.NET 10 MAUI Android emulator shows blank screen on login page after working yesterday

Hi @guo tuo , thank you for confirming that restoring the [Application] attribute in MainApplication.cs resolved the issue.

To provide some additional context on the solution, missing attributes may not necessarily result in an obvious build error or exception, so they can cause hard-to-trace issues and easily be overlooked during troubleshooting. Thus, checking for them could be a useful troubleshooting step.

As you found in this case, the missing attribute in Platforms/Android/MainApplication.cs was the cause. The [Application] attribute is important because it tells Android to use MainApplication when the app starts. Without it, the normal .NET MAUI initialization through MainApplication may not take place.

using Android.App;
using Android.Runtime;
namespace YourApp;

[Application]
public class MainApplication : MauiApplication
{
    public MainApplication(IntPtr handle, JniHandleOwnership ownership)
        : base(handle, ownership)
    {
    }
    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
}

For similar project-specific issues, comparing the files under Platforms/Android with those from a newly created .NET MAUI project can also help identify accidental changes or omissions.

If you found my explanation was helpful or informative to the solution, I would greatly appreciate it if you could follow this guide so others with the same issue can benefit as well. Thank you. 

logcat --pid=<PID> instead to narrow down to your

Hi @guo tuo , and thank you for reaching out. 

I will need more information to troubleshoot this issue, as a blank white screen alone does not indicate what is failing. 

Here are some suggestions of what you can do now:  

• Check the login page and the flow leading to it – see if there's any code, components, APIs that are actually not supported on Android. 
• Run 'adb logcat'.  (Better yet, use adb logcat *:E instead to narrow down output to error logs, or adb logcat --pid=<PID> instead to narrow down to your own app's logs.  You can get the running app's PID with adb shell pidof <package-name>.) 
• Test the app on a physical Android device – if it works normally there this should likely be an emulator-only issue. 

You can also provide the relevant login page code and any errors from adb logcat if you need help troubleshooting further. Please feel free to ask if you have any questions or need clarification on any of the steps above. 

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation. Thank you.