[Mono.Android] Fix NRT warnings in hand bound code.

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

@@ -1,5 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 using Android.Runtime;
 
 namespace Android.App {
@@ -9,8 +8,7 @@ public partial class Dialog {
 		protected Dialog (Android.Content.Context context, bool cancelable, EventHandler cancelHandler) 
 			: this (context, cancelable, new Android.Content.IDialogInterfaceOnCancelListenerImplementor () { Handler = cancelHandler }) {}
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();

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

@@ -1,22 +1,18 @@
-using System.Diagnostics.CodeAnalysis;
 using Android.OS;
 using Android.Runtime;
 
 #if ANDROID_11
 namespace Android.App {
 	public partial class FragmentManager {
-		[return: MaybeNull]
-		public T FindFragmentById<T> (int id) where T : Fragment
+		public T? FindFragmentById<T> (int id) where T : Fragment
 		{
 			return FindFragmentById (id).JavaCast<T> ();
 		}
-		[return: MaybeNull]
-		public T FindFragmentByTag<T> (string tag) where T : Fragment
+		public T? FindFragmentByTag<T> (string tag) where T : Fragment
 		{
 			return FindFragmentByTag (tag).JavaCast<T> ();
 		}
-		[return: MaybeNull]
-		public T GetFragment<T> (Bundle bundle, string key) where T : Fragment
+		public T? GetFragment<T> (Bundle bundle, string key) where T : Fragment
 		{
 			return GetFragment (bundle, key).JavaCast<T> ();
 		}

src/Mono.Android/Android.Graphics/Color.cs

@@ -416,7 +416,7 @@ public override void DestroyGenericArgumentState (Color value, ref JniValueMarsh
 
 		public override Expression CreateParameterToManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize, Type targetType)
 		{
-			var c = typeof (Color).GetConstructor (new[]{typeof (int)});
+			var c = typeof (Color).GetConstructor (new[]{typeof (int)})!;
 			var v = Expression.Variable (typeof (Color), sourceValue.Name + "_val");
 			context.LocalVariables.Add (v);
 			context.CreationStatements.Add (Expression.Assign (v, Expression.New (c, sourceValue)));

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

@@ -88,9 +88,8 @@ public AsyncTask ()
 		}
 
 		static IntPtr id_get;
-		[return: MaybeNull]
 		[Register ("get", "()Ljava/lang/Object;", "")]
-		public TResult GetResult ()
+		public TResult? GetResult ()
 		{
 			if (id_get == IntPtr.Zero)
 				id_get = JNIEnv.GetMethodID (class_ref, "get", "()Ljava/lang/Object;");

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

@@ -747,7 +747,7 @@ public static void CopyArray (IntPtr src, string[] dest)
 
 		static TValue GetConverter<TValue>(Dictionary<Type, TValue> dict, Type? elementType, IntPtr array)
 		{
-			TValue converter;
+			TValue? converter;
 
 			if (elementType != null) {
 				if (elementType.IsEnum)

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

@@ -386,8 +386,7 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
-		public IEnumerator<T> GetEnumerator ()
+		public IEnumerator<T?> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator());
 		}

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

@@ -444,8 +444,7 @@ public JavaDictionary (IDictionary<K, V> items) : this ()
 		//
 		//     https://developer.android.com/reference/java/util/Map#get(java.lang.Object)
 		//
-		[return: MaybeNull]
-		internal V Get (K key)
+		internal V? Get (K key)
 		{
 			if (id_get == IntPtr.Zero)
 				id_get = JNIEnv.GetMethodID (map_class, "get", "(Ljava/lang/Object;)Ljava/lang/Object;");

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

@@ -727,8 +727,7 @@ public JavaList (IEnumerable<T> items) : this ()
 		//
 		//     https://developer.android.com/reference/java/util/List.html?hl=en#get(int)
 		//
-		[return: MaybeNull]
-		internal unsafe T InternalGet (int location)
+		internal unsafe T? InternalGet (int location)
 		{
 			const string id = "get.(I)Ljava/lang/Object;";
 			JniObjectReference obj;
@@ -880,8 +879,7 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
-		public IEnumerator<T> GetEnumerator ()
+		public IEnumerator<T?> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator ());
 		}

