1. 在ViewController的viewDidLoad方法裡延時。

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //[NSThread sleepForTimeInterval:3];
}

@end

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions；方法裡延時。

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    [NSThread sleepForTimeInterval:3.0];
    return YES;
}