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A selection button that works with other Radio Buttons in a mutually exclusive way - if one button is selected, none of the others in the group can be selected.
Source position: stdctrls.pp line 1421
type TRadioButton = class(TCustomCheckBox) end; |
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protected |
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class procedure WSRegisterClass; override; |
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Registers this component class with the current WidgetSet. |
procedure ApplyChanges; override; |
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Asks the widget to update the visual appearance of the object. |
function DialogChar(); override; |
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Do something useful with accelerators etc. |
procedure RealSetText(); override; |
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Sets the Caption property. |
procedure DoClickOnChange; override; |
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procedure CreateParams(); override; |
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public |
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constructor Create(); override; |
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published |
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Specifies the placement of the control inside its Parent. |
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property Alignment: TLeftRight; |
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The set of anchor definitions for this control. |
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property AutoSize: Boolean; |
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Allows to automatically adjust the size of the control, according to its content. |
property BidiMode: TBiDiMode; |
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Customization (of text controls) in bidirectional reading environments. |
property BorderSpacing: TControlBorderSpacing; |
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Determines the inner and outer border spacing for this control. |
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The text describing the control to the user. |
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property Checked: Boolean; |
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The state of the check mark. Here always False, can be implemented in derived classes. |
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The background color of the control. |
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property Constraints: TSizeConstraints; |
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The minimal and maximal Width and Height of this control. |
property DragCursor: TCursor; |
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The cursor shape shown while the control is dragged. |
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The operation when the control is dragged - Drag or Dock. |
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Allows the user to drag the control. |
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property Enabled: Boolean; |
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Determines whether the control reacts on mouse or keyboard input. |
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The font to be used for text display in this control. |
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property Hint: TTranslateString; |
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The text to show in the Hint window for this control. |
property OnChange: TNotifyEvent; |
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Handler for any change in properties of the control. |
property OnChangeBounds: TNotifyEvent; |
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Event handler for a change of the Bounds of the control. |
property OnClick: TNotifyEvent; |
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Notification handler for mouse clicks. |
property OnContextPopup: TContextPopupEvent; |
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Invoked when a context-sensitive pop-up menu is requested. |
property OnDragDrop: TDragDropEvent; |
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This handler determines the action on an drop onto this control, in a drag-drop operation. |
property OnDragOver: TDragOverEvent; |
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Event handler for a control being dragged over this control. |
property OnEndDrag: TEndDragEvent; |
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Notification handler for the end of a dragging operation. |
property OnEnter: TNotifyEvent; |
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Handler for control receiving the focus. |
property OnExit: TNotifyEvent; |
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Handler for control loosing the focus. This is a good place for checking the finished user input. |
property OnKeyPress: TKeyPressEvent; |
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property OnMouseDown: TMouseEvent; |
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Event handler for mouse button going down. |
property OnMouseEnter: TNotifyEvent; |
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Event handler for mouse entering the area of the control. |
property OnMouseLeave: TNotifyEvent; |
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Event handler for mouse leaving the area of the control. |
property OnMouseMove: TMouseMoveEvent; |
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Event handler for mouse movement within the control. |
property OnMouseUp: TMouseEvent; |
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Event handler for mouse button going up. |
property OnMouseWheel: TMouseWheelEvent; |
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property OnMouseWheelDown: TMouseWheelUpDownEvent; |
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property OnMouseWheelUp: TMouseWheelUpDownEvent; |
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property OnResize: TNotifyEvent; |
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Notification handler for a resize of the control. |
property OnStartDrag: TStartDragEvent; |
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Event handler for the start of a dragging operation. |
property ParentBidiMode: Boolean; |
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Allows to use the BiDiMode settings of Parent. Default is true. |
property ParentColor: Boolean; |
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If true, the Color of the control will be the same as the one from the Parent. Default is true. |
property ParentFont: Boolean; |
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If true, the Font of the control will be the same as the one from the Parent. Default is true. |
property ParentShowHint: Boolean; |
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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; |
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A context-sensitive menu that pops up when the right mouse button is clicked over this control |
property ShowHint: Boolean; |
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Enables the Hint display. |
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Determines the sequence of controls, reachable when the user presses the Tab key. |
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property TabStop: Boolean; |
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Allows the user to navigate to this control, by pressing the Tab key. |
property Visible: Boolean; |
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Allows to show or hide the control, and all of its children. |
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A selection button that works with other Radio Buttons in a mutually exclusive way - if one button is selected, none of the others in the group can be selected. |
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The base class for checkbox components. |
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The base class for various button controls. |
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The base class for controls which can contain other (child) controls. |
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The base class for visible controls. |
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The base class for LCL components associated with widgets. |
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TComponent |
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TObject |
The Application Programmer is responsible for ensuring that the OnClick event handler for each button has a unique Action, and that the Actions of the other (deselected and therefore inactive) buttons are turned off.
TRadioGroup behaves differently from a group of TRadioButton controls placed arbitrarily around 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
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How to use StdCtrls, ComCtrls or ExtCtrls |
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TRadioGroup : A group of related but mutually exclusive radio buttons, requiring the user to select one af a set of alternatives |
{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;
lazarus-ccr.sourceforge.net |