public class RadioButton
extends CheckButton

A special kind of CheckButton used to select from a mutually exclusive set of options.

A RadioButton is somewhat similar to a CheckButton, but it is shown as an empty circle (rather than an empty square) and the selected Button in the group us shown with a dot inside (rather than a check mark).

However, while a CheckButton can be used alone to choose between two states, a RadioButton is used together in a group of other (related) RadioButtons to offer a choice of one of those Buttons. Only a single Button in a group can the active at any one time.

To create a group of RadioButtons, you first create a RadioGroup and then construct the RadioButtons passing them that group object.

 RadioGroup group;
 RadioButton opt1, opt2, opt3;
 
 group = new RadioGroup();
 
 opt1 = new RadioButton(group, "Option _1");
 opt2 = new RadioButton(group, "Option _2");
 opt3 = new RadioButton(group, "Option _3");
 

You can get the active option at any time with RadioButtonGroup's getActive() method. And while you can still connect a handler to the ToggleButton's TOGGLED signal, the GROUP_TOGGLED signal is provided as a convenience.

You should generally place related RadioButtons together, better if disposed vertically, as this makes them easier to scan visually - in other words, pack them into a VBox. It is also frequently a good idea to place a descriptive Label at the top of the Container holding the RadioButtons. A Frame is a possible way to fit both requirements, as you can use it to place the RadioButtons altogether with a Label at the top:

 Frame option;
 VBox buttons;
 
 // Create a Frame with a descriptive Label and without outline...
 option = new Frame("Option:");
 option.setBorderWidth(3);
 option.setShadowType(ShadowType.NONE);
 
 // ... and with a VBox to layout the RadioButtons
 buttons = new VBox(false, 2);
 option.add(buttons);
 
 buttons.add(opt1);
 buttons.add(opt2);
 buttons.add(opt3);
 

In your applications you will usually use RadioButtons you have two or more mutually exclusive values for an option. Note that if such values are equivalent to the concept of enable/disable a given option, CheckButton or ToggleButton are probably a better alternative. In the same way, if you have too many possible values, you should consider using a ComboBox instead, or even think about the possibility of simplifying your user interface.