Listen to selection on TreeItem in TreeView

controls view

 val controlsView = new TreeView[String]() {
    hgrow = javafx.scene.layout.Priority.ALWAYS
    minWidth = 200
    editable = true
    root = rootTreeItem
    id = "page-tree"
  }
  controlsView.getSelectionModel.setSelectionMode(SelectionMode.SINGLE)
  controlsView.getSelectionModel.selectedItemProperty.addListener(new ChangeListener[Any] {
    def changed(observable: ObservableValue[_], oldValue: Any, newValue: Any) {
      val selItem =  newValue.asInstanceOf[javafx.scene.control.TreeItem[String]]
      println("clicked " + selItem.getValue())
    }
  })