how to get full width for button in flutter code example

Example: raisedbutton full width flutter

FractionallySizedBox(
   widthFactor: 1, // means 100%, you can change this to 0.8 (80%)
     child: RaisedButton.icon(
     onPressed: () {
     	print(comment);
     },
     label: Text('Edit Comment', style: TextStyle(color: Colors.white)),
     icon: Icon(Icons.check, color: Colors.white),
     ),
 ),