How can I display an image on the entire device screen with UIImageView on iPhone/iPad?

Question

How can I display an image on the entire device screen with UIImageView on iPhone/iPad?

Kim Strasser 1,321

I want to display an image on the entire device screen. The image needs to be displayed until I execute LogoView.RemoveFromSuperview();.

stackoverflow ios-fit-image-to-screen
I use the code from stackoverflow but it's not working because I don't know what I should use for my View.
I get an error message in Program.cs if I use View:

Error CS0103: The name 'View' does not exist in the current context

Program.cs:

using System;  
using Foundation;  
using UIKit;  
  
namespace MyProject  
{  
[Register("AppDelegate")]  
class Program : UIApplicationDelegate  
{  
    private UIImageView LogoImage;  
  
    public override void FinishedLaunching(UIApplication app)  
    {  
        global::Xamarin.Forms.Forms.Init();  
        LogoImage = new UIImageView(UIImage.FromFile("Launchscreenlogo.png"));  
        LogoImage.Tag = 1234;  
        LogoImage.Frame = View.Frame;  
        View.AddSubview(LogoImage);  
        View.BringSubviewToFront(LogoImage);  
    }  
  
    private void G_RemoveLogo(object sender, System.EventArgs e)  
    {  
        //remove image  
        var LogoView = View.ViewWithTag(1234);  
        if (null != LogoView)  
            LogoView.RemoveFromSuperview();  
    }  
}  
}

How can I display an image on the entire device screen with UIImageView on iPhone/iPad?
Is it possible to use my image from Assets.xcassets(launch.png, ******@2x.png, ******@3x.png) in UIImageView?

Accepted answer

1 additional answer

Your answer

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

You got this error because there is no view in AppDelegate, I add the RootViewController and add this LogoImage into its View, you could refer to the following code:

public override bool FinishedLaunching(UIApplication app, NSDictionary options)  
    {  
        global::Xamarin.Forms.Forms.Init();  
        LoadApplication(new App());  
    Window = new UIWindow(UIScreen.MainScreen.Bounds);  
    var MainViewController = new UIViewController();  
    Window.RootViewController = MainViewController;  
    Window.MakeKeyAndVisible();  

    MainViewController.View.BackgroundColor = UIColor.White;  
    LogoImage = new UIImageView(UIImage.FromBundle("Launchscreenlogo"));// load the Assets.xcassets image  
    LogoImage.ContentMode = UIViewContentMode.ScaleAspectFill;  
    LogoImage.Tag = 1234;  
    LogoImage.Frame = MainViewController.View.Frame;  
    MainViewController.View.AddSubview(LogoImage);  
    MainViewController.View.BringSubviewToFront(LogoImage);  
    return true;    
}

You could also create a new controller to load a imageview and add a button to test, right click the iOS project ->new Item -> UIViewController(Apple) ->named( my class name is MyViewController) , then refer to the following code:

 private UIImageView LogoImage;  
        public override void ViewDidLoad()  
        {  
            View = new UniversalView();  
  
            base.ViewDidLoad();  
            View.BackgroundColor = UIColor.White;  
            LogoImage = new UIImageView(UIImage.FromBundle("Launchscreenlogo"));  
            LogoImage.ContentMode = UIViewContentMode.ScaleAspectFill;  
            LogoImage.Tag = 1234;  
            LogoImage.Frame = new CoreGraphics.CGRect(0,0,UIScreen.MainScreen.Bounds.Size.Width, UIScreen.MainScreen.Bounds.Size.Height);// important  
            View.AddSubview(LogoImage);  
              
  
            UIButton mybutton = new UIButton(new CoreGraphics.CGRect(0, 100, 100, 40));  
            mybutton.SetTitle("click to remove", UIControlState.Normal);// add this button to test  
            mybutton.TouchUpInside += (sender, e) => {  
                G_RemoveLogo(sender, e);  
            };  
            View.AddSubview(mybutton);  
        }  
        private void G_RemoveLogo(object sender, System.EventArgs e)  
        {  
            //remove image  
            var LogoView = View.ViewWithTag(1234);  
            if (null != LogoView)  
                LogoView.RemoveFromSuperview();  
        }

