当应用程序进行后台并进入前景时，请致电UiviewController方法

Question

当应用程序进行背景时，如何调用方法并更改某些活动，例如移动的时间或日期，然后进入前景（应用程序活动模式）。

然后我想在uiviewController类中调用方法

firstViewController类方法。

-(void)refreshItems{
// Your item refresh code.
}

Answer 1

在ViewController中添加以下代码

 override func viewDidLoad() {
 super.viewDidLoad()
//Mark:- application move to bckground
 let backgorundNotificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector:#selector(appMovedToBackground), name: UIApplication.willResignActiveNotification, object: nil)
//Mark:- application move to foreground
let foregroundNotificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector:#selector(appMovedToForeground),name: UIApplication.willEnterForegroundNotification, object: nil)
 }
//Mark:- background method implementation
@objc func appMovedToBackground() {
print("App moved to background!")
 }
 //Mark:- foreground method implementation
@objc func appMovedToForeground() {
   print("App moved to foreground!")
}

Answer 2

我想你只需要

[[NSNotificationCenter defaultCenter] addobserver：self Selector：@selector（RefReshitems）名称：uiapplicationdidbecomeactivenotification对象：nil];

Answer 3

检查此代码（如果FirstViewController是Window的rootviewController，则在AppDelegate中使用FirstViewController的实例，并检查NULL）

）

func applicationDidEnterBackground(_ application: UIApplication) {
    if let appDelegate = UIApplication.shared.delegate as? AppDelegate,
        let controller = appDelegate.window?.rootViewController as? FirstViewController {
        controller.refreshItems()
    }
}
func applicationWillEnterForeground(_ application: UIApplication) {
    if let appDelegate = UIApplication.shared.delegate as? AppDelegate,
        let controller = appDelegate.window?.rootViewController as? FirstViewController {
        controller.refreshItems()
    }
}

在Objective-C

中

- (void)applicationDidEnterBackground:(UIApplication *)application {
   AppDelegate *appDelegate = (AppDelegate*)[UIApplication sharedApplication].delegate;
   FirstViewController *controller = (FirstViewController*)[[appDelegate window] rootViewController];
   [controller refreshItems];
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    AppDelegate *appDelegate = (AppDelegate*)[UIApplication sharedApplication].delegate;
    FirstViewController *controller = (FirstViewController*)[[appDelegate window] rootViewController];
    [controller refreshItems];
}

Answer 4

you have set notification in appDelegate class
    - (void)applicationWillEnterForeground:(UIApplication *)application {
        [[NSNotificationCenter defaultCenter] postNotificationName:@"forground"      object:nil];
    }
and add observer to your viewcontroller class viewdidload() methos
     [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(showMainMenu:)
                                                     name:@"refreshItems" object:nil];