Expanded widgets must be placed inside Flex widgets

Question

New to flutter, can some one tells me whats wrong with below code

  class GamePage extends StatelessWidget {
  int _row;
  int _column;

  GamePage(this._row,this._column);

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.deepPurpleAccent,
      child:new Expanded(
          child:new GridView.count(crossAxisCount: _column,children: new List.generate(_row*_column, (index) {
        return new Center(
            child: new CellWidget()
        );
      }),) )


    );
  }
}

Attaching error screenshot.

Answer 1

You do not have a Flex ancestor.

An Expanded widget must be a descendant of a Row, Column, or Flex, and the path from the Expanded widget to its enclosing Row, Column, or Flex must contain only StatelessWidgets or StatefulWidgets (not other kinds of widgets, like RenderObjectWidgets).

I am not sure about the need for Expanded in your case. But removing it or wrapping it in a Column should fix the problem.

Answer 2

Crash

This crashes because Expanded is not a descendant of a Flex widget:

Container(
  child: Expanded(
    child: MyWidget(),
  ),
)

Acceptable

Here Expanded is a descendant of Flex:

Flex(
  direction: Axis.horizontal,
  children: [
    Expanded(
      child: MyWidget(),
    ),
  ],
)

Row is also a Flex widget:

Row(
  children: [
    Expanded(
      child: MyWidget(),
    ),
  ],
)

And so is Column:

Column(
  children: [
    Expanded(
      child: MyWidget(),
    ),
  ],
)

Another option is to just get rid of the Expanded widget:

Container(
  child: MyWidget(),
)