Using UIScreen to drive a VGA display - doesn't seem to show the UIWindow?

Question

HI there,

I'm trying to use UIScreen to drive a separate screen with the VGA dongle on my iPad.

Here's what I've got in my root view controller's viewDidLoad:

//Code to detect if an external display is connected to the iPad.
 NSLog(@"Number of screens: %d", [[UIScreen screens]count]);

 //Now, if there's an external screen, we need to find its modes, itereate through them and find the highest one. Once we have that mode, break out, and set the UIWindow.

 if([[UIScreen screens]count] > 1) //if there are more than 1 screens connected to the device
 {
  CGSize max;
  UIScreenMode *maxScreenMode;
  for(int i = 0; i < [[[[UIScreen screens] objectAtIndex:1] availableModes]count]; i++)
  {
   UIScreenMode *current = [[[[UIScreen screens]objectAtIndex:1]availableModes]objectAtIndex:i];
   if(current.size.width > max.width);
   {
    max = current.size;
    maxScreenMode = current;
   }
  }
  //Now we have the highest mode. Turn the external display to use that mode.
  UIScreen *external = [[UIScreen screens] objectAtIndex:1];
  external.currentMode = maxScreenMode;
  //Boom! Now the external display is set to the proper mode. We need to now set the screen of a new UIWindow to the external screen
  external_disp = [externalDisplay alloc];
  external_disp.drawImage = drawViewController.drawImage;
  UIWindow *newwindow = [UIWindow alloc];
  [newwindow addSubview:external_disp.view];
  newwindow.screen = external;
 }

Answer 1

[newwindow makeKeyAndVisible];?

Answer 2

You need to init your window...

UIWindow *newwindow = [[UIWindow alloc] init];

Answer 3

Did anybody manage to solve this problem?

All I see is a black screen at the projector.

Thanks.

Answer 4

Can you post ALL the code? I have only what you posted and I am getting errors.

Thanks.

Answer 5

I think your problem is the externalDisplay. Create a viewcontroller outside your code (maybe do a simply Add new file ViewController and put stuff in the .xib) and try it out to make sure that viewcontroller is working before you call it into the external display. Here's your code with my suggested changes -- [mainViewController view] is the viewcontroller you created outside.

//Code to detect if an external display is connected to the iPad.
NSLog(@"Number of screens: %d", [[UIScreen screens]count]);

//Now, if there's an external screen, we need to find its modes, iterate
//through them and find the highest one. Once we have that mode, break out,
//and set the UIWindow.

if([[UIScreen screens]count] > 1) //if there are more than 1 screens connected
                                  //to the device
{
 CGSize max;
 UIScreenMode *maxScreenMode;
 for(int i = 0; i < [[[[UIScreen screens] objectAtIndex:1] availableModes]count]; i++)
 {
  UIScreenMode *current = [[[[UIScreen screens]objectAtIndex:1]availableModes]objectAtIndex:i];
  if(current.size.width > max.width);
  {
   max = current.size;
   maxScreenMode = current;
  }
 }
 //Now we have the highest mode. Turn the external display to use that mode.
 UIScreen *external = [[UIScreen screens] objectAtIndex:1];
 external.currentMode = maxScreenMode;
 //Boom! Now the external display is set to the proper mode. We need to now
 //set the screen of a new UIWindow to the external screen

 UIWindow *newwindow = [UIWindow alloc];

 [newwindow addSubview:[mainViewController view]];
 newwindow.screen = external;

 [newwindow makeKeyAndVisible];
 [newwindow setHidden:NO];
}

Answer 6

I've uploaded sample .xcodeproj into github.

I refered to this page mainly.

Thanks a lot. :)

http://github.com/igaiga/iPadDisplayOutSample

Answer 7

Sorry to add a Question on here, but is it also possible to reverse this so that removing the external display doesn't kill the application?

Answer 8

It seems that the touches interaction don't work when on the external monitor. Have you noticed that?

How can I rotate the screen? When the app runs on the iPad it is on Landscape mode , but when the external monitor the app runs on Portrait mode.