Painting issue with JLayer and JPanel

Question

I want to paint an icon when user's input is invalid. I've found an example by Oracle and modified it for my purposes. The painting of Icon works correctly but when I change the value to correct the icon goes not completly invisible: the part which is drawn over the JPanel is still displayed.

Here is my code:

import java.awt.AlphaComposite;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.text.NumberFormat;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayer;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.plaf.LayerUI;

public class FieldValidator extends JPanel {
    private static final int ICON_SIZE = 12;
    private static final Icon ICON = createResizedIcon((ImageIcon) UIManager.getIcon("OptionPane.errorIcon"));
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createUI();
            }
        });
    }

    public static void createUI() {
        final JFrame f = new JFrame ("FieldValidator");

        final JComponent content = createContent();

        f.add (content);

        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo (null);
        f.setVisible (true);
    }

    private static JComponent createContent() {
        final LayerUI<JPanel> panelUI = new ValidationLayerUI();

        // Number field.
        final JLabel numberLabel = new JLabel("Number:");

        final NumberFormat numberFormat = NumberFormat.getInstance();
        final JFormattedTextField numberField = new JFormattedTextField(numberFormat) {
            /**
             * {@inheritDoc}
             */
            @Override
            public void replaceSelection(String content) {
                super.replaceSelection(content);
                getParent().repaint();
            }
        };
        numberField.setColumns(16);
        numberField.setFocusLostBehavior(JFormattedTextField.PERSIST);
        numberField.setValue(42);

        final int i = (ICON_SIZE / 2) + (ICON_SIZE % 2);
        final JPanel numberPanel = new JPanel();
        numberPanel.add(numberLabel);
        final JPanel panel = new JPanel(new GridBagLayout());
        final GridBagConstraints constr = new GridBagConstraints();
        constr.insets = new Insets(i, i, i, i);
        constr.weightx = 1;
        constr.weighty = 1;
        constr.fill = GridBagConstraints.BOTH;
        panel.add(numberField, constr);
        numberPanel.add(new JLayer<JPanel>(panel, panelUI));

        return numberPanel;
    }

    //Icon resized to 12x12
    private static Icon createResizedIcon(ImageIcon anIcon) {
        final BufferedImage result = new BufferedImage(ICON_SIZE, ICON_SIZE, BufferedImage.TYPE_INT_ARGB);
        final Graphics2D g = result.createGraphics();
        g.setComposite(AlphaComposite.Src);
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BICUBIC);
        g.drawImage(anIcon.getImage(), 0, 0, ICON_SIZE, ICON_SIZE, null);
        g.dispose();
        return new ImageIcon(result);

    }
    static class ValidationLayerUI extends LayerUI<JPanel> {

        @Override
        public void paint (Graphics g, JComponent c) {
            super.paint (g, c);
            final JLayer jlayer = (JLayer) c;
            final JPanel panel = (JPanel) jlayer.getView();
            final JFormattedTextField ftf = (JFormattedTextField) panel.getComponent(0);
            if (!ftf.isEditValid()) {
                ICON.paintIcon(panel, g, 0, panel.getHeight() - ICON.getIconHeight());
            }
        }

    }
}

Here is the screens: Initial all is correct

When I paint invalid Icon all is still correct

But when the value goes correct only the text field will be repainted

How can I force the JPanel to repaint???

P.S. I've already found an approach with JLayeredPane which works correct, but I want to know what is wrong in my code?

Answer 1

How about using the DocumentListener:

numberField.getDocument().addDocumentListener(new DocumentListener() {
  @Override public void insertUpdate(DocumentEvent e) {
    //Container c = numberField.getParent();
    Container c = SwingUtilities.getUnwrappedParent(numberField);
    if (c != null) {
      c.repaint();
    }
  }
  @Override public void removeUpdate(DocumentEvent e) {
    insertUpdate(e);
  }
  @Override public void changedUpdate(DocumentEvent e) {}
});

Edit

Quote from this link: Painting in AWT and Swing

The RepaintManager The purpose of Swing's RepaintManager class is to maximize the efficiency of repaint processing on a Swing containment hierarchy, and also to implement Swing's 'revalidation' mechanism (the latter will be a subject for a separate article). It implements the repaint mechanism by intercepting all repaint requests on Swing components (so they are no longer processed by the AWT) and maintaining its own state on what needs to be updated (known as "dirty regions"). Finally, it uses invokeLater() to process the pending requests on the event dispatching thread, as described in the section on "Repaint Processing" (option B).

In this case the parent JPanel is not dirty region when isEditValid() status changed. so remaining previous Icon paint.