iOS 按住Home键的代理

1.按住home键怎么保存程序的运行状态:

监听按home键的时候程序挂起的状态（通知），然后让其重新进入程序[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:)
name:UIApplicationWillResignActiveNotification object:nil];

2.当程序运行时 按下home键 iOS会调用哪个代理:

.- (void)applicationWillResignActive:(UIApplication *)application {}