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

@@ -390,7 +390,6 @@ System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
 			return GetEnumerator ()!;
 		}
 
-		[return: MaybeNull]
 		public IEnumerator<T> GetEnumerator ()
 		{
 			return System.Linq.Extensions.ToEnumerator_Dispose<T> (Iterator ());

src/Mono.Android/Android.Runtime/XmlPullParserReader.cs

@@ -72,7 +72,7 @@ public QName (XmlPullParserReader r, string name)
 			}
 
 			public string LocalName;
-			public string Namespace;
+			public string? Namespace;
 		}
 
 		public XmlPullParserReader (IJavaObject source)
@@ -140,7 +140,7 @@ public override bool EOF {
 				throw new ArgumentOutOfRangeException ();
 		}
 
-		public override string? GetAttribute (string localName, string namespaceName)
+		public override string? GetAttribute (string localName, string? namespaceName)
 		{
 			return namespaceName == xmlns_uri ? source.GetNamespace (localName) : source.GetAttributeValue (namespaceName, localName);
 		}
@@ -179,7 +179,7 @@ public override string? LocalName {
 			}
 		}
 
-		public override string LookupNamespace (string prefix)
+		public override string? LookupNamespace (string prefix)
 		{
 			return nsmgr.LookupNamespace (prefix);
 		}
@@ -192,7 +192,7 @@ public override void MoveToAttribute (int i)
 			attr_value = false;
 		}
 
-		public override bool MoveToAttribute (string localName, string namespaceName)
+		public override bool MoveToAttribute (string localName, string? namespaceName)
 		{
 			if (namespaceName == xmlns_uri) {
 				for (int i = 0; i < ns_count; i++)
@@ -251,7 +251,7 @@ public override string? Name {
 			get { return String.IsNullOrEmpty (Prefix) ? LocalName : Prefix + ':' + LocalName; }
 		}
 
-		public override XmlNameTable NameTable {
+		public override XmlNameTable? NameTable {
 			get { return nsmgr.NameTable; }
 		}
 
@@ -297,9 +297,14 @@ public override XmlNodeType NodeType {
 			}
 		}
 
-		public override string Prefix {
+		public override string? Prefix {
 			// getPrefix(), getAttributePrefix(), getNamespacePrefix() are not supported!!!
-			get { return nsmgr.LookupPrefix (NamespaceURI); }
+			get {
+				if (NamespaceURI is null)
+					return null;
+
+				return nsmgr.LookupPrefix (NamespaceURI);
+			}
 		}
 
 		public override bool Read ()
@@ -331,14 +336,14 @@ public override bool Read ()
 			if (wasEmptyElement || NodeType == XmlNodeType.EndElement)
 				nsmgr.PopScope ();
 			if (NodeType == XmlNodeType.Element) {
-				if (NamespaceURI != String.Empty && nsmgr.LookupPrefix (NamespaceURI) != String.Empty)
+				if (!string.IsNullOrEmpty (NamespaceURI) && nsmgr.LookupPrefix (NamespaceURI) != String.Empty)
 					nsmgr.AddNamespace (String.Empty, NamespaceURI);
 				else if (NamespaceURI == String.Empty && nsmgr.DefaultNamespace != String.Empty)
 					nsmgr.AddNamespace (String.Empty, String.Empty);
 				for (int i = 0; i < source.AttributeCount; i++) {
 					string? ns = source.GetAttributeNamespace (i);
-					if (ns != String.Empty && nsmgr.LookupPrefix (ns) == null)
-						nsmgr.AddNamespace ("p" + i, source.GetAttributeNamespace (i));
+					if (!string.IsNullOrEmpty (ns) && nsmgr.LookupPrefix (ns) == null)
+						nsmgr.AddNamespace ("p" + i, ns);
 				}
 				nsmgr.PushScope ();
 			}

src/Mono.Android/Android.Runtime/XmlReaderPullParser.cs

@@ -111,11 +111,11 @@ public int GetIdAttributeResourceValue (int defaultValue)
 			return GetAttributeResourceValue (null, "id", defaultValue);
 		}
 
