为iOS App增加启动渐变效果

转自：http://blog.youkuaiyun.com/jasonblog/article/details/8029081

由于目前苹果没有支持该功能，所以只能自己在App启动后做一个过度效果：

[cpp]  view plain copy

1. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions  
2. {  
3.     self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];  
4.     // Override point for customization after application launch.  
5.     self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController" bundle:nil] autorelease];  
6.     self.window.rootViewController = self.viewController;  
7.     [self.window makeKeyAndVisible];  
8.       
9.     UIImageView *splashScreen = [[[UIImageView alloc] initWithFrame:self.window.bounds] autorelease];  
10.     splashScreen.image = [UIImage imageNamed:@"Default"];  
11.     [self.window addSubview:splashScreen];  
12.       
13.     [UIView animateWithDuration:1.0 animations:^{  
14.         CATransform3D transform = CATransform3DMakeScale(1.5, 1.5, 1.0);  
15.         splashScreen.layer.transform = transform;  
16.         splashScreen.alpha = 0.0;  
17.     } completion:^(BOOL finished) {  
18.         [splashScreen removeFromSuperview];  
19.     }];  
20.       
21.     return YES;  
22. }