Hover Effects with Java Swing

Question

In my main window I have two panels. They are leftPanel and rightPanel. In the leftPanel I have two buttons: matchButton and simulatorButton. In my rightPanel I have an image drawn on it. I tried to add a hover effect to both buttons. When hovering the mouse over the matchButton the image contained in the rightPanel would change to a new image. When removing the mouse from the matchButton the image on the rightPanel would revert to the default image. It would be the same with simulatorButton. For that I created a separate class and added the following code:

public class ImgPanelStart extends JPanel {
    private Image backgroundImage;
    private BufferedImage imgBg;

    public ImgPanelStart() {
        try {
            backgroundImage = ImageIO.read(new File("./apsProject/assets/img0.jpg"));
        } catch (IOException ex) {
            System.out.println("Falha ao carregar imagem de fundo");
        }
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (backgroundImage != null) {
            g.drawImage(imgBg, 0, 0, null);
        }
        Dimension dim = this.getSize();
        int dWidth = (int) dim.getWidth();
        int dHeight = (int) dim.getHeight();
        imgBg = new BufferedImage(dWidth, dHeight, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = imgBg.createGraphics();
        g2.drawImage(backgroundImage, 0, 0, dWidth, dHeight, null);
        g2.dispose();
        g.drawImage(imgBg, 0, 0, null);
    }

    private void setImgBackground(Image img) {
        backgroundImage = img;
        if (imgBg == null) {
            imgBg = new BufferedImage(850, 600, BufferedImage.TYPE_INT_RGB);
        }
        Graphics2D g2 = imgBg.createGraphics();
        g2.drawImage(backgroundImage, 0, 0, getWidth(), getHeight(), null);
        g2.dispose();
        repaint();
    }

    public void addHoverEffect(JButton button, JButton button2) {
        button.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                try {
                    setImgBackground(ImageIO.read(new File("./apsProject/assets/wall.jpg")));
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }

            @Override
            public void mouseExited(MouseEvent e) {
                try {
                    setImgBackground(ImageIO.read(new File("./apsProject/assets/img0.jpg")));
                } catch (IOException e1) {
                    e1.printStackTrace();
                };
            }
        });

        button2.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                try {
                    setImgBackground(ImageIO.read(new File("./apsProject/assets/img2.jpg")));
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }

            @Override
            public void mouseExited(MouseEvent e) {
                try {
                    setImgBackground(ImageIO.read(new File("./apsProject/assets/img0.jpg")));
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
        });
    }
}

I call my method in the main class like this:

ImgPanelStart effects = new ImgPanelStart();
effects.addHoverEffect(matchButton, simulationButton);

However, the drawing made on the panel is not updated when hovering the mouse over it.

It would be something like, I hovered the mouse over the button button it would change the image in my rightPanel to wall.jpg. I removed the mouse and it would return to the image img0.jpg.

I hovered the mouse over the button2 button, it would change the image in my rightPanel to img2.jpg. When I removed the mouse it would return to the image img0.jpg.

Does anyone know what could be wrong, or give me a tip on what I can do to fix this problem?

Answer 1

Since your code was not a complete runnable example, I went ahead and created the following GUI.

Here's the same GUI when you hover over the simulation button.

Oracle has a helpful tutorial, Creating a GUI With Swing. Skip the Learning Swing with the NetBeans IDE section.

I read the images I wanted to use before I constructed the GUI. That way, I only read the images one time.

Here's the complete runnable code. I made the additional classes inner classes so I could post the code as one block.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class HoverEffects implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new HoverEffects());
    }

    private final DrawingPanel drawingPanel;

    private final LoadImages loadImages;

    public HoverEffects() {
        this.loadImages = new LoadImages();
        this.drawingPanel = new DrawingPanel(loadImages.getWallpaper());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Hover Effects");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createButtonPanel(), BorderLayout.WEST);
        frame.add(drawingPanel, BorderLayout.CENTER);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createButtonPanel() {
        JPanel outerPanel = new JPanel();

        JPanel panel = new JPanel(new GridLayout(0, 1, 5, 5));
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

        JButton matchButton = new JButton("Match");
        matchButton.addMouseListener(
                new HoverListener(this, loadImages, matchButton));
        panel.add(matchButton);

