Models/team.dart

import 'package:flutter/foundation.dart';

class Team {
  Team({ @required this.name, this.score = 0 });

  String name;
  int score;
}

// screens/game_setup.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:game_score/models/team.dart';

class _TeamTileState extends State<_TeamTile> {
  bool _editing = false;
  TextEditingController _textFieldController;
  FocusNode _focusNode;

  @override
  void initState() {
    super.initState();
    _textFieldController = TextEditingController.fromValue(TextEditingValue(text: widget.team.name));
    _focusNode = FocusNode();
    _focusNode.addListener(() {
      if (!_focusNode.hasFocus) {
        _toggleEditing();
        widget.setTeamName(_textFieldController.text);
      }
    });
  }

  void _focusOnNode() {
    Timer(const Duration(milliseconds: 100),
            () => FocusScope.of(context).requestFocus(_focusNode));
  }

  Widget _buildShowTile() {
    return GestureDetector(
        onTap: () {
          _toggleEditing();
          _focusOnNode();
        },
        child: Text(widget.team.name)
    );
  }

  Widget _buildEditTile() {
    return TextField(controller: _textFieldController, focusNode: _focusNode);
  }

  void _toggleEditing() {
    setState(() {
      _editing = !_editing;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
        children: <Widget>[
          ListTile(
              title: _editing ? _buildEditTile() : _buildShowTile()
          ),
          Divider()
        ]
    );
  }
}

class _TeamTile extends StatefulWidget {
  _TeamTile({ @required this.team, @required Function setTeamName }) : this._setTeamName = setTeamName;
  final Function _setTeamName;
  final Team team;


  @override
  State<StatefulWidget> createState() {
    return _TeamTileState();
  }

  void setTeamName(String name) {
    _setTeamName(team, name);
  }
}


class GameSetup extends StatelessWidget {
  GameSetup({ this.teams, this.setTeamName });

  List<Team> teams;
  Function setTeamName;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: Text("Game Score App")),
        body: ListView.builder(itemCount: 3, itemBuilder: (builderContext, i) {
          if (i < 2) {
            return _TeamTile(team: teams[i], setTeamName: setTeamName);
          } else {
            return ListTile(
                onTap: () {
                  print("Starts a new game!");
                },
                title: Center(
                    child: Text("Start new game",
                        style: TextStyle(color: Colors.green)
                    )
                )
            );
          }
        })
    );
  }
}