Xamarin iOS - development app is deployed on IPhone, but I cannot start it

Ganesh Gebhard 366

I have an app in Xamarin that I want to test on a physical IPhone (normally I test it on Android). I'm connected to a Mac, the development certificate is working and everything is deployed to the point that the app is actually installed on the IPhone itself. The issue however is that when I press the icon to start the app, it tries to start it and then is closes right after that (like it crashes or something).

I'm using Visual Studio for Windows, and it is stated that: "XAML Hot Reload encountered a problem and failed to start. Verify the Mono Interpreter for is enabled in the project settings, clean and rebuild the solution.". Mono Interpreter is enabled, I cleaned the solution and rebuild it multiple times. There are no errors given.

The app that is installed now shows the Xamarin icon and Xamarin splash screen (so not the custom one I designed). I don't mind that, but I'm not sure if that has something to do with this.

Does someone know what is wrong here and how to fix it?

Visual Studio for Windows version 17.4.1 iOS version 15.5

Note: this issue is only with the development and deployment directly from Visual Studio from Windows. When the app is distributed to the users (in App Center) the app works as it should.

Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-01-18T06:16:54.97+00:00

Can you run the app on the simulator? Are there any errors/warnings when you debug the project on simulator? Does your App need some permissions? You said "The issue however is that when I press the icon to start the app", the app won't run automatically and you need to click the icon to run it, right? What's your Xcode version on Mac?

For the XAML Hot Reload error, you can try to set iOS Linker settings to Don't Link and Enable the Mono interpreter， refer to the Troubleshooting.
Ganesh Gebhard 366 Reputation points

2023-01-18T13:34:19.81+00:00

Yes, I can run it in the simulator. No errors and no warnings.

No, I know that the app won't run automatically and that is fine. When I press the icon to start the app, it shows the splash screen for a short moment and then it closes the entire app (like it crashes). No errors are given there.

XCode version on the Mac is 12.4.

The iOS Linker is set to Don't Link and the Mono Interpreter is enabled.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-01-19T02:56:37.37+00:00

You cannot have iOS version 15.5 SDK in Xcode 12.4. You can download Xcode 14.1 from the downloads page in the Apple Developer Portal, then try to deploy the app again.
Ganesh Gebhard 366 Reputation points

2023-01-19T14:01:43.04+00:00

I am able to deploy the app in my iPhone from Windows without being connected to a Mac (ever since a VS update some time ago). How is this Xcode update on the Mac help me being able to opened the deployed app?
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-01-20T01:53:25.2566667+00:00

If you deploy the app from Windows (and connect your device with your Windows machine), it means that you are using Xamarin Hot Restart , it's not related to Xcode. You said you connected to a Mac in the question, it means that you are using Pair to Mac for Xamarin.iOS development and connect the device to your Mac. It will access to Apple's build tools on your Mac. And you cannot have iOS version 15.5 SDK in Xcode 12.4, so it's recommended that you update Xcode.
You can determine which method you are using, and check if you still cannot run the app when you change the deploying way.
Ganesh Gebhard 366 Reputation points

2023-01-20T02:30:19.9833333+00:00

Okay I see that I explained in not properly, my apologies.

I'm using Visual Studio for Windows and my iPhone is connected to my Windows system. If I want to use an emulator, I need to connect to a Mac. With my physical iPhone however, I don't need this connection anymore. So yes, I am using Xamarin Hot Restart.

The issue remains the same: the app is deployed on my iPhone, but when I tap on the icon it opens on the splash screen for a couple of seconds and then it closes (like it crashes).

Looking at the link you send me, I think the issue is related to the Storyboard that is loaded at runtime. So the question now is: how do I prevent this? I know I can user the preprocessor HOTRESTART in C#, but the Storyboard is not called in C#, only in the Info.plist. How can I use the preprocessor HOTRESTART to prevent Storyboard from loading at runtime?
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-01-25T03:08:15.1533333+00:00

You said you can run the app in the simulator and there are no errors and warnings. It might be caused by the Storyboard file with Hot Restart. I agree with you, you can try to connect your device to your Mac and select the Remote Device (your iPhone) in the drop-down menu, then deploy the app on your device by Pairing to Mac.
In this way, you can determine whether it is related to the limitation of Hot Restart or not.

I know I can user the preprocessor HOTRESTART in C#, but the Storyboard is not called in C#, only in the Info.plist. How can I use the preprocessor HOTRESTART to prevent Storyboard from loading at runtime?

I saw you create a new thread for this question, let's focus on that one.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-01-26T08:12:47.36+00:00

Do you use development certificate and provisioning profiles when you deploy the app on your device? If you use distribution profile, it cannot start.
And can you test on another physical device?
Would you mind sharing the detailed crash log with me ? (Go to Tools > iOS> Device Log and{user}/AppData/Local/Xamarin/logs)
Ganesh Gebhard 366 Reputation points

2023-02-04T01:13:06.0733333+00:00

I checked the things you asked: the certificate is a Development profile, no other device works and there is no crash log.
Wenyan Zhang (Shanghai Wicresoft Co,.Ltd.) 25,996 Reputation points Microsoft Vendor

2023-02-06T02:42:56.7+00:00

Since I still cannot reproduce the issue and there is no log to investigate further, it's recommended that you open a support ticket for this. Please contact our paid phone support at MS Support. You will get 1:1 support on that.