import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.net.URL;
public class ListDataEventDemo extends JApplet
implements ListSelectionListener {
private JList list;
private DefaultListModel listModel;
private static final String addString = "Add";
private static final String deleteString = "Delete";
private static final String upString = "Move up";
private static final String downString = "Move down";
private JButton addButton;
private JButton deleteButton;
private JButton upButton;
private JButton downButton;
private JTextField nameField;
private JTextArea log;
static private String newline = "\n";
public void init() {
//Create and populate the list model.
listModel = new DefaultListModel();
listModel.addElement("Whistler, Canada");
listModel.addElement("Jackson Hole, Wyoming");
listModel.addElement("Squaw Valley, California");
listModel.addElement("Telluride, Colorado");
listModel.addElement("Taos, New Mexico");
listModel.addElement("Snowbird, Utah");
listModel.addElement("Chamonix, France");
listModel.addElement("Banff, Canada");
listModel.addElement("Arapahoe Basin, Colorado");
listModel.addElement("Kirkwood, California");
listModel.addElement("Sun Valley, Idaho");
listModel.addListDataListener(new MyListDataListener());
//Create the list and put it in a scroll pane.
list = new JList(listModel);
list.setSelectionMode(
ListSelectionModel.SINGLE_INTERVAL_SELECTION);
list.setSelectedIndex(0);
list.addListSelectionListener(this);
JScrollPane listScrollPane = new JScrollPane(list);
//Create the list modifying buttons.
addButton = new JButton(addString);
addButton.setActionCommand(addString);
addButton.addActionListener(new AddButtonListener());
deleteButton = new JButton(deleteString);
deleteButton.setActionCommand(deleteString);
deleteButton.addActionListener(
new DeleteButtonListener());
upButton = new JButton(
new ImageIcon(getURL("images/up.gif")));
upButton.setMargin(new Insets(0,0,0,0));
upButton.setActionCommand(upString);
upButton.addActionListener(new UpDownListener());
downButton = new JButton(
new ImageIcon(getURL("images/down.gif")));
downButton.setMargin(new Insets(0,0,0,0));
downButton.setActionCommand(downString);
downButton.addActionListener(new UpDownListener());
JPanel upDownPanel = new JPanel(new GridLayout(2, 1));
upDownPanel.add(upButton);
upDownPanel.add(downButton);
//Create the text field for entering new names.
nameField = new JTextField(15);
nameField.addActionListener(new AddButtonListener());
String name = listModel.getElementAt(list.getSelectedIndex())
.toString();
nameField.setText(name);
//Create a control panel (uses the default FlowLayout).
JPanel buttonPane = new JPanel();
buttonPane.add(nameField);
buttonPane.add(addButton);
buttonPane.add(deleteButton);
buttonPane.add(upDownPanel);
//Create the log for reporting list data events.
log = new JTextArea(10, 20);
JScrollPane logScrollPane = new JScrollPane(log);
//Create a split pane for the log and the list.
JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
listScrollPane, logScrollPane);
Container contentPane = getContentPane();
contentPane.add(buttonPane, BorderLayout.NORTH);
contentPane.add(splitPane, BorderLayout.CENTER);
}
class MyListDataListener implements ListDataListener {
public void contentsChanged(ListDataEvent e) {
log.append("contentsChanged: " + e.getIndex0() +
", " + e.getIndex1() + newline);
}
public void intervalAdded(ListDataEvent e) {
log.append("intervalAdded: " + e.getIndex0() +
", " + e.getIndex1() + newline);
}
public void intervalRemoved(ListDataEvent e) {
log.append("intervalRemoved: " + e.getIndex0() +
", " + e.getIndex1() + newline);
}
}
class DeleteButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
/*
* This method can be called only if
* there's a valid selection,
* so go ahead and remove whatever's selected.
*/
ListSelectionModel lsm = list.getSelectionModel();
int firstSelected = lsm.getMinSelectionIndex();
int lastSelected = lsm.getMaxSelectionIndex();
listModel.removeRange(firstSelected, lastSelected);
int size = listModel.size();
if (size == 0) {
//List is empty: disable delete, up, and down buttons.
deleteButton.setEnabled(false);
upButton.setEnabled(false);
downButton.setEnabled(false);
} else {
//Adjust the selection.
if (firstSelected == listModel.getSize()) {
//Removed item in last position.
firstSelected--;
}
list.setSelectedIndex(firstSelected);
}
}
}
/** A listener shared by the text field and add button. */
class AddButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (nameField.getText().equals("")) {
//User didn't type in a name...
Toolkit.getDefaultToolkit().beep();
return;
}
int index = list.getSelectedIndex();
int size = listModel.getSize();
//If no selection or if item in last position is selected,
//add the new one to end of list, and select new one.
if (index == -1 || (index+1 == size)) {
listModel.addElement(nameField.getText());
list.setSelectedIndex(size);
//Otherwise insert the new one after the current selection,
//and select new one.
} else {
listModel.insertElementAt(nameField.getText(), index+1);
list.setSelectedIndex(index+1);
}
}
}
//Listen for clicks on the up and down arrow buttons.
class UpDownListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//This method can be called only when
//there's a valid selection,
//so go ahead and move the list item.
int moveMe = list.getSelectedIndex();
if (e.getActionCommand().equals(upString)) {
//UP ARROW BUTTON
if (moveMe != 0) {
//not already at top
swap(moveMe, moveMe-1);
list.setSelectedIndex(moveMe-1);
list.ensureIndexIsVisible(moveMe-1);
}
} else {
//DOWN ARROW BUTTON
if (moveMe != listModel.getSize()-1) {
//not already at bottom
swap(moveMe, moveMe+1);
list.setSelectedIndex(moveMe+1);
list.ensureIndexIsVisible(moveMe+1);
}
}
}
}
//Swap two elements in the list.
private void swap(int a, int b) {
Object aObject = listModel.getElementAt(a);
Object bObject = listModel.getElementAt(b);
listModel.set(a, bObject);
listModel.set(b, aObject);
}
//Listener method for list selection changes.
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting() == false) {
if (list.getSelectedIndex() == -1) {
//No selection: disable delete, up, and down buttons.
deleteButton.setEnabled(false);
upButton.setEnabled(false);
downButton.setEnabled(false);
nameField.setText("");
} else if (list.getSelectedIndices().length > 1) {
//Multiple selection: disable up and down buttons.
deleteButton.setEnabled(true);
upButton.setEnabled(false);
downButton.setEnabled(false);
} else {
//Single selection: permit all operations.
deleteButton.setEnabled(true);
upButton.setEnabled(true);
downButton.setEnabled(true);
nameField.setText(list.getSelectedValue().toString());
}
}
}
protected URL getURL(String filename) {
URL codeBase = this.getCodeBase();
URL url = null;
try {
url = new URL(codeBase, filename);
} catch (java.net.MalformedURLException e) {
System.out.println("Couldn't create image: badly specified URL");
return null;
}
return url;
}
}
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