TCustomTreeView.OnHasChildren

Event handler signalled to determine if a given node in the tree view has child nodes.

Declaration

Source position: comctrls.pp line 3666

Description

OnHasChildren is a TTVHasChildrenEvent property with the event handler signalled to determine whether a specified node has child nodes. It is signalled (when assigned) from the NodeHasChildren method, and allows the control to determine whether child nodes for a given node can be displayed on the control. It occurs when a TTreeNode instance gets the value for its HasChildren property and updates the States for the node.

Arguments to the event handler include:

Sender

The TCustomTreeView instance for the event.

ANode

The TTreeNode instance examine for child nodes in the handler routine.

The handler routine returns a Boolean value which indicates whether the specified node has child nodes which can be displayed on the control. The return value can be set to False - even when the tree node actually has child nodes. This allows properties in child nodes, like Data or Level, to be used to determine their effective visibility.

See also