How to use external display in iOS

Issue #473

Before iOS 13

Use UIScreen.didConnectNotification

NotificationCenter.default.addObserver(forName: UIScreen.didConnectNotification,
                         object: nil, queue: nil) { (notification) in
        // Get the new screen information.
        let newScreen = notification.object as! UIScreen
        let screenDimensions = newScreen.bounds

        // Configure a window for the screen.
        let newWindow = UIWindow(frame: screenDimensions)
        newWindow.screen = newScreen
        // Install a custom root view controller in the window.
        self.configureAuxilliaryInterface(with: newWindow)

        // You must show the window explicitly.
        newWindow.isHidden = false
        // Save a reference to the window in a local array.
        self.additionalWindows.append(newWindow)}

From iOS 13

Handle configurationForConnecting

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

var newWindow: UIWindow!

    // MARK: UISceneSession Lifecycle

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.


                        print(UIApplication.shared.connectedScenes)
        let scene = UIWindowScene(session: connectingSceneSession, connectionOptions: options)

                        // Configure a window for the screen.
                        self.newWindow = UIWindow(frame: CGRect(x: 0, y: 0, width: 1000, height: 500))
        //                self.newWindow.backgroundColor = UIColor.yellow
                        // Install a custom root view controller in the window.

                        let viewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "other") as! OtherViewController
                        self.newWindow.rootViewController = viewController
                        self.newWindow.windowScene = scene

                        // You must show the window explicitly.
                        self.newWindow.isHidden = false

        return UISceneConfiguration(name: "External configuration", sessionRole: connectingSceneSession.role)
    }
}

Or we can declare in plist

<dict>
    <key>UIApplicationSupportsMultipleScenes</key>
    <false/>
    <key>UISceneConfigurations</key>
    <dict>
        <key>UIWindowSceneSessionRoleApplication</key>
        <array>
            <dict>
                <key>UISceneConfigurationName</key>
                <string>Default Configuration</string>
                <key>UISceneDelegateClassName</key>
                <string>$(PRODUCT_MODULE_NAME).SceneDelegate</string>
                <key>UISceneStoryboardFile</key>
                <string>Main</string>
            </dict>
        </array>
        <key>UIWindowSceneSessionRoleExternalDisplay</key>
        <array>
            <dict>
                <key>UISceneConfigurationName</key>
                <string>External configuration</string>
                <key>UISceneDelegateClassName</key>
                <string>$(PRODUCT_MODULE_NAME).OtherSceneDelegate</string>
                <key>UISceneStoryboardFile</key>
                <string>Other</string>
            </dict>
        </array>
    </dict>
</dict>

Read more

• External Display Support on iOS
• Supporting External Displays
• Building iPad Pro features in Swift
• How can I display different content on different screens in iOS 13?
• Displaying Content on a Connected Screen
• Adding External Display Support To Your iOS App Is Ridiculously Easy