Load Viewcontroller Swift - Black Screen

presentViewController shows black page

You are not entering the nib name for the user Interface:

SuccessOrFailViewController *sfvc = [[SuccessOrFailViewController alloc] initWithNibName:@"SuccessOrFailViewController" bundle:nil];
[self presentViewController:sfvc animated:NO completion:NULL];

For storyboard this is the way to go:

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];
SuccessOrFailViewController *sfvc = [storyboard instantiateViewControllerWithIdentifier:@"SuccessOrFailViewController"];
[sfvc setModalPresentationStyle:UIModalPresentationFullScreen];
[self presentModalViewController:sfvc animated:YES];

swift _ Pushing ViewController in gives a black screen

It looks like MapViewController is designed in the storyboard. (If it were not, you would not be talking about @IBOutlet weak var map: MKMapView!)

But if so, then saying MapViewController(coor: category.coordinates) is not how to retrieve the instance that you designed in the storyboard. If you say that, you will indeed get basically an empty interface.

Instead, give that instance in the storyboard an identifier, and in your code, ask the storyboard to instantiate the view controller that has that identifier.

You will also have to rearrange your initialization completely. The storyboard is going to call init(coder:), not init(coor:). In fact, you can get rid of the latter entirely:

@IBOutlet weak var map: MKMapView!
var coor = [Double]()
required init?(coder: NSCoder) {
    super.init(coder:coder)
}
override func viewDidLoad() {
    super.viewDidLoad()
    let lat = coor[0]
    let long = coor[1]
    print(lat)
    print(long)
}

Now when you instantiate MapViewController from the storyboard, immediately also set mapView.coor before pushing.

Black when screen when settings initial controller programmatically

The problem is that, in an attempt to make the project stop using the scene delegate and use the app delegate instead, you mangled the UIApplicationSceneManifest entry in the Info.plist. Instead, you would need to delete that entry entirely. Its mere presence is what causes the scene delegate architecture to be used.

It would be better, however, to make this work for both iOS 12 using an app delegate and iOS 13 using a scene delegate (as I have described at https://stackoverflow.com/a/58405507/341994).

Pushing Viewcontroller through navigation controller , Showing Black screen

let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
let resultViewController = storyBoard.instantiateViewControllerWithIdentifier("ViewController") as! ViewController
self.navigationController?.pushViewController(resultViewController, animated: true)

Load Screen with from a View Controller

A couple of things are wrong here. It's okay, as SceneDelegate.swift was just added recently.

Your main issue here is that in your SceneDelegate's willConnectTo your if let window = self.window is nil, thus the rest of your code inside will not get executed resulting to a black screen.

In order to make Coordinator pattern work with storyboard in SceneDelegate.swift add these 2 properties and replace willConnectTo to the following:

    var coordinator: MainCoordinator?
    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {        
        let navController = UINavigationController() //create navController
        coordinator = MainCoordinator(navigationController: navController) //initialize our coordinator
        coordinator?.start() //start coordinator

        guard let windowScene = (scene as? UIWindowScene) else { return }
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = navController //make it our root
        window?.makeKeyAndVisible()
        window?.windowScene = windowScene
    }

Lastly, your AppDelegate.swift's didFinishLaunchingWithOptions function body does not need anything but return true to implement Coordinator pattern

Feel free to use this as reference: https://github.com/SamuelFolledo/NewsApp/blob/646a005e1be9b90a4c63cb99bf92d5b2be6691cc/NewsApp/SceneDelegate.swift

iOS Black screen when close modally presented view controller

You can do it with UITabBarControllerDelegate.

Option 1: Creating subclass of UITabBarController

class MyTabBar: UITabBarController, UITabBarControllerDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
    }

    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        if let currentlySelectedViewController = self.viewControllers?[self.selectedIndex] as? YourThirdTabViewController,
           let presentedViewController = currentlySelectedViewController.presentedViewController {
            presentedViewController.dismiss(animated: false, completion: nil)
        }
        return true
    }
}

Here I am assuming that I have my own sub class of UITabBarController which is set as UITabBarControllerDelegate using self.delegate = self in view didLoad.

Option 2: Make TabBarController's ViewController UITabBarControllerDelegate in their ViewDidLoad

If you dont wanna have your own subclass of UITabBarController all you have to do is simply set your self as UITabBarControllerDelegate in each ViewController's ViewDidLoad

You can have a common protocol or extension to UIViewController and confirm UITabBarControllerDelegate to avoid code duplication if you decide to go down the path of not subclassing UITabBarController

protocol TabBarControllerProtocol: UITabBarControllerDelegate where Self: UIViewController {}

extension TabBarControllerProtocol {
    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        if let currentlySelectedViewController = self.tabBarController?.viewControllers?[self.tabBarController?.selectedIndex ?? 0] as? SomeViewController,
           let presentedViewController = currentlySelectedViewController.presentedViewController {
            presentedViewController.dismiss(animated: false, completion: nil)
        }
        return true
    }
}

In whichever ViewController, you want this logic to kick in you can say

class SomeViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.tabBarController?.delegate = self
    }
}

extension SomeViewController: TabBarControllerProtocol {}

Thats it.

shouldSelect viewController gets called every time user taps on tab to switch.

The if condition checks if ViewController at selectedIndex (already selected not the new one) is viewController of specific interest or not and also checks if this view controller has presented anything or not, if it has presented it will call dismiss on it

This way when user switches tab from 3rd tab to any other tab, if third tab VC has presented another view controller modally it will dismiss it before it switches tab.

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