如何訪問「func applicationWillResignActive」內的UIViewController的變量？斯威夫特的iOS的Xcode

Question

我有我UIViewController類設置是這樣的：

class ViewController: UIViewController { 

    var currentTask: NSURLSessionTask? 

    ... 

} 

如果用戶按下Home按鈕，我想要做的

self.currentTask.cancel() 

但我怎麼可以訪問的AppDelegate這個變量。迅速？

func applicationWillResignActive(application: UIApplication) { 

} 

Answer 1

在viewDidLoad中（）UIViewController類內

，添加

// Add UIApplicationWillResignActiveNotification observer 
    NSNotificationCenter.defaultCenter().addObserver(
     self, 
     selector: "resigningActive", 
     name: UIApplicationWillResignActiveNotification, 
     object: nil 
    ) 
    NSNotificationCenter.defaultCenter().addObserver(
     self, 
     selector: "becomeActive", 
     name: UIApplicationDidBecomeActiveNotification, 
     object: nil 
    ) 

爲夫特4的iOS 11，使用：

NotificationCenter.default.addObserver(
    self, 
    selector: #selector(ViewController.resigningActive), 
    name: NSNotification.Name.UIApplicationWillResignActive, 
    object: nil) 

NotificationCenter.default.addObserver(
    self, 
    selector: #selector(ViewController.becomeActive), 
    name: NSNotification.Name.UIApplicationDidBecomeActive, 
    object: nil) 

這兩個函數最後添加到視圖控制器：

@objc fileprivate func resigningActive() { 
    print("== resigningActive ==") 
} 

@objc fileprivate func becomeActive() { 
    print("== becomeActive ==") 
}