fix responder issue.

src/iOS/Avalonia.iOS/AvaloniaView.Text.cs

@@ -54,12 +54,18 @@ public class AvaloniaResponder : UIResponder, IUITextInput
         }
     }
 
-    public AvaloniaResponder()
+    private UIResponder _nextResponder;
+
+    public AvaloniaResponder(AvaloniaView view, ITextInputMethodClient client)
     {
+        _nextResponder = view;
+        _client = client;
         _tokenizer = new UITextInputStringTokenizer(this);
         
     }
 
+    public override UIResponder NextResponder => _nextResponder;
+
     public override bool CanPerform(Selector action, NSObject? withSender)
     {
         return base.CanPerform(action, withSender);
@@ -241,7 +247,8 @@ public class AvaloniaResponder : UIResponder, IUITextInput
             return new AvaloniaTextRange(range);
         }
 
-        throw new Exception();
+        return null;
+        //throw new Exception();
     }
 
     UITextPosition IUITextInput.GetPosition(UITextPosition fromPosition, nint offset)

src/iOS/Avalonia.iOS/AvaloniaView.cs

@@ -27,11 +27,9 @@ namespace Avalonia.iOS
         private TouchHandler _touches;
         private ITextInputMethodClient _client;
         private bool _isActive;
-        private AvaloniaResponder _textResponder;
 
         public AvaloniaView()
         {
-            _textResponder = new AvaloniaResponder();
             _topLevelImpl = new TopLevelImpl(this);
             _touches = new TouchHandler(this, _topLevelImpl);
             _topLevel = new EmbeddableControlRoot(_topLevelImpl);
@@ -56,8 +54,6 @@ namespace Avalonia.iOS
 
         public override bool CanResignFirstResponder => true;
 
-        public override UIResponder NextResponder => _textResponder;
-
         internal class TopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost,
             ITopLevelImplWithStorageProvider
         {
@@ -164,6 +160,8 @@ namespace Avalonia.iOS
 
         bool ITextInputMethodImpl.IsActive => _isActive;
 
+        private AvaloniaResponder _currentResponder;
+
         void ITextInputMethodImpl.SetClient(ITextInputMethodClient client)
         {
             if (_client != null)
@@ -175,21 +173,23 @@ namespace Avalonia.iOS
 
             if (_client is { })
             {
-                //_client.CursorRectangleChanged += ClientOnCursorRectangleChanged;
-                //_client.SurroundingTextChanged += ClientOnSurroundingTextChanged;
-                _textResponder.BecomeFirstResponder();
+                if (_currentResponder != null && _currentResponder.IsFirstResponder)
+                {
+                    _currentResponder.ResignFirstResponder();
+                    _currentResponder = null;
+                }
 
-                var x = _textResponder.IsFirstResponder;
-
-                var keyWindow = UIApplication.SharedApplication.KeyWindow;
+                _currentResponder = new AvaloniaResponder(this, _client);
+                //_client.CursorRectangleChanged += ClientOnCursorRectangleChanged;
 
-                var windowNextResponder = keyWindow.NextResponder;
+                //_client.SurroundingTextChanged += ClientOnSurroundingTextChanged;
+                _currentResponder.BecomeFirstResponder();
 
-                var nr1 = windowNextResponder.NextResponder;
+                var x = _currentResponder.IsFirstResponder;
             }
             else
             {
-                _textResponder.ResignFirstResponder();
+                _currentResponder.ResignFirstResponder();
             }
         }
 
@@ -265,7 +265,7 @@ namespace Avalonia.iOS
 
         void ITextInputMethodImpl.Reset()
         {
-            _textResponder?.ResignFirstResponder();
+            _currentResponder?.ResignFirstResponder();
         }
     }
 }