Swinging scroll bar for scaled image

Question

I created a custom JSliderone that is used to enlarge and reduce the image. I want to add a scrollbar when the image becomes large, to fit into my 400x400 frame so that the user can pan the image, there should be no scrollbar if the image matches the frame. I am very new to Swing, so any help would be greatly appreciated, I cannot get anything to work.

public class GraphicsOnly extends JComponent implements ChangeListener {  
JPanel gui;
/** Displays the image. */
JLabel imageCanvas;
Dimension size;  
double scale = 1.0;  
private BufferedImage image;




public GraphicsOnly() {  
    size = new Dimension(10,10);  
    setBackground(Color.black);  
    try {                
        image = ImageIO.read(new File("car.jpg"));

     } catch (IOException ex) {

     }
}  

public void setImage(Image image) {
    imageCanvas.setIcon(new ImageIcon(image));
}



public void initComponents() {
    if (gui==null) { 
        gui = new JPanel(new BorderLayout());
        gui.setBorder(new EmptyBorder(5,5,5,5));
        imageCanvas = new JLabel();
        JPanel imageCenter = new JPanel(new GridBagLayout());
        imageCenter.add(imageCanvas);
        JScrollPane imageScroll = new JScrollPane(imageCenter);
        imageScroll.setPreferredSize(new Dimension(300,100));
        gui.add(imageScroll, BorderLayout.CENTER);
    }
}



public Container getGui() {
    initComponents();
    return gui;
}



public void stateChanged(ChangeEvent e) {  
    int value = ((JSlider)e.getSource()).getValue();  
    scale = value/100.0;  
    repaint();  
    revalidate();  
}  


 protected void paintComponent(Graphics g) {
     super.paintComponent(g);
     Graphics2D g2 = (Graphics2D)g;  
     g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,  
             RenderingHints.VALUE_ANTIALIAS_ON); 
     int w = getWidth();  
     int h = getHeight();  
     int imageWidth = image.getWidth();  
     int imageHeight = image.getHeight();  
     double x = (w - scale * imageWidth)/2;  
     double y = (h - scale * imageHeight)/2;  
     AffineTransform at = AffineTransform.getTranslateInstance(x,y);  
     at.scale(scale, scale);  
     g2.drawRenderedImage(image, at);  
     setImage(image);

 }


public Dimension getPreferredSize() {  
    int w = (int)(scale*size.width);  
    int h = (int)(scale*size.height);  
    return new Dimension(w, h);  
}  



private JSlider getControl() {  
    JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 500, 50);  
    slider.setMajorTickSpacing(50);  
    slider.setMinorTickSpacing(25);  
    slider.setPaintTicks(true);  
    slider.setPaintLabels(true);  
    slider.addChangeListener(this);  
    return slider;          
}  


public static void main(String[] args) {  
    GraphicsOnly app = new GraphicsOnly();  
    JFrame frame = new JFrame();  
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
    frame.setContentPane(app.getGui());
    app.setImage(app.image);

   // frame.getContentPane().add(new JScrollPane(app));  
    frame.getContentPane().add(app.getControl(), "Last");  
    frame.setSize(700, 500);  
    frame.setLocation(200,200);  
    frame.setVisible(true);  
} 
}  

Answer 1

. , , , . paintComponent, .

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.*;

import java.net.URL;
import javax.imageio.ImageIO;

public class GraphicsOnly extends JComponent implements ChangeListener {

    JPanel gui;
    /**
     * Displays the image.
     */
    JLabel imageCanvas;
    Dimension size;
    double scale = 1.0;
    private BufferedImage image;

    public GraphicsOnly() {
        size = new Dimension(10, 10);
        setBackground(Color.black);
        try {
            image = ImageIO.read(new URL("http://i.stack.imgur.com/7bI1Y.jpg"));
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public void setImage(Image image) {
        imageCanvas.setIcon(new ImageIcon(image));
    }

    public void initComponents() {
        if (gui == null) {
            gui = new JPanel(new BorderLayout());
            gui.setBorder(new EmptyBorder(5, 5, 5, 5));
            imageCanvas = new JLabel();
            JPanel imageCenter = new JPanel(new GridBagLayout());
            imageCenter.add(imageCanvas);
            JScrollPane imageScroll = new JScrollPane(imageCenter);
            imageScroll.setPreferredSize(new Dimension(300, 100));
            gui.add(imageScroll, BorderLayout.CENTER);
        }
    }

    public Container getGui() {
        initComponents();
        return gui;
    }

    public void stateChanged(ChangeEvent e) {
        int value = ((JSlider) e.getSource()).getValue();
        scale = value / 100.0;
        paintImage();
    }

    protected void paintImage() {
        int w = getWidth();
        int h = getHeight();
        int imageWidth = image.getWidth();
        int imageHeight = image.getHeight();
        BufferedImage bi = new BufferedImage(
                (int)(imageWidth*scale), 
                (int)(imageHeight*scale), 
                image.getType());
        Graphics2D g2 = bi.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        double x = (w - scale * imageWidth) / 2;
        double y = (h - scale * imageHeight) / 2;
        AffineTransform at = AffineTransform.getTranslateInstance(0, 0);
        at.scale(scale, scale);
        g2.drawRenderedImage(image, at);
        setImage(bi);
    }

    public Dimension getPreferredSize() {
        int w = (int) (scale * size.width);
        int h = (int) (scale * size.height);
        return new Dimension(w, h);
    }

    private JSlider getControl() {
        JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 500, 50);
        slider.setMajorTickSpacing(50);
        slider.setMinorTickSpacing(25);
        slider.setPaintTicks(true);
        slider.setPaintLabels(true);
        slider.addChangeListener(this);
        return slider;
    }

    public static void main(String[] args) {
        GraphicsOnly app = new GraphicsOnly();
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(app.getGui());
        app.setImage(app.image);

        // frame.getContentPane().add(new JScrollPane(app));  
        frame.getContentPane().add(app.getControl(), "Last");
        frame.setSize(700, 500);
        frame.setLocation(200, 200);
        frame.setVisible(true);
    }
}