FinishedLaunching in AppDelegate

public override bool FinishedLaunching(UIApplication app, NSDictionary options)  
        {  
            global::Xamarin.Forms.Forms.Init();  
            LoadApplication(new App());  
            Window = new UIWindow(UIScreen.MainScreen.Bounds);  
            var MainViewController = new MyViewController();  
            Window.RootViewController = MainViewController;  
            Window.MakeKeyAndVisible();  
  
            return true;  
        }

You could also load ViewController from forms refer to https://stackoverflow.com/questions/63812069/display-viewcontroller-from-native-forms.
About how to displaythe image in Xamarin.iOS, you could refer to https://learn.microsoft.com/en-us/xamarin/ios/app-fundamentals/images-icons/displaying-an-image?tabs=macos

------------update-----------
Program class(use MyViewController )

 using System.Linq;  
    using System.Text;  
    using UIKit;  
      
    namespace ImageViewDemo.iOS  
    {  
    [Register("AppDelegate")]  
   public class Program : UIApplicationDelegate  
    {  
        private MyViewController MainViewController;  
        public override void FinishedLaunching(UIApplication application)  
        {  
            var Window = new UIWindow(UIScreen.MainScreen.Bounds);  
            MainViewController = new MyViewController();  
            Window.RootViewController = MainViewController;  
            Window.MakeKeyAndVisible();  
        }    
    }  
}

Program class(use UIViewController )

namespace ImageViewDemo.iOS  
{  
    [Register("AppDelegate")]  
   public class Program : UIApplicationDelegate  
    {  
        private UIViewController MainViewController;  
        private UIImageView LogoImage;  
        public override void FinishedLaunching(UIApplication application)  
        {  
            var Window = new UIWindow(UIScreen.MainScreen.Bounds);  
            MainViewController = new UIViewController();  
            Window.RootViewController = MainViewController;  
            Window.MakeKeyAndVisible();  
            MainViewController.View.BackgroundColor = UIColor.White;  
            LogoImage = new UIImageView(UIImage.FromBundle("Launchscreenlogo"));  
            LogoImage.ContentMode = UIViewContentMode.ScaleAspectFill;  
            LogoImage.Tag = 1234;  
            LogoImage.Frame = MainViewController.View.Frame;  
            MainViewController.View.AddSubview(LogoImage);  
            MainViewController.View.BringSubviewToFront(LogoImage);  
            RunGame();  
        }  
        private void G_RemoveLogo(object sender, System.EventArgs e)  
        {  
            //remove the image  
            ......  
        }  
  
        internal static void RunGame()  
        {  
           ......  
             
        }  
    }  
}

Pay attition to comment out this line of code in Appdelegate.cs

// [Register("AppDelegate")]

Best Regards,
Wenyan Zhang

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Kim Strasser 1,321 Reputation points

2021-12-08T15:18:38.66+00:00

I don't have a class named Appdelegate.cs in my project.
In addition, I get an error message in MyViewController.cs:

View = new UniversalView();

Error CS0246: The type or namespace name 'UniversalView' could not be found (are you missing a using directive or an assembly reference?)

using UIKit; namespace MyProject { public partial class MyViewController : UIViewController { private UIImageView LogoImage; public MyViewController() : base("MyViewController", null) { } public override void ViewDidLoad() { base.ViewDidLoad(); // Perform any additional setup after loading the view, typically from a nib. View = new UniversalView(); base.ViewDidLoad(); View.BackgroundColor = UIColor.White; // ... } private void G_RemoveLogo(object sender, System.EventArgs e) { //remove image var LogoView = View.ViewWithTag(1234); if (null != LogoView) LogoView.RemoveFromSuperview(); } public override void DidReceiveMemoryWarning() { base.DidReceiveMemoryWarning(); // Release any cached data, images, etc that aren't in use. } } }
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 36,436 Reputation points Microsoft External Staff

2021-12-09T02:15:52.887+00:00

Try to replace View = new UniversalView(); with

View = new UIView();
Kim Strasser 1,321 Reputation points

2021-12-09T23:01:48.413+00:00

Is it better to use Program class(use UIViewController) instead of Program class(use MyViewController) if I want to call G_RemoveLogo from Game1.cs? In addition, the player doesn't need to click on a button to remove the image. The image should be removed when a certain point is reached in Game1.cs.
I have tried to call G_RemoveLogo located in MyViewController.cs but it is not working to call it from Game1.cs.

I found out that I need to use (UIApplication.SharedApplication.Delegate as Myproject.Program).G_RemoveLogo(); instead of RemoveLogo?.Invoke(this, new EventArgs()); in Game1.cs because my breakpoints are not executed in G_RemoveLogo located in Program.cs when I use RemoveLogo?.Invoke(this, new EventArgs());.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 36,436 Reputation points Microsoft External Staff

2021-12-10T02:40:06.66+00:00

I'm not clear about the Game1.cs, it seams like an another issue. Anyway, you could try to find the MyViewController and call G_RemoveLogo .

