dotnet · simonrozsival · Sep 1, 2026 · Sep 1, 2026 · github-actions · Sep 1, 2026
@@ -120,7 +120,7 @@ static void WriteClassDeclaration (JavaPeerInfo type, TextWriter writer, string?
 		// implements clause — always includes IGCUserPeer, plus any implemented interfaces
 		writer.Write ("\timplements\n\t\tmono.android.IGCUserPeer");
 
-		foreach (var iface in type.ImplementedInterfaceJavaNames) {
+		foreach (var iface in type.JavaCallableWrapperInterfaceJavaNames ?? type.ImplementedInterfaceJavaNames) {
 			writer.Write ($",\n\t\t{JniSignatureHelper.JniNameToJavaName (iface)}");
 		}
 

@@ -58,11 +58,16 @@ public sealed record JavaPeerInfo
 	public string? BaseJavaName { get; init; }
 
 	/// <summary>
-	/// JNI names of Java interfaces this type implements, e.g., ["android/view/View$OnClickListener"].
-	/// Needed by JCW Java source generation ("implements" clause).
+	/// JNI names of direct Java interfaces this type implements, in managed metadata order.
 	/// </summary>
 	public IReadOnlyList<string> ImplementedInterfaceJavaNames { get; init; } = Array.Empty<string> ();
 
+	/// <summary>
+	/// Ordered JNI names to emit in the Java callable wrapper's implements clause.
+	/// Redundant parent interfaces and duplicate Java names are omitted.
+	/// </summary>
+	internal IReadOnlyList<string>? JavaCallableWrapperInterfaceJavaNames { get; init; }
+
 	/// <summary>
 	/// Java annotations forwarded from managed custom attributes decorated with
 	/// <c>Android.Runtime.AnnotationAttribute</c>.

@@ -26,6 +26,7 @@ enum HashedPackageNamingPolicy {
 
 	readonly record struct ResolvabilityResult (bool IsResolvable, string? UnresolvedTypeName, string? UnresolvedAssemblyName);
 	readonly record struct PublicConstructorInfo (ImmutableArray<TypeRefData> ParameterTypes, string JniParameterSignature);
+	readonly record struct ImplementedInterfaceInfo (TypeRefData Type, string JavaName);
 
 	readonly Dictionary<string, AssemblyIndex> assemblyCache = new (StringComparer.Ordinal);
 	readonly Dictionary<(string typeName, string assemblyName), ActivationCtorInfo> activationCtorCache = new ();
@@ -366,7 +367,7 @@ void ScanAssembly (AssemblyIndex index, Dictionary<(string ManagedName, string A
 			var baseJavaName = ResolveBaseJavaName (typeDef, index, results);
 
 			// Resolve implemented Java interface names
-			var implementedInterfaces = ResolveImplementedInterfaceJavaNames (typeDef, index);
+			var (implementedInterfaces, javaCallableWrapperInterfaces) = ResolveImplementedInterfaceJavaNames (typeDef, index);
 
 			// Collect marshal methods (including constructors).
 			// Override and interface detection is only for user ACW class types:
@@ -403,6 +404,7 @@ void ScanAssembly (AssemblyIndex index, Dictionary<(string ManagedName, string A
 				IsFrameworkAssembly = frameworkAssemblyNames.Contains (index.AssemblyName),
 				BaseJavaName = baseJavaName,
 				ImplementedInterfaceJavaNames = implementedInterfaces,
+				JavaCallableWrapperInterfaceJavaNames = javaCallableWrapperInterfaces,
 				Annotations = annotationParser.Parse (typeDef.GetCustomAttributes (), index),
 				IsInterface = isInterface,
 				IsAbstract = isAbstract,
@@ -1668,26 +1670,86 @@ static string GetJavaAccess (MethodAttributes access)
 		return null;
 	}
 
