我在第一次使用空白屏幕登录应用程序时遇到了一个小问题,并且收到警告“尝试呈现不在窗口层次结构中的 View !”关闭并重新启动后, View 看起来不错。我相信它与 rootViewController
有关,但不确定......提前感谢您的任何帮助或指导!
应用程序委托(delegate)
@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
}
导航 Controller 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
})
}
}
//登录函数调用
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)
}
最佳答案
好吧,所以我的最后一个答案是错误的(我删除了它),问题是应用程序中有一个键窗口,这是你的导航 Controller ,并且你不能在这个窗口上呈现任何内容,直到它加载其 subview (即使它没有任何),这会发生在 viewdidappear 上,因此您应该将 viewdidload 中的代码放在那里。
关于swift - 第一次启动应用程序 xcode 时出现黑屏,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43421445/