/// Requests that the text input control become visible.
  void show() {
    assert(attached);
    TextInput._instance._show();
  }

  void _show() {
    _channel.invokeMethod<void>('TextInput.show');
  }

mixin TextInputBindingMixin on WidgetsFlutterBinding {
  @override
  BinaryMessenger createBinaryMessenger() {
    return TextInputBinaryMessenger(super.createBinaryMessenger());
  }
}

class YourBinding extends WidgetsFlutterBinding with TextInputBindingMixin,YourBindingMixin {
 }
 void main() {
   YourBinding();
   runApp(const MyApp());
 }

class TextInputBinaryMessenger extends BinaryMessenger {
  TextInputBinaryMessenger(this.origin);
  final BinaryMessenger origin;
  @override
  Future<ByteData?>? send(String channel, ByteData? message) {
    // TODO: implement send
    throw UnimplementedError();
  }
  @override
  void setMessageHandler(String channel, MessageHandler? handler) {
    // TODO: implement setMessageHandler
  }
  @override
  Future<void> handlePlatformMessage(String channel, ByteData? data,
      PlatformMessageResponseCallback? callback) {
    // TODO: implement handlePlatformMessage
    throw UnimplementedError();
  }
}

  static const MethodChannel platform = OptionalMethodChannel(
      'flutter/platform',
      JSONMethodCodec(),
  );

class TextInputBinaryMessenger extends BinaryMessenger {
  TextInputBinaryMessenger(this.origin);
  final BinaryMessenger origin;
  @override
  Future<ByteData?>? send(String channel, ByteData? message) {
    // TODO: 處理我們自己的邏輯
    return origin.send(channel, message);
  }
  @override
  void setMessageHandler(String channel, MessageHandler? handler) {
    origin.setMessageHandler(channel, handler);
  }
  @override
  Future<void> handlePlatformMessage(String channel, ByteData? data,
      PlatformMessageResponseCallback? callback) {
    return origin.handlePlatformMessage(channel, data, callback);
  }
}

  static const MethodChannel textInput = OptionalMethodChannel(
      'flutter/textinput',
      JSONMethodCodec(),
  );

  @override
  Future<ByteData?>? send(String channel, ByteData? message) async {
    if (channel == SystemChannels.textInput.name) {
      final MethodCall methodCall =
          SystemChannels.textInput.codec.decodeMethodCall(message);
      switch (methodCall.method) {
        case 'TextInput.show':
          // 處理是否需要濾過(guò)這次消息。
          return SystemChannels.textInput.codec.encodeSuccessEnvelope(null);
        default:
      }
    }
    return origin.send(channel, message);
  }

class TextInputFocusNode extends FocusNode {
  /// no system keyboard show
  /// if it's true, it stop Flutter Framework send `TextInput.show` message to Flutter Engine
  bool ignoreSystemKeyboardShow = true;
}

  Future<ByteData?>? send(String channel, ByteData? message) async {
    if (channel == SystemChannels.textInput.name) {
      final MethodCall methodCall =
          SystemChannels.textInput.codec.decodeMethodCall(message);
      switch (methodCall.method) {
        case 'TextInput.show':
          final FocusNode? focus = FocusManager.instance.primaryFocus;
          if (focus != null &&
              focus is TextInputFocusNode &&
              focus.ignoreSystemKeyboardShow) {
             return SystemChannels.textInput.codec.encodeSuccessEnvelope(null);
          }
          break;
        default:
      }
    }
    return origin.send(channel, message);
  }

final TextInputFocusNode _focusNode = TextInputFocusNode()..debugLabel = 'YourTextField';
  @override
  Widget build(BuildContext context) {
    return TextField(
      focusNode: _focusNode,
    );
  }

  PersistentBottomSheetController<void>? _bottomSheetController;
  final TextInputFocusNode _focusNode = TextInputFocusNode()..debugLabel = 'YourTextField';
  @override
  void initState() {
    super.initState();
    _focusNode.addListener(_handleFocusChanged);
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: TextField(
          // you must use TextInputFocusNode
          focusNode: _focusNode,
          ),
    );
  }  
  void _onTextFiledTap() {
    if (_bottomSheetController == null) {
      _handleFocusChanged();
    }
  }
  void _handleFocusChanged() {
    if (_focusNode.hasFocus) {
      // just demo, you can define your custom keyboard as you want
      _bottomSheetController = showBottomSheet<void>(
          context: FocusManager.instance.primaryFocus!.context!,
          // set false, if don't want to drag to close custom keyboard
          enableDrag: true,
          builder: (BuildContext b) {
            // your custom keyboard
            return Container();
          });
      // maybe drag close
      _bottomSheetController?.closed.whenComplete(() {
        _bottomSheetController = null;
      });
    } else {
      _bottomSheetController?.close();
      _bottomSheetController = null;
    }
  }
  @override
  void dispose() {
    _focusNode.removeListener(_handleFocusChanged);
    super.dispose();
  }

Column(
  children: <Widget>[
    // 你的頁(yè)面
    Expanded(child: Container()),
    // 你的自定義鍵盤
    Container(),
  ],
);

  static const BasicMessageChannel<Object?> keyEvent = BasicMessageChannel<Object?>(
      'flutter/keyevent',
      JSONMessageCodec(),
  );