When I click text fields on the main page (main.dart) which is the default dart given by the flutter. I can see a glitch when soft keyboard appears and there is no delay when soft keyboard disappears.I have attached a gif below for this case.
void main() {
 SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle(
 statusBarColor: primaryColor, //blue
   statusBarIconBrightness: Brightness.dark,
));
 runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
  theme: ThemeData(
    // This is the theme of your application.
    //
    // Try running your application with "flutter run". You'll see the
    // application has a blue toolbar. Then, without quitting the app, try
    // changing the primarySwatch below to Colors.green and then invoke
    // "hot reload" (press "r" in the console where you ran "flutter run",
    // or simply save your changes to "hot reload" in a Flutter IDE).
    // Notice that the counter didn't reset back to zero; the application
    // is not restarted.
    primarySwatch: Colors.pink,
    primaryColor: primaryColor,
    primaryColorBrightness: Brightness.dark,
  ),
  home: MyHomePage(title: 'Flutter Demo Home Page'),
);
  }
class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.
  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".
  final String title;
  @override
  _MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  void _incrementCounter() {
    // setState(() {
    //   // This call to setState tells the Flutter framework that something has
    //   // changed in this State, which causes it to rerun the build method below
    //   // so that the display can reflect the updated values. If we changed
    //   // _counter without calling setState(), then the build method would not be
    //   // called again, and so nothing would appear to happen.
    //   _counter++;
    // });
    setState(() {
      Navigator.push(
          context,
          MaterialPageRoute(builder: (context) => PhoneAuth()));
    });
  }
  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      backgroundColor: Colors.red,
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text('hell0000000'),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Container(
          color: Colors.white,
          child: ListView(
            children: [
              Column(
                children: <Widget>[
                  Text(
                    'You have pushed the button this many times:',
                  ),
                  Text(
                    '$_counter',
                    style: Theme.of(context).textTheme.headline4,
                  ),
                  SizedBox(
                    height: 200,
                  ),
                  Align(
                    alignment: Alignment.bottomCenter,
                    child: new Container(
                      child: TextField(
                        decoration: new InputDecoration(
                          hintText: 'Chat message',
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ],
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
main.dart glich
Also, When I click text fields on the other page (UserChatView.dart). I can see a glitch when soft keyboard appearing and disappearing. In this dart file, That glitch happening for both actions(Keyboard opening and closing). I have attached a gif below for this case.
class UserChatView extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
      return UserChatViewPage();
  }
}
class UserChatViewPage extends StatefulWidget {
  UserChatViewPage({Key key}) : super(key: key);
  @override
  _UserChatViewPageState createState() =>  _UserChatViewPageState();
}
class _UserChatViewPageState extends State<UserChatViewPage> {
  final TextEditingController _textController = new TextEditingController();
  @override
  Widget build(BuildContext context) {
    final focus = FocusNode();
    return new Scaffold(
      backgroundColor: Colors.red, // Scaffold background Color
      appBar: new AppBar(
        title: Row(
          children: <Widget>[
            // new Container(
            //     child: CircleAvatar(
            //       backgroundImage: AssetImage("assets/male_icon.png"),
            //     )
            // ),
            new SizedBox(
              width: 5.00,
            ),
            new Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget> [
                new Container(
                  child: new Text("Alex Marko",
                    style: TextStyle(color: Colors.white,
                        fontFamily: 'Roboto_Bold',
                        letterSpacing: 1.00
                    ),
                  ),
                ),
                new Container(
                  child: new Text("Online",
                    style: TextStyle(color: Colors.white,
                      fontFamily: 'Roboto_Medium',
                      letterSpacing: 1.00,
                      fontSize: 12.00,
                    ),
                  ),
                ),
              ],
            ),
          ],
        ),
        centerTitle: false,
        titleSpacing: 0.0,
        backgroundColor: primaryColor,
        elevation: 0.0,
        bottomOpacity: 0.0,
        actions: <Widget>[
          IconButton(
            icon: Icon(
              Icons.expand_more_rounded,
              color: Colors.white,
            ),
            onPressed: () {
              // do something
            },
          ),
        ],
      ),
    body:  Center(
        child: new Container(
          color: Colors.grey,
          child: new Column(
                     children: <Widget>[
          
                            new Expanded(
                               child: _PageListView(),
                                       ),
                               new Container(
                                 color: Colors.yellow,
                                               padding: new EdgeInsets.all(10.0),
                                      child: _buildTextComposer(),
                                                ),
                                          ],
                                       ),
                                     ),
                                    ),
                                  );
}
Widget _buildTextComposer() {
    return new Container(
      color: Colors.yellow,//modified
        margin: const EdgeInsets.symmetric(horizontal: 8.0),
        child: new Row(
          children: <Widget>[
            new Flexible(
              child: new TextField(
                controller: _textController,
                onSubmitted: _handleSubmitted,
                decoration: new InputDecoration.collapsed(
                    hintText: "Send a message"),
              ),
            ),
            new Container(
              margin: new EdgeInsets.symmetric(horizontal: 4.0),
              child: new IconButton(
                  icon: new Icon(Icons.send),
                  onPressed: () => _handleSubmitted(_textController.text)),
            ),
          ],
        ),
      );                                                            
  }
 Widget _PageListView(){
    return new Container(
    child: ListView.builder(
      reverse: true,
      itemCount: 20,
      itemBuilder: (context, position) {
        return Card(
          child: Padding(
            padding: const EdgeInsets.all(16.0),
            child: Text(position.toString(), style: TextStyle(fontSize: 22.0),),
          ),
        );
      },
    ),
    );
  }
UserChatView.dart Glich


 
     
    