[Android] OnIdiom throws NotImplementedException

[fagertjan]

Description

Our customer reports crashes in our maui app. In appcenter we find this crash multiple times. It happens on their Galaxy XCover 5 with Android 14. We had this issue in maui 9.0.21 but have it also in 9.0.70. I cannot reproduce it myself.

We use the OnIdiom in a getter like this:

public static class AppConstants
{
    public static double TaskListItemHeight => new OnIdiom<double>()
    {
        Phone = 140,
        Tablet = 160,
        Desktop = 160
    };
}

And then use that getter in code like this:
var xyz = AppConstants.TaskListItemHeight;

The exception with relevant stack trace is:
System.NotImplementedException: Do not know how to dispose: Invalid.

Java.Interop.JniObjectReference.Dispose(JniObjectReference& )
Java.Interop.JniRuntime.JniValueManager.DisposePeer(JniObjectReference , IJavaPeerable )
Java.Interop.JniRuntime.JniValueManager.DisposePeer(IJavaPeerable )
Java.Lang.Object.Dispose()
Microsoft.Maui.Devices.DeviceInfoImplementation.get_Idiom()
Microsoft.Maui.Devices.DeviceInfo.get_Idiom()
Microsoft.Maui.Controls.OnIdiom`1[[System.Double, System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].op_Implicit(OnIdiom`1 onIdiom)
AppConstants.get_TaskListItemHeight()
...

Steps to Reproduce

No response

Link to public reproduction project repository

No response

Version with bug

9.0.70 SR7

Is this a regression from previous behavior?

Yes, this used to work in Xamarin.Forms

Last version that worked well

No response

Affected platforms

Android

Affected platform versions

14

Did you find any workaround?

No response

Relevant log output

[jfversluis]

Without any repro or (more) relevant code it will be pretty much impossible to say anything useful about this I'm afraid.

[fagertjan]

I tried to make a repro. I don't get the same crash as listed in appcenter that our customer is experiencing, but I do get a crash.

The crash happens when multiple threads are accessing the OnIdiom simultaneously. The try/catch around the offending code is not working. The catch is not being called. The app closes instead with in the console of rider the message: "JNI DETECTED ERROR IN APPLICATION: JNI ERROR (app bug): jobject is an invalid global reference: 0x65da".

TestOnIdiom.zip

[PureWeen]

@jonathanpeppers this look familiar ?

[jonathanpeppers]

The crash happens when multiple threads are accessing the OnIdiom simultaneously.

Should MAUI even support this? Is the answer "don't do that"?

There are two using statements in the method, that could be removed to help:

maui/src/Essentials/src/DeviceInfo/DeviceInfo.android.cs

Lines 37 to 82 in 3d584fa

	public DeviceIdiom Idiom
	{
	get
	{
	var currentIdiom = DeviceIdiom.Unknown;
	// first try UIModeManager
	using var uiModeManager = UiModeManager.FromContext(Application.Context);
	try
	{
	var uiMode = uiModeManager?.CurrentModeType ?? UiMode.TypeUndefined;
	currentIdiom = DetectIdiom(uiMode);
	}
	catch (Exception ex)
	{
	System.Diagnostics.Debug.WriteLine($"Unable to detect using UiModeManager: {ex.Message}");
	}
	// then try Configuration
	if (currentIdiom == DeviceIdiom.Unknown)
	{
	var configuration = Application.Context.Resources?.Configuration;
	if (configuration != null)
	{
	var minWidth = configuration.SmallestScreenWidthDp;
	var isWide = minWidth >= tabletCrossover;
	currentIdiom = isWide ? DeviceIdiom.Tablet : DeviceIdiom.Phone;
	}
	else
	{
	// start clutching at straws
	using var metrics = Application.Context.Resources?.DisplayMetrics;
	if (metrics != null)
	{
	var minSize = Math.Min(metrics.WidthPixels, metrics.HeightPixels);
	var isWide = minSize * metrics.Density >= tabletCrossover;
	currentIdiom = isWide ? DeviceIdiom.Tablet : DeviceIdiom.Phone;
	}
	}
	}
	// hope we got it somewhere
	return currentIdiom;
	}
	}

1. Either of these are in the middle of being disposed: uiModeManager, metrics
2. Another thread calls OnIdiom, and the code calls into Android/Java
3. Java returns the same instance of one of the objects
4. Java.Interop locates the previous C# object and uses it
5. The same C# object is double-disposed

Removing the using could be a good first step, but I don't know if you would just encounter a different problem.