Universal way to detect field changes?

[Phil Chuang]

Now, maybe this is just me, but I thought that the main field components (JTextField, JTextArea, JCheckBox, JComboBox, etc.) would've had some sort of addValueChangeListener method, that catches all data value modifications to the field - like changes to the text field, checkbox checked/unchecked, etc.

But there isn't any such thing. I've tried using ActionListener, KeyListener, ChangeListener, ItemListener, PropertyChangeListener, etc., but none of them do the trick. The closest thing I can do is use a FocusListener that compares entry/exit data values.

Is there any way I can get a listener that fires immediately upon value changes?

[Gregg Bolinger]

You need to use a DocumentListener for this. Something like this:

textField.getDocument().addDocumentListener(new MyDocumentListener());
 
class MyDocumentListener implements DocumentListener {
    String newline = "\n";
 
    public void insertUpdate(DocumentEvent e) {
        updateLog(e, "inserted into");
    }
    public void removeUpdate(DocumentEvent e) {
        updateLog(e, "removed from");
    }
    public void changedUpdate(DocumentEvent e) {
        //Plain text components don't fire these events
    }
 
    public void updateLog(DocumentEvent e, String action) {
        Document doc = (Document)e.getDocument();
        int changeLength = e.getLength();
        displayArea.append(
            changeLength + " character" +
            ((changeLength == 1) ? " " : "s ") +
            action + doc.getProperty("name") + "." + newline +
            "  Text length = " + doc.getLength() + newline);
    }
}

hth
[ September 09, 2004: Message edited by: Gregg Bolinger ]

[Phil Chuang]

What do you suggest for JComboBox, or other non-Text fields?