JPanel is resized if it is larger than its parent

Question

I have a JScrollPanel, I add a JPanel containing an image to the JScrollPanel and it works, but if the image within the JPanel is larger that the JScrollPanel either in width, height, or both the panel is then resized to about 20x20. Why is it doing that? I am using the GridBagLayout on the viewport of the JScrollPanel. What I am expecting is that if the JPanel is larger than the JScrollPanel it will add scroll bars, but that isn't what is happening. Any suggestions?

private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
    WebFileChooser wfc = null;
    if(wfc == null){
        wfc = new WebFileChooser(this, "Open an Image");
        wfc.setSelectionMode(SelectionMode.SINGLE_SELECTION);
        wfc.setAvailableFilter(GlobalConstants.IMAGES_AND_FOLDERS_FILTER);
        wfc.setChooseFilter(GlobalConstants.IMAGES_FILTER);
        wfc.setCurrentDirectory("/Users/Ryan/Desktop");
    }
    wfc.setVisible(true);

    if(wfc.getResult() == StyleConstants.OK_OPTION){
        String file = wfc.getSelectedFile().getPath();
        try{
            imagePane.remove(canvas);
        }catch(Exception e){
        }
        canvas = new Canvas();
        canvas.setVisible(true);
        canvas.setImage(file);
        //imagePane.getViewport().setLayout(new GridBagLayout());
        canvas.setSizeFromLoaded();
        imagePane.getViewport().add(canvas);
        imagePane.repaint();
        imagePane.revalidate();
    }
}

Here is the Canvas Class:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package pocketshop;

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import pocketshop.util.ImageSync;

/**
 *
 * @author Ryan
 */
public class Canvas extends CanvasShadow{

    public static BufferedImage image = null, preview = null;
    public static int width, height;

    public void setImage(String filename){
        try{
            Canvas.image = ImageIO.read(new File(filename));
            Canvas.width = image.getWidth();
            Canvas.height = image.getHeight();
            ImageSync.originalPixels = new int[width * height];
            ImageSync.previewPixels = new int[width * height];
            Canvas.image.getRGB(0, 0, width, height, ImageSync.originalPixels, 0, width);
        }catch(IOException e){
        }
    }

    public static void setImage(BufferedImage image){
        Canvas.image = image;
        Canvas.width = image.getWidth();
        Canvas.height = image.getHeight();
        ImageSync.originalPixels = new int[width * height];
        ImageSync.previewPixels = new int[width * height];
        Canvas.image.getRGB(0, 0, width, height, ImageSync.originalPixels, 0, width);
    }

    public static void setPreview(BufferedImage img, Container parent){
        preview = img;
        parent.repaint();
    }

    public static BufferedImage deepCopy(){
        ColorModel cm = Canvas.image.getColorModel();
        boolean isAlphaPremultiplied = cm.isAlphaPremultiplied();
        WritableRaster raster = Canvas.image.copyData(null);
        return new BufferedImage(cm, raster, isAlphaPremultiplied, null);
    }

    public void setSizeFromLoaded(){
        try{
            this.setPreferredSize(new Dimension(Canvas.width + 10, Canvas.height + 10));
            this.setSize(Canvas.width + 10, Canvas.height + 10);
        }catch(Exception e){
            e.getMessage();
        }
    }

    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        if(Canvas.preview != null){
            g.drawImage(Canvas.preview, 5, 5, width, height, Color.black, null);
        }else{
            g.drawImage(Canvas.image, 5, 5, width, height, Color.black, null);
        }
    }
}

And here is the CanvasShadow Class:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package pocketshop;

import java.awt.Color;
import org.jdesktop.swingx.JXPanel;
import org.jdesktop.swingx.border.DropShadowBorder;

public class CanvasShadow extends JXPanel{

    public CanvasShadow(){
        DropShadowBorder shadow = new DropShadowBorder();
        shadow.setShadowColor(Color.BLACK);
        shadow.setShowLeftShadow(true);
        shadow.setShowRightShadow(true);
        shadow.setShowBottomShadow(true);
        shadow.setShowTopShadow(true);
        this.setBorder(shadow);

        float[] hsb = new float[3];

        Color.RGBtoHSB(255, 255, 255, hsb);

        this.setBackground(Color.getHSBColor(hsb[0], hsb[1], hsb[2]));
    }
}

Here is the actual image: http://images2.fanpop.com/images/photos/4800000/Beach-beaches-4843817-1280-800.jpg

Answer 1

I already told you get rid of that GridBagLayout. Setting the layout on the JScrollPane will resize the panel so it's never bigger than the container. You're panel has to lay itself out so that it's the size of the the image in order for the JScrollPane to see it's too big to display. It's only then does JScrollPane add the scrollbars. So if your image is 2000x2000 then your panel needs to set it's preferred size to 2000x2000 and act like it can be that big. The JScrollPane will do all of the heavy lifting to crop and make sure the panel only renders the portion visible based on the scroll bars. If your panel is always the same size as the viewport of the JScrollPane then the scroll pane thinks it fits and there is no need for scroll bars.

Update: Quick google search revealed the answer: http://chaosinmotion.com/blog/?p=168