Having a JTextArea as a node of a JTree

Main.java:

import javax.swing.border.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.net.*;
 
public class Main extends JFrame
{
   public Main() {
      DefaultMutableTreeNode root = createNodes();
      JTree tree = new JTree(root);
      //tree.setCellEditor(new DefaultCellEditor(new JTextField())); 
      tree.setCellRenderer(new DelegateDefaultCellRenderer());
      tree.setRowHeight(-1);
 
      getContentPane().add(new JScrollPane(tree));
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
   }
 
   public static DefaultMutableTreeNode createNodes() {
      DefaultMutableTreeNode root = new DefaultMutableTreeNode("Java");
      
      DefaultMutableTreeNode j2se = new DefaultMutableTreeNode("J2SE");
      DefaultMutableTreeNode j2ee = new DefaultMutableTreeNode("J2EE");
      DefaultMutableTreeNode j2me = new DefaultMutableTreeNode("J2ME");
 
      j2se.add(new DefaultMutableTreeNode("http://java.sun.com/j2se/"));
      j2ee.add(new DefaultMutableTreeNode("http://java.sun.com/j2ee/"));
      j2me.add(new DefaultMutableTreeNode("http://java.sun.com/j2me/"));
 
      root.add(j2se);
      root.add(j2ee);
      root.add(j2me);
 
      return root;
   }
 
   public static void main(String []args) {
      Main main = new Main();
      main.setSize(400, 400);
      main.setVisible(true);
   }
}
 
class DelegateDefaultCellRenderer extends DefaultTreeCellRenderer 
{
   TextAreaRenderer taRenderer = new TextAreaRenderer();
 
   public DelegateDefaultCellRenderer() {
      taRenderer.setBackgroundNonSelectionColor(getBackgroundNonSelectionColor());
      taRenderer.setBackgroundSelectionColor(getBackgroundSelectionColor());
      taRenderer.setTextNonSelectionColor(getTextNonSelectionColor());  
      taRenderer.setTextSelectionColor(getTextSelectionColor()); 
   }
 
   public Component getTreeCellRendererComponent(JTree tree, Object value,
                                  boolean selected, boolean expanded, boolean leaf,
                                  int row, boolean hasFocus)
   {
      if (!leaf) {
         return super.getTreeCellRendererComponent(tree, value, selected, 
                                                   expanded, leaf, row, hasFocus);
      }
      else {
         return taRenderer.getTreeCellRendererComponent(tree, value, selected, 
                                                        expanded, leaf, row, hasFocus);
      }
   }
}   
 
class TextAreaRenderer extends JScrollPane implements TreeCellRenderer
{
   JTextArea textarea;
   Color backgroundNonSelectionColor;
   Color backgroundSelectionColor;
   Color textNonSelectionColor;
   Color textSelectionColor;
 
   public TextAreaRenderer() {
      textarea = new JTextArea(3, 40);
      textarea.setLineWrap(true);
      textarea.setWrapStyleWord(true);
      textarea.setBorder(new TitledBorder("This is a JTextArea"));
      getViewport().add(textarea);
   }
 
   public void setBackgroundNonSelectionColor(Color c) {
      this.backgroundNonSelectionColor = c;
   }
 
   public void setBackgroundSelectionColor(Color c) {
      this.backgroundSelectionColor = c;
   }
  
   public void setTextNonSelectionColor(Color c) {
      this.textNonSelectionColor = c;
   }
  
   public void setTextSelectionColor(Color c) {
      this.textSelectionColor = c;
   }
 
   public Component getTreeCellRendererComponent(JTree tree, Object value,
                                  boolean selected, boolean expanded, boolean leaf,
                                  int row, boolean hasFocus)
   {
      if (selected) {
         setForeground(textSelectionColor);
         setBackground(backgroundSelectionColor);
         textarea.setForeground(textSelectionColor);
         textarea.setBackground(backgroundSelectionColor);
      } else {
         setForeground(textNonSelectionColor);
         setBackground(backgroundNonSelectionColor);
         textarea.setForeground(textNonSelectionColor);
         textarea.setBackground(backgroundNonSelectionColor);
      }
 
      textarea.setText(""+((DefaultMutableTreeNode) value).getUserObject()); 
      textarea.setCaretPosition(0);
 
      return this;
   }
}

Adding a popup listener to a JTable row

Main.java:

import javax.swing.table.*;
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);
 
      final TablePopup tablePopup = new TablePopup(table);
      table.addMouseListener(new MouseAdapter() {
         public void mouseReleased(MouseEvent me) {
            int row = table.rowAtPoint(me.getPoint());
            System.out.println("You clicked at row " + row);
            // possibly use row variable here to do something specific with your popup menu
            if (me.isPopupTrigger()) {
               tablePopup.show(me.getComponent(), me.getX(), me.getY());
            }
         }
      });
 
      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;
   }
}
 
class TablePopup extends JPopupMenu {
   public TablePopup(JTable tree) {
      JMenuItem itemEdit = new JMenuItem("Edit");
      JMenuItem itemDelete = new JMenuItem("Delete");
      itemEdit.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            System.out.println("Edit child");
         }
      });
      itemDelete.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            System.out.println("Delete selected");
         }
      });
 
      add(itemEdit);
      add(new JSeparator());
      add(itemDelete);
   }
}

Validating a textfield using the regex package

You can use a custom InputVerifier in which you try to match the desired regular expression for that textfield.

