Catching events while an image is being read using ImageIO

Add an IIOReadProgressListener to your reader.

   IIOReadProgressListener listener = new MyReadProgressListener();
   reader.addIIOReadProgressListener(listener);

It’ll throw events while the reading process is going on. The following example shows a JProgressBar while reading the image fruit.png, to be used as background.

Main.java:

import javax.imageio.metadata.*; 
import javax.imageio.stream.*;
import javax.imageio.event.*;
import javax.imageio.*;
 
import javax.swing.event.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*; 
import java.io.*;
  
public class Main extends JFrame
{
   JProgressBar progressBar;
   BufferedImage background = null;
  
   public Main() {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      });
 
      progressBar = new JProgressBar(0, 100);
 
      getContentPane().setLayout(new BorderLayout());
      getContentPane().add(BorderLayout.NORTH, progressBar);
    }
 
   public void loadBackgroundImage(String filename) throws Exception {
      Iterator readers = ImageIO.getImageReadersByFormatName("png");
      ImageReader reader = (ImageReader) readers.next();
 
      IIOReadProgressListener listener = new MyReadProgressListener();
      reader.addIIOReadProgressListener(listener);
 
      ImageInputStream iis = ImageIO.createImageInputStream(new File(filename));
      reader.setInput(iis, true);
      background = reader.read(0);
   }
 
   public static void main(String []args) throws Exception {
      Main main = new Main();
      main.setSize(400, 150);
      main.setVisible(true);
  
      main.loadBackgroundImage("fruit.png");
   }
 
   public void paint(Graphics g) {
      System.out.println(background);
      if (background != null) {
         g.drawImage(background, 0, 0, getWidth(), getHeight(), this);
      }
   }
 
   class MyReadProgressListener implements IIOReadProgressListener {
 
	public MyReadProgressListener() {}
 
        public void imageProgress(ImageReader source, final float percentageDone) {
           System.out.println("imageProgress: " + percentageDone);
 
           SwingUtilities.invokeLater(new Runnable() {
              public void run() {
                 progressBar.setValue((int) percentageDone);
              }
           });   
        }
 
        public void imageComplete(ImageReader source) {
           SwingUtilities.invokeLater(new Runnable() {
              public void run() {
                 try {
                    // wait for a bit until bufferedimage is assigned by reader
                    Thread.sleep(50);
                 }
                 catch(InterruptedException e) { }
                 repaint();
              }
           });              
        }
 
        public void imageStarted(ImageReader source, int imageIndex)  { }
        public void readAborted(ImageReader source)                   { }
        public void sequenceComplete(ImageReader source)              { }
        public void sequenceStarted(ImageReader source, int minIndex) { }
        public void thumbnailComplete(ImageReader source)             { }
        public void thumbnailProgress(ImageReader source, float percentageDone) { }
        public void thumbnailStarted(ImageReader source, int imageIndex, int thumbnailIndex) { }
   }
}

Adding blank space between elements of a JToolBar

Set an empty border on your JButtons that you add to your JToolBar!

Main.java:

import javax.swing.border.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
  
public class Main extends JFrame {
   public Main() {
      super("JToolBar example");
 
      final JTextArea textArea = new JTextArea(5, 30);
      JToolBar toolBar = new JToolBar();
 
      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");
         }
      });
 
      gifButton.setBorder(new EmptyBorder(new Insets(10,10,10,1)));
      jpgButton.setBorder(new EmptyBorder(new Insets(10,10,10,10)));
      tiffButton.setBorder(new EmptyBorder(new Insets(10,10,10,10)));
 
      toolBar.add(gifButton);
      toolBar.add(jpgButton);
      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));
   }
 
   public static void main(String[] args) {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);
   }
}

images used in this app:


Setting the background image for a JInternalFrame

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.net.*;
 
public class Main extends JFrame {
   JDesktopPane desktop;
   int nframes = 0;
 
   public Main() {
      getContentPane().setLayout(new BorderLayout());
      desktop = new JDesktopPane(); 
      createInternalFrame();
      getContentPane().add(BorderLayout.CENTER, desktop);
      setJMenuBar(createMenuBar());
  
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   
      setTitle("Transparent JInternalFrame Demonstration");
      setSize(new Dimension(400, 400));
   }
 
   protected JMenuBar createMenuBar() {
      JMenuBar menuBar = new JMenuBar();
 
