Prevent the user from closing a JOptionPane with the X button

Embed your JOptionPane in a JDialog. Set the default close operation on that JDialog to DO_NOTHING_ON_CLOSE and add a PropertyChangeListener in which you listen for VALUE_PROPERTY and INPUT_VALUE_PROPERTY and hide the JDialog.

Main.java:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.beans.*;
  
public class Main
{
   public static void main(String []args) {
      JFrame frame = new JFrame();
 
      final JOptionPane pane = new JOptionPane("Are you sure you want to import this file?n" +
                                               "(try presssing the x button!)", 
                                               JOptionPane.QUESTION_MESSAGE,
                                               JOptionPane.YES_NO_CANCEL_OPTION);
      final JDialog dialog = new JDialog(frame, "Question", true);
      dialog.setContentPane(pane);
 
      dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
 
      pane.addPropertyChangeListener(new PropertyChangeListener() {
         public void propertyChange(PropertyChangeEvent e) {
            String prop = e.getPropertyName();
            if (dialog.isVisible() 
             && (e.getSource() == pane)
             && (prop.equals(JOptionPane.VALUE_PROPERTY) ||
                 prop.equals(JOptionPane.INPUT_VALUE_PROPERTY)))
            {
               System.out.println("Caught, JOptionPane is ready to close!");
               dialog.setVisible(false);
            }
         }
      });
 
      dialog.pack();
      dialog.setVisible(true);
      Object value = pane.getValue();
      System.out.println("Option " + value + " selected!");
      
      System.exit(1);
   }
}

Displaying an image as the background of a JPanel

Override the JPanel’s method paintComponent, draw the image using g.drawImage and call the superclass’ paintComponent. Make sure the JPanel is opaque.

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
 
public class Main extends JFrame
{
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      JPanel panel = createPanel();
 
      getContentPane().add(BorderLayout.CENTER, panel);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   public static JPanel createPanel() {
      JPanel panel = new JPanel() {
         public void paintComponent(Graphics g) {
            ImageIcon img = new ImageIcon("c:\mong.jpg");
            System.out.println(g.drawImage(img.getImage(), 0, 0, null));
            super.paintComponent(g);
         }
      };
      panel.setOpaque(false);
      panel.setLayout(new GridLayout(20, 4, 10, 10));
 
      for (int i=0; i<20; i++) {
         for (int j=0; j<4; j++) {
            JLabel label = new JLabel("label " + i + ", " + j);
            label.setFont(new Font("Helvetica", Font.PLAIN, 30));
            panel.add(label);            
         }
      }
 
      return panel;
   }
 
   public static void main(String [] args) {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);
   } 
} 

BTW, here’s the image I used:



Creating a nested JTabbedPane

The following example nests JTabbedPanes recursively until 10 levels deep:

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.beans.*;
 
public class Main extends JFrame {
 
   public Main() {
      getContentPane().setLayout(new BorderLayout());
      JTabbedPane tabbedPane = new JTabbedPane();
 
      getContentPane().add(BorderLayout.CENTER, tabbedPane);
  
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
 
      setTitle("JTabbedPane Nested Demonstration");
      setSize(new Dimension(400, 400));
 
      createTab(tabbedPane, 0);
   }
 
   protected void createTab(JTabbedPane jtp, int ct) {
      if (ct > 10) return;
      JTabbedPane tp = new JTabbedPane();
      tp.setTabPlacement(getNextOrientation(jtp.getTabPlacement()));
      jtp.addTab("TabLevel #" + ct, tp);
      createTab(tp, ct+1);
   }
 
   private int getNextOrientation(int tabPlacement) {
      if (tabPlacement == JTabbedPane.TOP) return JTabbedPane.RIGHT;
      if (tabPlacement == JTabbedPane.RIGHT) return JTabbedPane.BOTTOM;
      if (tabPlacement == JTabbedPane.BOTTOM) return JTabbedPane.LEFT;
      else return JTabbedPane.TOP;
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.show();
   }
}

Hiding a JToolBar that has been made floatable

Here’s an example that will hide a JToolBar, whether or not they have been made floatable.

Main.java:

import javax.swing.border.*;
import javax.swing.plaf.basic.*;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*;
import java.awt.*;
  
public class Main extends JFrame {
   public Main() {
      super("JToolBar hide/show example");
 
      final JTextArea textArea = new JTextArea(5, 30);
      final MyJToolBar toolBar = new MyJToolBar();
 
      JButton gifButton = new JButton(new ImageIcon("gifIcon.gif"));
      JButton jpgButton = new JButton(new ImageIcon("jpgIcon.gif"));
      JButton tiffButton = new JButton(new ImageIcon("tiffIcon.gif"));
 
      gifButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            textArea.append("gifButton clicked!n");
         }
      });
  
      jpgButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            textArea.append("jpgButton clicked!n");
         }
      });
        
      tiffButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            textArea.append("tiffButton clicked!n");
         }
      });
 
      toolBar.add(gifButton);
      toolBar.add(new JToolBar.Separator());
      toolBar.add(jpgButton);
      toolBar.add(new JToolBar.Separator());
      toolBar.add(tiffButton);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
 
      getContentPane().setLayout(new BorderLayout());
      getContentPane().add(BorderLayout.NORTH, toolBar);
      getContentPane().add(BorderLayout.CENTER, new JScrollPane(textArea));
 