        JButton simulatorButton = new JButton("Simulation");
        simulatorButton.addMouseListener(
                new HoverListener(this, loadImages, simulatorButton));
        panel.add(simulatorButton);

        outerPanel.add(panel);

        return outerPanel;
    }

    public void setImage(Image image) {
        drawingPanel.setImage(image);
        drawingPanel.repaint();
    }

    public class DrawingPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        private Image image;

        public DrawingPanel(Image image) {
            setImage(image);
            this.setPreferredSize(new Dimension(800, 600));
        }

        public void setImage(Image image) {
            this.image = image;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(image, 0, 0, this);
        }

    }

    public class HoverListener extends MouseAdapter {

        private final HoverEffects view;

        private final LoadImages model;

        private final JButton button;

        public HoverListener(HoverEffects view, LoadImages model,
                JButton button) {
            this.view = view;
            this.model = model;
            this.button = button;
        }

        @Override
        public void mouseEntered(MouseEvent event) {
            String text = button.getText();
            if (text.equals("Match")) {
                view.setImage(model.getNature1());
            } else {
                view.setImage(model.getNature2());
            }
        }

        @Override
        public void mouseExited(MouseEvent event) {
            view.setImage(model.getWallpaper());
        }

    }

    public class LoadImages {

        private Image nature1, nature2, wallpaper;

        public LoadImages() {
            try {
                URL url = new URL(
                        "http://www.thewowstyle.com/wp-content/uploads/"
                                + "2015/01/nature-wallpaper-27.jpg");
                Image image = ImageIO.read(url);
                wallpaper = image.getScaledInstance(800, 600,
                        Image.SCALE_SMOOTH);
                url = new URL("http://www.thewowstyle.com/wp-content/uploads/"
                        + "2015/01/nature-images..jpg");
                image = ImageIO.read(url);
                nature1 = image.getScaledInstance(800, 600, Image.SCALE_SMOOTH);
                url = new URL("http://www.thewowstyle.com/wp-content/uploads/"
                        + "2015/01/nature-images.jpg");
                image = ImageIO.read(url);
                nature2 = image.getScaledInstance(800, 600, Image.SCALE_SMOOTH);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public Image getNature1() {
            return nature1;
        }

        public Image getNature2() {
            return nature2;
        }

        public Image getWallpaper() {
            return wallpaper;
        }

    }

}

Answer 2

I don't know, if I solved it the best way but it worked, I'm going to try to study more about Java Swing and its components.

Code:

public class ImgPanelStart extends JPanel{

private Image backgroundImage;
private BufferedImage imgBg;
private LoadImages images;

public ImgPanelStart() {

    images = new LoadImages();
    backgroundImage = images.getWallpaper();
    
}

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);

    if (backgroundImage != null) {
        Dimension dim = this.getSize();
        int dWidth = (int) dim.getWidth();
        int dHeight = (int) dim.getHeight();

        imgBg = new BufferedImage(dWidth, dHeight, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = imgBg.createGraphics();

        g2.drawImage(backgroundImage, 0, 0, dWidth, dHeight, null);
        g2.dispose();

        g.drawImage(imgBg, 0, 0, null);
    }
}


private void setImgBackground(int imageIndex) {
    switch (imageIndex) {
        case 1:
            backgroundImage = images.getMatchImg();
            break;
        case 2:
            backgroundImage = images.getSimuImg();
            break;
        case 3:
            backgroundImage = images.getWallpaper();
            break;
        default:
            break;
    }
    repaint();
}

public class HoverEffects extends MouseAdapter {

    private final JButton button;

    public HoverEffects(JButton button) {
        this.button = button;
    }

    @Override
    public void mouseEntered(MouseEvent event) {
        String text = button.getText();
        if (text.equals("Match")) {
            setImgBackground(1);
        } else {
            setImgBackground(2);
        }
    }

    @Override
    public void mouseExited(MouseEvent event) {
        setImgBackground(3);
    }

}


public class LoadImages {

    private Image matchImg, simuImg, wallpaper;

    public LoadImages() {
        try {
    
            Image image = ImageIO.read(new File("./ApsProject/src/assets/img0.jpg"));
            wallpaper = image.getScaledInstance(850, 600, Image.SCALE_SMOOTH);
            image = ImageIO.read(new File("./ApsProject/src/assets/SimuScreenRightPanel.png"));
            matchImg = image.getScaledInstance(850, 600, Image.SCALE_SMOOTH);
            image = ImageIO.read(new File("./ApsProject/src/assets/MatchScreenRightPanel.png"));
            simuImg = image.getScaledInstance(850, 600, Image.SCALE_SMOOTH);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public Image getMatchImg() {
        return matchImg;
    }

    public Image getSimuImg() {
        return simuImg;
    }

    public Image getWallpaper() {
        return wallpaper;
    }

}

}