从AppDelegate调用委托函数不起作用 [英] Calling delegate function from AppDelegate not working

问题描述

我试图在AppDelegate中调用委托函数，但似乎永远不会被调用。

I am trying to call delegate function in AppDelegate, but seems like it never get invoked.

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate,appdelegate {

    var window: UIWindow?


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        if let navigationController = window?.rootViewController, let
            viewController = navigationController.childViewControllers.first as? ViewController {
            viewController.delegate = self
        }
        // Override point for customization after application launch.
        return true
    }

    func callfromDelegte(indicator: UIActivityIndicatorView) {
        indicator.stopAnimating()
    }

ViewController - ：

import UIKit

protocol appdelegate:class {
    func callfromDelegte(indicator:UIActivityIndicatorView)
}
class ViewController: UIViewController {

    @IBOutlet weak var indicator: UIActivityIndicatorView!
   weak var delegate:appdelegate?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        indicator.startAnimating()
        indicator.hidesWhenStopped = true
    }

    @IBAction func rotateAction(_ sender: UIButton) {
        if delegate != nil{
        delegate?.callfromDelegte(indicator: indicator)
        }
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

代表总是没有，它永远不会进入内部功能。那我现在不是关于代表的话是什么？ Google GIDSignInDelegate 及其委托函数如何从控制器类中调用AppDelegate？我知道这可能是一个非常愚蠢的问题，但我仍然想知道。谢谢

Delegate is always nil, it never goes inside function. What is that i don't now about delegates yet? How does Google GIDSignInDelegate and its delegate functions get called inside AppDelegate from controller class? I know it might be very stupid question but I would still like to know.Thanks

好的，因为我没有使用navigationController嵌入我的控制器。因此，如果让，它不会进入。它的工作原理如下 - ：

Ok it worked as i have not embeded my controller with navigationController. So it was not going inside if let. It worked simply like this-:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
//        if let navigationController = window?.rootViewController, let
//            viewController = navigationController.childViewControllers.first as? ViewController {
//            viewController.delegate = self
//        }
        // Override point for customization after application launch.

        let controller = window?.rootViewController as! ViewController
        controller.delegate = self
        return true
    }

推荐答案

您无法直接创建 Viewcontroller 对象并在< c>中设置委托 code> app delegate 。您需要首先访问 Viewcontroller 对象，因为它位于 rootViewController 中，因此您需要像这样实现

You cannot create the Viewcontroller object directly and set the delegate inside your app delegate. You need to access the Viewcontroller object first because it is the inside the rootViewController so you need to implement like this

if let navigationController = window?.rootViewController, let 
   viewController = navigationController.childViewControllers.first as? ViewController {
 viewController.delegate = self
}

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