如何将有状态小部件作为grid.tile的子项处理

Question

I am new to flutter. and I am trying to make an xo game. I am still on the very first steps of the app. I am using gridview.count to make the layout of the game. The problem is the properties of the stateful widget(choice, onTap()) is not defined in the gridview tile. This is my code

return Scaffold(
        appBar: AppBar(title: Text('Tic Tac Toe')),
        body: GridView.count(
          crossAxisCount: 3,
          crossAxisSpacing: 2.0,
          mainAxisSpacing: 2.0,
          children: List<Widget>.generate(
            9,
            (int index) {return new GridTile(
             child:GridCell(

                    choice: _choice,
                    onTap: ()=>onTap(context),
                  ),
                );
            })))

and the class is:

class GridCellState extends State<TicTacToe> {
  final String choice;
  final VoidCallback onTap;
   GridCellState({Key key, this.choice, this.onTap}) : 
  super(key: key);
   @override
  Widget build(BuildContext context) {
   return GestureDetector(
     onTap:onTap,
     child:Container(
       child: Text(choice),
       height:20.0,
       color:Theme.of(context).primaryColor,
     ),
   );
  }
}

Thanks in advance.

Answer 1

That is because you are wiring up the constructor in a wrong way, you do not construct the object from the State object, that is the job of the StatefulWidget is to construct the State object. You construct an instance of a StatefulWidget called GridCell so GridCell needs to have the fields and the constructor moved to it.

In short ,you need to move the GridCellState fields and constructor up to the StatefulWidget itself like this:

class GridCell extends StatefulWidget {
  final String choice;
  final VoidCallback onTap;

  GridCell({Key key, this.choice, this.onTap}) : 
  super(key: key);

  @override
  GridCellState createState() {
    return new GridCellState();
  }
}

and then use widget.fieldName from inside the State object to access any field in the StatefulWidget object, see I use widget.onTap and widget.choice to get fields data from my StatefulWidget above.

class GridCellState extends State<GridCell> {
  @override
  Widget build(BuildContext context) {
   return GestureDetector(
     onTap:widget.onTap,
     child:Container(
       child: Text(widget.choice),
       height:20.0,
       color:Theme.of(context).primaryColor,
     ),
   );
  }
}

Alternatively, you can just convert your GridCell to a SatelessWidget instead, both approaches will solve your issue so it depends whether you need to keep the StatefulWidget or not.