iPhone上实现Default.png动画

原理：
添加一张和Default.png一样的图片，对这个图片进行动画，从而实现Default动画的渐变消失的效果。
操作：
在- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions中添加如下代码：
 // Make this interesting.
    UIImageView *splashView = [[UIImageView alloc] initWithFrame:CGRectMake(0,0, 320, 480)];
    splashView.image = [UIImage imageNamed:@"Default.png"];
    [self.window addSubview:splashView];
    [self.window bringSubviewToFront:splashView];
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:2.0];
    [UIView setAnimationTransition:UIViewAnimationTransitionNone forView: self.window cache:YES];
    [UIView setAnimationDelegate:self]; 
    [UIView setAnimationDidStopSelector:@selector(startupAnimationDone:finished:context:)];
    splashView.alpha = 0.0;
    splashView.frame = CGRectMake(-60, -85, 440, 635);
    [UIView commitAnimations];
就ok了