[英]Blank screen first time launching app xcode
I am having a little issue with logging into an app the first time with a blank screen and I am getting the warning "Attempt to present on whose view is not in the window hierarchy!" 我第一次在空白屏幕上登录应用程序时遇到了一个小问题,并且收到警告“尝试在其视图不在窗口层次结构中显示的提示!”。 After I close and relaunch, the views appear fine.
关闭并重新启动后,视图看起来很好。 I believe it has something to do with the
rootViewController
but not sure... Thanks in advance for any help or direction! 我相信它与
rootViewController
但是不确定...预先感谢您的帮助或指导!
App delegate 应用委托
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
var ref:FIRDatabaseReference?
var databaseHandle:FIRDatabaseHandle?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
window = UIWindow(frame: UIScreen.main.bounds)
window?.makeKeyAndVisible()
window?.rootViewController = MainNavigationController()
FIRApp.configure()
ref = FIRDatabase.database().reference()
return true
}
Navigation controller as rootViewController
导航控制器为
rootViewController
class MainNavigationController: UINavigationController {
var segmentedController: UISegmentedControl!
override func viewDidLoad() {
super.viewDidLoad()
let vc1 = TravelersFeedVC()
let vc2 = ProfileVC()
if isLoggedIn() {
// assume user is logged in
let homeController = HomeController()
viewControllers = [homeController]
homeController.firstViewController = vc1
homeController.secondViewController = vc2
} else {
perform(#selector(showLoginController), with: nil, afterDelay: 0.01)
}
}
fileprivate func isLoggedIn() -> Bool {
return UserDefaults.standard.isLoggedIn()
}
func showLoginController() {
let loginController = LoginController()
present(loginController, animated: true, completion: {
// perhaps do something here later
})
}
}
// log in function called //登录名为
func finishLoggingIn() {
let rootViewController = UIApplication.shared.keyWindow?.rootViewController
guard let mainNavigationController = rootViewController as? MainNavigationController else { return }
let vc1 = TravelersFeedVC()
let vc2 = ProfileVC()
if isLoggedIn() {
// assume user is logged in
let homeController = HomeController()
mainNavigationController.viewControllers = [HomeController()]
homeController.firstViewController = vc1
homeController.secondViewController = vc2
} else {
perform(#selector(showLoginController), with: nil, afterDelay: 0.01)
}
UserDefaults.standard.setIsLoggedIn(value: true)
dismiss(animated: true, completion: nil)
}
好的,所以我的最后一个答案是错误的(我将其删除了),原因是在应用程序中有一个键盘窗口,它是您的navcontroller,并且在此窗口上无法显示任何内容,直到它将加载其子视图(即使它没有加载) t any),而这将发生在viewdidappear上,因此您应该将代码从viewdidload放到那里。
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