UIWindow window = UIApplication.SharedApplication.KeyWindow; MyViewController vc = (MyViewController)window.RootViewController; vc.G_RemoveLogo();

In addition , I have chenaged the private void G_RemoveLogo(object sender, System.EventArgs e) method to public void G_RemoveLogo();

Using MeaasgeCenter is an easy way, you could call the method whenever the message is received.
Kim Strasser 1,321 Reputation points

2021-12-10T09:39:46.733+00:00

I get an exception if I use this code in Game1.cs:

System.InvalidCastException has been thrown
Specified cast is not valid.

Game1.cs(located in SharedCode project):

using MyProject; UIWindow window = UIApplication.SharedApplication.KeyWindow; MyViewController vc = (MyViewController)window.RootViewController; vc.G_RemoveLogo();

MyViewController.cs(located in MyProject project)

public void G_RemoveLogo() { //remove image var LogoView = View.ViewWithTag(1234); if (null != LogoView) LogoView.RemoveFromSuperview(); }
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 36,436 Reputation points Microsoft External Staff

2021-12-14T03:20:05.903+00:00

This error message may mean that (MyViewController)window.RootViewController can't convert RootViewController to MyViewController this type . I'm not sure if you have changed the RootViewController .
In Program class(use MyViewController) , the RootViewController is

MainViewController = new MyViewController(); Window.RootViewController = MainViewController;

You could try to use MeaasgeCenter. When you want to call the method , send the message in Game1.cs.

MessagingCenter.Send<Game1>(this, "Hi");

You could Subscribe the mesage in ViewDidLoad() of MyViewController and call the method whenever the message is received

public override void ViewDidLoad() { View = new UIView(); base.ViewDidLoad(); MessagingCenter.Subscribe<Game1>(this, "Hi", (sender) => { G_RemoveLogo(); }); }
Kim Strasser 1,321 Reputation points

2021-12-14T23:15:25.12+00:00

I use this code in Program class and I get the error message in Game1 when I want to remove the image:

private MyViewController MainViewController; public override void FinishedLaunching(UIApplication app) { var Window = new UIWindow(UIScreen.MainScreen.Bounds); MainViewController = new MyViewController(); Window.RootViewController = MainViewController; Window.MakeKeyAndVisible(); }

But it works with MessagingCenter. The image gets removed if I use MessagingCenter in Game1.

Answer 2

I get an error message if I add the line LoadApplication(new App()); to my Program.cs.
In addition and I get the following exception if I don't use "var" before Window:

Foundation.ModelNotImplementedException
Exception of type 'Foundation.ModelNotImplementedException' was thrown.

But if I use "var" before Window then it seems to work. I get no error messages with this code:

        private UIViewController MainViewController;

        public override void FinishedLaunching(UIApplication app)
        {
            global::Xamarin.Forms.Forms.Init();
            var Window = new UIWindow(UIScreen.MainScreen.Bounds);
            MainViewController = new UIViewController();
            Window.RootViewController = MainViewController;
            Window.MakeKeyAndVisible();
            MainViewController.View.BackgroundColor = UIColor.White;
            LogoImage = new UIImageView(UIImage.FromBundle("Image"));// load the Assets.xcassets image
            LogoImage.ContentMode = UIViewContentMode.ScaleAspectFill;
            LogoImage.Tag = 1234;
            LogoImage.Frame = MainViewController.View.Frame;
            MainViewController.View.AddSubview(LogoImage);
            MainViewController.View.BringSubviewToFront(LogoImage);

            RunGame();
        }

        private void G_RemoveLogo(object sender, System.EventArgs e)
        {
            //remove the image
            var LogoView = MainViewController.View.ViewWithTag(1234);
            if (null != LogoView)
                LogoView.RemoveFromSuperview();
        }

        internal static void RunGame()
        {
            int w1 = (int)(UIScreen.MainScreen.Bounds.Size.Width * UIScreen.MainScreen.Scale);
            int h1 = (int)(UIScreen.MainScreen.Bounds.Size.Height * UIScreen.MainScreen.Scale);
            game = new Game1(w1, h1);
            game.Run();
        }

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 36,436 Reputation points Microsoft External Staff

2021-12-08T02:30:29.753+00:00

Sorry, I didn't provid the whole class code before, the FinishedLaunching was in Appdelegate.cs, I will edit the answer.

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How can I display an image on the entire device screen with UIImageView on iPhone/iPad?

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