我如何添加多个组合框到JavaFX，一旦一个项目被选中，费用显示在下面？

Question

我想向JavaFX添加多个组合框，在用户选择一个项目后，该项目的成本将显示在组合框下。此外，所有选定项目的总成本将显示在底部。我知道如何制作一个组合框来显示所选一个项目的成本，但不知道如何制作多个组合框并显示所选所有项目的成本

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.util.StringConverter;
import javafx.collections.FXCollections;

public class Animals extends Application {

    Stage window;
    Scene scene;
    Button button;
    ComboBox<Animal> comboBox = new ComboBox<Animal>();
    Text textNamePrice = new Text();

    static public TextField[] tfLetters = new TextField[37];

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        window = primaryStage;
        window.setTitle("ComboBox ");
        button = new Button("Submit");

        comboBox = new ComboBox<Animal>();

        comboBox.setConverter(new StringConverter<Animal>() {
            @Override
            public String toString(Animal object) {
                return object.getName();
            }

            @Override
            public Animal fromString(String string) {
                return null;
            }
        });

        comboBox.setItems(FXCollections.observableArrayList(new Animal("Dog", 30.12), new Animal("Cat", 23.23),
                new Animal("Bird", 15.0)));

        comboBox.valueProperty().addListener((obs, oldVal, newVal) -> {
            String selectionText = "Price of the " + newVal.getName() + " is : " + newVal.getPrice();

            System.out.println(selectionText);
            textNamePrice.setText(selectionText);
        });

        VBox layout = new VBox(10);
        layout.setPadding(new Insets(60, 60, 60, 60));
        layout.getChildren().addAll(comboBox, textNamePrice, button);

        scene = new Scene(layout, 500, 350);
        window.setScene(scene);
        window.show();
    }

    public class Animal {
        private String name;
        private Double price;

        public Double getPrice() {
            return price;
        }

        public String getName() {
            return name;
        }

        public Animal(String name, Double price) {
            this.name = name;
            this.price = price;
        }
    }
}

Answer 1

使用自定义节点typeAnimalChooser显示组合框价格可能是最简单的方法。这样，可以在一个地方处理一个选择价格显示的功能。此外，您还可以根据选择提供价格属性，以便从应用程序类中对其进行汇总。

以下示例将所有这些AnimalChooser放在一个VBox中，并将侦听器添加到子列表中，以便在子列表中添加和删除侦听器，如果它被修改，这将允许您动态地将这些AnimalChooser添加/删除到/从VBox中，并且仍然可以获得正确更新的总和。

public class Animal {

    private final String name;
    // primitive type should be prefered here
    private final double price;

    public double getPrice() {
        return price;
    }

    public String getName() {
        return name;
    }

    public Animal(String name, double price) {
        this.name = name;
        this.price = price;
    }
}

public class AnimalChooser extends VBox {

    private final ComboBox<Animal> animalCombo;
    private final ReadOnlyDoubleWrapper price;
    private final Text text;

    public AnimalChooser(ObservableList<Animal> items) {
        setSpacing(5);
        animalCombo = new ComboBox<>(items);

        // converter for using a custom string representation of Animal in the
        // combobox
        animalCombo.setConverter(new StringConverter<Animal>() {

            @Override
            public String toString(Animal object) {
                return object == null ? "" : object.getName();
            }

            @Override
            public Animal fromString(String string) {
                if (string == null || string.isEmpty()) {
                    return null;
                } else {

                    // find suitable animal from list
                    Animal animal = null;

                    for (Animal item : items) {
                        if (string.equals(item.getName())) {
                            animal = item;
                            break;
                        }
                    }

                    return animal;
                }
            }

        });

        text = new Text();
        price = new ReadOnlyDoubleWrapper();

        getChildren().addAll(animalCombo, text);

        // bind price value to price property
        price.bind(Bindings.createDoubleBinding(new Callable<Double>() {

            @Override
            public Double call() throws Exception {
                Animal animal = animalCombo.getValue();
                return animal == null ? 0d : animal.getPrice();
            }
        }, animalCombo.valueProperty()));

        // bind text to content of Text node
        text.textProperty().bind(Bindings.when(animalCombo.valueProperty().isNull()).then("").otherwise(price.asString("%.2f $")));
    }

    public final double getPrice() {
        return this.price.get();
    }

    public final ReadOnlyDoubleProperty priceProperty() {
        return this.price.getReadOnlyProperty();
    }

}

@Override
public void start(Stage primaryStage) {

    VBox animalChoosers = new VBox(20);

    ObservableList<Animal> animals = FXCollections.observableArrayList(
            new Animal("cat", 1000.99),
            new Animal("dog", 20.50),
            new Animal("goldfish", 15.22)
    );

    final DoubleProperty total = new SimpleDoubleProperty();

    InvalidationListener listener = new InvalidationListener() {

        @Override
        public void invalidated(Observable observable) {
            double sum = 0d;
            for (Node n : animalChoosers.getChildren()) {
                AnimalChooser chooser = (AnimalChooser) n;
                sum += chooser.getPrice();
            }

            total.set(sum);
        }
    };

    // just in case you want to add AnimalChooser s dynamially to animalChoosers
    animalChoosers.getChildren().addListener(new ListChangeListener<Node>() {

        @Override
        public void onChanged(ListChangeListener.Change<? extends Node> c) {
            while (c.next()) {
                // add remove listeners updating the total
                for (Node n : c.getRemoved()) {
                    AnimalChooser chooser = (AnimalChooser) n;
                    chooser.priceProperty().removeListener(listener);
                }
                for (Node n : c.getAddedSubList()) {
                    AnimalChooser chooser = (AnimalChooser) n;
                    chooser.priceProperty().addListener(listener);
                }
            }

            listener.invalidated(null);
        }

    });

    for (int i = 0; i < 10; i++) {
        animalChoosers.getChildren().add(new AnimalChooser(animals));
    }

    BorderPane root = new BorderPane(animalChoosers);
    Text totalText = new Text();
    totalText.textProperty().bind(total.asString("total: %.2f $"));

    root.setBottom(totalText);
    BorderPane.setMargin(totalText, new Insets(20));

    Scene scene = new Scene(root);

    primaryStage.setScene(scene);
    primaryStage.show();
}