Main.java:

import java.util.regex.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.text.*;
 
public class Main extends JFrame
{
   public Main() {
      super("JFormattedTextField REGEX example");
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0);
         }
      });
 
      getContentPane().setLayout(new BorderLayout());
      JFormattedTextField ftf = new JFormattedTextField();
      getContentPane().add(BorderLayout.NORTH, ftf);
      ftf.setInputVerifier(new RegExFieldVerifier("[abcd]+"));
 
      getContentPane().add(BorderLayout.SOUTH, new JTextField("Normal textfield"));
      getContentPane().add(BorderLayout.CENTER, 
                               new JLabel("<HTML>REGEX USED:  [abcd]+   allowed: " +
                                          "one or more of the following characters: " +
                                          "a,b,c or d.<BR>Use the TAB key to switch!</HTML>"));
 
   }
 
   public static void main(String []args) throws Exception {
      Main main = new Main();
      main.setSize(300, 300);
      main.setVisible(true);
   }
}
 
class RegExFieldVerifier extends InputVerifier {
   Pattern pattern;
 
   public RegExFieldVerifier(String regex) {
      pattern = Pattern.compile(regex);
   }
 
   public boolean verify(JComponent input) {
      if (input instanceof JFormattedTextField) {
         JFormattedTextField ftf = (JFormattedTextField)input;
         String line = ftf.getText();
         Matcher m = pattern.matcher(line);
         if (!m.matches()) 
            System.out.println("Doesn't match regular expression " + 
                               pattern.pattern());      
         return m.matches();
      }        
      return true;     
   }
 
   public boolean shouldYieldFocus(JComponent input) {
      return verify(input);
   }
}

Setting a background image for a JDesktop

A JDesktopPane extends is a JLayeredPane. This container adds the notion of depth, allowing components to overlap each other. You specify the depth with an integer value, where higher-valued components sit on top of lower-valued components. To create a background image, just place it at the lowest layer: eg. the MIN_VALUE of an integer object. All other components must be layed out on top of this one.
Here’s an example, look at the method setBackgroundImage().

import java.awt.image.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import java.awt.*;
import java.net.*;

public class Main extends JFrame
{
   JDesktopPane desktop;
 
   public Main() {
      desktop = new JDesktopPane(); 
      setContentPane(desktop);
      setBackgroundImage();
      createInternalFrame();
      setSize(new Dimension(500, 300));
      setLocation(100, 100);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(0); 
         }
      });
   }
 
   protected void setBackgroundImage() {
      try {
         ImageIcon icon = new ImageIcon(new URL("http://www.esus.com/images/mong.jpg"));
         JLabel label = new JLabel(icon);
         label.setBounds(0, 0, icon.getIconWidth(), icon.getIconHeight());
  
         desktop.add(label, new Integer(Integer.MIN_VALUE));
      } catch(MalformedURLException e) {
         System.out.println(e);
      }
   }
  
   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);
      try {
         frame.setSelected(true);
      } catch (java.beans.PropertyVetoException e) {}
   }
 
   public static void main(String []args) throws Exception {
      Main main = new Main();
      main.show();      
   }
}

Externalizing a JInternalFrame in a JFrame

You can get the contentpane of a JInternalFrame and put it inside a JFrame. Check out the following example, specifically the classes MyJInternalFrame and MyJFrame.

Main.java:

import java.awt.event.*;
import javax.swing.*;
import java.beans.*;
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;
      MyJInternalFrame frame = new MyJInternalFrame(title,
         true,    // resizable
         true,    // closable
         true,    // maximizable
         true);   // iconifiable
      frame.setVisible(true); 
 
      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);
   }
} 
 
class MyJInternalFrame extends JInternalFrame 
                       implements VetoableChangeListener { 
   MyJFrame externalFrame = null;
 
   public MyJInternalFrame(String title, boolean resizable, 
                           boolean closable, boolean maximizable, 
                           boolean iconifiable) { 
      super(title, resizable, closable, maximizable, iconifiable); 
      addVetoableChangeListener(this); 
 
      getContentPane().setLayout(new GridLayout(3, 1));
      getContentPane().add(new JLabel("JLabel"));
      getContentPane().add(new JButton("JButton"));
      getContentPane().add(new JCheckBox("JCheckBox"));
   } 
 
   public void vetoableChange(PropertyChangeEvent pce) 
                                 throws PropertyVetoException { 
      if (pce.getPropertyName().equals(IS_CLOSED_PROPERTY)) { 
         boolean changed = ((Boolean) pce.getNewValue()).booleanValue(); 
         if (changed) { 
            setVisible(false);
            boolean packFrame = false;
            if (externalFrame == null) {
               externalFrame = new MyJFrame(this.getTitle(), this);
               packFrame = true;
            }
            Container cp = this.getContentPane();
            this.getRootPane().setContentPane(new JPanel());
            externalFrame.getRootPane().setContentPane(cp);
            externalFrame.setVisible(true);
 
