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...change the OnClick behavior of a TRadioButton, TCombobox?
Autor: P. Below
Homepage: http://www.teamb.com
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Tip Rating (6):  
     


// Q: It appears that programatically setting Item.Index for the Radio Button
// fires the onClick event.  It also appears  doing the same for the
// ComboBox does NOT fire the OnClick event. Does another property the two
// control effect this behavior.

// A: No, it is caused by the way Windows sends the notifications that fire the
// event when the control state is changed by a program action.

// Q: I have an instance where I need each of
// the control to exhibit the opposite behavior.

// A: For a TRadiobutton you can disconnect the OnClick handler, change the
// state, then reconnect the handler.

procedure ChangeRadiobuttonState(ARadiobutton: TRadiobutton;
  checkit: Boolean);
var
  
oldhandler: TNotifyEvent;
begin
  
oldhandler := ARadiobutton.Onclick;
  ARadiobutton.Onclick := nil;
  ARadiobutton.Checked := checkit;
  ARadiobutton.OnClick := oldhandler;
end;


// To make the combobox "click" after setting the item index simply call its
// Click method. The control inherits this method from TControl, but it is
// protected. So you need a bit of hoop-jumping:

Type
  
TComboCracker = class(TCombobox);

procedure SetComboboxIndex(ACombobox: TCombobox; Index: Integer);
begin
  
ACombobox.ItemIndex := Index;
  TCombocracker(ACombobox).Click;
end;


 

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