Question

我有两个UIViewControllers，每当他们进入视图时我都想更新。

在 DashBordViewControlller 中，我添加了此代码：

override func viewDidLoad() {
    super.viewDidLoad()

    let appDelegate:AppDelegate = UIApplication.sharedApplication().delegate! as AppDelegate
    appDelegate.dashboardViewController = self

并在 DetailViewController 中使用此代码：

override func viewDidLoad() {
    super.viewDidLoad()

    let appDelegate:AppDelegate = UIApplication.sharedApplication().delegate! as AppDelegate
    appDelegate.detailViewController = self

在 AppDelegate 中，我添加了以下代码：

class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

var dashboardViewController:DashboardViewController?
var detailViewController:DetailViewController?

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

func applicationWillResignActive(application: UIApplication) {
  }

func applicationDidEnterBackground(application: UIApplication) {
     println("Goodbye world")
}

func applicationWillEnterForeground(application: UIApplication) {
    println("Hello again world")
    dashboardViewController?.cleanCDandQueryHKLoop()
    detailViewController?.rememberWhatSegmentIsPressed()
}

我的问题是只要ViewController进入视图，两者 UIViewControllers都会更新。例如，如果我关闭应用程序（主页），然后重新打开它。

如何在AppDelegate中检查哪个ViewController进入视图并仅更新该视图？任何帮助将非常感谢 - 谢谢！

Answer 1

您应该在视图控制器的viewWillAppear中添加一个观察者，如下所示：

override func viewWillAppear(animated: Bool) {
  super.viewWillAppear(animated)
  NSNotificationCenter.defaultCenter().addObserver(self, selector: "willEnterForeground:", name: UIApplicationWillEnterForegroundNotification, object: nil)
}

之后，实现你的功能：

func willEnterForeground(notification: NSNotification!) {
  // View Controller is brought to Foreground
}

哦，不要忘记在viewWillDisappear上删除观察者：

override func viewWillDisappear(animated: Bool) {
  super.viewWillDisappear(animated)
  NSNotificationCenter.defaultCenter().removeObserver(self, name: nil, object: nil)
}

进入视图时更新特定的ViewController

1 个答案: