ComoboBox loads and saves items automatically from a file
import java.awt.BorderLayout;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.net.URL;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.event.HyperlinkEvent;
import javax.swing.event.HyperlinkListener;
public class MemComboBoxDemo extends JFrame {
protected MemComboBox urlComboBox = new MemComboBox();
public MemComboBoxDemo() {
super();
setSize(300, 100);
getContentPane().setLayout(new BorderLayout());
JPanel p = new JPanel();
p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));
p.add(new JLabel("Address"));
urlComboBox.load("addresses.dat");
ComboBoxListener lst = new ComboBoxListener();
urlComboBox.addActionListener(lst);
MemComboAgent agent = new MemComboAgent(urlComboBox);
p.add(urlComboBox);
getContentPane().add(p, BorderLayout.NORTH);
WindowListener wndCloser = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
urlComboBox.save("addresses.dat");
System.exit(0);
}
};
addWindowListener(wndCloser);
setVisible(true);
urlComboBox.grabFocus();
}
class ComboBoxListener implements ActionListener{
public void actionPerformed(ActionEvent evt) {
System.out.println( urlComboBox.getSelectedItem());
}
}
public static void main(String argv[]) {
new MemComboBoxDemo();
}
}
class MemComboAgent extends KeyAdapter {
protected JComboBox comboBox;
protected JTextField editor;
public MemComboAgent(JComboBox c) {
comboBox = c;
editor = (JTextField) c.getEditor().getEditorComponent();
editor.addKeyListener(this);
}
public void keyReleased(KeyEvent e) {
char ch = e.getKeyChar();
if (ch == KeyEvent.CHAR_UNDEFINED || Character.isISOControl(ch))
return;
int pos = editor.getCaretPosition();
String str = editor.getText();
if (str.length() == 0)
return;
for (int k = 0; k < comboBox.getItemCount(); k++) {
String item = comboBox.getItemAt(k).toString();
if (item.startsWith(str)) {
editor.setText(item);
editor.setCaretPosition(item.length());
editor.moveCaretPosition(pos);
break;
}
}
}
}
class MemComboBox extends JComboBox {
public static final int MAX_MEM_LEN = 30;
public MemComboBox() {
super();
setEditable(true);
}
public void add(String item) {
removeItem(item);
insertItemAt(item, 0);
setSelectedItem(item);
if (getItemCount() > MAX_MEM_LEN)
removeItemAt(getItemCount() - 1);
}
public void load(String fName) {
try {
if (getItemCount() > 0)
removeAllItems();
File f = new File(fName);
if (!f.exists())
return;
FileInputStream fStream = new FileInputStream(f);
ObjectInput stream = new ObjectInputStream(fStream);
Object obj = stream.readObject();
if (obj instanceof ComboBoxModel)
setModel((ComboBoxModel) obj);
stream.close();
fStream.close();
} catch (Exception e) {
System.err.println("Serialization error: " + e.toString());
}
}
public void save(String fName) {
try {
FileOutputStream fStream = new FileOutputStream(fName);
ObjectOutput stream = new ObjectOutputStream(fStream);
stream.writeObject(getModel());
stream.flush();
stream.close();
fStream.close();
} catch (Exception e) {
System.err.println("Serialization error: " + e.toString());
}
}
}
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