Question

我实现了一个具有以下要求的ViewController：如果用户在15分钟后返回应用程序，视图应该重新加载数据。

我正在考虑使用viewDidDisappear来保存应用程序转到后台时的时间戳，viewDidAppear用于检查以前保存的值并在需要时刷新，但在切换应用程序时不会调用此方法

如何以简单的方式解决这个问题？

Answer 1

使用UIApplicationDidBecomeActive表示简历，UIApplicationWillResignActive表示处理后台

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationWillResignActive, object: nil)
     NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
}

override func viewDidLoad() {
    super.viewDidLoad()

    NotificationCenter.default.addObserver(self, selector: #selector(self.closeActivityController), name: NSNotification.Name.UIApplicationWillResignActive, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.openactivity), name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)


}

并将该方法处理为

func closeActivityController()  {


}

func openactivity()  {

    //view should reload the data.
}

其他通知类型

extension NSNotification.Name { 
@available(iOS 4.0, *)
public static let UIApplicationDidEnterBackground: NSNotification.Name

@available(iOS 4.0, *)
public static let UIApplicationWillEnterForeground: NSNotification.Name

public static let UIApplicationDidFinishLaunching: NSNotification.Name

public static let UIApplicationDidBecomeActive: NSNotification.Name

public static let UIApplicationWillResignActive: NSNotification.Name

public static let UIApplicationDidReceiveMemoryWarning: NSNotification.Name

public static let UIApplicationWillTerminate: NSNotification.Name

}

Answer 2

快捷键5

let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: UIApplication.willResignActiveNotification, object: nil)
notificationCenter.addObserver(self, selector: #selector(appBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)

方法：

@objc func appMovedToBackground() {
       print("App moved to background!")
    }
@objc func appBecomeActive() {
       print("App become active")
    }

删除观察者

override func viewWillDisappear(_ animated: Bool) {
      let notificationCenter = NotificationCenter.default
        notificationCenter.removeObserver(self, name:UIApplication.willResignActiveNotification, object: nil)
        notificationCenter.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)
    }

Answer 3

UIApplicationDelegate有以下两个功能：

applicationDidEnterBackground(_:)
applicationDidBecomeActive(_:)

这些可能就是你所需要的。

检测视图控制器何时进入后台并恢复

3 个答案: