Question

我在“主页”视图控制器中更新当前日期标签时出现问题，如下所示：

func settingTodayLabel() {

  let todayFormatter = NSDateFormatter()
  todayFormatter.dateFormat = "d MMM YYYY"       
  todayLabel.text = todayFormatter.stringFromDate(NSDate()) 
}

当'ApplicationDidBecomeActive'调用此函数时，我希望在第二天从背景调用app但今天没有更改时更新今天的标签文本。显示旧日期。但是，如果我在设置中手动修改日期，则可以正常工作..

override func viewDidLoad() {        
super.viewDidLoad()

  NSNotificationCenter.defaultCenter().addObserver(self, selector: "settingTodayLabel", name: UIApplicationDidBecomeActiveNotification, object: nil)
}

Answer 1

仅当应用程序变为活动状态时才会触发

UIApplicationDidBecomeActiveNotification，因此您需要在0:00每天触发另一个通知以更新标签。

创建一个本地推送通知，该通知在0:00触发并让它广播您收听的自定义NSNotification，如

NSNotificationCenter.defaultCenter().addObserver(self, selector: "settingTodayLabel", name: "DateChangedNewDay", object: nil)

AppDelegate中

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

        let notificationType = UIUserNotificationType.None
        let settings = UIUserNotificationSettings(forTypes: notificationType, categories: nil)
        application.registerUserNotificationSettings(settings)


        var localNotification:UILocalNotification = UILocalNotification()

        localNotification.fireDate = NSCalendar.currentCalendar().startOfDayForDate(NSDate())
        localNotification.repeatInterval = NSCalendarUnit.CalendarUnitDay  // for testing: .CalendarUnitMinute
        UIApplication.sharedApplication().scheduleLocalNotification(localNotification)


        return true
    }

    func application(application: UIApplication, didReceiveLocalNotification notification: UILocalNotification) {
        NSNotificationCenter.defaultCenter().postNotificationName("DateChangedNewDay", object: nil)
    }

}

视图控制器

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var todayLabel: UILabel!

    deinit{
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        NSNotificationCenter.defaultCenter().addObserver(self, selector: "settingTodayLabel", name: UIApplicationDidBecomeActiveNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "settingTodayLabel", name: "DateChangedNewDay", object: nil)

    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        self.settingTodayLabel()
    }

    func settingTodayLabel() {

        let todayFormatter = NSDateFormatter()
        todayFormatter.dateFormat = "d MMM yyyy"  // for testing: "d MMM yyyy HH:mm"
        todayLabel.text = todayFormatter.stringFromDate(NSDate())
    }
}

我在网上放了一个示例应用程序，每分钟更新一次：https://github.com/vikingosegundo/LabelUpdatingEachMinute

"d MMM YYYY"最有可能是"d MM yyyy"，因为Y代表年份＃34;一年中的一周＆＃34; 年份没有＆＃39} ; t从1月1日开始，但仅在几周之间切换：1月的前3天可以属于12月到下一年的最后3天的最后一年。 y代表我们所知的年份：从1月1日开始。

今天UILabel自动更新

1 个答案: