如何将值从 SceneDelegate 文件传输到 ViewController (Swift 5)
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【中文标题】如何将值从 SceneDelegate 文件传输到 ViewController (Swift 5)【英文标题】:How to transfer a value from a SceneDelegate file to a ViewController (Swift 5) 【发布时间】:2020-08-18 14:20:42 【问题描述】:在其中一个 SceneDelegate 方法中,我想为另一个 ViewController 中的变量赋值。我怎样才能做到这一点?总是为零。我尝试了不同的方法,但由于某种原因它们不起作用,我想使用完成处理程序,但似乎我无法在 SceneDelegate 方法中做到这一点
class SceneDelegate: UIResponder, UIWindowSceneDelegate
var viewController: ViewController?
...
//This method works when I click on a cell
func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>)
if let url = URLContexts.first?.url
let oauthCompletion: DropboxOAuthCompletion =
if let authResult = $0
switch authResult
case .success:
self.dropboxManager.fetchFiles()
UserDefaults.standard.set(true, forKey:"userAuthorizedInDropbox")
//I want to assign a value here
self.viewController?.someString = "Some Text"
print("Success! User is logged into Dropbox.")
case .cancel:
print("Authorization flow was manually canceled by user!")
case .error(_, let description):
print("Error: \(String(describing: description))")
DropboxClientsManager.handleRedirectURL(url, completion: oauthCompletion)
...
class ViewController: UIViewController
...
//But it's still nil
var someString: String?
...
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
dropboxManager.openDropboxAutorization(controller: self)
.....
class MainTabBarController: UITabBarController
let viewController: ViewController = ViewController.loadFromStoryboard()
override func viewDidLoad()
super.viewDidLoad()
viewControllers = [
generateVC(rootViewController: viewController, image: nil, title: "Import")
...
]
private func generateVC(rootViewController: UIViewController, image: UIImage?, title: String) -> UIViewController
let navigationVC = UINavigationController(rootViewController: rootViewController)
navigationVC.tabBarItem.image = image
navigationVC.tabBarItem.title = NSLocalizedString(title, comment: "")
rootViewController.navigationItem.title = NSLocalizedString(title, comment: "")
return navigationVC
...
【问题讨论】:
显示分配viewController: ViewController?
的时间和地点。
我在标签栏控制器中执行此操作。我在问题中添加了代码
【参考方案1】:
您可以从场景委托中的rootViewController
访问您想要的ViewController
。在以下示例中,我正在考虑您所需的视图控制器位于标签栏控制器的第一个标签中。
if let tabbarController = self.window?.rootViewController as? UITabBarController,
let navigationController = tabbarController.viewControllers?.first as? UINavigationController,
let desiredController = navigationController.viewControllers.first as? ViewController
desiredController.someString = "some value"
但在我看来,这不是推荐的方法,因为可能有很多情况可能取决于应用程序或导航堆栈的状态。
你可以做的是在你想要的ViewController
中添加一个观察者,然后像这样从SceneDelegate
发布通知:
NotificationCenter.default.post(name: Notification.Name(rawValue: "someeventname"), object: "some value")
你可以像这样添加和监听观察者:
import UIKit
class ViewController: UIViewController
override func viewDidLoad()
super.viewDidLoad()
// Do any additional setup after loading the view.
NotificationCenter.default.addObserver(self, selector: #selector(someEventNotificationReceived(notification:)), name: Notification.Name(rawValue: "someeventname"), object: nil)
deinit
NotificationCenter.default.removeObserver(self, name: Notification.Name(rawValue: "someeventname"), object: nil)
@objc func someEventNotificationReceived(notification: Notification)
if let value = notification.object as? String
//handle the event here
【讨论】:
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