Question

I am using a popup menu in Delphi. I want to use it in a ‘radio group’ fashion where if the user selects an item it is checked and the other items are not checked. I tried using the AutoCheck property, but this allows multiple items to be checked. Is there a way to set the popup menu so that only one item can be checked?

Answer 1

Zartog is right, but if you want to keep the checkbox, assign this event to every item in the popup menu.

Note that this code is a little hairy looking because it does not depend on knowing the name of your popup menu (hence, looking it up with ‘GetParentComponent’).

procedure TForm2.OnPopupItemClick(Sender: TObject); var   i : integer; begin   with (Sender as TMenuItem) do begin     //if they just checked something...     if Checked then begin       //go through the list and *un* check everything *else*       for i := 0 to (GetParentComponent as TPopupMenu).Items.Count - 1 do begin         if i <> MenuIndex then begin  //don't uncheck the one they just clicked!           (GetParentComponent as TPopupMenu).Items[i].Checked := False;         end;  //if not the one they just clicked       end;  //for each item in the popup     end;  //if we checked something   end;  //with end; 

You can assign the event at runtime to every popup box on your form like this (if you want to do that):

procedure TForm2.FormCreate(Sender: TObject); var   i,j: integer; begin   inherited;    //look for any popup menus, and assign our custom checkbox handler to them   if Sender is TForm then begin     with (Sender as TForm) do begin       for i := 0 to ComponentCount - 1 do begin         if (Components[i] is TPopupMenu) then begin           for j := 0 to (Components[i] as TPopupMenu).Items.Count - 1 do begin             (Components[i] as TPopupMenu).Items[j].OnClick := OnPopupItemClick;           end;  //for every item in the popup list we found         end;  //if we found a popup list       end;  //for every component on the form     end;  //with the form   end;  //if we are looking at a form end; 

In response to a comment below this answer: If you want to require at least one item to be checked, then use this instead of the first code block. You may want to set a default checked item in the oncreate event.

procedure TForm2.OnPopupItemClick(Sender: TObject); var   i : integer; begin   with (Sender as TMenuItem) do begin     //go through the list and make sure *only* the clicked item is checked     for i := 0 to (GetParentComponent as TPopupMenu).Items.Count - 1 do begin       (GetParentComponent as TPopupMenu).Items[i].Checked := (i = MenuIndex);     end;  //for each item in the popup   end;  //with end;