Widget radio
A radio button.
Radio buttons change their value attribute to
true when pressed. Radio buttons should also have a group
attribute. When a radio button is pressed, other radio buttons
in the same layout with the same group attribute change their values
to false.
Changing the value of a radio button causes it to change its appearance to indicate its value. The standard themes use the icon attribute for this purpose. If a custom icon is provided when using the standard themes, the widget's value should be indicated in some other way.