Main widget part 2

main_part2.dart

 @override
  Widget build(BuildContext contGameOfLifeext) {
    final screenSize = MediaQuery.of(context).size;
    _cellSize = Size(
        screenSize.width / GameOfLife.rowLength,
        (screenSize.height - kToolbarHeight) /
            (GameOfLife.worldSize / GameOfLife.rowLength));

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        actions: <Widget>[
          FlatButton(
            child: Icon(Icons.restore),
            onPressed:() {
              if(_game.running)
                _game.toggleGame();
                setState(() {
                  _game.resetWorld();    
                });
            } ,
          )
           
        ],
      ),
      body: StreamBuilder<double>(
        stream: _game.stateController.stream,
        builder: (context, snapshot) {
          return GameBoard(
            GameOfLife.cellMargin,
            _game.world,
            GameOfLife.rowLength,
            cellSize: _cellSize,
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _toggleGame,
        tooltip: 'Start/Stop',
        child: _game.running ? Icon(Icons.pause) : Icon(Icons.play_arrow),
      ),
    );
  }