Radio<T> constructor Null safety

const Radio<T>(
  1. {Key? key,
  2. required T value,
  3. required T? groupValue,
  4. required ValueChanged<T?>? onChanged,
  5. MouseCursor? mouseCursor,
  6. bool toggleable: false,
  7. Color? activeColor,
  8. MaterialStateProperty<Color?>? fillColor,
  9. Color? focusColor,
  10. Color? hoverColor,
  11. MaterialStateProperty<Color?>? overlayColor,
  12. double? splashRadius,
  13. MaterialTapTargetSize? materialTapTargetSize,
  14. VisualDensity? visualDensity,
  15. FocusNode? focusNode,
  16. bool autofocus: false}
)

Creates a material design radio button.

The radio button itself does not maintain any state. Instead, when the radio button is selected, the widget calls the onChanged callback. Most widgets that use a radio button will listen for the onChanged callback and rebuild the radio button with a new groupValue to update the visual appearance of the radio button.

The following arguments are required:

  • value and groupValue together determine whether the radio button is selected.
  • onChanged is called when the user selects this radio button.

Implementation

const Radio({
  Key? key,
  required this.value,
  required this.groupValue,
  required this.onChanged,
  this.mouseCursor,
  this.toggleable = false,
  this.activeColor,
  this.fillColor,
  this.focusColor,
  this.hoverColor,
  this.overlayColor,
  this.splashRadius,
  this.materialTapTargetSize,
  this.visualDensity,
  this.focusNode,
  this.autofocus = false,
}) : assert(autofocus != null),
     assert(toggleable != null),
     super(key: key);