combobox with custom drop down (treeview)

[Dave Novo 51]

Hello,

Does anyone have any tips how to make a combo box with a custom drop down editor? For example, I would like to have the dropdown editor be a treeview, and ideally use a virtual string tree as the dropdown editor. Is there a base class in the Delphi hiearchy that is designed for this, or examples of a working one. My google searches have not turned up a nice example.

Edited October 26, 2021 by Dave Novo

[Remy Lebeau 1394]

11 hours ago, Dave Novo said:

Does anyone have any tips how to make a combo box with a custom drop down editor?

The native VCL TComboBox does not support a custom drop down.

11 hours ago, Dave Novo said:

For example, I would like to have the dropdown editor be a treeview, and ideally use a virtual string tree as the dropdown editor.

There is nothing like that for the native VCL TComboBox, so you will have to use a 3rd party solution (for instance, TMS has a TAdvTreeComboBox component, and there is (an older) TreeComboBox available on Torry.net).  Otherwise, you would have to write your own component.

11 hours ago, Dave Novo said:

Is there a base class in the Delphi hiearchy that is designed for this

No.

[Fr0sT.Brutal 900]

I'm pretty sure there are many implementations, one of them is in EhLib. Search for "custom panel + combobox", take a look at main component packs (check awesome Delphi list in my signature). The component shouldn't be too complicated

Edited October 27, 2021 by Fr0sT.Brutal

[Turan Can 3]

Add dropdown menu and when clicked. Activate a hidden treeview menu. 

For example, I'm using a panel instead of a button because there is no color in the buttons 🙂

[davornik 4]

After searching myself for way to populate ComboBoxEx with items from TListView in order to be able to filter data I have made recursive function which iterates through all ListView data. It may be usefull.

 

procedure TForm1.btnPopulateClick(Sender: TObject);
var
  lvl: Integer;
  mNode: TTreeNode;
//--
procedure PlaceTreeItem(nTree: TTreeNode; nLvl: Integer);
var
  nIndent, nImg: Integer;
  NextNode, LastNode: TTreeNode;
begin
  nIndent:=nLvl * 2;
  if nTree.HasChildren then nImg:=0 else nImg:=1;
  ComboBoxEx1.ItemsEx.AddItem(nTree.Text, nImg, nImg, nImg, nIndent, nTree.Data);
  if nTree.HasChildren then
    begin
      Inc(lvl);
      NextNode := nTree.getFirstChild;
      LastNode := nTree.GetLastChild;
      while NextNode <> nil do begin
        PlaceTreeItem(NextNode, lvl);
        if NextNode = LastNode then Dec(lvl);
        NextNode := NextNode.getNextSibling;
      end;
    end;
end;
//--
begin
  ComboBoxEx1.Clear;
  lvl:=0;
  mNode := TreeView1.Items.GetFirstNode;
  while Assigned(mNode) do begin
    PlaceTreeItem(mNode, 0);
    mNode := mNode.getNextSibling;
  end;
end;