获取附加到javafx选项卡的对象

我在使用javafx标签时遇到了一些问题。我需要在新表上获取附加的对象，该对象属于BillingTable类。我希望将其分配给字段表，但是我不断收到异常消息，告诉我强制转换不起作用。选项卡存储在带有名称选项卡的tabPane中。这是我的代码：

tabs.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<Tab>() {
            @Override
            public void changed(ObservableValue<? extends Tab> ov, Tab oldTab, Tab newTab) {
                System.out.println("Tab Selection changed");
                TreeTableView<BillingTable> treeTableView = (TreeTableView<BillingTable>) newTab.getContent();
                table = treeTableView.getRoot().getValue();
            }
        });

BillingTable类：

public class BillingTable {

private TreeTableView<BillingTableRow> table;
private TreeItem<BillingTableRow> root;
private TreeTableColumn<BillingTableRow, String> nameColumn;
private TreeTableColumn<BillingTableRow, Double> totalColumn;
private TreeTableColumn<BillingTableRow, Double> dayColumn;
private TreeTableColumn<BillingTableRow, Double> eveningColumn;
private TreeTableColumn<BillingTableRow, Double> nightColumn;
private TreeTableColumn<BillingTableRow, Double> weekendColumn;
private TreeTableColumn<BillingTableRow, Double> holidayColumn;
private TreeTableColumn<BillingTableRow, Boolean> billedColumn;

/**
 * Create a new billing table.
 */
public BillingTable() {
    initiateTable();
}

/**
 * Add row to the billing table.
 * 
 * @return Added row.
 */
public TreeItem<BillingTableRow> addRow(BillingTableRow row) {
    TreeItem<BillingTableRow> child = new TreeItem<>(row);
    root.getChildren().add(child);
    return child;
}

/**
 * Add TreeItem to the table root.
 * 
 * @param treeItem
 *            TreeItem to add to the root.
 * @return Added row.
 */
public TreeItem<BillingTableRow> addRow(TreeItem<BillingTableRow> treeItem) {
    root.getChildren().add(treeItem);
    root.getValue().addChild(treeItem.getValue());
    return treeItem;
}

/**
 * Add client to the billing table.
 * 
 * @param client
 *            Client to add.
 * @return Created row in billing table.
 */
public TreeItem<BillingTableRow> addClient(Client client) {
    TreeItem<BillingTableRow> row = new TreeItem<>(new BillingTableRow(client));
    addRow(row);
    return row;
}

/**
 * Initiate TreeTableView of billing data.
 */
private void initiateTable() {
    table = new TreeTableView<>();

    // Define columns
    nameColumn = new TreeTableColumn<>("Namn");
    totalColumn = new TreeTableColumn<>("Summa");
    dayColumn = new TreeTableColumn<>("Dag");
    eveningColumn = new TreeTableColumn<>("Kväll");
    nightColumn = new TreeTableColumn<>("Natt");
    weekendColumn = new TreeTableColumn<>("Helg");
    holidayColumn = new TreeTableColumn<>("Storhelg");
    billedColumn = new TreeTableColumn<>("Faktureras");

    // Change column sizing
    nameColumn.setPrefWidth(150);
    totalColumn.setPrefWidth(60);
    dayColumn.setPrefWidth(60);
    eveningColumn.setPrefWidth(60);
    nightColumn.setPrefWidth(60);
    weekendColumn.setPrefWidth(60);
    holidayColumn.setPrefWidth(60);
    billedColumn.setPrefWidth(80);

    // Bind columns to variables
    nameColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("name"));
    totalColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeTotal"));
    dayColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeDay"));
    eveningColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeEvening"));
    nightColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeNight"));
    weekendColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeWeekend"));
    holidayColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("timeHoliday"));
    billedColumn.setCellValueFactory(new TreeItemPropertyValueFactory<>("billed"));

    // Make cells editable for all columns
    makeEditableCells();

    // Add columns to table
    table.getColumns().add(nameColumn);
    table.getColumns().add(totalColumn);
    table.getColumns().add(dayColumn);
    table.getColumns().add(eveningColumn);
    table.getColumns().add(nightColumn);
    table.getColumns().add(weekendColumn);
    table.getColumns().add(holidayColumn);
    table.getColumns().add(billedColumn);

    root = new TreeItem<BillingTableRow>(new BillingTableRow("Root"));
    root.setExpanded(true);

    table.setRoot(root);
    table.setShowRoot(false);
    table.setTableMenuButtonVisible(true);

}
...

和例外：

Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: gui.BillingTableRow cannot be cast to gui.BillingTable
at application.Main$1.changed(Main.java:136)
at application.Main$1.changed(Main.java:1)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(Unknown Source)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(Unknown Source)
at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(Unknown Source)
at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(Unknown Source)
at javafx.beans.property.ObjectPropertyBase.markInvalid(Unknown Source)
at javafx.beans.property.ObjectPropertyBase.set(Unknown Source)
at javafx.scene.control.SelectionModel.setSelectedItem(Unknown Source)
at javafx.scene.control.TabPane$TabPaneSelectionModel.select(Unknown Source)
at javafx.scene.control.TabPane$TabPaneSelectionModel.select(Unknown Source)
at javafx.scene.control.TabPane$TabPaneSelectionModel.findNearestAvailableTab(Unknown Source)
at javafx.scene.control.TabPane$TabPaneSelectionModel.lambda$new$17(Unknown Source)
at javafx.scene.control.TabPane$TabPaneSelectionModel$$Lambda$66/1951002621.onChanged(Unknown Source)
at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(Unknown Source)
at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(Unknown Source)
at javafx.collections.ObservableListBase.fireChange(Unknown Source)
at javafx.collections.ListChangeBuilder.commit(Unknown Source)
at javafx.collections.ListChangeBuilder.endChange(Unknown Source)
at javafx.collections.ObservableListBase.endChange(Unknown Source)
at javafx.collections.ModifiableObservableListBase.add(Unknown Source)
at java.util.AbstractList.add(Unknown Source)
at application.Main.addTab(Main.java:705)
at application.Main.start(Main.java:142)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(Unknown Source)
at com.sun.javafx.application.LauncherImpl$$Lambda$69/1795971577.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/1051754451.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/1600778379.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(Unknown Source)
at com.sun.javafx.application.PlatformImpl$$Lambda$46/1775282465.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/1109371569.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)