[Mono.Android] Java.Lang.Object.GetObject<T>() implementation (#9728)

Context: #9630
Context: #9716
Context: dotnet/java-interop@e288589

@jonathanpeppers attempted to prototype MAUI startup in a NativeAOT
environment, which promptly crashes similar to:

	E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.DllNotFoundException: DllNotFound_Linux, xa-internal-api, 
	E AndroidRuntime: dlopen failed: library "xa-internal-api" not found
	E AndroidRuntime: dlopen failed: library "libxa-internal-api" not found
	E AndroidRuntime: 
	E AndroidRuntime:    at System.Runtime.InteropServices.NativeLibrary.LoadLibErrorTracker.Throw(String) + 0x47
	E AndroidRuntime:    at Internal.Runtime.CompilerHelpers.InteropHelpers.FixupModuleCell(InteropHelpers.ModuleFixupCell*) + 0xe2
	E AndroidRuntime:    at Internal.Runtime.CompilerHelpers.InteropHelpers.ResolvePInvokeSlow(InteropHelpers.MethodFixupCell*) + 0x35
	E AndroidRuntime:    at Android.Runtime.RuntimeNativeMethods.monodroid_TypeManager_get_java_class_name(IntPtr) + 0x22
	E AndroidRuntime:    at Java.Interop.TypeManager.GetClassName(IntPtr) + 0xe
	E AndroidRuntime:    at Java.Interop.TypeManager.CreateInstance(IntPtr, JniHandleOwnership, Type) + 0x69
	E AndroidRuntime:    at Java.Lang.Object._GetObject[T](IntPtr, JniHandleOwnership) + 0x4e
	E AndroidRuntime:    at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) + 0x89
	E AndroidRuntime: 	at my.MainApplication.n_onCreate(Native Method)
	E AndroidRuntime: 	at my.MainApplication.onCreate(MainApplication.java:24)
	E AndroidRuntime: 	at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1182)
	E AndroidRuntime: 	at android.app.ActivityThread.handleBindApplication(ActivityThread.java:6460)
	E AndroidRuntime: 	at android.app.ActivityThread.access$1300(ActivityThread.java:219)
	E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1859)
	E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:107)
	E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:214)
	E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7356)
	E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
	E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
	E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

because:

 1. MAUI apps provide an `Android.App.Application` sublass, and

 2. [`Application` is "special"][0], and

 3. When `Java.Lang.Object.GetObject<T>()` is hit for an instance
    which doesn't already have an instance mapping -- i.e.
    `Object.PeekObject()` returns `null` -- then we'd hit
    `TypeManager.CreateInstance()`, which is a codepath full of
    P/Invokes, and P/Invokes don't currently work on NativeAOT [^1].

The solution is to partially resuscitate PR #9630, but this time have
`Java.Lang.Object.GetObject<T>()` call
`Java.Interop.JniRuntime.JniValueManager.GetPeer()` instead of
`Java.Interop.JniRuntime.JniValueManager.GetValue()`; see also
dotnet/java-interop@e288589d.

This allows `Application` subclasses to be used (along with other
build system changes present in #9716).

This also cleans up a few things if `Java.Lang.Object` introduces an
internal `DynamicallyAccessedMemberTypes Constructors` field.

[0]: https://learn.microsoft.com/en-us/previous-versions/xamarin/android/internals/architecture#java-activation

[^1]: It's *not* that NativeAOT doesn't support P/Invokes; it does.
      The problem is that for a P/Invoke to work, we need to know the
      name of the native library we're P/Invoking into, and our
      NativeAOT sample environment doesn't include any `.so` files
      other than the one for the app, i.e. whatever we'd P/Invoke
      into doesn't exist.

Author: jonathanpeppers

src/Mono.Android/Android.App/Activity.cs

@@ -6,8 +6,6 @@ namespace Android.App {
 
 	partial class Activity {
 
-		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 		public T? FindViewById<
 				[DynamicallyAccessedMembers (Constructors)]
 				T

src/Mono.Android/Android.App/Dialog.cs

@@ -10,7 +10,7 @@ protected Dialog (Android.Content.Context context, bool cancelable, EventHandler
 			: this (context, cancelable, new Android.Content.IDialogInterfaceOnCancelListenerImplementor () { Handler = cancelHandler }) {}
 
 		public T? FindViewById<
-				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+				[DynamicallyAccessedMembers (Constructors)]
 				T
 		> (int id)
 			where T : Android.Views.View

