检测视图控制器何时进入后台并恢复

Question

我正在实现具有以下要求的ViewController：如果用户在15分钟后返回到应用程序，则视图应重新加载数据。

我正在考虑使用viewDidDisappear该方法在应用程序进入后台时保存时间戳，并viewDidAppear检查以前保存的值并在需要时刷新，但是在应用程序之间切换时不会调用此方法。

我该如何轻松解决呢？

Answer 1

斯威夫特 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")
    }

移除观察者

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 2

使用UIApplicationDidBecomeActive了简历，并UIApplicationWillResignActive进行手柄变为背景

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)


}

并处理该方法为

func closeActivityController()  {


}

func openactivity()  {

    //view should reload the data.
}

其他通知类型是

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

}