java - Swing - 自定义 JComboBox 项目

Question

我在 JFrame 中创建了一个 JComboBox

JComboBox itemsComboBox = new JComboBox();

然后创建一个类

public class ItemCombo {

    Product p;

    public ItemCombo(Product p) {
        this.p = p;
    }

    @Override
    public String toString(){
        return p.getName();
    }

    public Float getPrice() {
        return p.getPrice();
    }    
}

就我对组合框的了解而言，现在我应该能够做到

itemsComboBox.addItem(new ItemCombo(Product));

但是，它说它无法将 ItemCombo 对象转换为字符串。我究竟做错了什么？是否有另一种方法来创建这样的自定义 JComboBox？

Answer 1

您会发现从 JComboBox 模型中添加/删除项目比直接从 JComboBox 中添加/删除项目更好。因此创建一个DefaultComboBoxModel<ItemCombo>对象，让它成为你的JComboBox<ItemCombo>的模型。然后将项目添加到模型中，你应该是金色的。例如:

DefaultComboBoxModel<ItemCombo> comboModel = new DefaultComboBoxModel<>();
JComboBox<ItemCombo> itemsComboBox = new JComboBox<>(comboModel);  // *** fixed ***

// ......

comboModel.addItem(new ItemCombo(someProduct));

概念验证代码:

import java.awt.Dimension;
import javax.swing.*;

public class TestCombo extends JPanel {
    private static final Product[] products = {
            new Product("One", 1.0),
            new Product("Two", 2.0),
            new Product("Three", 3.0),
            new Product("Four", 4.0),
            new Product("Five", 5.0),
    };

    private DefaultComboBoxModel<ItemCombo> comboModel = new DefaultComboBoxModel<>();
    private JComboBox<ItemCombo> itemsComboBox = new JComboBox<>(comboModel);

    public TestCombo() {
        add(itemsComboBox);
        for (Product product : products) {
            comboModel.addElement(new ItemCombo(product));
        }
        itemsComboBox.addActionListener(e -> {
            ItemCombo itemCombo = (ItemCombo) itemsComboBox.getSelectedItem();
            System.out.println("Selection: " + itemCombo.getProduct());
        });

        setPreferredSize(new Dimension(400, 150));
    }

    private static void createAndShowGui() {
        JFrame frame = new JFrame("TestCombo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new TestCombo());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}


class ItemCombo {

    private Product product;

    public ItemCombo(Product p) {
        this.product = p;
    }

    @Override
    public String toString(){
        return product.getName();
    }

    public double getPrice() {
        return product.getPrice();
    }   

    public Product getProduct() {
        return product;
    }
}

class Product {

    private String name;
    private double price;

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

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }

    @Override
    public String toString() {
        return "Product [name=" + name + ", price=" + price + "]";
    }
}