src/Mono.Android/Android.App/FragmentManager.cs

@@ -5,8 +5,6 @@
 #if ANDROID_11
 namespace Android.App {
 	public partial class FragmentManager {
-		const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 		public T? FindFragmentById<
 				[DynamicallyAccessedMembers (Constructors)]
 				T

src/Mono.Android/Android.OS/AsyncTask.cs

@@ -18,8 +18,6 @@ public abstract class AsyncTask<
 			TResult
 	> : AsyncTask {
 
-		const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 		static IntPtr java_class_handle;
 		internal static IntPtr class_ref {
 			get {

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

@@ -662,7 +662,13 @@ public static void CopyArray (IntPtr src, string[] dest)
 					AssertIsJavaObject (type);
 
 					IntPtr elem = GetObjectArrayElement (source, index);
-					return Java.Lang.Object.GetObject (elem, JniHandleOwnership.TransferLocalRef, type);
+					return GetObject (elem, type);
+
+					// FIXME: Since a Dictionary<Type, Func> is used here, the trimmer will not be able to properly analyze `Type t`
+					// error IL2111: Method 'lambda expression' with parameters or return value with `DynamicallyAccessedMembersAttribute` is accessed via reflection. Trimmer can't guarantee availability of the requirements of the method.
+					[UnconditionalSuppressMessage ("Trimming", "IL2067", Justification = "FIXME: https://github.com/xamarin/xamarin-android/issues/8724")]
+					static object? GetObject (IntPtr e, Type t) =>
+						Java.Lang.Object.GetObject (e, JniHandleOwnership.TransferLocalRef, t);
 				} },
 				{ typeof (Array), (type, source, index) => {
 					IntPtr  elem      = GetObjectArrayElement (source, index);

src/Mono.Android/Android.Runtime/JavaArray.cs

@@ -1,12 +1,15 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-
+using System.Diagnostics.CodeAnalysis;
 
 namespace Android.Runtime {
 
 	[Register ("mono/android/runtime/JavaArray", DoNotGenerateAcw=true)]
-	public sealed class JavaArray<T> : Java.Lang.Object, IList<T> {
+	public sealed class JavaArray<
+			[DynamicallyAccessedMembers (Constructors)]
+			T
+	> : Java.Lang.Object, IList<T> {
 
 		public JavaArray (IntPtr handle, JniHandleOwnership transfer)
 			: base (handle, transfer)

src/Mono.Android/Android.Runtime/JavaCollection.cs

@@ -14,8 +14,6 @@ namespace Android.Runtime {
 	// java.util.Collection allows null values
 	public class JavaCollection : Java.Lang.Object, System.Collections.ICollection {
 
-		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 		internal static IntPtr collection_class = JNIEnv.FindClass ("java/util/Collection");
 
 		internal static IntPtr id_add;

src/Mono.Android/Android.Runtime/JavaDictionary.cs

@@ -12,8 +12,6 @@ namespace Android.Runtime {
 	// java.util.HashMap allows null keys and values
 	public class JavaDictionary : Java.Lang.Object, System.Collections.IDictionary {
 
-		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 		class DictionaryEnumerator : IDictionaryEnumerator {
 
 			IEnumerator simple_enumerator;

src/Mono.Android/Android.Runtime/JavaList.cs

@@ -10,7 +10,6 @@ namespace Android.Runtime {
 	// java.util.ArrayList allows null values
 	public partial class JavaList : Java.Lang.Object, System.Collections.IList {
 
-		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
 		internal static readonly JniPeerMembers list_members = new XAPeerMembers ("java/util/List", typeof (JavaList), isInterface: true);
 
 		//

src/Mono.Android/Android.Runtime/JavaSet.cs

@@ -269,7 +269,7 @@ public static IntPtr ToLocalJniHandle (ICollection? items)
 	[Register ("java/util/HashSet", DoNotGenerateAcw=true)]
 	// java.util.HashSet allows null
 	public class JavaSet<
-			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+			[DynamicallyAccessedMembers (Constructors)]
 			T
 	> : JavaSet, ICollection<T> {
 

src/Mono.Android/Android.Util/SparseArray.cs

@@ -9,7 +9,7 @@ namespace Android.Util
 {
 	[Register ("android/util/SparseArray", DoNotGenerateAcw=true)]
 	public partial class SparseArray<
-			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+			[DynamicallyAccessedMembers (Constructors)]
 			E
 	> : SparseArray
 	{

