[Overview][Constants][Types][Classes][Procedures and functions][Index] Reference for unit 'StdCtrls' (#lcl)

TRadioButton

[Properties (by Name)] [Methods (by Name)] [Events (by Name)]

Implement a radio button control.

Declaration

Source position: stdctrls.pp line 1491

type TRadioButton = class(TCustomCheckBox)

protected

  class procedure WSRegisterClass; override;

  

Registers this component class with the current WidgetSet.

  procedure ApplyChanges; override;

  

Updates the state for sibling radio buttons in the parent.

  function DialogChar(); override;

  

Implements support for an accelerator key in the control.

  procedure RealSetText(); override;

  

Sets the value for the text and/or caption in the control.

  procedure DoClickOnChange; override;

  

Performs actions needed when the control has been changed using a mouse click.

  procedure CreateParams(); override;

  

Initializes the creation parameters for the class instance.

public

  constructor Create(); override;

  

Constructor for the class instance.

published

  property Align: TAlign;

  

Specifies the placement of the control inside its Parent.

  property Alignment: TLeftRight;

  

Indicates the alignment for the caption text in the control.

  property Anchors: TAnchors;

  

The set of anchor definitions for this control.

  property AutoSize: Boolean;

  

Enables or disables auto-sizing the control to its content.

  property BidiMode: TBiDiMode;

  

Customization (of text controls) in bidirectional reading environments.

  property BorderSpacing: TControlBorderSpacing;

  

Determines the inner and outer border spacing for this control.

  property Caption: TCaption;

  

The text describing the control to the user.

  property Checked: Boolean;

  

Indicates the checked state for the control.

  property Color: TColor;

  

The background color of the control.

  property Constraints: TSizeConstraints;

  

The minimum and maximum Width and Height for the control.

  property DoubleBuffered: Boolean;

  

Allows to reduce flicker in the painting of the control.

  property DragCursor: TCursor;

  

The cursor shape shown while the control is dragged.

  property DragKind: TDragKind;

  

The operation when the control is dragged - Drag or Dock.

  property DragMode: TDragMode;

  

Allows the user to drag the control.

  property Enabled: Boolean;

  

Determines whether the control reacts on mouse or keyboard input.

  property Font: TFont;

  

The font to be used for text display in this control.

  property Hint: TTranslateString;

  

The text to show in the Hint window for the control.

  property OnChange: TNotifyEvent;

  

Event handler for changes to properties in the control.

  property OnChangeBounds: TNotifyEvent;

  

Event handler for a change of the Bounds of the control.

  property OnClick: TNotifyEvent;

  

Notification handler for mouse clicks.

  property OnContextPopup: TContextPopupEvent;

  

Invoked when a context-sensitive pop-up menu is requested.

  property OnDragDrop: TDragDropEvent;

  

This handler determines the action on an drop onto this control, in a drag-drop operation.

  property OnDragOver: TDragOverEvent;

  

Event handler for a control being dragged over this control.

  property OnEndDrag: TEndDragEvent;

  

Notification handler for the end of a dragging operation.

  property OnEnter: TNotifyEvent;

  

Handler for control receiving the focus.

  property OnExit: TNotifyEvent;

  

Handler for control loosing the focus; This is a good place for checking the finished user input.

  property OnKeyDown: TKeyEvent;

  

Handler for keyboard key pressed.

  property OnKeyPress: TKeyPressEvent;

  

Handler for a character entered by the user.

  property OnKeyUp: TKeyEvent;

  

Handler for keyboard key released.

  property OnMouseDown: TMouseEvent;

  

Event handler for mouse button going down.

  property OnMouseEnter: TNotifyEvent;

  

Event handler for mouse entering the area of the control.

  property OnMouseLeave: TNotifyEvent;

  

Event handler for mouse leaving the area of the control.

  property OnMouseMove: TMouseMoveEvent;

  

Event handler for mouse movement within the control.

  property OnMouseUp: TMouseEvent;

  

Event handler for mouse button going up.

  property OnMouseWheel: TMouseWheelEvent;

  

Event handler for mouse wheel turned.

  property OnMouseWheelDown: TMouseWheelUpDownEvent;

  

Event handler for downward movement of mouse wheel.

  property OnMouseWheelUp: TMouseWheelUpDownEvent;

  

Event handler for upward movement of the mouse wheel.

  property OnResize: TNotifyEvent;

  

Notification handler for a resize of the control.

  property OnStartDrag: TStartDragEvent;

  

Event handler for the start of a dragging operation.

  property ParentBidiMode: Boolean;

  

Allows to use the BiDiMode settings in the Parent control. Default is true.

  property ParentColor: Boolean;

  

Use the Color from the Parent control, when enabled.

  property ParentDoubleBuffered: Boolean;

  

Value from the DoubleBuffered property in a Parent control.

  property ParentFont: Boolean;

  

If true, the Font of the control will be the same as the one from the Parent. Default is true.

  property ParentShowHint: Boolean;

  

If true, the value of ShowHint for the control will be the same as the one from the Parent. Default is true.

  property PopupMenu: TPopupMenu;

  

A context-sensitive menu that pops up when the right mouse button is clicked over this control.

  property ShowHint: Boolean;

  

Enables the Hint display.

  property TabOrder: TTabOrder;

  

Determines the sequence of control navigation when the user presses the Tab key.

  property TabStop: Boolean;

  

Enables navigation using the Tab key.

  property Visible: Boolean;

  

Allows the control, and all of its children, to be displayed or hidden.

end;

Inheritance

TRadioButton

  

Implement a radio button control.

|

TCustomCheckBox

  

The base class for a check box component.

|

TButtonControl

  

Specifies a base class for button controls.

|

TWinControl

  

The base class for controls which can contain other (child) controls.

|

TControl

  

The base class for visible controls.

|

TLCLComponent

  

The base class for LCL components which have an associated widget.

|

TComponent

?

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

  

How to use StdCtrls, ComCtrls or ExtCtrls.

TRadioGroup

  

TRadioGroup is a group of related but mutually exclusive radio buttons, requiring the user to select one of a set of alternatives.

Example

{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;
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