Question

因此，如下所示的代码，函数loadView 3应该在用户点击按钮后运行300秒（5分钟）。但是当我构建并运行时，却没有。我也做了一些实验，我把计时器更改为5秒，就可以了。应用程序从iOS系统暂停后，NSTimer不再运行了吗？那么问题是什么，我该如何解决呢？

@IBAction func buttonTapped(sender: AnyObject) {
    NSTimer.scheduledTimerWithTimeInterval(300, target: self, selector: #selector(ViewController.loadView3), userInfo: nil, repeats: false)    
    createLocalNotification()
}

func createLocalNotification() {
    let localnotification = UILocalNotification()
    localnotification.fireDate = NSDate(timeIntervalSinceNow: 300)
    localnotification.applicationIconBadgeNumber = 1
    localnotification.soundName = UILocalNotificationDefaultSoundName
    localnotification.alertBody = "Hello!"
    UIApplication.sharedApplication().scheduleLocalNotification(localnotification)
}

func loadView3() {
    label.text = "e89saa"
}

Answer 1

你可以尝试这样的事情。方法是，如果计时器工作继续使用相同的逻辑，否则（可能app被杀或进入后台），保存firedDate并更新UI，然后在方法viewWillAppear中显示控制器。

@IBAction func buttonTapped(sender: AnyObject) {
    NSTimer.scheduledTimerWithTimeInterval(300, target: self, selector: #selector(ViewController.loadView3), userInfo: nil, repeats: false)    
    createLocalNotification()
}

func createLocalNotification() {
    let localnotification = UILocalNotification()
    localnotification.fireDate = NSDate(timeIntervalSinceNow: 300)
    localnotification.applicationIconBadgeNumber = 1
    localnotification.soundName = UILocalNotificationDefaultSoundName
    localnotification.alertBody = "Hello!"
    UIApplication.sharedApplication().scheduleLocalNotification(localnotification)

    // save in UserDefaults fireDate
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.setObject(localnotification.fireDate, forKey: "firedDate")
    defaults.synchronize()
}

func loadView3() {
    // reset in UserDefaults fireDate
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.removeObjectForKey("firedDate")
    defaults.synchronize()

    label.text = "e89saa"
}

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated) // No need for semicolon

    // retrieve fireDate from UserDefaults
    let defaults = NSUserDefaults.standardUserDefaults()
    let fireDate = defaults.objectForKey("firedData")

    // check if we should update UI
    if let _ = fireDate as? NSDate! {
        if currentDate.compare(firedDate) == NSComparisonResult.OrderedDescending {
            loadView3()
        }
    }
}

使用NSTimer调用函数

1 个答案: