Adding a border to a widget in Flutter

Suragch

Dec 30, 2018·3 min read

This is a repost of an answer I wrote on Stack Overflow.

There are a couple ways to add a border to a Flutter widget. The most basic way is to wrap your widget in a DecoratedBox. However, the Container widget also has a DecoratedBox built in. In the following examples I will use Container for the convenience of adding margin and padding.

Here is the general setup.

Widget myWidget() {
  return Container(
    margin: const EdgeInsets.all(30.0),
    padding: const EdgeInsets.all(10.0),
    decoration: myBoxDecoration(), //       <--- BoxDecoration here
    child: Text(
      "text",
      style: TextStyle(fontSize: 30.0),
    ),
  );
}

where the BoxDecoration is

BoxDecoration myBoxDecoration() {
  return BoxDecoration(
    border: Border.all(),
  );
}

Border width

These have a border width of 1, 3, and 10 respectively.

BoxDecoration myBoxDecoration() {
  return BoxDecoration(
    border: Border.all(
      width: 1, //                   <--- border width here
    ),
  );
}

Border color

These have a border color of

• Colors.red
• Colors.blue
• Colors.green

Code

BoxDecoration myBoxDecoration() {
  return BoxDecoration(
    border: Border.all(
      color: Colors.red, //                   <--- border color
      width: 5.0,
    ),
  );
}

Border side

These have a border side of

• left (3.0), top (3.0)
• bottom (13.0)
• left (blue[100], 15.0), top (blue[300], 10.0), right (blue[500], 5.0), bottom (blue[800], 3.0)

Code

BoxDecoration myBoxDecoration() {
  return BoxDecoration(
    border: Border(
      left: BorderSide( //                   <--- left side
        color: Colors.black,
        width: 3.0,
      ),
      top: BorderSide( //                    <--- top side
        color: Colors.black,
        width: 3.0,
      ),
    ),
  );
}

Border radius

The radius affects the roundness of the corners.

These have border radii of 5, 10, and 30 respectively.

BoxDecoration myBoxDecoration() {
  return BoxDecoration(
    border: Border.all(
      width: 3.0
    ),
    borderRadius: BorderRadius.all(
        Radius.circular(5.0) //         <--- border radius here
    ),
  );
}

Going on

DecoratedBox/BoxDecoration are very flexible. Read Flutter — BoxDecoration Cheat Sheet for many more ideas.