加载一个视图控制器依次调用：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
return YES;
}
- (void)viewDidLoad {
[super viewDidLoad];
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
}
进入后台时
- (void)applicationWillResignActive:(UIApplication *)application {
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
}
重新进入前台时
- (void)applicationWillEnterForeground:(UIApplication *)application {
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
}
原文：http://www.cnblogs.com/isItOk/p/4631390.html