Delphi bug (Hate to say bug, hope anyone else can say something else)

[Nordlund]

Hi there mates.

I've tripped over a bug in Delphi 5, 6, 7.
I don't know if it's really a bug, but the behaivor is really strange.

I'm using a TSpeedButton, and in the OnClick event I change the checked property of a TRadioButton. Then I show a message with the procedure "ShowMessage". When closing the message, the newly checked Radiobutton i not checked anymore.

Make a new Application and replace the content in uni1.pas and see for you self...

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Buttons, StdCtrls;

type
  TForm1 = class(TForm)
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    SpeedButton1: TSpeedButton;
    procedure SpeedButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
  RadioButton2.Checked := true;
  ShowMessage('Radiobutton 2 became checked! Or?');
end;

end.

//Nordlund

 

[GHolden]

Hi,

This happens because the first radiobutton becomes re-checked because it recieves the focus after you click the okay on the message box (which is the same as clicking on it). To illustrate add a bit button (or any other control) and set focus to it like this...

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Buttons, StdCtrls;

type
  TForm1 = class(TForm)
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    SpeedButton1: TSpeedButton;
    BitBtn1: TBitBtn;
    procedure SpeedButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
  RadioButton2.Checked := true;
  BitBtn1.SetFocus;
  ShowMessage('Radiobutton 2 became checked! Or?');

end;

end.

The problem goes away...


There are two ways to write error-free programs; only the third one works.

 

[Nordlund]

Yes. But is it correct to let the focused Checkbox be checked when giving it focus?
Then the checked property will be "obsolete".

Normally, the focus property and the checked property follow each other lika brother and sister, but you can separate checked and focused by holding down the mousepointer in the nonchecked radiobutton and drag away from the component....

I think the TRadioButton acts a little weird. (In my eyes at least)

//Nordlund

 

[GHolden]

I agree that it does seem odd behaviour, not sure if it's by design or a bug. Can't think of a good reason for it to be that way.....



There are two ways to write error-free programs; only the third one works.

 

[Nordlund]

Conclusion:
...If anyone has a strange TRadiobutton problem, remember this thread...

//Nordlund

 

[DelphiAaron]

try using a checkbox instead of a radiobutton, they dont check with focus.

Aaron Taylor
John Mutch Electronics

http://www.jme.com.au

 

[buho]

If memory serves, it is not a Delphi "feature" but a Win "feature" (bug).

Bill, in His Infinite Knowledge wanted it to work the way it works.

buho (A).