TRadioGroup: what changed

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Title: TRadioGroup

New		Line
1	+	A TRadioGroup ![](/wiki-images/e/e8/Tradiogroup.png) is a group of related but mutually exclusive [[TRadioButton\|TRadioButtons]], requiring the user to select one of a set of alternatives. It's like a [[TGroupBox]] with integrated [[TRadioButton\|TRadioButtons]].
2	+
3	+	## Usage
4	+
5	+	To use a TRadioGroup on a [[TForm\|form]], you can simply select it on the [[Standard tab]] of the [[Component Palette]] and place it by clicking on the form.
6	+
7	+	### Small example
8	+
9	+	Geometric figures should be drawn randomly and depending on the TRadioGroups to the form. The first RadioGroup determines the shape, the second RadioGroup detrmines the number.
10	+
11	+	- create a new application and place two TRadioGroups on your form
12	+	- change in the Object Inspector the [[Property\|property]] Name of RadioGroup1 to rgShape, also RadioGroup2 to rgCount
13	+	- change identical Caption of rgShape to Shape and that of rgCount to Count
14	+	- add the RadioButtons for rgShape:
15	+	- in the Object Inspector select the property Items of rgShape
16	+	- click on the button \[...\], the character chain editor opens
17	+	- write among each other Lines Rectangles Ellipses and complete the entry with the button OK
18	+	- add identical the RadioButtons for rgCount (written among each other): 1 5 10 20 50 100
19	+	- set the first RadioButton as the currently selected, by setting the property ItemIndex of rgShape and rgCount from -1 to 0
20	+	- create the OnClick event handler of rgShape by double clicking rgShape
21	+	- also use these event handler for rgCount:
22	+	- in the Object Inspector select rgCount
23	+	- now select the tab Events in the Object Inspector
24	+	- go to the OnClick event and select in the adjacent ComboBox rgShapeClick
25	+	- whenever rgShape or rgCount is clicked, the form should be redrawn, therefore write following code in the event handler:
26	+
27	+	``` pascal
28	+	procedure TForm1.rgShapeClick(Sender: TObject);
29	+	begin
30	+	Repaint;
31	+	end;
32	+	```
33	+
34	+	- whenever the form is redrawn, the shapes should be drawn:
35	+	- in the Object Inspector select Form1
36	+	- select the tab Events
37	+	- click on the button \[...\] next to the event OnPaint
38	+	- the handler is created, enter the following code:
39	+
40	+	``` pascal
41	+	procedure TForm1.FormPaint(Sender: TObject);
42	+	var
43	+	i: Integer;
44	+	begin
45	+	if TryStrToInt(rgCount.Items[rgCount.ItemIndex], i) then
46	+	for i:=1 to i do begin
47	+	Canvas.Pen.Color:=Random($1000000);
48	+	Canvas.Brush.Color:=Random($1000000);
49	+	case rgShape.Items[rgShape.ItemIndex] of
50	+	'Lines': Canvas.Line(Random(ClientWidth), Random(ClientHeight), Random(ClientWidth), Random(ClientHeight));
51	+	'Rectangles': Canvas.Rectangle(Random(ClientWidth), Random(ClientHeight), Random(ClientWidth), Random(ClientHeight));
52	+	'Ellipses': Canvas.Ellipse(Random(ClientWidth), Random(ClientHeight), Random(ClientWidth), Random(ClientHeight));
53	+	end;
54	+	end;
55	+	end;
56	+	```
57	+
58	+	- start your program, it could look like:
59	+
60	+	![](/wiki-images/6/6a/ExampleTRadioGroup.png)
61	+
62	+	## See also
63	+
64	+	- [[doc:lcl/extctrls/tradiogroup.html\|TRadioGroup doc]]
65	+	- [[TRadioButton]]
66	+	- [[TGroupBox]]
67	+
68	+	---
69	+	From the Free Pascal wiki, page "TRadioGroup", as it stood on 2022-04-17 after a change by Bart, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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