Need help with using graphics in swing components

Question

Hi. I'm new to Java and trying to learn it while also developing an application for class this semester. I've been following online tutorials for about 2 months now, though, and so I'm not sure my question counts as a "new to Java" question any more as the code is quite long.
Here is the basic problem. I started coding the application as a basic awt Applet (starting at "Hello World") and about a month in realized that Swing components offer better buttons, panels, layouts, etc. So I converted the application, called BsfAp, to a new JApplet and started adding JPanels and JComponents with layout managers. My problem is, none of the buffered graphics run in any kind of JPanel, only the buttons do. I assume the buffered graphics are written straight to the JApplet top level container instead but I'm not entirely sure.
So as to not inundate the forum with code, the JApplet runs online at:
http://mason.gmu.edu/~dho2/files/sensor.html
The source code is also online at:
http://mason.gmu.edu/~dho2/files/BsfAp.java
What I would like to do is this - take everything in the GUI left of the tabbed button pane and put it into a JScrollPane so that I can use a larger grid size with map display I can scroll around. The grid size I would like to use is more like 700x1000 pixels, but I only want to display about 400x400 pixels of it at a time in the JScrollPane. Then I could also move this JScrollPane around with layout manager. I think this is possible, but I don't know how to do it.
I'm sure the code is not organized or optimized appropriately to those of you who use Java every day, but again I'm trying to learn it. ;-)
Thanks for any help or insight you could provide in this.
Matt

Answer 1

Couple of recs:
* Don't override paint and paint directly on the JApplet. Paint on a JPanel and override paintComponent.
* The simplest way to display a graphic is to put an image into an ImageIcon and show this in a JLabel. This can then easily go inside of the JScrollPane.
* You can also create a graphics JPanel that overrides the paintComponent, draw the image in that and show that inside of the JScrollPane.
* don't call paint() directly. Call repaint if you want the graphic to repaint.
Here's a trivial example quickly put together:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.RenderingHints;
import java.awt.geom.Ellipse2D;
import java.lang.reflect.InvocationTargetException;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
public class BsfCrap extends JApplet
    private JPanel mainPanel = new JPanel();
    private JScrollPane scrollPane;
    private JPanel graphicsPanel = new JPanel()
        @Override
        protected void paintComponent(Graphics g)
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D)g;
            RenderingHints rh = new RenderingHints(
                RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.setRenderingHints(rh);
            Paint gPaint = new GradientPaint(0, 0, Color.blue,
                40, 40, Color.magenta, true);
            g2d.setPaint(gPaint);
            g2d.fill(new Ellipse2D.Double(0, 0, 800, 800));
    public BsfCrap()
        mainPanel.setPreferredSize(new Dimension(400, 400));
        mainPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
        graphicsPanel.setPreferredSize(new Dimension(800, 800));
        graphicsPanel.setBackground(Color.white);
        scrollPane = new JScrollPane(graphicsPanel);
        scrollPane.setPreferredSize(new Dimension(300, 300));
        mainPanel.add(scrollPane);
    public JPanel getMainPanel()
        return mainPanel;
    @Override
    public void init()
        try
            SwingUtilities.invokeAndWait(new Runnable()
                public void run()
                    setSize(new Dimension(400, 400));
                    getContentPane().add(new BsfCrap().getMainPanel());
        catch (InterruptedException e)
            e.printStackTrace();
        catch (InvocationTargetException e)
            e.printStackTrace();
}