change the size of JTextField on KeyPress

Question

I have to extend the size of JTextField on KeyPressed event as user enter the text in textfield.please give me some idea how to achieve this?

thanks in advance

Answer 1

Depends if you are using a LayoutManager or not. If not, attach a KeyListener to the JTextField and on keyRelease you need to calculate the length of the String (in pixels) and determine if the field needs to be updated

addDocumentListener(new DocumentListener() {

    public void changedUpdate(DocumentEvent e) {
        updateField();
    }

    public void insertUpdate(DocumentEvent e) {
        updateField();
    }

    public void removeUpdate(DocumentEvent e) {
        updateField();
    }

    public void updateField() {

        FontMetrics fm = getFontMetrics(getFont());
        String text = getText();

        int length = fm.stringWidth(text);

        Dimension size = getPreferredSize();
        Insets insets = getInsets();
        if (length < min) {

            size.width = min;

        } else {

            size.width = length + (insets.left + insets.right);

        }

        setSize(size);
        invalidate();
        repaint();

    }

});

Possibly a more sensible solution might be:

addDocumentListener(new DocumentListener() {

    public void changedUpdate(DocumentEvent e) {
        updateField();
    }

    public void insertUpdate(DocumentEvent e) {
        updateField();
    }

    public void removeUpdate(DocumentEvent e) {
        updateField();
    }

    public void updateField() {

        setColumns(getText().length());

    }

});

I would also pay attention to what kleopatra & mKorbel have to say. While KeyListener might seem like a good idea, there are just to many situation's where it won't be notified - setText is the major one.