Thread: Updating JPanel on JTabbedPane with a Resize Event

Folks,

I have been struggling for some time with a problem. I think I have it half solved, but as a beginner at Java (and hindered by decades of programming in older languages), I can't get it solved. Any help would be appreciated, and pardon if I don't follow protocol well.

I have a JPanel that populates a JTabbedPane. It seems to work fine. Right now I've just got it painting full of random pixels. A couple other tabs are present, and the panel is only on the first tab, so success. I need to redraw that image as a simulation progresses. I also want to redraw it when the JFrame is resized. Right now I am just looking for the random pixels to change during a resize.

I've got the Resize plugged in correctly, I think. The text I asked to be echoed does print. But I can't get the panel to update. I worry about creating 1000 instances of the JPanel, or worse the entire tab. I will attach the most relevant code below. I've tried many variations not shown here, with repaint, revalidate, etc. Just can't figure it out. Thank you for any insights!

Randy

//***********************
public final class M_Move extends JPanel {
 
    static Random generator;
    static JComponent panel1; 
 
    public M_Move() {
        super(new GridLayout(1, 1));
 
        JTabbedPane tabbedPane = new JTabbedPane();
        ImageIcon icon1 = createImageIcon("http://www.javaprogrammingforums.com/images/map.gif");
        ImageIcon icon2 = createImageIcon("http://www.javaprogrammingforums.com/images/input.gif");
        ImageIcon icon3 = createImageIcon("http://www.javaprogrammingforums.com/images/output.gif");
 
  //      JComponent panel1 = makeTextPanel("Spatial");
  //      JComponent panel1 = new MakeBufferedImage(640, 480);
        panel1 = new MakeBufferedImage(640, 480);
        tabbedPane.addTab("Spatial", icon1, panel1, "Map agent movements");
        tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
        panel1.setPreferredSize(new Dimension(640, 480));
 
       < snip ... panels 2 and 3 are set up, and work>
 
        //Add the tabbed pane to this panel.
        add(tabbedPane);
 
    }
 
    protected JComponent makeTextPanel(String text) {     < snipped >     }
    protected static ImageIcon createImageIcon(String path) {  < snipped >    }
 
    private static void createAndShowGUI() {
        //Create and set up the window.
        //JFrame frame = new JFrame("Multi Move");
        JFrame frame = new Main();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Set up the content pane.
        addComponentsToPane(frame.getContentPane());
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);                
    }
 
 
    public static void main(String[] args) {
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        generator = new Random();
 
 
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                //Turn off metal's use of bold fonts
        // UIManager.put("swing.boldMetal", Boolean.FALSE);
        createAndShowGUI();
            }
        });
    }
 
 
//**************************
package m_move;
 
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;
 
public final class MakeBufferedImage extends JPanel {
 
    private BufferedImage canvas;
 
    public MakeBufferedImage(int width, int height) {
        canvas = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        for (int y=0; y<height; y++) {
            for (int x=0; x<width; x++) {
                int r = M_Move.generator.nextInt(256);
                int g = M_Move.generator.nextInt(256);
                int b = M_Move.generator.nextInt(256);
                int rgb = new Color(r,g,b).getRGB();
                canvas.setRGB(x, y, rgb);
            }
        }
    }
 
    @Override
    public Dimension getPreferredSize() {
        return new Dimension(canvas.getWidth(), canvas.getHeight());
    }
 
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.drawImage(canvas, null, null);
    }
 
    public void redrawer() {        
     System.out.println("IN REDRAWER!!!!!!!!!!!!!!!!!!!!!!!!!!!");   
        canvas = new BufferedImage(640, 480, BufferedImage.TYPE_INT_ARGB);
        for (int y=0; y<480; y++) {                                              
            for (int x=0; x<640; x++) {                                          
                int r = M_Move.generator.nextInt(256);                           
                int g = M_Move.generator.nextInt(256);                           
                int b = M_Move.generator.nextInt(256);                           
                int rgb = new Color(r,g,b).getRGB();                             
                canvas.setRGB(x, y, rgb);                                        
            }                                                                    
        }                                                         
 
