Creating a Blurred Transperent JPanel

Question

I'm attempting to make a Subclass to JLabel, which I named BlurPanel. I want the class to act like any normal swing container, only it must as default have a transparent background i.e. (setOpaque(false)) and it must blur the background of the parent frame. So far i've managed to blur BufferedImages and resized them, but when using standard swing layout managers i'm having a hard time at cropping the frame picture to the BlurPanels position. Does anyone have a good strategy to do this? Maybe it can be done without copying the underlying picture?

Answer 1

Use GlassPane Luke

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.MouseAdapter;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;
import javax.swing.WindowConstants;

/**
 * Glass pane used to blur the content of the window.
 *
 * @author SMedvynskyy
 */
@SuppressWarnings("serial")
public class SplashGlassPane extends JPanel implements FocusListener {

    /**
     * Creates new GlassPane.
     */
    public SplashGlassPane() {
        addMouseListener(new MouseAdapter() {});
        addMouseMotionListener(new MouseAdapter() {});
        addFocusListener(this);
        setOpaque(false);
        setFocusable(true);
        setBackground(new Color(0, 0, 0, 190));
    }

    @Override
    public final void setVisible(boolean v) {
        // Make sure we grab the focus so that key events don't go astray.
        if (v) {
            requestFocus();
        }
        super.setVisible(v);
    }

    // Once we have focus, keep it if we're visible
    @Override
    public final void focusLost(FocusEvent fe) {
        if (isVisible()) {
            requestFocus();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public final void paint(Graphics g) {
        final Color old = g.getColor();
        g.setColor(getBackground());
        g.fillRect(0, 0, getSize().width, getSize().height);
        g.setColor(old);
        super.paint(g);
    }

    @Override
    public void focusGained(FocusEvent fe) {
        // nothing to do
    }

    public static void main(String[] args) {
        final JFrame frm = new JFrame("Test blurring");
        frm.add(new JTextField("It's first component"), BorderLayout.NORTH);
        frm.add(new JTextField("It's second component"), BorderLayout.SOUTH);
        final JButton btn = new JButton("Start blur");
        btn.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                frm.getGlassPane().setVisible(true);
                final Timer t = new Timer(5000, new ActionListener() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        frm.getGlassPane().setVisible(false);
                    }
                });
                t.setRepeats(false);
                t.start();
            }
        });
        frm.add(btn);
        frm.setSize(500, 400);
        frm.setGlassPane(new SplashGlassPane());

        frm.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frm.setVisible(true);
    }
}