      JMenuBar menuBar = new JMenuBar();
      JMenu menu = new JMenu("Toolbar");
      final JMenuItem hideShowMenuItem = new JCheckBoxMenuItem("Hide");
      menu.add(hideShowMenuItem);
      menuBar.add(menu);
      setJMenuBar(menuBar);
   
      hideShowMenuItem.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            toolBar.setVisible(!hideShowMenuItem.isSelected());
         }
      });
   }
 
   public static void main(String[] args) {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);
   }
}
 
class MyJToolBar extends JToolBar
{
   public MyJToolBar() {
      super();
   }
 
   public MyJToolBar(int orientation) {
      super(orientation);
   }
 
   public MyJToolBar(String name) {
      super(name);
   }
 
   public MyJToolBar(String name, int orientation) {
      super(name, orientation);
   }
 
   public void setVisible(boolean visible) {
      boolean isFloating = false;
      if (getUI() instanceof BasicToolBarUI) {
         isFloating = ((BasicToolBarUI) ui).isFloating();
      }
 
      if (isFloating) {
         SwingUtilities.getRoot(this).setVisible(visible);
      }
      else {
         super.setVisible(visible);
      }
   }
}

Preventing a JInternalFrame from being closed

Just specify so when you create a JInternalFrame, in the constructor, or call the method setClosable(false).

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
import java.net.*;
 
public class Main extends JFrame {
   JDesktopPane desktop;
   int nframes = 0;
  
   public Main() {
      desktop = new JDesktopPane(); 
      setContentPane(desktop);
      setJMenuBar(createMenuBar());
      createInternalFrame(); 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   protected JMenuBar createMenuBar() {
      JMenuBar menuBar = new JMenuBar();
 
      JMenu createMenu = new JMenu("Create");
      createMenu.setMnemonic(KeyEvent.VK_C);
      JMenuItem newMenuItem = new JMenuItem("New");
      newMenuItem.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            createInternalFrame();
         }
      }); 
      newMenuItem.setMnemonic(KeyEvent.VK_N);
      createMenu.add(newMenuItem);
      menuBar.add(createMenu);
 
      return menuBar;
   }
 
   protected void createInternalFrame() {
      nframes++;
      String title = "JInternalFrame #" + nframes;
      JInternalFrame frame = new JInternalFrame(title,
         true,    // resizable
         true,    // closable
         true,    // maximizable
         true);   // iconifiable
      frame.setVisible(true); 
 
      // disable closing the frame
      frame.setClosable(false);
 
      desktop.add(frame);
      frame.setSize(200, 200);
      frame.setLocation(30*nframes, 30*nframes);
      try {
         frame.setSelected(true);
      } catch (java.beans.PropertyVetoException e) {}
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(500, 300);
      main.setVisible(true);
   }
}

Assigning a shortcut key to a JCheckBox

Swings JButton inherits from AbstractButton that defines a method setMnemonic.
You can use it as follows:

import javax.swing.*;
import java.util.*;
import java.awt.*;
   
public class Main extends JFrame
{
   public Main() throws Exception {
      JCheckBox cbox1 = new JCheckBox("Check me or press ALT-C");
      JCheckBox cbox2 = new JCheckBox("Check me or press ALT-D");
      cbox1.setMnemonic('C');
      cbox2.setMnemonic('D');
 
      getContentPane().setLayout(new GridLayout(2, 1));
      getContentPane().add(cbox1);
      getContentPane().add(cbox2);
      pack();
 
      cbox1.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
            System.out.println("First JCheckBox checked!");
         }
      });

      cbox2.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
            System.out.println("Second JCheckBox checked!");
         }
      });
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
   }
 
   public static void main(String args[]) throws Exception {
      Main main = new Main();
      main.show();
   }
}

Creating an editable JComboBox

Use the method setEditable. Here’s an example:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
   
public class Main extends JFrame
{ 
   public Main() {
      getContentPane().setLayout(new BorderLayout());
      final JComboBox combobox = new JComboBox();
      final JList list = new JList(new DefaultListModel());
 
      getContentPane().add(BorderLayout.NORTH, combobox);
      getContentPane().add(BorderLayout.CENTER, list); 
 
      combobox.setEditable(true);
      combobox.addItemListener(new ItemListener() {
         public void itemStateChanged(ItemEvent ie) {
            if (ie.getStateChange() == ItemEvent.SELECTED) {
               ((DefaultListModel) list.getModel()).addElement(combobox.getSelectedItem());
               combobox.insertItemAt(combobox.getSelectedItem(), 0);
            }
         }
      });
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });      
   
      setSize(new Dimension(200, 200));
   } 
 
   public static void main(String[] args) throws Exception {
      Main main = new Main();
      main.setVisible(true);
   }
}

