[NativeAOT] Use XAJavaInterop1 codegen target and unify GC bridge

Documentation/docs-mobile/TOC.yml

@@ -308,6 +308,8 @@
         href: messages/xa4237.md
       - name: XA4239
         href: messages/xa4239.md
+      - name: XA4240
+        href: messages/xa4240.md
       - name: XA4241
         href: messages/xa4241.md
       - name: XA4242

Documentation/docs-mobile/messages/index.md

@@ -211,6 +211,7 @@ Either change the value in the AndroidManifest.xml to match the $(SupportedOSPla
 + [XA4236](xa4236.md): Cannot download Maven artifact '{group}:{artifact}'. - {jar}: {exception} - {aar}: {exception}
 + [XA4237](xa4237.md): Cannot download POM file for Maven artifact '{artifact}'. - Failed to resolve POM for Maven artifact '{dependency}' from '{url}'. - {exception}
 + [XA4239](xa4239.md): Unknown Maven repository: '{repository}'.
++ [XA4240](xa4240.md): The Java callable wrapper code generation target '{0}' is no longer supported. The '_AndroidJcwCodegenTarget' property only supports 'XAJavaInterop1'; 'XamarinAndroid' and 'JavaInterop1' are not supported.
 + [XA4241](xa4241.md): Java dependency '{artifact}' is not satisfied.
 + [XA4242](xa4242.md): Java dependency '{artifact}' is not satisfied. Microsoft maintains the NuGet package '{nugetId}' that could fulfill this dependency.
 + [XA4243](xa4243.md): Attribute '{name}' is required when using '{name}' for '{element}' item '{itemspec}'.

Documentation/docs-mobile/messages/xa4240.md

@@ -0,0 +1,34 @@
+---
+title: .NET for Android error XA4240
+description: XA4240 error code
+ms.date: 08/24/2026
+f1_keywords:
+  - "XA4240"
+---
+
+# .NET for Android error XA4240
+
+## Example messages
+
+```
+error XA4240: The Java callable wrapper code generation target 'XamarinAndroid' is no longer supported. The '_AndroidJcwCodegenTarget' property only supports 'XAJavaInterop1'; 'XamarinAndroid' and 'JavaInterop1' are not supported.
+error XA4240: The Java callable wrapper code generation target 'JavaInterop1' is no longer supported. The '_AndroidJcwCodegenTarget' property only supports 'XAJavaInterop1'; 'XamarinAndroid' and 'JavaInterop1' are not supported.
+```
+
+## Issue
+
+The project sets the internal `_AndroidJcwCodegenTarget` MSBuild property to
+`XamarinAndroid` or `JavaInterop1`. These Java callable wrapper code generation
+targets are no longer supported for any .NET for Android runtime.
+
+## Solution
+
+Remove any `_AndroidJcwCodegenTarget` assignment that uses `XamarinAndroid` or
+`JavaInterop1`, for example:
+
+```xml
+<_AndroidJcwCodegenTarget>JavaInterop1</_AndroidJcwCodegenTarget>
+```
+
+The property defaults to `XAJavaInterop1`. If a build customization must set
+it explicitly, update the value to `XAJavaInterop1`.

src/Mono.Android/Android.Runtime/AndroidRuntimeInternal.cs

@@ -1,13 +1,17 @@
 #if INSIDE_MONO_ANDROID_RUNTIME
 using System;
 using System.Reflection;
+using System.Threading;
 using Microsoft.Android.Runtime;
 
 namespace Android.Runtime
 {
 	public static class AndroidRuntimeInternal
 	{
 		internal static readonly Action<Exception> mono_unhandled_exception;
+		static int bridgeProcessingGeneration;
+
+		internal static int BridgeProcessingGeneration => Volatile.Read (ref bridgeProcessingGeneration);
 
 #pragma warning disable CS0649 // Field is never assigned to.  This field is assigned from monodroid-glue.cc.
 		internal static volatile bool BridgeProcessing; // = false
@@ -40,6 +44,11 @@ static void MonoUnhandledException (Exception ex)
 			RuntimeNativeMethods.monodroid_debugger_unhandled_exception (ex);
 		}
 
+		internal static void NotifyBridgeProcessingFinished ()
+		{
+			Interlocked.Increment (ref bridgeProcessingGeneration);
+		}
+
 		public static void WaitForBridgeProcessing ()
 		{
 			Java.Interop.JniEnvironment.Runtime.ValueManager.WaitForGCBridgeProcessing ();

src/Mono.Android/Android.Runtime/JNIEnv.cs

@@ -120,6 +120,11 @@ public static void WaitForBridgeProcessing ()
 			JniEnvironment.Runtime.ValueManager.WaitForGCBridgeProcessing ();
 		}
 
