vbAccelerator TreeView Control
A fully-featured TreeView with enhanced Drag-Drop support
This article provides a new TreeView control that provides an alternative to the standard
version provided with VB. Enhancements include much wider support for item colours and formatting,
better drag-drop support including node auto-expand and scrolling, styles to support numbering
items and an IE-style history mode and an improved object model.
About the TreeView control
This control is a significantly revised version of the XuiTreeView control
written by Dan Litwin which is still available on the legacy version
of the site. This time around the control has an object model, not to mention
many bug fixes and enhancements over the last version.
This control has a similar object model to the standard VB TreeView, but with a
notable exception. In the VB TreeView, the Nodes
collection is the collection of all in the control. In
this control, the Nodes collection refers to the
collection of nodes at a particular level. In this way the object model is
more similar to the DOM interfaces provided in
XML parsers. This seems a more natural way to look at the TreeView, since now
each Node has a Children
object which can be used to access just the child nodes of that node.
The diagram below shows the object model in the control.
TreeView Object Model
Here's a brief tour of the features:
The vbalTreeViewCtl provides access to the object collections,
raises events and lets you configure the visual properties of the control.
The new and changed features are:
This allows you to associate a handle to an image list with the control rather than just
an ImageList object. This allows you to use an System Image
List as a source of icons, as shown in the demo.
Please note that MSCOMCTL.OCX (VB6 Windows Common Controls) ImageLists are not supported as the hImageList handle returned by this object is incorrect. This may be resolved in the future by an update from Microsoft (see KB).
Gets/sets whether nodes will auto-expand when you are dragging over them.
Gets/sets the drag style of the TreeView. The default drag style is etvwInsertMark. Using this
mode, the exact order of nodes within a tree can be controlled. This is useful when using a
Tree to represent hierarchies where ordering is important, such as the Favourites dialog.
Alternatively, the drag style can be set to etvwDropHighlight,
which only allows you to drop
items on a particular node in the tree. This mode is useful when the order of items in
a particular branch isn't either fixed, or isn't important, such as views of the file
- DragInsertNode, DragInsertAbove
During a drag operation, DragInsertNode returns the node which has the
insert point, if any, and DragInsertAbove returns whether the insert
location is above or below this node.
When an OLE Drag-Drop operation is performed using a Node, the control adds text format and
private internal formats to the drag Data argument. The Node
associated with this data can be extracted using this function. Note that any instance of
the TreeView control can be used, not just the source of the node that is being dragged.
If the node is from another control, it is located and the information is populated by the
Gets/sets whether custom-draw is disabled for the control. When custom draw is disabled,
the display is faster, but you cannot configure colours or formatting on a per-item
basis. Note that by default this is True.
- ShowNumber, HistoryStyle
Get/set two new styles which are provided for the control. In both cases the
NoCustomDraw flag must be set to False
in order for the mode to draw. When the ShowNumber mode is set,
any ItemNumber value above zero associated with a node is
displayed next to the item in brackets, like Outlook. If HistoryStyle
is set, then the control renders a border around the selected node tree in the same way
that IE does in the History bar. These styles are mutually exclusive.
TreeView control with Number and History styles applied
- Colour properties
When NoCustomDraw is set False, you
can set a number of default colours for the rendering of the control (these can also
be overridden for individual items). In all cases except BackColor,
ForeColor and LineColor setting a
property to -1 will mean the default colours are used.
The list of colours supported are:
Gets/sets the background colour of the control. Works regardless of the setting of the
Gets/sets the foreground colour of the control. Works regardless of the setting of the
Gets/sets the colour of the lines shown in the control. Works regardless of the setting of the
- MouseOverForeColor, MouseOverBackColor
Gets/sets the colour of an item when it is highlighted using hot-tracking.
- SelectedForeColor, SelectedBackColor
Gets/sets the normal colour of an item when it is selected.
- SelectedMouseOverForeColor, SelectedMouseOverBackColor
Gets/sets the colour of an item when it is selected and the mouse is over.
- SelectedNoFocusForeColor, SelectedNoFocusBackColor
Gets/sets the colour of an item when it is selected and the control is out of focus.
This behaves int the same way as the standard version except as noted before a
collection only contains the children of the parent node. Also For..Each is not supported.
This object is largely compatible with the standard VB Node
object, with these enhancements:
Returns a cTreeViewNodes collection containing the
children for this node, if any, otherwise Nothing.
Moves this Node to another position in the tree. The new location is specified
by a relative node and the relationship of the new position to it.
- InsertNodeBefore, InsertNodeAfter
Adds a new node and inserts it either before or after this node. These are
convenient alternatives to the cTreeViewNodes
Adds a new child node to this node. This is a convenient alternative to the
collection when building up a tree recursively.
- StartEdit, EndEdit
These methods allow you to programmatically control editing of nodes.
Gets/sets whether this node has a checkbox in a TreeView with the
Gets/sets whether the plus/minus button is shown for this item, regardless
of whether the item contains children. This is useful when creating a TreeView
that is dynamically populated - in the standard TreeView you have to add a
dummy item to the node to allow it to be expanded, here you can simply
set ShowPlusMinus to True.
- Colour Properties
The same set of colours that can be customised globally for the TreeView control
can also be customised for an individual node.
Gets/sets a specific font used to render this node, or Nothing
to use the default font.
Gets/sets a number to display in brackets next to the node when the
control has the ShowNumbers style. Otherwise,
it can be used to store data against the item.
Gets the 1-based index of this item within its parent tree.
This TreeView control provides a comprehensive replacement for the standard VB
TreewView with enhanced formatting, drag and drop and style support. Other articles
in this section provide more details of how to use drag-drop, show Shell folders and files
and customising the behaviour and display of the TreeView.