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使用过渡场景在多个场景的切换COCOS2D(4)

分类: IT文章 • 2022-07-29 08:55:02

CCNode有三个方法，使用CCDirector的replaceScene方法替换场景时，每个节点都会调用这三个方法：

onEnter与onExit方法在改变场景过程中的特定时刻被调用，这取决于是否使用CCTransitionScene。

onEnterTransitionDidFinish方法在替换结束时调用。

必须总是调用这些方法的超类实现来避免难输入问题和内存泄漏。

01 -(void) onEnter 
02 { 
03     CCLOG(@"%@: %@", NSStringFromSelector(_cmd), self); 
04        
05     // must call super here: 
06     [super onEnter]; 
07 } 
08    
09 -(void) onEnterTransitionDidFinish 
10 { 
11     CCLOG(@"%@: %@", NSStringFromSelector(_cmd), self); 
12        
13     // must call super here: 
14     [super onEnterTransitionDidFinish]; 
15 } 
16    
17 -(void) onExit 
18 { 
19     CCLOG(@"%@: %@", NSStringFromSelector(_cmd), self); 
20        
21     // must call super here: 
22     [super onExit]; 
23 }

编写过渡场景：

LoadingScene充当一个中间场景的角色，它是cocos2d中的CCScene类的派生类，不必为每一次场景创建一个新的LoadingScene。

代码清单：LoadingScene.h

01 #import <Foundation/Foundation.h> 
02 #import "cocos2d.h" 
03    
04 typedef enum 
05 { 
06     TargetSceneINVALID = 0, 
07     TargetSceneFirstScene, 
08     TargetSceneOtherScene, 
09     TargetSceneMAX, 
10 } TargetScenes; 
11    
12 <a href="http://my.oschina.net/interface" class="referer" target="_blank">@interface</a>  LoadingScene : CCScene { 
13        
14     TargetScenes targetScene_; 
15 } 
16    
17 +(id) sceneWithTargetScene:(TargetScenes)targetScene; 
18 -(id) initWithTargetScene:(TargetScenes)targetScene; 
19    
20 <a href="http://my.oschina.net/u/567204" class="referer" target="_blank">@end</a>

使用enum给各个场景编个号，而且将enum的第一个值设为0,在Objective－c中变量的值会自动初始化为0.并在最后设了个MAX值。

代码清单：LoadingScene.m

01 #import "LoadingScene.h" 
02 #import "MyFirstScene.h" 
03 #import "OtherScene.h" 
04    
05 <a href="http://my.oschina.net/interface" class="referer" target="_blank">@interface</a>  LoadingScene (PrivateMethods) 
06 -(void) update:(ccTime)delta; 
07 <a href="http://my.oschina.net/u/567204" class="referer" target="_blank">@end</a>  
08    
09 @implementation LoadingScene 
10 +(id) sceneWithTargetScene:(TargetScenes)targetScene; 
11 { 
12     CCLOG(@"==========================================="); 
13     CCLOG(@"%@: %@", NSStringFromSelector(_cmd), self); 
14        
15     // This creates an autorelease object of self (the current class: LoadingScene) 
16     return [[[self alloc] initWithTargetScene:targetScene] autorelease]; 
17        
18     // Note: this does the exact same, it only replaced self with LoadingScene. The above is much more common. 
19     //return [[[LoadingScene alloc] initWithTargetScene:targetScene] autorelease]; 
20 } 
21    
22 -(id) initWithTargetScene:(TargetScenes)targetScene 
23 { 
24     if ((self = [super init])) 
25     { 
26         targetScene_ = targetScene; 
27            
28         CCLabelTTF* label = [CCLabelTTF labelWithString:@"Loading ..." fontName:@"Marker Felt" fontSize:64]; 
29         CGSize size = [[CCDirector sharedDirector] winSize]; 
30         label.position = CGPointMake(size.width / 2, size.height / 2); 
31         [self addChild:label]; 
32            
33         // Must wait one frame before loading the target scene! 
34         // Two reasons: first, it would crash if not. Second, the Loading label wouldn't be displayed. 
35         [self scheduleUpdate]; 
36     } 
37        
38     return self; 
39 } 
40    
41 -(void) update:(ccTime)delta 
42 { 
43     // It's not strictly necessary, as we're changing the scene anyway. But just to be safe. 
44     [self unscheduleAllSelectors]; 
45        
46     // Decide which scene to load based on the TargetScenes enum. 
47     // You could also use TargetScene to load the same with using a variety of transitions. 
48     switch (targetScene_) 
49     { 
50         case TargetSceneFirstScene: 
51             [[CCDirector sharedDirector] replaceScene:[MyFirstScene scene]]; 
52             break; 
53         case TargetSceneOtherScene: 
54             [[CCDirector sharedDirector] replaceScene:[OtherScene scene]]; 
55             break; 
56                
57         default: 
58             // Always warn if an unspecified enum value was used. It's a reminder for yourself to update the switch 
59             // whenever you add more enum values. 
60             NSAssert2(nil, @"%@: unsupported TargetScene %i", NSStringFromSelector(_cmd), targetScene_); 
61             break; 
62     } 
63        
64     // Tip: example usage of the INVALID and MAX enum values to iterate over all enum values 
65     for (TargetScenes i = TargetSceneINVALID + 1; i < TargetSceneMAX; i++) 
66     { 
67     } 
68 } 
69    
70 -(void) dealloc 
71 { 
72     CCLOG(@"%@: %@", NSStringFromSelector(_cmd), self); 
73        
74     // don't forget to call "super dealloc" 
75     [super dealloc]; 
76 } 
77 <a href="http://my.oschina.net/u/567204" class="referer" target="_blank">@end</a>

