|
// objc with cocos2d-iphone
if ( self = [super initWithColor:ccc4(255,255,255,255)] )
|
编译后运行，你就可以看到带头大哥孤独地站在白色背景上了，寂寞得泪流满面
四、移动目标
有了带头大哥后，我们就需要添加一些虾兵蟹将让大哥砍。英雄人物一般不喜欢砍木桩，所以我们就用void addTarget()方法在屏幕右边创建一些跑龙套的小兵，让他们以随机速度向左移动。
先到HelloWorldScene.h里添加函数声明 void addTarget(); 然后回到HelloWorldScene.cpp里实现函数
// cpp with cocos2d-x
void HelloWorld::addTarget()
{
CCSprite *target = CCSprite::spriteWithFile("Target.png",
CGRectMake(0,0,27,40) );
// Determine where to spawn the target along the Y axis
CGSize winSize = CCDirector::getSharedDirector()->getWinSize();
int minY = target->getContentSize().height/2;
int maxY = winSize.height - target->getContentSize().height/2;
int rangeY = maxY - minY;
srand( TimGetTicks() );
int actualY = ( rand() % rangeY ) + minY;
// Create the target slightly off-screen along the right edge,
// and along a random position along the Y axis as calculated
target->setPosition(
ccp(winSize.width + (target->getContentSize().width/2),
actualY) );
this->addChild(target);
// Determine speed of the target
int minDuration = (int)2.0;
int maxDuration = (int)4.0;
int rangeDuration = maxDuration - minDuration;
srand( TimGetTicks() );
int actualDuration = ( rand() % rangeDuration ) + minDuration;
// Create the actions
CCFiniteTimeAction* actionMove =
CCMoveTo::actionWithDuration( (ccTime)actualDuration,
ccp(0 - target->getContentSize().width/2, actualY) );
CCFiniteTimeAction* actionMoveDone =
CCCallFuncN::actionWithTarget( this,
callfuncN_selector(HelloWorld::spriteMoveFinished));
target->runAction( CCSequence::actions(actionMove,
actionMoveDone, NULL) );
}
|
// objc with cocos2d-iphone
-(void)addTarget
{
CCSprite *target = [CCSprite spriteWithFile:@"Target.png"
rect:CGRectMake(0, 0, 27, 40)];
// Determine where to spawn the target along the Y axis
CGSize winSize = [[CCDirector sharedDirector] winSize];
int minY = target.contentSize.height/2;
int maxY = winSize.height - target.contentSize.height/2;
int rangeY = maxY - minY;
int actualY = (arc4random() % rangeY) + minY;
// Create the target slightly off-screen along the right edge,
// and along a random position along the Y axis as calculated
target.position =
ccp(winSize.width + (target.contentSize.width/2),
actualY);
[self addChild:target];
// Determine speed of the target
int minDuration = 2.0;
int maxDuration = 4.0;
int rangeDuration = maxDuration - minDuration;
int actualDuration = (arc4random() % rangeDuration) + minDuration;
// Create the actions
id actionMove =
[CCMoveTo actionWithDuration:actualDuration
position:ccp(-target.contentSize.width/2, actualY)];
id actionMoveDone =
[CCCallFuncN actionWithTarget:self
selector:@selector(spriteMoveFinished:)];
[target runAction:[CCSequence actions:actionMove,
actionMoveDone, nil]];
}
|
这里用callfuncN_selector(HelloWorld::spriteMoveFinished)回调了spriteMoveFinished方法，我们需要实现之。同样别忘记在头文件里加入声明, 然后实现之
// cpp with cocos2d-x
void HelloWorld::spriteMoveFinished(CCNode* sender)
{
CCSprite *sprite = (CCSprite *)sender;
this->removeChild(sprite, true);
}
|
// objc with cocos2d-iphone
-(void)spriteMoveFinished:(id)sender
{
CCSprite *sprite = (CCSprite *)sender;
[self removeChild:sprite cleanup:YES];
}
|
有了addTarget后，我们需要定时地调用它。所以在init函数返回前增加这个函数调用
// cpp with cocos2d-x
// Call game logic about every second
this->schedule( schedule_selector(HelloWorld::gameLogic), 1.0 );
|
// objc with cocos2d-iphone
// Call game logic about every second
[self schedule:@selector(gameLogic:) interval:1.0];
|
然后实现gameLogic这个回调函数
// cpp with cocos2d-x
void HelloWorld::gameLogic(ccTime dt)
{
this->addTarget();
}
|
// objc with cocos2d-iphone
-(void)gameLogic:(ccTime)dt
{
[self addTarget];
}
|
不要忘记在头文件里增加函数声明，并且应为public函数，否则回调是调用不到的。
编译运行，现在你应该看到小喽啰们张牙舞爪地向大哥扑过来。于是拯救世界、维护人类和平的重任就交给大哥了。
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