Java Example Program / Sample Source Code
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*
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*
* - Redistributions in binary form must reproduce the above copyright
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*
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*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* ContainerEventDemo.java requires no other files.
*/
import javax.swing.*;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;
public class ContainerListenerExample extends JPanel implements
ContainerListener, ActionListener {
JTextArea display;
JPanel buttonPanel;
JButton addButton, removeButton, clearButton;
Vector<JButton> buttonList;
static final String ADD = "add";
static final String REMOVE = "remove";
static final String CLEAR = "clear";
static final String newline = "\n";
public ContainerListenerExample() {
super(new GridBagLayout());
GridBagLayout gridbag = (GridBagLayout) getLayout();
GridBagConstraints c = new GridBagConstraints();
// Initialize an empty list of buttons.
buttonList = new Vector<JButton>(10, 10);
// Create all the components.
addButton = new JButton("Add a button");
addButton.setActionCommand(ADD);
addButton.addActionListener(this);
removeButton = new JButton("Remove a button");
removeButton.setActionCommand(REMOVE);
removeButton.addActionListener(this);
buttonPanel = new JPanel(new GridLayout(1, 1));
buttonPanel.setPreferredSize(new Dimension(200, 75));
buttonPanel.addContainerListener(this);
display = new JTextArea();
display.setEditable(false);
JScrollPane scrollPane = new JScrollPane(display);
scrollPane.setPreferredSize(new Dimension(200, 75));
clearButton = new JButton("Clear text area");
clearButton.setActionCommand(CLEAR);
clearButton.addActionListener(this);
c.fill = GridBagConstraints.BOTH; // Fill entire cell.
c.weighty = 1.0; // Button area and message area have equal height.
c.gridwidth = GridBagConstraints.REMAINDER; // end of row
gridbag.setConstraints(scrollPane, c);
add(scrollPane);
c.weighty = 0.0;
gridbag.setConstraints(clearButton, c);
add(clearButton);
c.weightx = 1.0; // Add/remove buttons have equal width.
c.gridwidth = 1; // NOT end of row
gridbag.setConstraints(addButton, c);
add(addButton);
c.gridwidth = GridBagConstraints.REMAINDER; // end of row
gridbag.setConstraints(removeButton, c);
add(removeButton);
c.weighty = 1.0; // Button area and message area have equal height.
gridbag.setConstraints(buttonPanel, c);
add(buttonPanel);
setPreferredSize(new Dimension(400, 400));
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}
public void componentAdded(ContainerEvent e) {
displayMessage(" added to ", e);
}
public void componentRemoved(ContainerEvent e) {
displayMessage(" removed from ", e);
}
void displayMessage(String action, ContainerEvent e) {
display.append(((JButton) e.getChild()).getText() + " was" + action
+ e.getContainer().getClass().getName() + newline);
display.setCaretPosition(display.getDocument().getLength());
}
/*
* This could have been implemented as two or three classes or objects, for
* clarity.
*/
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (ADD.equals(command)) {
JButton newButton = new JButton("JButton #"
+ (buttonList.size() + 1));
buttonList.addElement(newButton);
buttonPanel.add(newButton);
buttonPanel.revalidate(); // Make the button show up.
} else if (REMOVE.equals(command)) {
int lastIndex = buttonList.size() - 1;
try {
JButton nixedButton = buttonList.elementAt(lastIndex);
buttonPanel.remove(nixedButton);
buttonList.removeElementAt(lastIndex);
buttonPanel.revalidate(); // Make the button disappear.
buttonPanel.repaint(); // Make the button disappear.
} catch (ArrayIndexOutOfBoundsException exc) {
}
} else if (CLEAR.equals(command)) {
display.setText("");
}
}
/**
* Create the GUI and show it. For thread safety, this method should be
* invoked from the event-dispatching thread.
*/
private static void createAndShowGUI() {
// Create and set up the window.
JFrame frame = new JFrame("ContainerListenerExample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create and set up the content pane.
JComponent newContentPane = new ContainerListenerExample();
newContentPane.setOpaque(true); // content panes must be opaque
frame.setContentPane(newContentPane);
// Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
// Schedule a job for the event-dispatching thread:
// creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
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