An Enhanced CCheckComboBox

• Download source files - 9 Kb
• Download demo project - 28 Kb

Introduction

I wanted a control with both the functionality of a combo and of a tree with checkboxes. Such a control would act like a combo showing a dropdown and also allowing checking and fast checking items.

By the time I finished coding I saw Magnus Egelberg's "CCheckComboBox" class, but I realize that my control has several advantages which anyway would had required the class to be completely rewrote.

My implementation (of a check list dropdown) is different from other implementations I seen, using a child, and not a popup window. Also for a better generality I use a tree, letting user see the checked items, by showing them in an edit box with a tool tip. I simulated a combo box by using an owner draw button, thus not directly deriving it from CWnd or CComboBox. I think this approach has several advantages.

To integrate these classes in a new project you would have to:

1. Add the files "Check*" to your project
2. On your form add a button with owner draw style and map it to a control
3. Change the name of the mapped control to "CCheckComboBox"

To add an item you have to specify a caption, an ID and a level. The root has the level 0 (ROOT_LEVEL). All other nodes must be added with levels greater than 0 (ROOT_LEVEL), in the order in which they appear in the full-expanded tree. At any time you can use the function "GetCheckedIDs" to get a string with all checked item's IDs on the highest level of the tree. It is also possible to get the checked IDs using the function "GetCheck".

// ADD tree items:
m_choCountries.AddString("North America");
    m_choCountries.AddString("USA",    5, ROOT_LEVEL + 2);
    m_choCountries.AddString("Canada", 6, ROOT_LEVEL + 2);
    m_choCountries.AddString("Europe");
    m_choCountries.AddString("UK",     7, ROOT_LEVEL + 2);

// CHECK all items
m_choCountries.CheckAll(TRUE);

// UNCHECK the item with ID = 6
m_choCountries.SetCheck(6, FALSE);

// GET all checked items
CString strCheckedItems = m_choCountries.GetCheckedIDs();

Any suggestions to improve this set of classes are welcome.

History

• 6 June 2002 - I let CTreeView alone interpret user keys, and introduced the OnGetDlgCode function for the combo.
• 11 Dec 2002 - In this update I fixed 2 bugs and I added a functionality.

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