+		/// <summary>
+		/// Gets the number of completed CoreCLR or NativeAOT GC bridge processing cycles.
+		/// </summary>
+		public static int BridgeProcessingGeneration => AndroidRuntimeInternal.BridgeProcessingGeneration;
+
 		public static IntPtr AllocObject (string jniClassName)
 		{
 			IntPtr jniClass = JNIEnv.FindClass (jniClassName);

src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalRegisteredPeers.cs

@@ -433,6 +433,8 @@ static unsafe void BridgeProcessingFinished (MarkCrossReferencesArgs* mcr)
 #pragma warning disable CA1416
 		JavaMarshal.FinishCrossReferenceProcessing (mcr, handlesToFree);
 #pragma warning restore CA1416
+
+		AndroidRuntimeInternal.NotifyBridgeProcessingFinished ();
 	}
 
 	static unsafe ReadOnlySpan<GCHandle> ProcessCollectedContexts (MarkCrossReferencesArgs* mcr)

src/Mono.Android/PublicAPI/API-35/PublicAPI.Unshipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
+static Android.Runtime.JNIEnv.BridgeProcessingGeneration.get -> int
 REMOVED Xamarin.Android.Net.AndroidClientHandler
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AndroidClientHandler() -> void
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AssertSelf() -> void

src/Mono.Android/PublicAPI/API-36.1/PublicAPI.Unshipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
+static Android.Runtime.JNIEnv.BridgeProcessingGeneration.get -> int
 REMOVED Xamarin.Android.Net.AndroidClientHandler
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AndroidClientHandler() -> void
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AssertSelf() -> void

src/Mono.Android/PublicAPI/API-36/PublicAPI.Unshipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
+static Android.Runtime.JNIEnv.BridgeProcessingGeneration.get -> int
 REMOVED Xamarin.Android.Net.AndroidClientHandler
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AndroidClientHandler() -> void
 REMOVED Xamarin.Android.Net.AndroidClientHandler.AssertSelf() -> void

src/Mono.Android/PublicAPI/API-37.1/PublicAPI.Unshipped.txt

@@ -1,3 +1,4 @@
 #nullable enable
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.get -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.set -> void
+static Android.Runtime.JNIEnv.BridgeProcessingGeneration.get -> int

src/Mono.Android/PublicAPI/API-37/PublicAPI.Unshipped.txt

@@ -4349,6 +4349,7 @@ static Android.Ranging.Wifi.PD.WifiPdRangingCapabilities.Creator.get -> Android.
 static Android.Ranging.Wifi.PD.WifiPdRangingParams.Creator.get -> Android.OS.IParcelableCreator!
 static Android.Ranging.Wifi.Rtt.RttStationRangingParams.Creator.get -> Android.OS.IParcelableCreator!
 static Android.Ranging.Wifi.Rtt.WifiRttSpecificData.Creator.get -> Android.OS.IParcelableCreator!
+static Android.Runtime.JNIEnv.BridgeProcessingGeneration.get -> int
 static Android.Runtime.JNIEnv.GetClassNameFromInstance(nint jobject) -> string?
 static Android.Security.NetworkSecurityPolicy.Instance.get -> Android.Security.NetworkSecurityPolicy!
 static Android.Service.Chooser.ChooserSessionToken.Creator.get -> Android.OS.IParcelableCreator!

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

@@ -43,7 +43,7 @@
     <!-- jar2xml is not supported -->
     <AndroidClassParser>class-parse</AndroidClassParser>
     <AndroidCodegenTarget Condition=" '$(AndroidCodegenTarget)' == '' ">XAJavaInterop1</AndroidCodegenTarget>
-    <_AndroidJcwCodegenTarget Condition=" '$(_AndroidJcwCodegenTarget)' == '' and '$(_AndroidRuntime)' != 'NativeAOT' ">XAJavaInterop1</_AndroidJcwCodegenTarget>
+    <_AndroidJcwCodegenTarget Condition=" '$(_AndroidJcwCodegenTarget)' == '' ">XAJavaInterop1</_AndroidJcwCodegenTarget>
     <AndroidTypeMapImplementation Condition=" '$(AndroidTypeMapImplementation)' == '' and '$(PublishAot)' == 'true' ">trimmable</AndroidTypeMapImplementation>
     <AndroidBoundInterfacesContainStaticAndDefaultInterfaceMethods Condition=" '$(AndroidBoundInterfacesContainStaticAndDefaultInterfaceMethods)' == '' ">true</AndroidBoundInterfacesContainStaticAndDefaultInterfaceMethods>
     <AndroidBoundInterfacesContainTypes Condition=" '$(AndroidBoundInterfacesContainTypes)' == '' ">true</AndroidBoundInterfacesContainTypes>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets

