Demo：

AppDelegate.m文件

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {// Override point for customization after application launch.self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];[self.window makeKeyAndVisible];/*以下代码皆是位于此*/return YES;
}

其中用到的相关代码：