Btukfyl

i have an application that i wish to show on external screen.

The problem is that when i go Hardware -> External displays and select one of them - the events aren't triggered. Why?

This also doesn't get entered:

if ([[UIScreen screens] count] > 1)

So i have added next code:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

     //SOME CODE ...

     [self checkForExistingScreenAndInitializeIfPresent];

     [self setUpScreenConnectionNotificationHandlers];

     return YES:

}



- (void)checkForExistingScreenAndInitializeIfPresent

{

if ([[UIScreen screens] count] > 1)

{

    // Get the screen object that represents the external display.

    UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];

    // Get the screen's bounds so that you can create a window of the correct size.

    CGRect screenBounds = secondScreen.bounds;



    self.secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];

    self.secondWindow.screen = secondScreen;



    self.externalWindow=[[ExternalDisplayViewController alloc]initWithNibName:@"ExternalDisplayViewController" bundle:nil];

    self.externalWindow.view.frame=screenBounds;



    self.secondWindow.rootViewController=self.externalWindow;

    // Set up initial content to display...

    // Show the window.

    self.secondWindow.hidden = NO;

    }

}



- (void)setUpScreenConnectionNotificationHandlers

{

NSNotificationCenter *center = [NSNotificationCenter defaultCenter];



[center addObserver:self selector:@selector(handleScreenDidConnectNotification:)

               name:UIScreenDidConnectNotification object:nil];

[center addObserver:self selector:@selector(handleScreenDidDisconnectNotification:)

               name:UIScreenDidDisconnectNotification object:nil];

}

ADDITION:

Just tried to add code in ViewDidLoad

Added this:

// Check for external screen.

if ([[UIScreen screens] count] > 1)

{



}

else {

}

Have the opened external display and simulator - does't enter the IF block

The problem might with the initialisation of the ExternalDisplayViewController :

self.externalWindow=[[ExternalDisplayViewController alloc]initWithNibName:@"ExternalDisplayViewController" bundle:nil];

Try this :

[[ExternalDisplayViewController alloc]initWithNibName:@"ExternalDisplayViewController" bundle:nil];

 UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

    self.externalWindow= = [storyboard instantiateViewControllerWithIdentifier:@"ExternalDisplayView"];

and also, you need to override this handleScreenDidConnectNotification

-(void)handleScreenDidConnectNotification : (NSNotification *)aNotification{

    UIScreen *newScreen = [aNotification object];

    CGRect screenBounds = newScreen.bounds;

    self.alertForNotifyDisplay =  [[UIAlertView alloc] initWithTitle:@"External Display Connected." message:Nil delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];

    [self.alertForNotifyDisplay show];



    if (!self.extWindow) {

        self.extWindow  = [[UIWindow alloc] initWithFrame:screenBounds];

        self.extWindow.screen = newScreen;



        [self checkForExistingScreenAndInitializeIfPresent];

    }



}

Here's my complete code in my UIViewController subclass. I have checked it with the 7.1 simulator and it works for me (I start the app, and then initialize the external display once it's already running):

- (void)viewDidLoad {

    // Other viewDidLoad code…

    // Check and initialize big screen

    [self checkForExistingScreenAndInitializeIfPresent]; 

}



- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];

    // Register for second screen notifications

    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];

    [center addObserver:self selector:@selector(handleScreenDidConnectNotification:)

               name:UIScreenDidConnectNotification object:nil];

    [center addObserver:self selector:@selector(handleScreenDidDisconnectNotification:)

               name:UIScreenDidDisconnectNotification object:nil];

}



- (void)handleScreenDidConnectNotification:(NSNotification *)notification {

    [self checkForExistingScreenAndInitializeIfPresent];

}



- (void)handleScreenDidDisconnectNotification:(NSNotification *)notification {

    [self checkForExistingScreenAndInitializeIfPresent];

}



- (void)checkForExistingScreenAndInitializeIfPresent {

    if ([[UIScreen screens] count] > 1) {

        // Get the screen object that represents the external display.

        UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];

        secondScreen.currentMode = secondScreen.preferredMode;

        secondScreen.overscanCompensation = 3;

        // Get the screen's bounds so that you can create a window of the correct size.

        CGRect screenBounds = CGRectMake(secondScreen.bounds.origin.x,

                                         secondScreen.bounds.origin.y,

                                         secondScreen.currentMode.size.width,

                                         secondScreen.currentMode.size.height);



        UIWindow *secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];

        secondWindow.screen = secondScreen;

        // Setup external VC

        [ExternalScreenViewController sharedExternalScreen].window = secondWindow;

        // Set VC for second window

        secondWindow.rootViewController = [ExternalScreenViewController sharedExternalScreen];

        // Show the window.

        secondWindow.hidden = NO;

    } else {

        // What to do if disconnected

    }

} 

It should work with minor changes.

The problem was in beta versions of OS and Xcode. Downgraded back to Maverics - and all works like a charm

This was driving me nuts.
I'm on Version 10.0 (10A255) and it wasn't working. The reason why is I was looking at application:didFinishLaunchingWithOptions: for a UIScreen.screens.count > 1

This will always be 1

Instead try this

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

   let center = NotificationCenter.default

   center.addObserver(self, selector: #selector(didConnect(notification:)), name: UIScreen.didConnectNotification, object: nil)

   return true

}



@objc func didConnect(notification: Notification) {

    if UIScreen.screens.count > 1 {

        if let screen = UIScreen.screens.last {

            let window = UIWindow(frame: screen.bounds)

            window.screen = screen



            let vc = UIViewController(nibName: nil, bundle: nil)

            vc.view.backgroundColor = .red



            window.isHidden = false

            window.rootViewController = vc

            self.secondWindow = window // Will not show unless window variable is retained.

        }

    }

}