@@ -16,7 +16,6 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
   <PropertyGroup>
     <_AndroidRuntimePackRuntime>NativeAOT</_AndroidRuntimePackRuntime>
     <_AndroidUseWorkloadNativeLinker Condition=" '$(_AndroidUseWorkloadNativeLinker)' == '' ">true</_AndroidUseWorkloadNativeLinker>
-    <_AndroidJcwCodegenTarget Condition=" '$(_AndroidJcwCodegenTarget)' == '' ">JavaInterop1</_AndroidJcwCodegenTarget>
     <AndroidTypeMapImplementation Condition=" '$(AndroidTypeMapImplementation)' == '' ">trimmable</AndroidTypeMapImplementation>
     <!-- .NET SDK gives: error NETSDK1191: A runtime identifier for the property 'PublishAot' couldn't be inferred. Specify a rid explicitly. -->
     <AllowPublishAotWithoutRuntimeIdentifier Condition=" '$(AllowPublishAotWithoutRuntimeIdentifier)' == '' ">true</AllowPublishAotWithoutRuntimeIdentifier>

src/Xamarin.Android.Build.Tasks/Properties/Resources.resx

@@ -1058,6 +1058,11 @@ To use a custom JDK path for a command line build, set the 'JavaSdkDirectory' MS
     <value>Unknown Maven repository: '{0}'.</value>
     <comment>The following are literal names and should not be translated: Maven
 {0} - User supplied Maven repository type</comment>
+  </data>
+  <data name="XA4240" xml:space="preserve">
+    <value>The Java callable wrapper code generation target '{0}' is no longer supported. The '_AndroidJcwCodegenTarget' property only supports 'XAJavaInterop1'; 'XamarinAndroid' and 'JavaInterop1' are not supported.</value>
+    <comment>The following are literal names and should not be translated: _AndroidJcwCodegenTarget, XAJavaInterop1, XamarinAndroid, JavaInterop1
+{0} - The name of the current Java callable wrapper code generation target</comment>
   </data>
   <data name="XA1038" xml:space="preserve">
     <value>The '{0}' MSBuild property has an invalid value of '{1}'. A valid value is one of: {2}.</value>

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/InvalidConfigTests.cs

@@ -45,5 +45,27 @@ public void XA0119AAB ()
 			}
 		}
 
+		[Test]
+		public void UnsupportedJcwCodegenTargetIsRejected (
+			[Values ("XamarinAndroid", "JavaInterop1")] string codegenTarget,
+			[Values (AndroidRuntime.MonoVM, AndroidRuntime.CoreCLR, AndroidRuntime.NativeAOT)] AndroidRuntime runtime)
+		{
+			var project = new XamarinAndroidApplicationProject {
+				IsRelease = runtime == AndroidRuntime.NativeAOT,
+			};
+			if (runtime == AndroidRuntime.MonoVM) {
+				project.SetProperty ("_DisableCheckForUnsupportedMonoMobileRuntime", "true");
+			}
+			project.SetRuntime (runtime);
+			project.SetProperty ("_AndroidJcwCodegenTarget", codegenTarget);
+			using (var builder = CreateApkBuilder ()) {
+				builder.Target = "_CheckForInvalidConfigurationAndPlatform";
+				builder.ThrowOnBuildFailure = false;
+				Assert.IsFalse (builder.Build (project), "Build should have failed.");
+				StringAssertEx.Contains ("error XA4240:", builder.LastBuildOutput, "Build should fail with XA4240.");
+				StringAssertEx.Contains (codegenTarget, builder.LastBuildOutput, "Error should identify the unsupported code generation target.");
+			}
+		}
+
 	}
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.NativeAOT.apkdesc

@@ -5,10 +5,10 @@
       "Size": 3124
     },
     "classes.dex": {
-      "Size": 22804
+      "Size": 404664
     },
     "lib/arm64-v8a/libUnnamedProject.so": {
-      "Size": 5747648
+      "Size": 5731688
     },
     "res/drawable-hdpi-v4/icon.png": {
       "Size": 2178
@@ -35,5 +35,5 @@
       "Size": 1904
     }
   },
-  "PackageSize": 2401051
+  "PackageSize": 2474779
 }

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -3042,6 +3042,14 @@ because xbuild doesn't support framework reference assemblies.
 
 <Import Project="$(MSBuildThisFileDirectory)Xamarin.Installer.Common.targets"
         Condition=" '$(DesignTimeBuild)' != 'true' "/>
+  <Target Name="_ValidateAndroidJcwCodegenTarget"
+      BeforeTargets="_CheckForInvalidConfigurationAndPlatform">
+    <AndroidError Code="XA4240"
+        ResourceName="XA4240"
+        FormatArguments="$(_AndroidJcwCodegenTarget)"
+        Condition=" '$(_AndroidJcwCodegenTarget)' == 'XamarinAndroid' or '$(_AndroidJcwCodegenTarget)' == 'JavaInterop1' " />
+  </Target>
+
   <Target Name="_ValidateAndroidTypeMapImplementation"
       BeforeTargets="_CheckForInvalidConfigurationAndPlatform">
     <Error Condition=" '$(AndroidTypeMapImplementation)' != '' and '$(AndroidTypeMapImplementation)' != 'llvm-ir' and '$(AndroidTypeMapImplementation)' != 'trimmable' "