ios - 尝试呈现其 View 不在窗口层次结构中的 UINavigationController! ( swift )

Question

我遇到了 View Controller 未显示的问题，即使调用 View Controller 的函数似乎正在运行。我在控制台中收到的错误是:

Warning: Attempt to present on whose view is not in the window hierarchy!

我已经尝试了“尝试在 View 不在窗口层次结构中的 UIViewController 上呈现 UIViewController”线程的建议，但没有任何进展。我正在以编程方式运行一切。

func handleNewPage(){
    print("this code works")
    let uid = Auth.auth().currentUser?.uid

    ref = Database.database().reference()

    let usersReference = ref.child("patient").child((uid)!)

    if usersReference.child("Doctor Code") != nil {
        func presentNewPage(){
            let firstPage = LandingPage()
            let navCon = UINavigationController(rootViewController: firstPage)
            present(navCon, animated: true, completion: nil)

        }
        presentNewPage()
        print("PRINT")
    } else{
        let newPage = PresentViewController() // doctor reg page
        let navController = UINavigationController(rootViewController: newPage)
        present(navController, animated: true, completion: nil)
    }
}

该函数被调用并且打印语句有效。然而， View Controller 不会出现。

Answer 1

你必须在你的if之外创建presentNewPage()函数???

if usersReference.child("Doctor Code") != nil {
        func presentNewPage(){
            let firstPage = LandingPage()
            let navCon = UINavigationController(rootViewController: firstPage)
            present(navCon, animated: true, completion: nil)

        }
    presentNewPage()
    print("PRINT")
} else{
    let newPage = PresentViewController() // doctor reg page
    let navController = UINavigationController(rootViewController: newPage)
    present(navController, animated: true, completion: nil)
}

这样改

func presentNewPage(){
            let firstPage = LandingPage()
            let navCon = UINavigationController(rootViewController: firstPage)
            present(navCon, animated: true, completion: nil)

        }

func handleNewPage(){
    print("this code works")
    let uid = Auth.auth().currentUser?.uid

ref = Database.database().reference()

let usersReference = ref.child("patient").child((uid)!)

if usersReference.child("Doctor Code") != nil {

    presentNewPage()
    print("PRINT")
} else{
    let newPage = PresentViewController() // doctor reg page
    let navController = UINavigationController(rootViewController: newPage)
    present(navController, animated: true, completion: nil)
}
}