    }  
 
}
 
// ********************************************
package m_move;
//
//import java.awt.Frame;
 
import java.awt.Frame;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.KeyEvent;
import javax.swing.JComponent;
import javax.swing.JFrame;
 
public class Main extends JFrame implements ComponentListener {
 
//  private BufferedImage canvas;
 
  public Main() {
    addComponentListener(this);
  }
 
    @Override
  public void componentHidden(ComponentEvent e) {
    System.out.println("componentHidden");
  }
 
    @Override
  public void componentMoved(ComponentEvent e) {
    System.out.println("componentMoved");
  }
 
    @Override
  public void componentResized(ComponentEvent e) {
   // M_Move.resizer();
   //    maker.Redrawer();
    M_Move.panel1 = new MakeBufferedImage(640, 480);
   //   panel1.revalidate();
   // MakeBufferedImage t = new MakeBufferedImage(640,480);
   // panel1.redrawer();
 
    System.out.println(" RESIZER!!! --- Resized ");            
 
    System.out.println("componentResized");
    System.out.println(getExtendedState());
 
    if (getExtendedState() == Frame.ICONIFIED) { 
      System.out.println("RESIZED TO ICONIFIED");
    } else if (getExtendedState() == Frame.NORMAL) {
      System.out.println("RESIZED TO NORMAL");
    } else {
      System.out.println("RESIZED TO MAXIMIZED");
    }
  }
 
    @Override
    public void componentShown(ComponentEvent e) {
//        throw new UnsupportedOperationException("Not supported yet.");
    }
 
}

I need to redraw that image as a simulation progresses.

Can you explain what you mean by that?

I also want to redraw it when the JFrame is resized.

When a JFrame is resized, it should repaint itself and all its children. If you override the paintComponent(Graphics g) method of the JPanel, as I think you've done, then this custom paint should be performed when the JFrame passes the repaint down to the JTabbedPane, and it down to the JPanel.

But I can't get the panel to update.

Do you mean that the JPanel doesn't repaint, or does your simulation not advance?

JTabbedPanes have methods called getTabComponentAt(int index). This method will allow you to get a component at a certain index in the JTabbedPane. If your JPanel is the first component, it can be reached by using index 0. Once you access the JPanel using that method, you can call repaint() on it.

This means that you just have to keep a reference to the JTabbedPane you create (in other words, you must assign a variable to the JTabbedPane so that you can access it from the main class whenever you need).

Thanks again, Snowguy. It ends up that the paintComponent procedure needed more of the code to paint material (plus 100 other errors, no doubt). A few days of debugging and learning have brought me much closer. I am all the way to having the dimensions of the resized frame being passed, and correctly echoed, within the window drawing class (with that class based on a Java example called DirectDrawDemo.java). It seems I'm quite close. However, the dimensions of the canvas being drawn do not change. The tabbedPanel resizes fine, but the canvas remains its initial 640 x 480 pixels.
Thanks again for any pointers you can provide.

Randy

The relevant code is:

package m_move;
 
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;
 
public final class MakeBufferedImage extends JPanel {
 
    public BufferedImage canvas;
 
    public MakeBufferedImage(int width, int height) {
        System.out.println("PASSED WIDTH AND HEIGHT: " + width + "   " + height);     // These values echo correctly.      
        canvas = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    }
 
    @Override
    public Dimension getPreferredSize() {
        System.out.println("GETTING PREFERRED SIZE");
        return new Dimension(canvas.getWidth(), canvas.getHeight());
    }
 
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        // Appears based on online materials to be a reasonable means of clearing a BufferedImage.  
        int clr = new Color(200, 200, 200).getRGB();              // Clearing to a light gray.
        // The following values never change ... always the initial values,
        // even though the WIDTH and HEIGHT above print correctly,
        // That is the dimensions of the resized frame are correctly passed and used in "new BufferedImage" above.
        // So the canvas = new BufferedImage doesn't seem to create a new canvas correctly.
        System.out.println("CANVAS WIDTH AND HEIGHT: " + canvas.getWidth() + "   " + canvas.getHeight());
        int w = canvas.getWidth();
        int h = canvas.getHeight();
        for (int y=0; y<h; y++) {
            for (int x=0; x<w; x++) {
                canvas.setRGB(x, y, clr);
            }
        }
 
        //** I DRAW SOME RANDOM PIXELS HERE, WHICH IS WORKING.  But canvas remains the original size. 
        //  g2.dispose(), canvus.flush() don't change anything.
 
       g2.drawImage(canvas, null, null);
       g2.dispose();
    }
}