      JMenu menu = new JMenu("JDesktopPane");
      JMenuItem menuItem1 = new JMenuItem("Create new JInternalFrame");
      menuItem1.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            createInternalFrame();
         }
      });
      menu.add(menuItem1);
      menuBar.add(menu);
 
      return menuBar;
   }
 
   protected void createInternalFrame() {
      JInternalFrame frame = new JInternalFrame("InternalFrame", 
         true,    // resizable
         true,    // closable
         true,    // maximizable
         true);   // iconifiable
      frame.setVisible(true); 
      desktop.add(frame);
      frame.setSize(200, 200);
      frame.setLocation(30*nframes, 30*nframes);
      nframes++;
      frame.setContentPane(new ImageBackgroundPanel(
                             new ImageIcon("mong.jpg")));
 
      frame.getContentPane().add(new JLabel("Your name"));
      frame.getContentPane().add(new JTextField(10));
 
      try {
         frame.setSelected(true);
      } catch (java.beans.PropertyVetoException e) {}
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.show();
   }
}
 
class ImageBackgroundPanel extends JPanel
{
   private ImageIcon bgImage;
 
   public ImageBackgroundPanel(ImageIcon bgImage) {
      this.bgImage = bgImage;
   }
 
   public void paintComponent(Graphics g) {    
      Dimension d = getSize();      
      g.drawImage(bgImage.getImage(), 0, 0, (int)d.getWidth(), (int)d.getHeight() , this);          
   }
}

Defining the size of a JComboBox

If you want to change the size of the JComboBox component itself, use:

   combobox.setPreferredSize(new Dimension(x, y));

If you want to have control over the popupwidth and popupheight, extend JComboBox and add the necessary functionality to a custom ComboBoxUI:
Main.java:

import javax.swing.plaf.metal.*;
import javax.swing.plaf.basic.*;
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<20; i++)
         v.addElement("ComboBox Item #" + i);
      SizedJComboBox combobox = new SizedJComboBox(v);
 
      combobox.setPopupWidth(190);
      combobox.setPopupHeight(30);
 
      getContentPane().add(combobox);
  
      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);
   }
}
 
class SizedJComboBox extends JComboBox {
   protected int popupWidth;
   protected int popupHeight;
 
   public SizedJComboBox(ComboBoxModel aModel) {
      super(aModel);
      setUI(new SizedComboBoxUI());
   }
 
   public SizedJComboBox(final Object[] items) { 
      super(items); 
      setUI(new SizedComboBoxUI());
   } 
 
   public SizedJComboBox(Vector items) { 
      super(items); 
      setUI(new SizedComboBoxUI()); 
   } 
 
   public void setPopupWidth(int width) { 
      popupWidth = width; 
   }
 
   public void setPopupHeight(int height) {
      popupHeight = height;
   } 
 
   public Dimension getPopupSize() { 
      Dimension size = getSize(); 
      if (popupWidth < 1) popupWidth = size.width; 
      return new Dimension(popupWidth, popupHeight); 
   } 
}
 
class SizedComboBoxUI extends MetalComboBoxUI {
   protected ComboPopup createPopup() { 
      BasicComboPopup popup = new BasicComboPopup(comboBox) { 
         public void show() { 
            Dimension popupSize = ((SizedJComboBox) comboBox).getPopupSize(); 
            popupSize.setSize(popupSize.width, popupSize.height < 1 ? getPopupHeightForRowCount(comboBox.getMaximumRowCount()) : popupSize.height); 
            Rectangle popupBounds = computePopupBounds( 0, 
                  comboBox.getBounds().height, popupSize.width, popupSize.height); 
            scroller.setMaximumSize(popupBounds.getSize()); 
            scroller.setPreferredSize(popupBounds.getSize()); 
            scroller.setMinimumSize(popupBounds.getSize()); 
            list.invalidate(); 
            int selectedIndex = comboBox.getSelectedIndex(); 
            if (selectedIndex == -1) { 
               list.clearSelection(); 
            } else { 
               list.setSelectedIndex( selectedIndex ); 
            } 
            list.ensureIndexIsVisible( list.getSelectedIndex() ); 
            setLightWeightPopupEnabled(comboBox.isLightWeightPopupEnabled()); 
 
            show(comboBox, popupBounds.x, popupBounds.y); 
         } 
      }; 
 
      popup.getAccessibleContext().setAccessibleParent(comboBox); 
      return popup; 
   } 
} 

Detecting a double-click on an element in a JList

For detecting double-clicking, add a MouseListener and catch the MouseEvents where clickCount is equal to 2.

