TRadioButton class

Declaration

TRadioButton = class(TCustomCheckBox)

Inheritance

1. TRadioButton
2. TCustomCheckBox
3. TButtonControl
4. TWinControl
5. TControl
6. TLCLComponent
7. TComponent
8. TPersistent
9. TObject

Description

TRadioButton is a TCustomCheckBox descendant which implements a selection button that works with other radio buttons in a mutually exclusive way. If one radio button is selected, none of the others in the group can be selected.

Ensure that the OnClick event handler for each button has a unique Action, and that Actions for the other (deselected and therefore inactive) buttons are turned off.

TRadioGroup behaves differently from a group of TRadioButton controls placed on a form.

In the case of TRadioButton, the mutual exclusivity is a feature that applies to any RadioButton anywhere in the Form, and the RadioButtons can be rearranged in any order or placed anywhere within the containing Form, while in TRadioGroup the exclusivity applies only to buttons within the Group, which are ordered strictly according to their ItemIndex within the Items stringlist.

TRadioButton is an entity in itself, with a number of additional properties, whereas the buttons within TRadioGroup are not separate entities, but rather are simply entries in a list of strings, each of which is associated with the on-screen image of a RadioButton.

The example shows the difference between the use of TRadioButton and TRadioGroup.

See also

• HowToUseStdCtrls
• TRadioGroup

Example: radiobutton.pas

{Using TRadioGroup with three entries in Items:
Index 0: Red
Index 1: Amber
Index 2: Green}

procedure TTrivialForm1.RadioGroup1Click(Sender: TObject);
begin
  case RadioGroup1.ItemIndex of
  0:   Shape1.brush.color := clRed;
  1:   Shape1.brush.color := clYellow;
  2:   Shape1.brush.color := clGreen
  end
end;



{Using three separate RadioButtons}

procedure TForm1.RadioButton1Click(Sender: TObject);
begin
  Shape1.brush.color := clRed
end;

procedure TForm1.RadioButton2Click(Sender: TObject);
begin
  Shape1.brush.color := clYellow
end;

procedure TForm1.RadioButton3Click(Sender: TObject);
begin
  Shape1.brush.color := clGreen
end;

Properties

Methods

Events

Inherited