API Reference > ui-components > Tree > TreeEvents TreeEvents Interface Beta Tree events that can occur while interacting with tree. Note: Selection and checkbox state change events payload is an Observable. Observable is a stream of data over time (e.g. in case of selection replaced event it is a stream of selected node items arrays). To access data inside stream '.subscribe()' method should be called. This method accepts any subset of 'next', 'error' and 'complete' callbacks. Once subscribe is called observable will start emitting data and calls 'next' callback each time new data is emitted. If some selected nodes are not loaded yet they will be loaded and observable will emit loaded node items. When all selected node items are emitted observable completes and calls 'complete' callback if supplied. Implemented by TreeEventHandler Methods Name Description onCheckboxStateChanged(event: TreeCheckboxStateChangeEvent): Subscription | undefined Optional Called when checkbox states for nodes are changed. onDelayedNodeClick(event: TreeNodeEvent): void Optional Called when selected tree node is clicked. onNodeCollapsed(event: TreeNodeEvent): void Optional Called when tree node is collapsed. onNodeExpanded(event: TreeNodeEvent): void Optional Called when tree node is expanded. onSelectionModified(event: TreeSelectionModificationEvent): Subscription | undefined Optional Called when tree selection is modified. onSelectionReplaced(event: TreeSelectionReplacementEvent): Subscription | undefined Optional Called when tree selection is replaced. Defined in ui/components/src/ui-components/tree/controlled/TreeEvents.ts Line 27 Last Updated: 13 June, 2024