Here’s an 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);
      }
      getContentPane().add(new JLabel("Double-clicked on: "));
      final JTextField dblTextField = new JTextField(15);
      getContentPane().add(dblTextField);
      final JList list = new JList(v);
 
      // catch double-click events
      list.addMouseListener(new MouseAdapter() {
         public void mouseClicked(MouseEvent me) {
            if (me.getClickCount() == 2) {
               dblTextField.setText(""+list.getSelectedValue()); 
            }
         }
      });
 
      getContentPane().add(new JScrollPane(list));    
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      setSize(200, 300);
   }
   
   public static void main(String[] args) {
      (new Main()).show();
   }
}

Changing the font of a JMenuItem

You can either embed HTML in the JMenuItem’s text, or you can call the method setFont.

Main.java:

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("Sex");
      JMenuItem menuItem1 = new JMenuItem("<html><font size=-1>male</font></html>");
      JMenuItem menuItem2 = new JMenuItem("<html><font size=+1>female</font></html>");
      JMenuItem menuItem3 = new JMenuItem("androgyne");
      menuItem3.setFont(new Font("Monospaced", Font.ITALIC, 36));
 
      // add the MenuItems to the Menu 
      menu.add(menuItem1);
      menu.add(menuItem2);
      menu.add(menuItem3);
 
      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();
   }
}

Limiting the length of text entered in a JTextField

Create a custom component that extends from JTextField and allow the user to specify a maximum length. The implementation is simple: capture the insertString method and execute super.insertString when the condition (current length < = maximumlength) is met.

Main.java:

import javax.swing.text.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;
import java.awt.*;
   
public class Main extends JFrame {
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      getContentPane().add(new LimitedTextField("Try typing more", 15, 15));
      getContentPane().add(new LimitedTextField(10, 3));
  
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      setSize(300, 300);
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}
 
class LimitedTextField extends JTextField
{
   private int maxCols = 0;
 
   public LimitedTextField(int maxCols) {
      super();
      this.maxCols = maxCols;
   }
 
   public LimitedTextField(int cols, int maxCols) {
      super(cols);
      this.maxCols = maxCols;
   }
  
   public LimitedTextField(String text, int maxCols) {
      super();
      this.maxCols = maxCols;
      setText(text);
   } 
 
   public LimitedTextField(String text, int cols, int maxCols) {
      super(cols);
      this.maxCols = maxCols;
      setText(text);
   }
 
   protected Document createDefaultModel() {
      return new LimitedDocument();
   }
  
   protected class LimitedDocument extends PlainDocument {
      public void insertString(int offset, String str, AttributeSet as) 
            throws BadLocationException  {
         if (str == null || getLength() + str.length() <= maxCols) {
            super.insertString(offset, str, as);
         }
         else {
            int remainder = maxCols – getLength();
            if (remainder > 0) {
               super.insertString(offset, str.substring(0, remainder), as);
            }
         }
      }
   }
}

Displaying the EURO sign in a JLabel

JLabel is able to render HTML (3.2). You can use the code € inside html tags as shown in following example:

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.text.*;
import java.awt.*;
   
public class Main extends JFrame {
   public Main() {
      getContentPane().setLayout(new FlowLayout());
 
      JLabel label = new JLabel("<html>&#8364;</html>");
      getContentPane().add(label);     
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      pack();
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}

Detecting a cell selection in a JTable

You can do so with a combination of a ColumnModelListener and a TableSelectionListener. An easier way is to register a MouseListener to your JTable as shown in following example.

Main.java:

import javax.swing.table.*;
import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
 
public class Main extends JFrame {
   public Main() {
      super("TableModel Demonstration");
 
      // create our own custom TableModel
      WineTableModel wineModel = new WineTableModel();
      final JTable table = new JTable(wineModel);
 
      // add rows to our TableModel, each row is represented as a Wine object
      wineModel.addWine(new Wine("Chateau Meyney, St. Estephe", "1994", 18.75f, true));
      wineModel.addWine(new Wine("Chateau Montrose, St. Estephe", "1975", 54.25f, true));
      wineModel.addWine(new Wine("Chateau Gloria, St. Julien", "1993", 22.99f, false));
      wineModel.addWine(new Wine("Chateau Beychevelle, St. Julien", "1970", 61.63f, false));
      wineModel.addWine(new Wine("Chateau La Tour de Mons, Margeaux", "1975", 57.03f, true));
      wineModel.addWine(new Wine("Chateau Brane-Cantenac, Margeaux", "1978", 49.92f, false));
 
      // create the scroll pane and add the table to it. 
      JScrollPane scrollPane = new JScrollPane(table);
 
      // add the scroll pane to this window.
      getContentPane().add(scrollPane, BorderLayout.CENTER);
 
      table.addMouseListener(new MouseAdapter() {
         public void mouseClicked(MouseEvent e) { 
            if (e.getClickCount() >= 1) {
               int row = table.getSelectedRow();
               int col = table.getSelectedColumn();
 
               if (row == -1 || col == -1) return;
               System.out.println("cell [" + row +","+ col +"]");
            }
         }
      });
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
   }
 
   public static void main(String[] args) {
      Main main = new Main();
      main.pack();
      main.setVisible(true);
   }
}
 