-		public string ClassAttribute {
+		public string? ClassAttribute {
 			get { return GetAttributeValue (null, "class"); }
 		}
 
-		public string IdAttribute {
+		public string? IdAttribute {
 			get { return GetAttributeValue (null, "id"); }
 		}
 
@@ -181,8 +181,11 @@ public string GetAttributeValue (int index)
 			return r.GetAttribute (index);
 		}
 
-		public string GetAttributeValue (string? namespaceURI, string? name)
+		public string? GetAttributeValue (string? namespaceURI, string? name)
 		{
+			if (name is null)
+				return null;
+
 			return r.GetAttribute (name, namespaceURI);
 		}
 
@@ -196,7 +199,7 @@ public bool GetFeature (string? name)
 			return false;
 		}
 
-		public string GetNamespace (string? prefix)
+		public string? GetNamespace (string prefix)
 		{
 			return r.LookupNamespace (prefix);
 		}

src/Mono.Android/Android.Telephony/CellInfo.cs

@@ -9,7 +9,7 @@ namespace Android.Telephony {
 
 	public partial class CellInfo {
 
-		static Delegate cb_getCellIdentity;
+		static Delegate? cb_getCellIdentity;
 #pragma warning disable 0169
 		static Delegate GetGetCellIdentityHandler ()
 		{
@@ -20,7 +20,7 @@ static Delegate GetGetCellIdentityHandler ()
 
 		static IntPtr n_GetCellIdentity (IntPtr jnienv, IntPtr native__this)
 		{
-			Android.Telephony.CellInfo __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			var __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer)!;
 			return JNIEnv.ToLocalJniHandle (__this.CellIdentity);
 		}
 #pragma warning restore 0169
@@ -32,15 +32,15 @@ public unsafe virtual Android.Telephony.CellIdentity CellIdentity {
 				const string __id = "getCellIdentity.()Landroid/telephony/CellIdentity;";
 				try {
 					var __rm = _members.InstanceMethods.InvokeVirtualObjectMethod (__id, this, null);
-					return global::Java.Lang.Object.GetObject<Android.Telephony.CellIdentity> (__rm.Handle, JniHandleOwnership.TransferLocalRef);
+					return global::Java.Lang.Object.GetObject<Android.Telephony.CellIdentity> (__rm.Handle, JniHandleOwnership.TransferLocalRef)!;
 				}
 		                catch (Java.Lang.NoSuchMethodError) {
 					throw new Java.Lang.AbstractMethodError (__id);
 				}
 			}
 		}
 
-		static Delegate cb_getCellSignalStrength;
+		static Delegate? cb_getCellSignalStrength;
 #pragma warning disable 0169
 		static Delegate GetGetCellSignalStrengthHandler ()
 		{
@@ -51,7 +51,7 @@ static Delegate GetGetCellSignalStrengthHandler ()
 
 		static IntPtr n_GetCellSignalStrength (IntPtr jnienv, IntPtr native__this)
 		{
-			Android.Telephony.CellInfo __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			var __this = global::Java.Lang.Object.GetObject<Android.Telephony.CellInfo> (jnienv, native__this, JniHandleOwnership.DoNotTransfer)!;
 			return JNIEnv.ToLocalJniHandle (__this.CellSignalStrength);
 		}
 #pragma warning restore 0169
@@ -63,7 +63,7 @@ public unsafe virtual Android.Telephony.CellSignalStrength CellSignalStrength {
 				const string __id = "getCellSignalStrength.()Landroid/telephony/CellSignalStrength;";
 				try {
 					var __rm = _members.InstanceMethods.InvokeVirtualObjectMethod (__id, this, null);
-					return global::Java.Lang.Object.GetObject<Android.Telephony.CellSignalStrength> (__rm.Handle, JniHandleOwnership.TransferLocalRef);
+					return global::Java.Lang.Object.GetObject<Android.Telephony.CellSignalStrength> (__rm.Handle, JniHandleOwnership.TransferLocalRef)!;
 				}
 				catch (Java.Lang.NoSuchMethodError) {
 					throw new Java.Lang.AbstractMethodError (__id);

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

@@ -22,8 +22,7 @@ public bool PerformAccessibilityAction (GlobalAction action, Bundle arguments)
 		}
 #endif
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();

