[generator] fix generic parameter code generation for interface.

tools/generator/CollectionSymbol.cs

@@ -52,6 +52,10 @@ public string ElementType {
 			get { return null; }
 		}
 
+		public bool MayHaveManagedGenericArguments {
+			get { return true; }
+		}
+
 		public string GetObjectHandleProperty (string variable)
 		{
 			return $"((global::Java.Lang.Object) {variable}).Handle";

tools/generator/GenericSymbol.cs

@@ -91,7 +91,8 @@ public string FromNative (CodeGenerationOptions opt, string varname, bool owned)
 
 		public string GetGenericType (Dictionary<string, string> mappings)
 		{
-			return gen.FullName + (mappings == null ? tps : MapTypeParams (mappings));
+			var rgm = gen as IRequireGenericMarshal;
+			return gen.FullName + (rgm != null && !rgm.MayHaveManagedGenericArguments ? null : mappings == null ? tps : MapTypeParams (mappings));
 		}
 
 		public string ToNative (CodeGenerationOptions opt, string varname)

tools/generator/IRequireGenericMarshal.cs

@@ -5,6 +5,7 @@ namespace MonoDroid.Generation
 {
 	public interface IRequireGenericMarshal
 	{
+		bool MayHaveManagedGenericArguments { get; }
 		string GetGenericJavaObjectTypeOverride ();
 		string ToInteroperableJavaObject (string varname);
 	}

tools/generator/InterfaceGen.cs

@@ -24,9 +24,14 @@ public ManagedInterfaceGen (TypeDefinition t)
 				AddMethod (new ManagedMethod (this, m));
 			}
 		}
+
 		public override string ArgsType {
 			get { throw new NotImplementedException (); }
 		}
+
+		public override bool MayHaveManagedGenericArguments {
+			get { return !this.IsAcw; }
+		}
 	}
 #endif
 
@@ -109,6 +114,10 @@ public bool IsListener {
 			get { return Name.EndsWith ("Listener") && Properties.Count == 0 && Interfaces.Count == 0; }
 		}
 
+		public virtual bool MayHaveManagedGenericArguments {
+			get { return false; }
+		}
+
 		public override string NativeType {
 			get { return "IntPtr"; }
 		}

tools/generator/Tests/GenericArguments.cs

@@ -0,0 +1,20 @@
+using System;
+using NUnit.Framework;
+
+namespace generatortests
+{
+	[TestFixture]
+	public class GenericArguments : BaseGeneratorTest
+	{
+		[Test]
+		public void GeneratedOK ()
+		{
+			RunAllTargets (
+					outputRelativePath: "GenericArguments",
+					apiDescriptionFile: "expected/GenericArguments/GenericArguments.xml",
+					expectedRelativePath: "GenericArguments",
+					additionalSupportPaths: null);
+		}
+	}
+}
+

tools/generator/Tests/expected.ji/GenericArguments/Com.Google.Android.Exoplayer.Drm.FrameworkMediaDrm.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using Android.Runtime;
+using Java.Interop;
+
+namespace Com.Google.Android.Exoplayer.Drm {
+
+	// Metadata.xml XPath class reference: path="/api/package[@name='com.google.android.exoplayer.drm']/class[@name='FrameworkMediaDrm']"
+	[global::Android.Runtime.Register ("com/google/android/exoplayer/drm/FrameworkMediaDrm", DoNotGenerateAcw=true)]
+	public sealed partial class FrameworkMediaDrm : global::Java.Lang.Object, global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm {
+
+		internal            static  readonly    JniPeerMembers  _members    = new JniPeerMembers ("com/google/android/exoplayer/drm/FrameworkMediaDrm", typeof (FrameworkMediaDrm));
+		internal static IntPtr class_ref {
+			get {
+				return _members.JniPeerType.PeerReference.Handle;
+			}
+		}
+
+		public override global::Java.Interop.JniPeerMembers JniPeerMembers {
+			get { return _members; }
+		}
+
+		protected override IntPtr ThresholdClass {
+			get { return _members.JniPeerType.PeerReference.Handle; }
+		}
+
+		protected override global::System.Type ThresholdType {
+			get { return _members.ManagedPeerType; }
+		}
+
+		internal FrameworkMediaDrm (IntPtr javaReference, JniHandleOwnership transfer) : base (javaReference, transfer) {}
+
+		// Metadata.xml XPath constructor reference: path="/api/package[@name='com.google.android.exoplayer.drm']/class[@name='FrameworkMediaDrm']/constructor[@name='FrameworkMediaDrm' and count(parameter)=0]"
+		[Register (".ctor", "()V", "")]
+		public unsafe FrameworkMediaDrm ()
+			: base (IntPtr.Zero, JniHandleOwnership.DoNotTransfer)
+		{
+			const string __id = "()V";
+
+			if (((global::Java.Lang.Object) this).Handle != IntPtr.Zero)
+				return;
+
+			try {
+				var __r = _members.InstanceMethods.StartCreateInstance (__id, ((object) this).GetType (), null);
+				SetHandle (__r.Handle, JniHandleOwnership.TransferLocalRef);
+				_members.InstanceMethods.FinishCreateInstance (__id, this, null);
+			} finally {
+			}
+		}
+
+		// Metadata.xml XPath method reference: path="/api/package[@name='com.google.android.exoplayer.drm']/class[@name='FrameworkMediaDrm']/method[@name='setOnEventListener' and count(parameter)=1 and parameter[1][@type='com.google.android.exoplayer.drm.ExoMediaDrm.OnEventListener<com.google.android.exoplayer.drm.FrameworkMediaCrypto>']]"
+		[Register ("setOnEventListener", "(Lcom/google/android/exoplayer/drm/ExoMediaDrm$OnEventListener;)V", "")]
+		public unsafe void SetOnEventListener (global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrmOnEventListener p0)
+		{
+			const string __id = "setOnEventListener.(Lcom/google/android/exoplayer/drm/ExoMediaDrm$OnEventListener;)V";
+			try {
+				JniArgumentValue* __args = stackalloc JniArgumentValue [1];
+				__args [0] = new JniArgumentValue ((p0 == null) ? IntPtr.Zero : ((global::Java.Lang.Object) p0).Handle);
+				_members.InstanceMethods.InvokeAbstractVoidMethod (__id, this, __args);
+			} finally {
+			}
+		}
+
+		// This method is explicitly implemented as a member of an instantiated Com.Google.Android.Exoplayer.Drm.IExoMediaDrm
+		void global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm.SetOnEventListener (global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrmOnEventListener p0)
+		{
+			SetOnEventListener (global::Java.Interop.JavaObjectExtensions.JavaCast<global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrmOnEventListener>(p0));
+		}
+
+	}
+}