Setting TRadioButton to checked causes OnClick event

Question

mybox.Checked := true;

Setting TRadioButton to checked (by code) causes OnClick event handler to be called.

How can I recognize if user is making the state change by GUI interaction

score 11 · Accepted Answer · answered May 18 '10 at 12:47

11

You can nil the OnClick event handler while changing a radiobutton state programmatically:

procedure TForm1.Button6Click(Sender: TObject);
var
  Save: TNotifyEvent;

begin
  Save:= RadioButton2.OnClick;
  RadioButton2.OnClick:= nil;
  RadioButton2.Checked:= not RadioButton2.Checked;
  RadioButton2.OnClick:= Save;
end;

answered May 18 '10 at 12:47

kludg

27,213
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2

Ideally you should wrap this in a try..finally if there was any more complex logic between `OnClick := nil` and `OnClick := Save;` – Gerry Coll May 18 '10 at 22:20

score 4 · Answer 2 · answered May 18 '10 at 12:42

4

 mybox.Tag := 666; 
 mybox.Checked :=true; 
 mybox.Tag := 0;

procedure myboxOnclick(Sender : TObject);
begin
if Tag = 0 then
//Do your thing
end;

answered May 18 '10 at 12:42

Mihaela

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27

I favor this approach but usually use an flag in the private section of the form class, something along the lines of "ChangingStuffRomCode:Boolean". The idea's that there usually are multiple radio buttons (and other controls that behave like this) and it's simpler to do set a single flag when initializing the form. – Cosmin Prund May 19 '10 at 09:58

score 3 · Answer 3 · answered May 18 '10 at 14:12

3

If you have an action connected to the radiobutton, you can set the checked property of the action instead. This will also prevent the OnClick event to be fired.

answered May 18 '10 at 14:12

Uwe Raabe

45,288
3
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130

But if you're using actions, you're probably using the action's OnExecute event, not the control's OnClick event. Does OnExecute get fired when you change the action's Checked property? – Rob Kennedy May 18 '10 at 14:29
1

@Rob Kennedy: No, it does not - Action.OnExecute and Button.OnClick is the same event here. An action temporally sets the radiobutton's protected 'ClicksDisabled' property to True to prevent radiobutton's 'OnClick' event to fire while changing 'Checked' property. – kludg May 18 '10 at 14:53

score 0 · Answer 4 · answered Jan 15 '20 at 16:02

TRadioButton (like TCheckBox) provides a protected property ClicksDisabled that can help you.

I use class helpers to add the needed functionality:

RadioButton1.SetCheckedWithoutClick(False);

with the following class helper for a VCL TRadioButton:

TRadioButtonHelper = class helper for TRadioButton
    procedure SetCheckedWithoutClick(AChecked: Boolean);
end;

procedure TRadioButtonHelper.SetCheckedWithoutClick(AChecked: Boolean);
begin
    ClicksDisabled := True;
    try
        Checked := AChecked;
    finally
        ClicksDisabled := False;
    end;
end;

Setting TRadioButton to checked causes OnClick event

4 Answers4