javaFX樹結構treeview使用

//---------------------------------------------------在JavaFX Scene Builder里已經加了widget，設置了fx:id

@FXML
    private TreeView<String> tv;
@Override
    public void initialize(URL location, ResourceBundle resources) {
        // TODO Auto-generated method stub
        initTreeView();
    }
    private void initTreeView(){
        TreeItem<String> item = new TreeItem<>("跟節點");
        tv.setRoot(item);
        item.setExpanded(false);
        TreeItem<String> i1 = new TreeItem<>("電影");
        TreeItem<String> i2 = new TreeItem<>("音樂");
        TreeItem<String> i3 = new TreeItem<>("游戲");
        item.getChildren().addAll(i1,i2,i3);
        TreeItem<String> i4 = new TreeItem<>("盪寇風雲");
        TreeItem<String> i5 = new TreeItem<>("變形金剛5");
        i1.setExpanded(false);
        i1.getChildren().addAll(i4,i5);
        
    }