How can I use applicationDidBecomeActive in UIViewController?

At the time of reactivation, if you want to carry a particular thing for a view controller, you should register a notification in its viewDidLoad method.

UIApplicationDidBecomeActiveNotification will automatically notify your application and given controller, if they registered for it.

 [[NSNotificationCenter defaultCenter]addObserver:self
                                         selector:@selector(yourMethod)
                                             name:UIApplicationDidBecomeActiveNotification
                                           object:nil];