Scrolling a JList to the selected item

You can use the method ensureIndexIsVisible as shown in following example:

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
  
public class Main extends JFrame {
 
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      Vector v = new Vector();
      for (int i=0; i<50; i++) {
         v.addElement("Item #" + i);
      }
      final JList list = new JList(v);
 
      final JTextField textfield = new JTextField(5);
      getContentPane().add(new JLabel("Scroll to:"));
      getContentPane().add(textfield);
      JButton button = new JButton("Scroll!");
      getContentPane().add(button);
      button.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            int n = Integer.parseInt(textfield.getText());
            list.ensureIndexIsVisible(n);
         }
      });
      getContentPane().add(new JScrollPane(list));    
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      setSize(200, 230);
   }
   
   public static void main(String[] args) {
      (new Main()).show();
   }
}

Adding a general JComponent to a JMenu

Create your own version of the JComponent that you would like to add to your Menu and have it implement the methods of MenuElement. Here’s an example that shows a JMenu with a JTextField and a JSlider as its elements:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
   
public class Main extends JFrame {
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      JMenuBar menuBar = new JMenuBar();
      JMenu menu = new JMenu("Menu");
      JMenuItem menuItem1 = new JMenuItem("item 1");
      JMenuItem menuItem2 = new JMenuItem("item 2");
      JMenuItemTextField menuItem3 = new JMenuItemTextField(20);
      JMenuItem menuItem4 = new JMenuItem("item 4");
      JMenuItemSlider menuItem5 = new JMenuItemSlider();
      menuItem5.setMajorTickSpacing(20);
      menuItem5.setMinorTickSpacing(5);
      menuItem5.setPaintTicks(true);
      JMenuItem menuItem6 = new JMenuItem("item 6");
 
      menu.add(menuItem1);
      menu.add(menuItem2);
      menu.add(menuItem3);
      menu.add(menuItem4);
      menu.add(menuItem5);
      menu.add(menuItem6);
 
      menuBar.add(menu);
 
      this.setJMenuBar(menuBar); 
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      setSize(400, 400);
   }
  
   public static void main(String[] args) {
      (new Main()).show();
   }
}
 
class JMenuItemTextField extends JTextField implements MenuElement
{
   public JMenuItemTextField(int length) {
      super(length);
   }
 
   public Component getComponent() {
      return this;
   }
 
   public MenuElement[] getSubElements() {
      return null;
   }
 
   public void menuSelectionChanged(boolean changed) {
   }
 
   public void processKeyEvent(KeyEvent kevt, MenuElement[] me, MenuSelectionManager msm) {
   }
 
   public void processMouseEvent(MouseEvent mevt, MenuElement[] me, MenuSelectionManager msm) {
   }
}
 
class JMenuItemSlider extends JSlider implements MenuElement
{
   public JMenuItemSlider() {
      super();
   }
 
   public Component getComponent() {
      return this;
   }
 
   public MenuElement[] getSubElements() {
      return null;
   }
 
   public void menuSelectionChanged(boolean changed) {
   }
 
   public void processKeyEvent(KeyEvent kevt, MenuElement[] me, MenuSelectionManager msm) {
   }
 
   public void processMouseEvent(MouseEvent mevt, MenuElement[] me, MenuSelectionManager msm) {
   }
}

Changing the color of a JSlider component

The JSlider component consists of several subcomponents (ticks, lines, labels, knob, …). Look at the plaf UI source code (eg. javax.swing.plaf.basic.BasicSliderUI) and you’ll notice that several times Color.black is hardcoded. So unless you rewrite a custom UI class for your JSlider, you will only be able to partially control the overall color.

This following example shows you how to set the JSlider fore and background color as well as the fore and background color for the labels.

Main.java:

import javax.swing.plaf.metal.*;
import javax.swing.event.*;
import javax.swing.plaf.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
   
public class Main extends JFrame {
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      final JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 30, 15);
      // draw the major tick marks (one for every tick label)
      slider.setMajorTickSpacing(10);
      // draw the minor tick marks (between the tick labels)
      slider.setMinorTickSpacing(1);
      // draw the tick marks
      slider.setPaintTicks(true);
      // draw the tick mark labels
      slider.setPaintLabels(true);
 
      slider.setForeground(Color.red);
      slider.setBackground(Color.yellow);
 
      Dictionary dictionary = slider.getLabelTable();
      if (dictionary != null) {
         Enumeration keys = dictionary.keys();
         while (keys.hasMoreElements()) {
            JLabel label = (JLabel) dictionary.get(keys.nextElement());
            label.setForeground(Color.blue);
            // uncomment these following lines to get a background for your labels
            label.setOpaque(true);
            label.setBackground(Color.green); 
         }
      }
 
      getContentPane().add(slider);
  
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      pack();
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}