sample keyboard

main.dart

import 'dart:async';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'keyboard test',
      theme: ThemeData.light(),
      darkTheme: ThemeData.dark(),
      home: KeyboardBarInput(
        child: MyHomePage(title: 'Flutter Demo Home Page'),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  TextEditingController myController = TextEditingController();

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  FocusNode focusNode = FocusNode();
  TextEditingController controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            GestureDetector(
              onTap: () {
                FocusScope.of(context).unfocus();
              },
              child: Text('You have pushed the button this many times:'),
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            TextButton(
              child: Text('open keyboard'),
              onPressed: openKeyboard,
            ),
            TextField(
              controller: myController,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }

  String lastTextInput = '';

  Future<void> openKeyboard() async {
    final control = KeyboardBarInput.of(context);
    if (control.isOpen) {
      control.close();
      return;
    }
    lastTextInput = await control.open(text: 'Hello');

    myController.text = lastTextInput;
    // setState(() {});
    print("search text: $lastTextInput");
  }
}



class KeyboardBarInput extends StatefulWidget {
  final Widget child;

  const KeyboardBarInput({
    Key? key,
    required this.child,
  }) : super(key: key);

  @override
  KeyboardBarInputState createState() => KeyboardBarInputState();

  static KeyboardBarInputState of(BuildContext context) {
    return context.findAncestorStateOfType<KeyboardBarInputState>()!;
  }
}

class KeyboardBarInputState extends State<KeyboardBarInput>
    with WidgetsBindingObserver {
  double keyboardHeight = 0.0;

  late final FocusNode _focusNode = FocusNode();
  late final TextEditingController _textController = TextEditingController();

  bool get isOpen => keyboardHeight > 0;
  late Completer<String> _completer;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance!.addObserver(this);
  }

  @override
  void didChangeMetrics() {
    // keyboardHeight = WidgetsBinding.instance?.window.viewInsets.bottom ?? 0.0;
    WidgetsBinding.instance!.addPostFrameCallback((timeStamp) {
      setState(() {
        if (_focusNode.hasFocus) {
          final mq = MediaQuery.of(context);
          keyboardHeight = mq.viewInsets.bottom;
        } else {
          keyboardHeight = 0;
        }
      });
    });
  }

  @override
  void dispose() {
    WidgetsBinding.instance!.removeObserver(this);
    _textController.dispose();
    _focusNode.dispose();
    super.dispose();
  }

  void _onCancelTap() {
    _completer.complete(Future.value(''));
    close();
  }

  void _onDoneTap() {
    _completer.complete(Future.value(_textController.text));
    close();
  }

  @override
  Widget build(BuildContext context) {
    const baseColor = CupertinoDynamicColor.withBrightness(
      color: Color(0xf3D6D7DC),
      darkColor: Color(0xf3373737),
    );
    final textColor = Theme.of(context).textTheme.bodyText1!.color;

    return Stack(
      children: [
        Positioned.fill(child: widget.child),
        Positioned(
          bottom: keyboardHeight,
          left: 0,
          right: 0,
          child: Visibility(
            maintainState: true,
            maintainAnimation: true,
            maintainInteractivity: true,
            maintainSize: true,
            visible: isOpen,
            child: Container(
              color: baseColor.resolveFrom(context),
              padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
              child: Row(
                children: [
                  Expanded(
                    child: CupertinoTextField(
                      focusNode: _focusNode,
                      controller: _textController,
                      enableInteractiveSelection: false,
                      keyboardType: TextInputType.name,
                      autocorrect: false,
                      style: TextStyle(color: textColor),
                      enableSuggestions: false,
                      expands: false,
                      maxLines: 1,
                      onSubmitted: (text) {
                        _completer.complete(Future.value(text));
                      },
                    ),
                  ),
                  CupertinoButton(child: Text('Done'), onPressed: _onDoneTap),
                  CupertinoButton(
                      child: Text('Cancel'), onPressed: _onCancelTap),
                ],
              ),
            ),
          ),
        ),
      ],
    );
  }

  void close() {
    _focusNode.unfocus();
  }

  Future<String> open({String? text}) async {
    if (text == null) {
      _textController.clear();
    } else {
      _textController.text = text;
    }
    _focusNode.requestFocus();
    _completer = Completer<String>();
    return _completer.future;
  }
}