// a simple object that holds data about a particular wine
class Wine {
   private String  name;
   private String  vintage;
   private float   price;
   private boolean inStock;
 
   public Wine(String name, String vintage, float price, boolean inStock) {
      this.name = name;
      this.vintage = vintage;
      this.price = price;
      this.inStock = inStock;
   }
 
   public String getName()     { return name; }
   public String getVintage()  { return vintage; }
   public float  getPrice()    { return price; } 
   public boolean getInStock() { return inStock; }
 
   public String toString() { 
      return "[" + name + ", " + vintage + ", " + price + ", " + inStock + "]"; }
}
 
class WineTableModel extends AbstractTableModel {
   // holds the strings to be displayed in the column headers of our table
   final String[] columnNames = {"Name", "Vintage", "Price", "In stock?"};
 
   // holds the data types for all our columns
   final Class[] columnClasses = {String.class, String.class, Float.class, Boolean.class};
 
   // holds our data
   final Vector data = new Vector();
  
   // adds a row
   public void addWine(Wine w) {
      data.addElement(w);
      fireTableRowsInserted(data.size()-1, data.size()-1);
   }
 
   public int getColumnCount() {
      return columnNames.length;
   }
         
   public int getRowCount() {
      return data.size();
   }
 
   public String getColumnName(int col) {
      return columnNames[col];
   }
 
   public Class getColumnClass(int c) {
      return columnClasses1;
   }
 
   public Object getValueAt(int row, int col) {
      Wine wine = (Wine) data.elementAt(row);
      if (col == 0)      return wine.getName();
      else if (col == 1) return wine.getVintage();
      else if (col == 2) return new Float(wine.getPrice());
      else if (col == 3) return new Boolean(wine.getInStock());
      else return null;
   }
 
   public boolean isCellEditable(int row, int col) {
      return false;
   }
}

Creating a JTable with images in the headers

Courtesy of Nobuo Tamemasa (http://www2.gol.com/users/tame/swing/examples/JTableExamples8.html)



AnimatedIconHeaderExample.java:

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.table.*;

/**
 * @version 1.0 06/19/99
 */
public class AnimatedIconHeaderExample extends JFrame {

  public AnimatedIconHeaderExample(){
    super( "AnimatedIconHeader Example" );
    
    final Object[][] data =  new Object[][]{
      {"Leopard","Lycaon"},
      {"Jagur"  ,"Jackal"},
      {"Cheetah","Coyote"},
      {"Puma"   ,"Dingo" },
      {"Lynx"   ,"Fox"   },
      {"Tom"    ,"Hot"  }};
    final String[] column = new String[]{"Cat","Dog"};
    
    ImageIcon[] icons = {new ImageIcon("images/3-119.gif"),
                         new ImageIcon("images/3-6.gif")};
        
    AbstractTableModel model = new AbstractTableModel() {
      public int getColumnCount() { return column.length; }
      public int getRowCount()    { return data.length; }
      public String getColumnName(int col) {
       return column[col]; 
      }
      public Object getValueAt(int row, int col) { 
        return data[row][col]; 
      }
    };
        
    JTable table = new JTable( model );
    JTableHeader header = table.getTableHeader();
    JLabel renderer;
    for (int i=0;i<model.getColumnCount();i++) {
      renderer = (JLabel)table.getColumn(column[i]).getHeaderRenderer();
      renderer.setIcon(icons[i]);
      
      // If you have only one column.
      // icons[i].setImageObserver(header);
      
      icons[i].setImageObserver(new HeaderImageObserver(header, i));
    }
    JScrollPane pane = new JScrollPane(table);
    getContentPane().add(pane);
  }
    
  class HeaderImageObserver implements ImageObserver {
    JTableHeader header;
    int col;
      
    HeaderImageObserver(JTableHeader header, int col) {
      this.header = header;
      this.col    = col;
    }
    
    public boolean imageUpdate(Image img, int flags,
                               int x, int y, int w, int h) {
      if ((flags & (FRAMEBITS|ALLBITS)) != 0) {
        Rectangle rect = header.getHeaderRect(col);
        header.repaint(rect);
      }
      return (flags & (ALLBITS|ABORT)) == 0;
    }
  }    
  
  public static void main(String[] args) {
    AnimatedIconHeaderExample frame = new AnimatedIconHeaderExample();
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    frame.setSize( 300, 140 );
    frame.setVisible(true);
  }
}