状態をテストするには、次のようにします。
[[UIApplication sharedApplication] applicationState]==UIApplicationStateInactive
また
[[UIApplication sharedApplication] applicationState]==UIApplicationStateActive
通知を受け取りたい場合は、次のことができます。
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(yourselector:)
name:UIApplicationDidBecomeActiveNotification object:nil];
また
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(yourselector:)
name:UIApplicationDidEnterBackgroundNotification object:nil];
他の通知も行うことができます ( https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplication_Class/から):
UIApplicationDidBecomeActiveNotification UIApplicationDidChangeStatusBarFrameNotification UIApplicationDidChangeStatusBarOrientationNotification UIApplicationDidEnterBackgroundNotification UIApplicationDidFinishLaunchingNotification UIApplicationDidReceiveMemoryWarningNotification UIApplicationProtectedDataDidBecomeAvailable UIApplicationProtectedDataWillBecomeUnavailable UIApplicationSignificantTimeChangeNotification UIApplicationUserDidTakeScreenshotNotification UIApplicationWillChangeStatusBarOrientationNotification UIApplicationWillChangeStatusBarFrameNotification UIApplicationWillEnterForegroundNotification UIApplicationWillResignActiveNotification UIApplicationWillTerminateNotification UIContentSizeCategoryDidChangeNotification
アプリ デリゲートを使用する場合は、次を使用できます。
- (void)applicationDidEnterBackground:(UIApplication *)application {}
また
- (void)applicationDidBecomeActive:(UIApplication *)application {}