如何在JComboBox中放置图像并设置其大小

Question

如何将图像放入左上角jComboBox中每个字符串的描述方法中？例如，我点击了苹果。然后描述将显示在中间，而图像将显示在面板的左上角。

这是代码。

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JFrame implements ActionListener,     ItemListener {
private static final long serialVersionUID = 1L;
private JComboBox<String> mainComboBox;
private JComboBox<String> subComboBox;
private JLabel label;
private String[][] descriptions;
private Hashtable<Object, Object> subItems = new Hashtable<Object, Object>  ();
public ComboBoxTwo() {
String[] items = {"Select Item", "Color", "Shape", "Fruit"};
this.getContentPane().setLayout(null);
this.setSize(400, 400);
mainComboBox = new JComboBox<String>(items);
mainComboBox.addActionListener(this);
mainComboBox.addItemListener(this);
mainComboBox.setSize(100, 100);
mainComboBox.setLocation(0, 100);

subComboBox = new JComboBox<String>();  
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
subComboBox.addItemListener(this);
subComboBox.setSize(100, 100);
subComboBox.setLocation(this.getSize().width - 120, 100);

String[] subItems1 = {"Select Color", "Red", "Blue", "Green"};
subItems.put(items[1], subItems1);
String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"};
subItems.put(items[2], subItems2);
String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"};
subItems.put(items[3], subItems3);

label = new JLabel();
label.setSize(300, 25);
label.setLocation(this.getSize().width /2 - label.getSize().width /2, 25);
label.setText("This is a label: currently nothing selected");
label.setVisible(true);

getContentPane().add(subComboBox);
getContentPane().add(mainComboBox);
getContentPane().add(label);
descriptions = new String[][]
{ 
    {"The red color", "The blue color", "A green color"}, 
    {"This shape is round", "Looks rectangular", "Has three sides"}, 
    {"Didn't fall far from the tree", "Seems quite orangy", "Look i've got a  banana in my trousers"} 
  };    
  }
  @Override
  public void actionPerformed(ActionEvent e) {
  String item = (String) mainComboBox.getSelectedItem();
  Object o = subItems.get(item);
  if (o == null) {
    subComboBox.setModel(new DefaultComboBoxModel<String>());
  } else {
    subComboBox.setModel(new DefaultComboBoxModel<String>((String[]) o));
  }
 }
 @SuppressWarnings("unchecked")
 @Override
 public void itemStateChanged(ItemEvent e) {
 if (e.getStateChange() == ItemEvent.SELECTED) {
 if (mainComboBox.getSelectedIndex() == 0 &&      subComboBox.getSelectedIndex() == 0)
    {
        label.setText("This is a label: currently nothing selected");
    }
    else if (mainComboBox.getSelectedIndex() >= 0)
    {
        label.setText("The first combobox has been altered");
    }
    if (e.getSource() == mainComboBox) {
        if (mainComboBox.getSelectedIndex() != 0) {
            FirstDialog firstDialog = new FirstDialog(ComboBoxTwo.this,
                    mainComboBox.getSelectedItem().toString(), "Please wait,    Searching for ..... ");
        }
    }
    else if (e.getSource() == subComboBox)
    {
        label.setText(descriptions[mainComboBox.getSelectedIndex() -1]     [((JComboBox<String>) e.getSource()).getSelectedIndex() -1]);
     }
   }
   }
 private class FirstDialog extends JDialog {
 private static final long serialVersionUID = 1L;
 FirstDialog(final Frame parent, String winTitle, String msgString) {
    super(parent, winTitle);
    setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
    JLabel myLabel = new JLabel(msgString);
    JButton bNext = new JButton("Stop Processes");
    add(myLabel, BorderLayout.CENTER);
    add(bNext, BorderLayout.SOUTH);
    bNext.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent evt) {
            setVisible(false);
        }
    });
    javax.swing.Timer t = new javax.swing.Timer(1000, new  ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            setVisible(false);
        }
    });
    t.setRepeats(false);
    t.start();
    setLocationRelativeTo(parent);
    setSize(new Dimension(400, 100));
    setVisible(true);
  }
  }
   public static void main(String[] args) {
   JFrame frame = new ComboBoxTwo();
   frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
   frame.setLocationRelativeTo(null);
   frame.setVisible(true);
  }

Answer 1

您必须创建自己的自定义渲染器。Oracle的Swing教程中提供了适当的示例。http://docs.oracle.com/javase/tutorial/uiswing/components/combobox.html

请参阅"提供自定义渲染"部分