[Mono.Android] fix leaking lrefs in TypeManager

src/Mono.Android/Java.Interop/TypeManager.cs

@@ -322,21 +322,26 @@ internal static IJavaPeerable CreateInstance (IntPtr handle, JniHandleOwnership
 			if (!typeSig.IsValid || typeSig.SimpleReference == null) {
 				throw new ArgumentException ($"Could not determine Java type corresponding to `{type.AssemblyQualifiedName}`.", nameof (targetType));
 			}
-			JniObjectReference typeClass;
+
+			JniObjectReference typeClass = default;
+			JniObjectReference handleClass = default;
 			try {
-				typeClass = JniEnvironment.Types.FindClass (typeSig.SimpleReference);
-			} catch (Exception e) {
-				throw new ArgumentException ($"Could not find Java class `{typeSig.SimpleReference}`.",
-						nameof (targetType),
-						e);
-			}
+				try {
+					typeClass = JniEnvironment.Types.FindClass (typeSig.SimpleReference);
+				} catch (Exception e) {
+					throw new ArgumentException ($"Could not find Java class `{typeSig.SimpleReference}`.",
+							nameof (targetType),
+							e);
+				}
 
-			var handleClass = JniEnvironment.Types.GetObjectClass (new JniObjectReference (handle));
-			if (!JniEnvironment.Types.IsAssignableFrom (handleClass, typeClass)) {
-				Logger.Log (LogLevel.Info, "*jonp*", $"# jonp: can't assign `{GetClassName(handleClass.Handle)}` to `{GetClassName(typeClass.Handle)}`");
+				handleClass = JniEnvironment.Types.GetObjectClass (new JniObjectReference (handle));
+				if (!JniEnvironment.Types.IsAssignableFrom (handleClass, typeClass)) {
+					Logger.Log (LogLevel.Info, "*jonp*", $"# jonp: can't assign `{GetClassName(handleClass.Handle)}` to `{GetClassName(typeClass.Handle)}`");
+					return null;
+				}
+			} finally {
 				JniObjectReference.Dispose (ref handleClass);
 				JniObjectReference.Dispose (ref typeClass);
-				return null;
 			}
 
 			IJavaPeerable? result = null;

tests/Mono.Android-Tests/Android.Content/SharedPreferencesTest.cs

@@ -0,0 +1,34 @@
+using System;
+using Android.App;
+using Android.Content;
+using NUnit.Framework;
+
+namespace Android.ContentTests;
+
+[TestFixture]
+public class SharedPreferencesTest
+{
+    const string Name = "testpreferences";
+    const int Count = 1000;
+
+    ISharedPreferences GetPreferences () =>
+        Application.Context.GetSharedPreferences (Name, FileCreationMode.Private);
+
+    // NOTE: test case on API 23 can trigger:
+    // art/runtime/indirect_reference_table.cc:115] JNI ERROR (app bug): local reference table overflow 
+    [Test]
+    public void PutAndGetManyValues ()
+    {
+        for (int i = 0; i < Count; i++) {
+            using var prefs = GetPreferences ();
+            using var editor = prefs.Edit ();
+            editor.PutString ("key" + i, "value" + i);
+            editor.Apply ();
+        }
+
+        for (int i = 0; i < Count; i++) {
+            using var prefs = GetPreferences ();
+            Assert.AreEqual ("value" + i, prefs.GetString ("key" + i, null));
+        }
+    }
+}

tests/Mono.Android-Tests/Mono.Android-Test.Shared.projitems

@@ -18,6 +18,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Android.App\ApplicationTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Content.Res\AssetManagerTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Content\IntentTest.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Android.Content\SharedPreferencesTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Graphics\NinePatchTests.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Runtime\AndroidEnvironmentTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Runtime\CharSequenceTest.cs" />