[flutter] Button Width Match Parent

After some research, I found out some solution, and thanks to @Günter Zöchbauer,

I used column instead of Container and

set the property to column CrossAxisAlignment.stretch to Fill match parent of Button

    new Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                new RaisedButton(
                  child: new Text(
                      "Submit",
                      style: new TextStyle(
                        color: Colors.white,
                      )
                  ),
                  colorBrightness: Brightness.dark,
                  onPressed: () {
                    _loginAttempt(context);
                  },
                  color: Colors.blue,
                ),
              ],
            ),