-	List<string> ResolveImplementedInterfaceJavaNames (TypeDefinition typeDef, AssemblyIndex index)
+	(List<string> ImplementedInterfaces, List<string> JavaCallableWrapperInterfaces) ResolveImplementedInterfaceJavaNames (
+		TypeDefinition typeDef,
+		AssemblyIndex index)
 	{
-		var result = new List<string> ();
-		var interfaceImpls = typeDef.GetInterfaceImplementations ();
-
-		foreach (var implHandle in interfaceImpls) {
+		var interfaces = new List<ImplementedInterfaceInfo> ();
+		var implementedInterfaces = new List<string> ();
+		foreach (var implHandle in typeDef.GetInterfaceImplementations ()) {
 			var impl = index.Reader.GetInterfaceImplementation (implHandle);
-			var ifaceJniName = ResolveInterfaceJniName (impl.Interface, index);
-			if (ifaceJniName is not null) {
-				result.Add (ifaceJniName);
+			var resolved = ResolveEntityHandle (impl.Interface, index);
+			if (resolved is null) {
+				continue;
+			}
+
+			var javaName = ResolveRegisterJniName (resolved.ManagedTypeName, resolved.AssemblyName);
+			if (javaName is not null) {
+				interfaces.Add (new ImplementedInterfaceInfo (resolved, javaName));
+				implementedInterfaces.Add (javaName);
 			}
 		}
 
-		return result;
+		var javaCallableWrapperInterfaces = new List<string> ();
+		var addedJavaNames = new HashSet<string> (StringComparer.Ordinal);
+		var assignabilityVisited = new HashSet<(string ManagedTypeName, string AssemblyName)> ();
+		foreach (var iface in interfaces) {
+			var isRedundant = false;
+			foreach (var other in interfaces) {
+				if (IsSameTypeDefinition (iface.Type, other.Type)) {
+					continue;
+				}
+
+				assignabilityVisited.Clear ();
+				if (IsInterfaceAssignableFrom (iface.Type, other.Type, assignabilityVisited)) {
+					isRedundant = true;
+					break;
+				}
+			}
+
+			if (isRedundant) {
+				continue;
+			}
+
+			if (addedJavaNames.Add (iface.JavaName)) {
+				javaCallableWrapperInterfaces.Add (iface.JavaName);
+			}
+		}
+
+		return (implementedInterfaces, javaCallableWrapperInterfaces);
+	}
+
+	bool IsInterfaceAssignableFrom (
+		TypeRefData target,
+		TypeRefData candidate,
+		HashSet<(string ManagedTypeName, string AssemblyName)> visited)
+	{
+		if (IsSameTypeDefinition (target, candidate)) {
+			return true;
+		}
+
+		var candidateKey = (candidate.ManagedTypeName, candidate.AssemblyName);
+		if (!visited.Add (candidateKey) ||
+		    !TryResolveType (candidate.ManagedTypeName, candidate.AssemblyName, out var candidateHandle, out var candidateIndex)) {
+			return false;
+		}
+
+		var candidateDefinition = candidateIndex.Reader.GetTypeDefinition (candidateHandle);
+		foreach (var implHandle in candidateDefinition.GetInterfaceImplementations ()) {
+			var impl = candidateIndex.Reader.GetInterfaceImplementation (implHandle);
+			var parent = ResolveEntityHandle (impl.Interface, candidateIndex);
+			if (parent is not null && IsInterfaceAssignableFrom (target, parent, visited)) {
+				return true;
+			}
+		}
+
+		return false;
 	}
 
-	string? ResolveInterfaceJniName (EntityHandle interfaceHandle, AssemblyIndex index)
+	static bool IsSameTypeDefinition (TypeRefData left, TypeRefData right)
 	{
-		var resolved = ResolveEntityHandle (interfaceHandle, index);
-		return resolved is not null ? ResolveRegisterJniName (resolved.ManagedTypeName, resolved.AssemblyName) : null;
+		return string.Equals (left.ManagedTypeName, right.ManagedTypeName, StringComparison.Ordinal) &&
+			string.Equals (left.AssemblyName, right.AssemblyName, StringComparison.Ordinal);
 	}
 
 	bool TryGetMethodRegisterInfo (MethodDefinition methodDef, AssemblyIndex index, out RegisterInfo? registerInfo, out ExportInfo? exportInfo)

