CCLayer

一个场景(Scene)上可能有多个Layer

引用

CCLayer 对象定义了可描绘的区域，定义了描绘的规则。CCLayer可以实现半透明的效果，令您看到它背后的layers。概括地说：CCLayer 用于定义外观和事件behavior。所以，当编写cocos2d程序的时候，大部分工作就是编写CCLayer的子类去实现所要的效果。
CCLayer 负责处理事件event。Events 会从第一个向最后一个layers传递，直至某个layer获取event并处理它。
虽然某个时候，你需要客户化一个CCLayer类， 但cocos2d已经实现了多种功能的layers（比如菜单layer: CCMenu, 颜色层layer: CCColorLayer,等等）。
Layers 可以包含CCSprite 对象, CCLabel 对象 和其它layer对象。layers是CCNode的子类，所以他们也可以使用actions来转 换坐标. See Actions for more detail about actions.

+(id) scene
{
    CCScene* scene = [CCScene node];
    CCLayer* backgroundLayer = [HelloWorldBackground node];
    [scene addChild: backgroundLayer];
    CCLayer* layer = [HelloWorld node];
    [scene addChild:layer];
    CCLayer* userInterfaceLayer = [HelloWorldUserInterface node];
    [scene addChild: userInterfaceLayer];
    return scene;
} 

* 和Scene一样，Layer没有宽高，只是一群可视对象的概念集合

获取Touch 输入

self.isTouchEnabled = YES; 

用户Touch动作跟以下方法相关

Called when a finger just begins touching the screen:
-(void) ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
Called whenever the finger moves on the screen:
-(void) ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
Called when a finger is lifted off the screen:
-(void) ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
Called to cancel a touch:
-(void) ccTouchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

获取Touch坐标

UITouch *touch = [touches anyObject];
CGPoint touchLocation = [touch locationInView: [touch view]];
return [[CCDirector sharedDirector] convertToGL:touchLocation]; 

如果要指定层消耗触摸

-(void) registerWithTouchDispatcher
{
[[CCTouchDispatcher sharedDispatcher] addTargetedDelegate:self
priority:INT_MIN+1 swallowsTouches:YES];
} 

如果此方法内容什么都不写，则不会接收任何触摸事件
这种情况下要用以下方法获取触摸事件

-(BOOL) ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event {}
-(void) ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {}
-(void) ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event {}
-(void) ccTouchCancelled:(UITouch *)touch withEvent:(UIEvent *)event {}

和上面的方法略有不同，并且，注意ccTouchBegan:withEvent:返回是BOOL类型，如果返回YES，则触摸事件不会冒泡到优先级较低的Layer

接收accelerometer事件

didAccelerate:(UIAcceleration *)acceleration
{
CCLOG(@"acceleration: x:%f / y:%f / z:%f",
acceleration.x, acceleration.y, acceleration.z);
}