如何在应用程序进入后台时得到通知?

在整个应用程序中实现所需功能的最佳方法是让应用程序导航到完全黑色的UIViewController。这样,当您长按home按钮并查看后台应用程序时,您就看不到任何内容。

这两个功能将发挥作用:

- (void) applicationDidEnterBackground:(UIApplication *)application
{
    //navigate to the black view controller
    BlackViewController *controller = [[BlackViewController alloc] init];

    [yourNavigationController pushViewController:viewController animated:yourAnimationSettings];

    [controller release];   
}

- (void) applicationWillEnterForeground:(UIApplication *)application
{
    //pop the black view controller so the user won't be bothered with it
    if(/*Check if your BlackViewController is the top of your navigationController stack*/)
    {
         [yourNavigationController popViewControllerAnimated:yourAnimationSettings];
    }
} 

您将在AppDelegate的 applicationDidEnterBackground