如何在 Flutter 中的新 OutlinedButton 小部件上实现圆角？

Question

With Flutter 1.22 we received a new widget OutlinedButton which is made to replace OutlineButton but how we can actually make its border rounded? borderSide and shape properties are not available anymore.

Answer 1

You can use OutlinedButton.styleFrom property:

OutlinedButton(
   style: OutlinedButton.styleFrom(
      shape: RoundedRectangleBorder(
         borderRadius: BorderRadius.circular(18.0),
      ),
      side: BorderSide(width: 2, color: Colors.green),
   ),
   onPressed: () {},
   child: Text('Button'),
)

From the source code

 /// All parameters default to null, by default this method returns
 /// a [ButtonStyle] that doesn't override anything.
 ///
 /// For example, to override the default shape and outline for an
 /// [OutlinedButton], one could write:
 ///
 /// ```dart
 /// OutlinedButton(
 ///   style: OutlinedButton.styleFrom(
 ///      shape: StadiumBorder(),
 ///      side: BorderSide(width: 2, color: Colors.green),
 ///   ),
 /// )
 /// ```

Answer 2

Screenshot:

If you need some extra control over the style like border should be ABC when the button is pressed, DEF when its hovered... XYZ when not interacted, you can use ButtonStyle .

OutlinedButton(
  onPressed: () {},
  style: ButtonStyle(
    shape: MaterialStateProperty.resolveWith<OutlinedBorder?>((states) {
      // Rounded button (when the button is pressed)
      if (states.contains(MaterialState.pressed)) {
        return RoundedRectangleBorder(borderRadius: BorderRadius.circular(20));
      }
    }),
  ),
  child: Text('OutlinedButton'),
)