由于LoadingScene类由CCScene派生出来，所以不需要调用［CCScene node］，sceneWithTargetScene方法先为self分配空间，然后调用initWithTargetScene初始化。

在MyFirstScene中调用LoadingScene：

1 CCScene *newScene = [LoadingScene sceneWithTargetScene:TargetSceneOtherScene]; 
2 [[CCDirector sharedDirector] replaceScene:newScene];

在OtherScene中调用基本类似，请读者自行实践。

下面给出了在执行过程中的一些输出信息，它详细的说明了各个方法的调用顺序：

view source
 
print ?
01 2012-10-06 13:50:03.404 MutiScene[1884:1be03] =========================================== 
02 2012-10-06 13:50:03.405 MutiScene[1884:1be03] scene: MyFirstScene 
03 2012-10-06 13:50:03.406 MutiScene[1884:1be03] init : <MyFirstScene = 0x94e2540 | Tag = -1> 
04 2012-10-06 13:50:08.610 MutiScene[1884:1be03] cocos2d: animation started with frame interval: 60.00 
05 2012-10-06 13:50:08.613 MutiScene[1884:1be03] cocos2d: surface size: 480x320 
06 2012-10-06 13:50:08.614 MutiScene[1884:1be03] onEnter: <MyFirstScene = 0x94e2540 | Tag = -1> 
07 2012-10-06 13:50:08.615 MutiScene[1884:1be03] onEnterTransitionDidFinish: <MyFirstScene = 0x94e2540 | Tag = -1> 
08 2012-10-06 13:50:11.844 MutiScene[1884:1be03] =========================================== 
09 2012-10-06 13:50:11.845 MutiScene[1884:1be03] scene: OtherScene 
10 2012-10-06 13:50:11.846 MutiScene[1884:1be03] init: <OtherScene = 0x9418280 | Tag = -1> 
11 2012-10-06 13:50:16.907 MutiScene[1884:1be03] onEnter: <OtherScene = 0x9418280 | Tag = -1> 
12 2012-10-06 13:50:19.944 MutiScene[1884:1be03] onExit: <MyFirstScene = 0x94e2540 | Tag = -1> 
13 2012-10-06 13:50:19.945 MutiScene[1884:1be03] onEnterTransitionDidFinish: <OtherScene = 0x9418280 | Tag = -1> 
14 2012-10-06 13:50:19.947 MutiScene[1884:1be03] dealloc : <MyFirstScene = 0x94e2540 | Tag = -1> 
15 2012-10-06 13:50:29.953 MutiScene[1884:1be03] =========================================== 
16 2012-10-06 13:50:29.954 MutiScene[1884:1be03] sceneWithTargetScene:: LoadingScene 
17 2012-10-06 13:50:29.961 MutiScene[1884:1be03] onExit: <OtherScene = 0x9418280 | Tag = -1> 
18 2012-10-06 13:50:29.962 MutiScene[1884:1be03] dealloc: <OtherScene = 0x9418280 | Tag = -1> 
19 2012-10-06 13:50:29.977 MutiScene[1884:1be03] =========================================== 
20 2012-10-06 13:50:29.979 MutiScene[1884:1be03] scene: MyFirstScene 
21 2012-10-06 13:50:29.980 MutiScene[1884:1be03] init : <MyFirstScene = 0x9418280 | Tag = -1> 
22 2012-10-06 13:50:35.031 MutiScene[1884:1be03] dealloc: <LoadingScene = 0x11a59950 | Tag = -1> 
23 2012-10-06 13:50:35.032 MutiScene[1884:1be03] onEnter: <MyFirstScene = 0x9418280 | Tag = -1> 
24 2012-10-06 13:50:35.032 MutiScene[1884:1be03] onEnterTransitionDidFinish: <MyFirstScene = 0x9418280 | Tag = -1>

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