使用过渡场景在多个场景的切换COCOS2D(4)

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：

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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>