swift ios - 如何从 AppDelegate 在 ViewController 中运行函数 [英] swift ios - How to run function in ViewController from AppDelegate

问题描述

我正在尝试使用 AppDelegate

func applicationDidBecomeActive(_ application: UIApplication) {
        ViewController().grabData()
}

但不知何故，当从后台进入应用程序后应用程序变为活动状态时，该功能似乎根本没有运行.

But somehow the function does not seem to run at all when the app has become active after entering the app from the background.

函数看起来像这样

func grabData() {
        self._DATASERVICE_GET_STATS(completion: { (int) -> () in
            if int == 0 {
                print("Nothing")
            } else {
                print(int)

                for (_, data) in self.userDataArray.enumerated() {
                    let number = Double(data["wage"]!)
                    let x = number!/3600
                    let z = Double(x * Double(int))
                    self.money += z
                    let y = Double(round(1000*self.money)/1000)

                    self.checkInButtonLabel.text = "\(y) KR"
                }

                self.startCounting()
                self.workingStatus = 1
            }
        })
    }

并使用这个变量

var money: Double = 0.000

我错过了什么?

谢谢！

推荐答案

ViewController().grabData() 将创建一个新的 ViewController 实例并调用这个函数.然后......由于视图控制器未使用，它将被垃圾收集/从内存中删除.您需要在正在使用的实际视图控制器上调用此方法.不是它的新实例.

ViewController().grabData() will create a new instance of the ViewController and call this function. Then.. as the view controller is not in use it will be garbage collected/removed from memory. You need to be calling this method on the actual view controller that is in use. Not a new instance of it.

最好的选择是监听 iOS 提供的 UIApplicationDidBecomeActive 通知.

The best option would be to listen for the UIApplicationDidBecomeActive notification that iOS provides.

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

确保你也移除了观察者，这通常是在 deinit 方法中完成的

make sure that you also remove the observer, this is usually done in a deinit method

deinit() {
    NotificationCenter.default.removeObserver(self)
} 

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