How to achieve expansion of a widget in both vertical (height) and horizontal (width) direction

Question

The code below lays out a chart in which I\'d need to achieve for the chart to be expanded in both vertical (height) and horizontal (width) direction. The suggested method (e.g.

Answer 1

For those who struggled to get gradient together with Material behaviour:

return new Stack(
  children: [
    new Material(
      elevation: 10,
      borderRadius: new BorderRadius.all(new Radius.circular(30.0)),
      color: Colors.transparent,
      child: new Container(
        constraints: BoxConstraints.expand(height: 50),
      ),
    ),
    new Container(
      constraints: BoxConstraints.expand(height: 50),
      decoration: BoxDecoration(
        borderRadius: new BorderRadius.all(new Radius.circular(30.0)),
        gradient: new LinearGradient(
            colors: [color1, color2],
            begin: Alignment.topCenter,
            end: Alignment.bottomCenter),
      ),
      child: new FloatingActionButton.extended(
        backgroundColor: Colors.transparent,
        foregroundColor: Colors.transparent,
        highlightElevation: 0,
        elevation: 0,
        onPressed: () {
          onPressed();
        },
        label: new Text(this.caption,
            textAlign: TextAlign.center,
            style: Theme.of(context).textTheme.body1),
      ),
    )
  ],
)