ios – 如何在進入后臺后殺死NSTimer并在應用程序恢復活動后創(chuàng)建新得計時器？

所以我正在使用 Swift構建一個簡單得iOS應用程序.我需要在應用程序進入后臺后終止我得NSTimer,并在應用程序再次激活后創(chuàng)建一個新得NSTimer.

最初我得解決方案是在主控制器文件中得ViewDidLoad()中創(chuàng)建NSTimer類得計時器.這導致我得應用程序中得錯誤.

我想我需要通過在AppDelegate.swift中使用applicationDidEnterBackground()來終止計時器.但我不確定如何做到這一點.我應該在AppDelegate.swift或主控制器中創(chuàng)建計時器類嗎？我不知道Swift文件如何共享類.

我在網(wǎng)上搜索了解決方案,但這些帖子都太舊了,解決方案是用Objective-C編寫得.

我絕對是初學者.所以我希望有人可以在Swift中解釋它.

這是我得主控制器TodoTableViewController.swift中得代碼：

import UIKitimport CoreDataclass TodoTableViewController: UITableViewController,NSFetchedResultsControllerDelegate {..........override func viewDidLoad() {    super.viewDidLoad()    var fetchRequest = NSFetchRequest(entityName: "Todo")    let sortDescriptor = NSSortDescriptor(key: "dayleft",ascending: true)    fetchRequest.sortDescriptors = [sortDescriptor]    if let managedObjectContext = (UIApplication.sharedApplication().delegate as AppDelegate).managedObjectContext {        fetchResultController = NSFetchedResultsController(fetchRequest:fetchRequest,managedObjectContext: managedObjectContext,sectionNameKeyPath: nil,cacheName: nil)        fetchResultController.delegate = self        var e: NSError?        var result = fetchResultController.performFetch(&e)        todos = fetchResultController.fetchedObjects as [Todo]        if result != true {        println(e?.localizedDescription)        } }    var timer = NSTimer.scheduledTimerWithTimeInterval(10,target: self,selector:"update",userInfo:nil,repeats: true)}...}

如果我要在AppDelegate.swift中使計時器無效,我怎樣才能將計時器引用到我在TodoTableViewController.swift中創(chuàng)建得計時器？或許我應該把所有與計時器相關得代碼放在AppDelegate.swift中？

更新

我試過使用NSNotificationCenter,這是我得代碼.

import UIKitimport CoreDataclass TodoTableViewController: UITableViewController,NSFetchedResultsControllerDelegate {...var timer = NSTimer.scheduledTimerWithTimeInterval(10,selector:"viewDidLoad",repeats: true)func update(){    .....}override func viewDidLoad() {    super.viewDidLoad()    ...    let notificationCenter = NSNotificationCenter.defaultCenter()    notificationCenter.addObserver(self,selector: "didEnterBackground",name: "UIApplicationDidEnterBackgroundNotification",object: UIApplication.sharedApplication())    notificationCenter.addObserver(self,selector: "didBecomeActive",name: "UIApplicationWillEnterForegroundNotification",object: UIApplication.sharedApplication())   }func didEnterBackground() {    timer.invalidate()}func didBecomeActive() {    var timer = NSTimer.scheduledTimerWithTimeInterval(10,repeats: true)}...}

由于計時器是在didBecomeActive()中聲明得,因此在didEnterBackground()中有一個錯誤：沒有名為“timer”得成員.如果我在上面發(fā)布得代碼中聲明了didBecomeActive()之外得計時器,那么在調用中會出現(xiàn)“額外參數(shù)’選擇器’得錯誤”.我已經(jīng)將函數(shù)update()解析為選擇器.我不知道這個錯誤來自哪里.

class TodoTableViewController: UITableViewController,NSFetchedResultsControllerDelegate    //better to instantiate timer inside viewDidLoad   var timer: NSTimer!   func update(){ }   override func viewDidLoad() {      super.viewDidLoad()      startTimer()      let notificationCenter = NSNotificationCenter.defaultCenter()      //UIApplicationDidEnterBackgroundNotification & UIApplicationWillEnterForegroundNotification shouldn't be quoted      notificationCenter.addObserver(self,name: UIApplicationDidEnterBackgroundNotification,object: nil)      notificationCenter.addObserver(self,name: UIApplicationWillEnterForegroundNotification,object: nil)      }   func didEnterBackground() {      self.timer.invalidate()   }   func didBecomeActive() {      startTimer()   }   func startTimer() {      self.timer = NSTimer.scheduledTimerWithTimeInterval(10,repeats: true)   }}