Persisting the Expanded State
The TreeView enables you to define and persist the expanded state of its nodes when the component is re-rendered.
The TreeView exposes the following options to control the expand state:
isExpanded(function)—Determines if a given node is expanded.
collapse(event)—Fired when a given node is about to be collapsed.
expand(event)—Fired when a given node is about to be expanded.
To persist the expanded state of the TreeView, either:
By default, the built-in
ExpandDirective persists the expanded items based on their hierarchical index.
The TreeView renders the expand icons only after the
hasChildrenfunctions are defined.
You can also persist the expanded state of the TreeView by item field—for example, the