Java GUI多项选择程序

Question

我在 GUI 方面遇到了困难。

基本上我想创建一个程序，可以从给定列表中选择和添加项目，并显示添加项目的总金额(项目的价格)。因此，当我从 leftlist 添加商品时，价格将显示在 rightlist 中，当我按下 totalbutton 时，总价将显示在 rightlist 中。所选项目将通过 JLabel 显示。示例为:

到目前为止，这就是我所做的:

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class MP2_1 extends JFrame{
private JList leftlist;
private JList rightlist;

private JButton addbutton;
private JButton totalbutton;
private static String[] items = {"item1", "item2", "item3", "item4", "item5"
, "item6", "item7", "item8", "item9", "item10"};

private JButton total;
public MP2_1()  {
super("MP2_1");
setLayout(new FlowLayout());

leftlist = new JList(items); 
leftlist.setVisibleRowCount(5);
leftlist.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
add(new JScrollPane(leftlist));

    addbutton = new JButton("ADD");
    addbutton.addActionListener(
            new ActionListener(){
                public void actionPerformed(ActionEvent event){
                    rightlist.setListData(leftlist.getSelectedValuesList().toArray());
                }
            }
    );
    add(addbutton);


    rightlist = new JList();
    rightlist.setVisibleRowCount(5);
    rightlist.setFixedCellWidth(55);
    rightlist.setFixedCellHeight(20);
    add(new JScrollPane(rightlist));

    totalbutton = new JButton("Total");
    totalbutton.addActionListener(
            new ActionListener(){
                public void actionPerformed(ActionEvent event){
                    rightlist.setListData(leftlist.getSelectedValuesList().toArray());
                }
            }
    );
    add(totalbutton);



}
    public static void main(String[] args) {
    MP2_1 list = new MP2_1();
    list.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    list.setSize(300,300);
    list.setVisible(true);
}
}

我一定在结构中犯了一个错误，比如使用setListData，但我想不出任何其他方式在那里传输商品的价格，现在它只传输商品本身。

Answer 1

基于“当我从左侧列表添加商品时，价格将显示在右侧列表中” 我可以想到几种方法来做到这一点，我将通过使用 ListCellRenderer 来演示它，它为您提供了很多自定义功能。 我已经指出了 Total value ，您可以将其与标签一起使用。

1. 创建项目对象。
2. 创建自定义 ListCellRenderer 并将其与列表一起使用。

封装公共(public)地板；

import java.awt.Color;
import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import javax.swing.*;

public class MP2_1 extends JFrame {

    private JList leftlist;
    private JList rightlist;

    private final JButton addbutton;
    private final JButton totalbutton;

    private static final Item[] items = {new Item("Item 0", 100), new Item("Item 1", 150), new Item("Item 2", 200), new Item("Item 3", 300)};

    private JButton bTotal;

    public MP2_1() {
        super("MP2_1");
        setLayout(new FlowLayout());

        leftlist = new JList(items);

        leftlist.setCellRenderer(new ItemCellRenderer(ItemCellRenderer.ITEM_NAME));
        leftlist.setVisibleRowCount(5);

        leftlist.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
        add(new JScrollPane(leftlist));

        addbutton = new JButton("ADD");
        addbutton.addActionListener((ActionEvent event) -> {
            rightlist.setListData(leftlist.getSelectedValuesList().toArray());

        });
        add(addbutton);

        rightlist = new JList();
        rightlist.setCellRenderer(new ItemCellRenderer(ItemCellRenderer.ITEM_PRICE));
        rightlist.setVisibleRowCount(5);
        rightlist.setFixedCellWidth(55);
        rightlist.setFixedCellHeight(20);
        add(new JScrollPane(rightlist));

        totalbutton = new JButton("Total");
        totalbutton.addActionListener((ActionEvent event) -> {
            int total = 0;
            for (int i = 0; i < rightlist.getModel().getSize(); i++) {
                Item item = (Item) rightlist.getModel().getElementAt(i);
                int itemPrice = item.getItemPrice();
                total += itemPrice;
            }
            System.out.println("Total " + total);
            // set the total label here
        });
        add(totalbutton);

    }

    public static void main(String[] args) {
        MP2_1 list = new MP2_1();
        list.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        list.setSize(300, 300);
        list.setVisible(true);
    }

}
 //Create an Item Object.  

class Item {

    private final String itemName;
    private final int itemPrice;

    Item(String itemName, int itemPrice) {
        this.itemPrice = itemPrice;
        this.itemName = itemName;
    }

    public String getItemName() {
        return itemName;
    }

    public int getItemPrice() {
        return itemPrice;
    }

}
//Create a Custom  CellRenderer and use it with the Lists.

class ItemCellRenderer extends JLabel implements ListCellRenderer<Object> {

    static int ITEM_NAME = 0;
    static int ITEM_PRICE = 1;
    private final int type;

    public ItemCellRenderer(int type) {
        this.type = type;
        setOpaque(true);

    }

    @Override
    public Component getListCellRendererComponent(JList<?> list,
            Object value,
            int index,
            boolean isSelected,
            boolean cellHasFocus) {
        Item item = (Item) value;
        setText(type == ITEM_NAME ? item.getItemName() : "" + item.getItemPrice());

        Color background;
        Color foreground;

        // check if this cell represents the current DnD drop location
        JList.DropLocation dropLocation = list.getDropLocation();
        if (dropLocation != null
                && !dropLocation.isInsert()
                && dropLocation.getIndex() == index) {

            background = Color.BLUE;
            foreground = Color.WHITE;

            // check if this cell is selected
        } else if (isSelected) {
            background = Color.RED;
            foreground = Color.WHITE;

            // unselected, and not the DnD drop location
        } else {
            background = Color.WHITE;
            foreground = Color.BLACK;
        }

        setBackground(background);
        setForeground(foreground);

        return this;
    }
}