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

@@ -6,8 +6,7 @@ namespace Android.Views {
 
 	partial class Window {
 
-		[return: MaybeNull]
-		public T FindViewById<T> (int id)
+		public T? FindViewById<T> (int id)
 			where T : Android.Views.View
 		{
 			return this.FindViewById (id).JavaCast<T> ();

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

@@ -185,9 +185,8 @@ public void Add (T @object)
 		}
 
 		static IntPtr id_getItem_I;
-		[return: MaybeNull]
 		[Register ("getItem", "(I)Ljava/lang/Object;", "GetGetItem_IHandler")]
-		public T GetItem (int position)
+		public T? GetItem (int position)
 		{
 			if (id_getItem_I == IntPtr.Zero)
 				id_getItem_I = JNIEnv.GetMethodID (class_ref, "getItem", "(I)Ljava/lang/Object;");

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

@@ -92,15 +92,13 @@ static Func<IntPtr, JniHandleOwnership, object> GetJniHandleConverterForType ([D
 					typeof (Func<IntPtr, JniHandleOwnership, object>), m);
 		}
 
-		[return: MaybeNull]
-		public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer)
+		public static T? FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer)
 		{
 			bool set;
 			return FromJniHandle<T>(handle, transfer, out set);
 		}
 
-		[return: MaybeNull]
-		public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out bool set)
+		public static T? FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out bool set)
 		{
 			if (handle == IntPtr.Zero) {
 				set = false;
@@ -109,7 +107,7 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 
 			var interned = (IJavaObject?) Java.Lang.Object.PeekObject (handle);
 			if (interned != null) {
-				T r = FromJavaObject<T>(interned, out set);
+				T? r = FromJavaObject<T>(interned, out set);
 				if (set) {
 					JNIEnv.DeleteRef (handle, transfer);
 					return r;
@@ -119,20 +117,20 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 			set = true;
 
 			if (typeof (IJavaObject).IsAssignableFrom (typeof (T)))
-				return (T) Java.Lang.Object._GetObject<T> (handle, transfer);
+				return (T?) Java.Lang.Object._GetObject<T> (handle, transfer);
 
 			var converter = GetJniHandleConverter (typeof (T)) ??
 				GetJniHandleConverter (GetTypeMapping (handle));
 			if (converter != null)
-				return (T) converter (handle, transfer);
+				return (T?) converter (handle, transfer);
 
 			var v = Java.Lang.Object.GetObject (handle, transfer);
 			if (v is T)
 				return (T) v;
 
 			// hail mary pass; perhaps there's a MCW which participates in normal
 			// .NET type conversion?
-			return (T) Convert.ChangeType (v, typeof (T), CultureInfo.InvariantCulture);
+			return (T?) Convert.ChangeType (v, typeof (T), CultureInfo.InvariantCulture);
 		}
 
 		public static object? FromJniHandle (IntPtr handle, JniHandleOwnership transfer, Type? targetType = null)
@@ -208,15 +206,13 @@ public static T FromJniHandle<T>(IntPtr handle, JniHandleOwnership transfer, out
 			return null;
 		}
 
-		[return: MaybeNull]
-		public static T FromJavaObject<T>(IJavaObject? value)
+		public static T? FromJavaObject<T>(IJavaObject? value)
 		{
 			bool set;
 			return FromJavaObject<T>(value, out set);
 		}
 
-		[return: MaybeNull]
-		public static T FromJavaObject<T>(IJavaObject? value, out bool set)
+		public static T? FromJavaObject<T>(IJavaObject? value, out bool set)
 		{
 			if (value == null) {
 				set = false;
@@ -244,7 +240,7 @@ public static T FromJavaObject<T>(IJavaObject? value, out bool set)
 			set = true;
 			var converter = GetJniHandleConverter (typeof (T));
 			if (converter != null)
-				return (T) converter (lrefValue, JniHandleOwnership.TransferLocalRef);
+				return (T?) converter (lrefValue, JniHandleOwnership.TransferLocalRef);
 			JNIEnv.DeleteLocalRef (lrefValue);
 			return (T) Convert.ChangeType (value, typeof (T), CultureInfo.InvariantCulture);
 		}