[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'ComCtrls' (#lcl)

# TCustomTreeView.OnHasChildren

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

## Declaration

Source position: comctrls.pp line 3689

`protected property TCustomTreeView.OnHasChildren : TTVHasChildrenEvent read FOnHasChildren write FOnHasChildren;`

## 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

TCustomTreeView.NodeHasChildren |  | Determines if the specified tree node has child nodes.
TTVHasChildrenEvent |  | Specifies an event handler signalled to determine if a given tree node has child nodes.
TTreeNode.HasChildren |  | Indicates whether the tree node has child nodes.
TTreeNode.States |  | Contains active state flags for the tree node.
TTreeNode.Items |  | Provides indexed access to the child nodes for the current node.