            // remember frame size if frame was already shown before
            if (packFrame) externalFrame.pack();
             
            throw new PropertyVetoException("Intercepted Closing",null); 
         } 
      } 
   }
} 
 
class MyJFrame extends JFrame
{
   MyJInternalFrame internalFrame;
 
   public MyJFrame(String title, MyJInternalFrame internalFrame) {
      super(title);
      this.internalFrame = internalFrame;
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) { 
            MyJFrame frame = MyJFrame.this;
            frame.setVisible(false);
            Container cp = frame.getContentPane();
            frame.getRootPane().setContentPane(new JPanel());
            frame.internalFrame.getRootPane().setContentPane(cp);
            frame.internalFrame.setVisible(true);
         } 
      });
   }
}

Trapping a drop-down event on a JComboBox

Since JDK1.4, you can add a PopupMenuListener to your JComboBox and receive the events.

Main.java:

import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
 
public class Main extends JFrame { 
   public Main() {
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent we) {
            System.exit(1);
         }
      }); 
 
      Vector v = new Vector();
      v.add("first element");
      v.add("second element");
      v.add("third element");
      v.add("fourth element");
      v.add("fifth element");
 
      final JComboBox cb = new JComboBox(v);
      cb.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            System.out.println(cb.getSelectedItem());
         }
      });
 
      cb.addPopupMenuListener(new PopupMenuListener() {
         public void popupMenuCanceled(PopupMenuEvent e) {
            System.out.println("PopupMenuCancel Event");
         }
 
         public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
            System.out.println("popupMenuWillBecomeVisible");
         }
 
         public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
            System.out.println("popupMenuWillBecomeInvisible");
         }
      });
      getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT, 10, 10));
      getContentPane().add(new JLabel("Select element:"));
      getContentPane().add(cb);
   } 
 
   public static void main(String []args) {
      Main main = new Main();
      main.setVisible(true);
      main.setSize(300, 150);
   }
}

Displaying animated GIFs in a JList

Try this example with the following two images:

import javax.swing.border.*;
import java.awt.image.*;
import javax.swing.*;
import java.util.*;
import java.awt.*;
 
public class Main {
   public static void main(String args[]) {
      JFrame frame = new JFrame("JList Background Demonstration");
 
      JList list = new JList();
 
      String [] imageIcon = new String[] {
         "female.gif", "male.gif"
      };
 
      // create model
      Vector v = new Vector();
      for (int i=0; i<10; i++) {
         ImageIcon ii = new ImageIcon(imageIcon[i % 2]);
         ii.setImageObserver(new AnimatedObserver(list, i));
         v.addElement(ii);
      }
 
      list.setListData(v);
  
      frame.getContentPane().add(BorderLayout.CENTER, list); //new JScrollPane(list));
      frame.setDefaultCloseOperation(3);
      frame.pack();
      frame.setVisible(true);
   }
}
 
class AnimatedObserver implements ImageObserver 
{ 
   JList list; 
   int index; 
 
   public AnimatedObserver(JList list, int index) { 
      this.list = list; 
      this.index = index; 
   }  
 
   public boolean imageUpdate (Image img, int infoflags, int x, int y, int width, int height) {
      if ((infoflags & (FRAMEBITS|ALLBITS)) != 0) { 
         Rectangle rect = list.getCellBounds(index, index); 
         list.repaint(rect); 
      } 
 
      return (infoflags & (ALLBITS|ABORT)) == 0; 
   }
} 

Dynamically removing a separator from a JMenu

Look in the JMenu API for the remove methods!

Main.java:

import javax.swing.event.*;
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();
      // used in inner class, so final
      final JMenu menu = new JMenu("Sex");
      JMenuItem menuItem0 = new JMenuItem("female");
      JMenuItem menuItem1 = new JMenuItem("male");
      JMenuItem menuItem2 = new JMenuItem("androgyn");
 
      // add the MenuItems to the Menu 
      menu.add(menuItem0);
      menu.add(menuItem1);
 
      // used in inner class, so final
      final JSeparator jsep = new JSeparator();
      menu.add(jsep);
      menu.add(menuItem2);
   
      menuBar.add(menu);
 
      this.setJMenuBar(menuBar); 
      final JButton button = new JButton("remove menu separator");
      button.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            menu.remove(jsep);
            button.setEnabled(false);
         }
      });
      getContentPane().add(button);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      setSize(400, 400);
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}

Changing the font color of a JLabel

Use the method setForeground.

Main.java:

import javax.swing.border.*;
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("The font and color of this JLabel have been changed!");
      getContentPane().add(label);  
      label.setFont(new Font("Tahoma", Font.ITALIC, 30));
      label.setForeground(Color.red);
 
      addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent event) {
            System.exit(0);   
         }      
      });
 
      pack();
   }
 
   public static void main(String[] args) {
      (new Main()).show();
   }
}