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Xamarin Forms my app not working on Android 12

My application works for all versions of Android except 12, Xamarin Forms does not show me the problem but Play Console showed me, I don't know how to solve this problem
enter image description here
I hope to solve this problem

There could be many problems with the code, and that error is really ambiguous.
When working with Android you need to know that there are many versions, as you can see in the version history: https://en.wikipedia.org/wiki/Android_version_history
There are some functionalities, such as the NotificationCompat Builder that change between versions. You should review your code and see which methods might differ given the version.
You are probably going to need to make this comparison:
if (Build.VERSION.SdkInt < BuildVersionCodes.S)
At some point in your code and make two different versions of a functionality for it to work on multiple devices.
I recommend to test on different physical or emulated devices with versions at least from Android Oreo upwards to cover most phones currently in the market.
Best regards.

Xamarin PCL Android app suddenly crashes in release mode

My Xamarin (PCL) Android application suddenly randomly crashes when it released. It sometimes happens even when you are not currently using it and then message that app stopped working appears.
I wonder, is there any way to track whats going on, maybe there are some logs which I could have a look, or anything else to find out what the issue as I said it randomly happens and hard to find the problem.
Many thanks in advance.

A fast solution would be to plug your device and use the Android Device Monitor to see if it print out something on the device logs. A more reliable solution would be of course to integrate a crash reporter system like what the others have suggested or Crashlytics.

You might need to add a crash reporting tool like HockeyApp or VS App Center, or wire up your own global exception handler

Xamarin.Android Deployment Error using Android Virtual Device

I am trying to setup a development environment in Visual Studio Community for development with Xamarin.Forms. In order to make sure the Android Emulator was working, I followed the QuickStart Xamarin.Android tutorial found here.
When I Start Debugging with any number of Virtual Devices the output is always the same; the application does not show up, but the AVD successfully starts up and I can also successfully interact with OS; when trying the close the AVD (with the x icon on the top right) a pop-up dialog appears saying "There were Deployment Errors. Do you wish to continue? Yes\No". The frustrating part is that no matter my response there is absolutely no useful error informations, or warnings or messages for that matter. You may think this is a duplicate question but it is not. I have had problems with a similar problem in which the fix was to downgrade my Android SDK BuildTools to a version lower than 24.0. The was to circumvent an upstream bug that provided the error message: java.lang.UnsupportedClassVersionError blah blah blah. The problem here is I get NO error and my highest version Build Tools are version 23.0.3 which should be fine. Here is a pic on start-up:
AVD
Unfortunately as I am only a begginer user I am not permitted to post more links and images. Apologies for the images as links I am still only permitted to post images in this way.
Thank you for taking the time to help me out.

Hi anyone with a similar problem, this is what worked for me in this particular case. I started the AVD before starting Debugging, the application then showed up in the emulators device menu and everthing is working. I have been stuck with this problem for Five whole day trying dozens of things. Pheeeeuuuuuuw!

XNA 4.0 game doesn't do anything when ran on another PC

This issue is getting real tiresome and I've been spending atleast 2 days looking around for an answer. Basically, I want to publish a game, and I've hired a friend of mine to test it out before I officially release it. Whenever he runs it, reports as "nothing happends".
These conditions are met:
He has installed the .NET Framework 4.0 and the XNA Redistributable 4.0 (he most likely also has installed other .NET Frameworks and XNA Frameworks as well, because nothing worked).
The game is compiled onto a Release build.
GamerService referenced is removed.
A possible issue could be that he's using Win8, but as my searching experience goes, XNA DEVELOPMENT is only restricted on Windows 8, right?
So, what's going on? I'm clueless.. I even put a MessageBox.Show(); after the execution of my game in my Program.cs file via try/catch, and no results.
Are there any extreme conditions in my code that I need to meet?
Any site describing 100% of all requirements to run an XNA game and the most proper way to build it?
Any issues when using non-distributable "developer tools" in XNA coding? If so, what includes in these "developer tools", and what do I need to modify? (I noticed that on another thread).
An answer to this issue would more than make my day...
Ah, and also, I tried running it on a virtual machine ( Windows 7 ) but then it spat out a messagebox saying Index outside the bounds of the array on a perfectly valid code execution, and various other random errors such as missing files when they clearly are there.
Thank you greatly!

In summary I think your app wont run on Windows 8, let me explain:
Windows 8
A possible issue could be that he's using Win8, but as my searching experience goes, XNA DEVELOPMENT is only restricted on Windows 8, right?
Officially, desktop games using unmodified Microsoft XNA 4/is not supported on Windows 8 in any form:
Microsoft officials have said the XNA tools/runtime environment used primarily by game developers isn't supported on Windows 8. - Read more...
Redistributables
Any issues when using non-distributable "developer tools" in XNA coding?
That depends on whether they are required at runtime on the target machine. That might sound like an oxymoron but in Windows c/c++, I can have an app that depends on Microsoft DLLs but we are not allowed to deploy the DLLs, one must depend on it being present in the OS; service pack or some other form. Is there something you are missing?
Windows 7
Ah, and also, I tried running it on a virtual machine ( Windows 7 ) but then it spat out a messagebox saying Index outside the bounds of the array on a perfectly valid code execution
This is more interesting and I suspect is one of the more testable aspects of your application (also that it is not Windows 8). I suggest you setup a remote-debug session to your Win7 VM or if that is not possible, use Debug.WriteLine() or equivalent displaying critical state contents.

develop C#/.NET on Android devices

I want to run C# programs on my HTC Magic, I can find the mono app on the Android market but I have no clue on how to run C# using.
The code is just for fun, I don't want official support and such. After coding Visual Basic on windows mobile, I really want to code C# on Android, whether directly using some sort of editor if exists, or compiling it on a PC then installing it on Android.
If anyone knows a way to do such please let me know.
Thank you

There's the androidmono project, which I gather pretty much works but is in relatively early stages.
EDIT: More recently: Mono for Android

As I originally answered this over two years ago...
These days I would look at Mono for Android, developed by the Mono team.
It's a commercial product, but yes, you can then sell your app on the Android Marketplace (aka Google Play store).

Xamarin supports C# coding for both Android and iPhone, and is based on Mono. For more details, check out:
http://xamarin.com/

You may want to have a look at dot42 at https://www.dot42.com/ I've never tried it myself, tough looking at various articles, it seems that this may be a valid option.