how to create toolbar searchview in flutter

Screenshot (Null safe):

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You should use SearchDelegate which comes out of the box with Flutter. Here is a small video how it works:

Full code:

class SearchPage extends StatefulWidget {
  @override
  _SearchPageState createState() => _SearchPageState();
}

class _SearchPageState extends State<SearchPage> {
  String? _result;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Search')),
      body: Center(
        child: Column(
          children: <Widget>[
            Text(_result ?? '', style: TextStyle(fontSize: 18)),
            ElevatedButton(
              onPressed: () async {
                var result = await showSearch<String>(
                  context: context,
                  delegate: CustomDelegate(),
                );
                setState(() => _result = result);
              },
              child: Text('Search'),
            ),
          ],
        ),
      ),
    );
  }
}

class CustomDelegate extends SearchDelegate<String> {
  List<String> data = nouns.take(100).toList();

  @override
  List<Widget> buildActions(BuildContext context) => [IconButton(icon: Icon(Icons.clear), onPressed: () => query = '')];

  @override
  Widget buildLeading(BuildContext context) => IconButton(icon: Icon(Icons.chevron_left), onPressed: () => close(context, ''));

  @override
  Widget buildResults(BuildContext context) => Container();

  @override
  Widget buildSuggestions(BuildContext context) {
    var listToShow;
    if (query.isNotEmpty)
      listToShow = data.where((e) => e.contains(query) && e.startsWith(query)).toList();
    else
      listToShow = data;

    return ListView.builder(
      itemCount: listToShow.length,
      itemBuilder: (_, i) {
        var noun = listToShow[i];
        return ListTile(
          title: Text(noun),
          onTap: () => close(context, noun),
        );
      },
    );
  }
}

If you want a simple search bar, you can do it with a customized TextField

import 'package:flutter/material.dart';

class SearchBar extends StatelessWidget {
  final void Function(String) onTextChange;

  SearchBar({ this.onTextChange });

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 50,
      padding: EdgeInsets.all(8),
      child: TextField(
        onChanged: onTextChange,
        decoration: InputDecoration(
          fillColor: Colors.black.withOpacity(0.1),
          filled: true,
          prefixIcon: Icon(Icons.search),
          hintText: 'Search something ...',
          border: OutlineInputBorder(borderRadius: BorderRadius.circular(10), borderSide: BorderSide.none),
          contentPadding: EdgeInsets.zero
        )
      )
    );
  }
}

You just need to alternate between the state whenever the user taps on the icon. Beside a little bit of refactoring an code cleaning on your side, this simple example should get you going.

class SearchAppBar extends StatefulWidget {
  @override
  _SearchAppBarState createState() => new _SearchAppBarState();
}

class _SearchAppBarState extends State<SearchAppBar> {
  Widget appBarTitle = new Text("AppBar Title");
  Icon actionIcon = new Icon(Icons.search);
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        centerTitle: true,
        title:appBarTitle,
        actions: <Widget>[
          new IconButton(icon: actionIcon,onPressed:(){
          setState(() {
                     if ( this.actionIcon.icon == Icons.search){
                      this.actionIcon = new Icon(Icons.close);
                      this.appBarTitle = new TextField(
                        style: new TextStyle(
                          color: Colors.white,

                        ),
                        decoration: new InputDecoration(
                          prefixIcon: new Icon(Icons.search,color: Colors.white),
                          hintText: "Search...",
                          hintStyle: new TextStyle(color: Colors.white)
                        ),
                      );}
                      else {
                        this.actionIcon = new Icon(Icons.search);
                        this.appBarTitle = new Text("AppBar Title");
                      }


                    });
        } ,),]
      ),
    );
  }
}

With the help @aziza answer i write detail code snippet of search view with list filter below. it will help for others

import 'package:flutter/material.dart';

class SearchList extends StatefulWidget {
  SearchList({ Key key }) : super(key: key);
  @override
  _SearchListState createState() => new _SearchListState();

}

class _SearchListState extends State<SearchList>
{
  Widget appBarTitle = new Text("Search Sample", style: new TextStyle(color: Colors.white),);
  Icon actionIcon = new Icon(Icons.search, color: Colors.white,);
  final key = new GlobalKey<ScaffoldState>();
  final TextEditingController _searchQuery = new TextEditingController();
  List<String> _list;
  bool _IsSearching;
  String _searchText = "";

  _SearchListState() {
    _searchQuery.addListener(() {
      if (_searchQuery.text.isEmpty) {
        setState(() {
          _IsSearching = false;
          _searchText = "";
        });
      }
      else {
        setState(() {
          _IsSearching = true;
          _searchText = _searchQuery.text;
        });
      }
    });
  }

  @override
  void initState() {
    super.initState();
    _IsSearching = false;
    init();

  }

  void init() {
    _list = List();
    _list.add("Google");
    _list.add("IOS");
    _list.add("Andorid");
    _list.add("Dart");
    _list.add("Flutter");
    _list.add("Python");
    _list.add("React");
    _list.add("Xamarin");
    _list.add("Kotlin");
    _list.add("Java");
    _list.add("RxAndroid");
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: key,
      appBar: buildBar(context),
      body: new ListView(
        padding: new EdgeInsets.symmetric(vertical: 8.0),
        children: _IsSearching ? _buildSearchList() : _buildList(),
      ),
    );
  }

  List<ChildItem> _buildList() {
    return _list.map((contact) => new ChildItem(contact)).toList();
  }

  List<ChildItem> _buildSearchList() {
    if (_searchText.isEmpty) {
      return _list.map((contact) => new ChildItem(contact))
          .toList();
    }
    else {
      List<String> _searchList = List();
      for (int i = 0; i < _list.length; i++) {
        String  name = _list.elementAt(i);
        if (name.toLowerCase().contains(_searchText.toLowerCase())) {
          _searchList.add(name);
        }
      }
      return _searchList.map((contact) => new ChildItem(contact))
          .toList();
    }
  }

  Widget buildBar(BuildContext context) {
    return new AppBar(
        centerTitle: true,
        title: appBarTitle,
        actions: <Widget>[
          new IconButton(icon: actionIcon, onPressed: () {
            setState(() {
              if (this.actionIcon.icon == Icons.search) {
                this.actionIcon = new Icon(Icons.close, color: Colors.white,);
                this.appBarTitle = new TextField(
                  controller: _searchQuery,
                  style: new TextStyle(
                    color: Colors.white,

                  ),
                  decoration: new InputDecoration(
                      prefixIcon: new Icon(Icons.search, color: Colors.white),
                      hintText: "Search...",
                      hintStyle: new TextStyle(color: Colors.white)
                  ),
                );
                _handleSearchStart();
              }
              else {
                _handleSearchEnd();
              }
            });
          },),
        ]
    );
  }

  void _handleSearchStart() {
    setState(() {
      _IsSearching = true;
    });
  }

  void _handleSearchEnd() {
    setState(() {
      this.actionIcon = new Icon(Icons.search, color: Colors.white,);
      this.appBarTitle =
      new Text("Search Sample", style: new TextStyle(color: Colors.white),);
      _IsSearching = false;
      _searchQuery.clear();
    });
  }

}

class ChildItem extends StatelessWidget {
  final String name;
  ChildItem(this.name);
  @override
  Widget build(BuildContext context) {
    return new ListTile(title: new Text(this.name));
  }

}

Output :