Javafx使用项目和价格并行数组计算按钮

Question

我无法从我的组合框中选择一个小计。我正在创建一个餐馆应用程序，有人从组合框中选择一个项目，然后该项目被添加到列表框中。随着项目的添加，我试图将这些项目存储到数组列表中。然后获取该数组列表并将价格一起添加到小计中。我可以添加任何项目选择到数组。所以1项。我无法将项目总计为打印小计。有人可以帮我一把。我已经在这2天了，我将不胜感激任何帮助。先感谢您。

    double bcost [] = { 1.95, 1.50, 1.25, 2.95, 2.50, 1.50 };
    double acost [] = { 5.95, 6.95, 8.95, 8.95, 10.95, 12.95, 6.95 };
    double mcost [] = { 15.95, 13.95, 13.95, 11.95, 19.95, 20.95, 18.95, 13.95, 14.95 };
    double dcost [] = { 5.95, 3.95, 5.95, 4.95, 5.95 };
    String [] beverages = { "Soda", "Tea", "Coffee", "Mineral Water", "Juice", "Milk" };
    String [] appetizers = { "Buffalo Wings", "Buffalo Fingers", "Potato Skins", "Nachos", "Mushroom Caps",
            "Shrimp Cocktail" };
    String [] maincourse = { "Seafood Alfredo", "Chicken Alfredo", "Chicken Picatta", "Turkey Club", "Lobster Pie",
            "Prime Rib", "Shrimp Scampi", "Turkey Dinner", "Stuffed Chicken" };
    String [] dessert = { "Apple Pie", "Sundae", "Carrot Cake", "Mud Pie", "Apple Crisp" }; 

//-------------------------------------------------------------------------------

ComboBox<String> beverageComboBox = new ComboBox<String>();
    ObservableList<String> items1 = FXCollections.observableArrayList(beverages);
    beverageComboBox.getItems().addAll(items1);

    Label bo = new Label("Beverage Ordered");
    pane.add(bo, 2, 5);

    ListView<String> list1 = new ListView<>();

    beverageComboBox.setOnAction((e) -> {
        list1.getItems().add(beverageComboBox.getSelectionModel().getSelectedItem());
    });

    list1.addEventHandler(MouseEvent.MOUSE_CLICKED, e -> {
        list1.getItems().remove(list1.getSelectionModel().getSelectedIndex());
    });

    pane.add(list1, 3, 5);
    GridPane.setRowSpan(list1, 5);
 // --------------------------------------------------------------------------------------------------------------------
    ComboBox<String> appetizerComboBox = new ComboBox<String>();
    ObservableList<String> items2 = FXCollections.observableArrayList(appetizers);
    appetizerComboBox.getItems().addAll(items2);

    Label ao = new Label("Appetizer Ordered");
    pane.add(ao, 2, 10);

    ListView<String> list2 = new ListView<>();

    appetizerComboBox.setOnKeyPressed((e) -> {
        list2.getItems().add(appetizerComboBox.getSelectionModel().getSelectedItem());
    });

    list2.addEventHandler(MouseEvent.MOUSE_CLICKED, e -> {
        list2.getItems().remove(list2.getSelectionModel().getSelectedIndex());
    });

    pane.add(list2, 3, 10);
    GridPane.setRowSpan(list2, 5);

   //-------------------------------------------------------------------------------


    Button cal = new Button("    Calculate Bill    ");

    // Setting an action for the Calculate button btn.setOnAction(new
    cal.setOnAction(new EventHandler<ActionEvent>() {

        @Override
        public void handle(ActionEvent e) {

            double tax = 0.00;
            double total = 0.00;

            ArrayList<Double> cal = new ArrayList<Double>();
            if (ActionEvent.getSource() == beverageComboBox) {
                cal.add(bcost[beverageComboBox.getSelectionModel().getSelectedIndex()]);
                double subtotal = 0;
                for (Double price : cal) {
                    subtotal += price;
                }

                // subtotal = cal;
                // tax = subtotal * .07;
                // total = subtotal + tax;

                tst.setText(Double.toString(subtotal));

                tt.setText(Double.toString(tax));
                tto.setText(Double.toString(total));
            }
        }
    });

    pane.add(cal, 3, 30);