src/Mono.Android/Android.Views/View.cs

@@ -13,9 +13,6 @@ public enum SystemUiFlags {
 #endif
 
 	public partial class View {
-
-		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
-
 #if ANDROID_16
 		[Obsolete ("This method uses wrong enum type. Please use PerformAccessibilityAction(Action) instead.")]
 		public bool PerformAccessibilityAction (GlobalAction action, Bundle arguments)

src/Mono.Android/Android.Views/Window.cs

@@ -7,7 +7,7 @@ namespace Android.Views {
 	partial class Window {
 
 		public T? FindViewById<
-				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+				[DynamicallyAccessedMembers (Constructors)]
 				T
 		> (int id)
 			where T : Android.Views.View

src/Mono.Android/Android.Widget/AdapterView.cs

@@ -51,7 +51,7 @@ public event EventHandler ItemSelectionCleared {
 
 	[Register ("android/widget/AdapterView", DoNotGenerateAcw=true)]
 	public abstract class AdapterView<
-			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+			[DynamicallyAccessedMembers (Constructors)]
 			T
 	> : AdapterView  where T : IAdapter {
 

src/Mono.Android/Android.Widget/ArrayAdapter.cs

@@ -9,7 +9,7 @@ namespace Android.Widget {
 
 	[Register ("android/widget/ArrayAdapter", DoNotGenerateAcw=true)]
 	public partial class ArrayAdapter<
-			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+			[DynamicallyAccessedMembers (Constructors)]
 			T
 	> : ArrayAdapter {
 

src/Mono.Android/Java.Lang/Object.cs

@@ -16,6 +16,8 @@ namespace Java.Lang {
 	[Serializable]
 	public partial class Object : global::Java.Interop.JavaObject, IJavaObject, IJavaObjectEx
 	{
+		internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
+
 		IntPtr IJavaObjectEx.ToLocalJniHandle ()
 		{
 			lock (this) {
@@ -130,39 +132,48 @@ protected void SetHandle (IntPtr value, JniHandleOwnership transfer)
 			return (T?)PeekObject (handle, typeof (T));
 		}
 
-		public static T? GetObject<T> (IntPtr jnienv, IntPtr handle, JniHandleOwnership transfer)
+		public static T? GetObject<
+				[DynamicallyAccessedMembers (Constructors)]
+				T
+		> (IntPtr jnienv, IntPtr handle, JniHandleOwnership transfer)
 			where T : class, IJavaObject
 		{
 			JNIEnv.CheckHandle (jnienv);
 			return GetObject<T> (handle, transfer);
 		}
 
-		public static T? GetObject<T> (IntPtr handle, JniHandleOwnership transfer)
+		public static T? GetObject<
+				[DynamicallyAccessedMembers (Constructors)]
+				T
+		> (IntPtr handle, JniHandleOwnership transfer)
 			where T : class, IJavaObject
 		{
 			return _GetObject<T>(handle, transfer);
 		}
 
-		internal static T? _GetObject<T> (IntPtr handle, JniHandleOwnership transfer)
+		internal static T? _GetObject<
+				[DynamicallyAccessedMembers (Constructors)]
+				T
+		> (IntPtr handle, JniHandleOwnership transfer)
 		{
 			if (handle == IntPtr.Zero)
 				return default (T);
 
 			return (T?) GetObject (handle, transfer, typeof (T));
 		}
 
-		internal static IJavaPeerable? GetObject (IntPtr handle, JniHandleOwnership transfer, Type? type = null)
+		internal static IJavaPeerable? GetObject (
+				IntPtr handle,
+				JniHandleOwnership transfer,
+				[DynamicallyAccessedMembers (Constructors)]
+				Type? type = null)
 		{
 			if (handle == IntPtr.Zero)
 				return null;
 
-			var r = PeekObject (handle, type);
-			if (r != null) {
-				JNIEnv.DeleteRef (handle, transfer);
-				return r;
-			}
-
-			return Java.Interop.TypeManager.CreateInstance (handle, transfer, type);
+			var r = JNIEnvInit.ValueManager!.GetPeer (new JniObjectReference (handle), type);
+			JNIEnv.DeleteRef (handle, transfer);
+			return r;
 		}
 
 		[EditorBrowsable (EditorBrowsableState.Never)]