JComboBox 中的多列 java swing

Question

how to create jcomboBox with two /multiple columns in the drop down let but when we select only one selected value show in Jcombobox

please give me any solution for this.

Answer 1

You might be able to use JList#setLayoutOrientation(JList.VERTICAL_WRAP) :

import java.awt.*;
import javax.accessibility.Accessible;
import javax.swing.*;
import javax.swing.plaf.basic.ComboPopup;

public class TwoColumnsDropdownTest {
  private Component makeUI() {
    DefaultComboBoxModel<String> model = new DefaultComboBoxModel<>();
    model.addElement("111");
    model.addElement("2222");
    model.addElement("3");
    model.addElement("44444");
    model.addElement("55555");
    model.addElement("66");
    model.addElement("777");
    model.addElement("8");
    model.addElement("9999");
    int rowCount = (model.getSize() + 1) / 2;
    JComboBox<String> combo = new JComboBox<String>(model) {
      @Override public Dimension getPreferredSize() {
        Insets i = getInsets();
        Dimension d = super.getPreferredSize();
        int w = Math.max(100, d.width);
        int h = d.height;
        int buttonWidth = 20; // ???
        return new Dimension(buttonWidth + w + i.left + i.right, h + i.top + i.bottom);
      }

      @Override public void updateUI() {
        super.updateUI();
        setMaximumRowCount(rowCount);
        setPrototypeDisplayValue("12345");

        Accessible o = getAccessibleContext().getAccessibleChild(0);
        if (o instanceof ComboPopup) {
          JList<?> list = ((ComboPopup) o).getList();
          list.setLayoutOrientation(JList.VERTICAL_WRAP);
          list.setVisibleRowCount(rowCount);
          list.setFixedCellWidth((getPreferredSize().width - 2) / 2);
        }
      }
    };
    JPanel p = new JPanel();
    p.add(combo);
    return p;
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      frame.getContentPane().add(new TwoColumnsDropdownTest().makeUI());
      frame.setSize(320, 240);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
    });
  }
}

Answer 2

You need to do a few things.

By default, what is displayed in the JComboBox , as the selected item, is the value returned by method toString of the items in the ComboBoxModel . Based on your comment I wrote an Item class and overrode the toString method.

In order to display something different in the drop-down list, you need a custom ListCellRenderer .

In order for the drop-down list to display the entire details of each item, the drop-down list needs to be wider than the JComboBox . I used code from the following SO question to achieve that:
How can I change the width of a JComboBox dropdown list?

import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Point;
import java.math.BigDecimal;
import java.text.NumberFormat;

import javax.accessibility.Accessible;
import javax.accessibility.AccessibleContext;
import javax.swing.BorderFactory;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListCellRenderer;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;
import javax.swing.plaf.basic.BasicComboPopup;

public class MultiColumnCombo implements PopupMenuListener {
    private JComboBox<Item>  combo;

    public void popupMenuCanceled(PopupMenuEvent event) {
        // Do nothing.
    }

    public void popupMenuWillBecomeInvisible(PopupMenuEvent event) {
        // Do nothing.
    }

    public void popupMenuWillBecomeVisible(PopupMenuEvent event) {
        AccessibleContext comboAccessibleContext = combo.getAccessibleContext();
        int comboAccessibleChildrenCount = comboAccessibleContext.getAccessibleChildrenCount();
        if (comboAccessibleChildrenCount > 0) {
            Accessible comboAccessibleChild0 = comboAccessibleContext.getAccessibleChild(0);
            if (comboAccessibleChild0 instanceof BasicComboPopup) {
                EventQueue.invokeLater(() -> {
                    BasicComboPopup comboPopup = (BasicComboPopup) comboAccessibleChild0;
                    JScrollPane scrollPane = (JScrollPane) comboPopup.getComponent(0);
                    Dimension d = setCurrentDimension(scrollPane.getPreferredSize());
                    scrollPane.setPreferredSize(d);
                    scrollPane.setMaximumSize(d);
                    scrollPane.setMinimumSize(d);
                    scrollPane.setSize(d);
                    Point location = combo.getLocationOnScreen();
                    int height = combo.getPreferredSize().height;
                    comboPopup.setLocation(location.x, location.y + height - 1);
                    comboPopup.setLocation(location.x, location.y + height);
                });
            }
        }
    }

    private void createAndDisplayGui() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(createCombo());
        frame.setSize(450, 300);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createCombo() {
        JPanel panel = new JPanel();
        Item[] items = new Item[]{new Item("A", "Item A", new BigDecimal(1.99d), new BigDecimal(2.99d)),
                                  new Item("B", "Item B", new BigDecimal(7.5d), new BigDecimal(9.0d)),
                                  new Item("C", "Item C", new BigDecimal(0.25d), new BigDecimal(3.15d))};
        combo = new JComboBox<>(items);
        AccessibleContext comboAccessibleContext = combo.getAccessibleContext();
        int comboAccessibleChildrenCount = comboAccessibleContext.getAccessibleChildrenCount();
        if (comboAccessibleChildrenCount > 0) {
            Accessible comboAccessibleChild0 = comboAccessibleContext.getAccessibleChild(0);
            if (comboAccessibleChild0 instanceof BasicComboPopup) {
                BasicComboPopup comboPopup = (BasicComboPopup) comboAccessibleChild0;
                comboPopup.getList().setCellRenderer(new MultiColumnRenderer());
            }
        }
        combo.addPopupMenuListener(this);
        panel.add(combo);
        return panel;
    }

    private Dimension setCurrentDimension(Dimension dim) {
        Dimension d = new Dimension(dim);
        d.width = 120;
        return d;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> new MultiColumnCombo().createAndDisplayGui());
    }
}

class Item {
    private String  code;
    private String  name;
    private BigDecimal  price;
    private BigDecimal  salePrice;

    public Item(String code, String name, BigDecimal price, BigDecimal salePrice) {
        this.code = code;
        this.name = name;
        this.price = price;
        this.salePrice = salePrice;
    }

    public String displayString() {
        return String.format("%s %s %s %s",
                             code,
                             name,
                             NumberFormat.getCurrencyInstance().format(price),
                             NumberFormat.getCurrencyInstance().format(salePrice));
    }

    public String toString() {
        return name;
    }
}

class MultiColumnRenderer implements ListCellRenderer<Object> {

    /** Component returned by method {@link #getListCellRendererComponent}. */
    private JLabel  cmpt;

    public MultiColumnRenderer() {
        cmpt = new JLabel();
        cmpt.setOpaque(true);
        cmpt.setBorder(BorderFactory.createEmptyBorder(1, 1, 1, 1));
    }

    public Component getListCellRendererComponent(JList<? extends Object> list,
                                                  Object value,
                                                  int index,
                                                  boolean isSelected,
                                                  boolean cellHasFocus) {
        String text;
        if (value == null) {
            text = "";
        }
        else {
            if (value instanceof Item) {
                text = ((Item) value).displayString();
            }
            else {
                text = value.toString();
            }
        }
        cmpt.setText(text);
        if (isSelected) {
            cmpt.setBackground(list.getSelectionBackground());
            cmpt.setForeground(list.getSelectionForeground());
        }
        else {
            cmpt.setBackground(list.getBackground());
            cmpt.setForeground(list.getForeground());
        }
        cmpt.setFont(list.getFont());
        return cmpt;
    }
}