@@ -103,7 +103,7 @@ internal bool ValidateJavaNames (IReadOnlyList<JavaPeerInfo> peers, string? appl
 			if (peer.BaseJavaName is not null) {
 				ReportInvalidJniSourceType (peer.BaseJavaName);
 			}
-			foreach (var interfaceName in peer.ImplementedInterfaceJavaNames) {
+			foreach (var interfaceName in peer.JavaCallableWrapperInterfaceJavaNames ?? peer.ImplementedInterfaceJavaNames) {
 				ReportInvalidJniSourceType (interfaceName);
 			}
 			foreach (var constructor in peer.JavaConstructors) {

@@ -131,6 +131,23 @@ public void Generate_ClickableView_UsesDotsForNestedInterfaceName ()
 			Assert.DoesNotContain ("View$OnClickListener", java);
 		}
 
+		[Fact]
+		public void Generate_RedundantInterfaceView_OmitsParentsAndDuplicateJavaNames ()
+		{
+			var java = GenerateFixture ("my/app/RedundantInterfaceView");
+
+			AssertContainsLine (
+				"""
+					implements
+						mono.android.IGCUserPeer,
+						android.view.View.INamedClickListener,
+						android.view.View.OnLongClickListener
+				{
+				""",
+				java
+			);
+		}
+
 		[Fact]
 		public void Generate_DeclaredDollarKeyword_PreservesDollar ()
 		{

@@ -194,6 +194,23 @@ public void Scan_MultipleInterfaces_AllResolved ()
 		Assert.Empty (FindFixtureByJavaName ("my/app/MyHelper").ImplementedInterfaceJavaNames);
 	}
 
+	[Fact]
+	public void Scan_JavaCallableWrapperInterfaces_OmitsParentsAndDuplicateJavaNames ()
+	{
+		var peer = FindFixtureByJavaName ("my/app/RedundantInterfaceView");
+
+		Assert.Equal ([
+			"android/view/View$OnClickListener",
+			"android/view/View$INamedClickListener",
+			"android/view/View$INamedClickListener",
+			"android/view/View$OnLongClickListener",
+		], peer.ImplementedInterfaceJavaNames);
+		Assert.Equal ([
+			"android/view/View$INamedClickListener",
+			"android/view/View$OnLongClickListener",
+		], peer.JavaCallableWrapperInterfaceJavaNames);
+	}
+
 	[Theory]
 	[InlineData ("android/app/Activity", "android/app/Activity")]
 	[InlineData ("my/app/MainActivity", "my/app/MainActivity")]

@@ -187,6 +187,11 @@ public interface INamedClickListener : IOnClickListener
 		string? Label { get; }
 	}
 
+	[Register ("android/view/View$INamedClickListener")]
+	public interface INamedClickListenerAlias
+	{
+	}
+
 	[Register ("mono/android/view/View_IOnClickListenerImplementor")]
 	public class View_IOnClickListenerImplementor : Java.Lang.Object
 	{
@@ -793,6 +798,17 @@ public void OnClick (Android.Views.View v) { }
 		public string? Label => "test";
 	}
 
+	[Register ("my/app/RedundantInterfaceView")]
+	public class RedundantInterfaceView : Android.Views.View, Android.Views.IOnClickListener,
+		Android.Views.INamedClickListener, Android.Views.INamedClickListenerAlias, Android.Views.IOnLongClickListener
+	{
+		protected RedundantInterfaceView (IntPtr handle, JniHandleOwnership transfer) : base (handle, transfer) { }
+
+		public void OnClick (Android.Views.View v) { }
+		public string? Label => "test";
+		public bool OnLongClick (Android.Views.View v) => false;
+	}
+
 	// --- Override detection test types ---
 	// These types override registered base methods WITHOUT [Register] on the override,
 	// mimicking real user code where the attribute is only on the base class in Mono.Android.