My panel object won't repaint(). Please help.

[Aji Prasetyo]

Hello guys,

I have a panel object. inside it there is paint(Graphics g) method.

I want the object to repaint() itself after I update the int[][] variable inside it.

So I put the repaint() method right after I update the int[][] variable, but nothing happened. as if the repaint() method wasn't there.

How do I force the repaint() method so I can get the result instantly?

Btw, same result with the validate() method.

Thank you so much beforehand.

[Michael Dunn]

> How do I force the repaint() method so I can get the result instantly?

post a sample program of how you are doing it.
(just a frame with panel and button, actionlistener for the button
to contain your int[][] and repaint() code)

[Aji Prasetyo]

post a sample program of how you are doing it.

This is how I do it:

public class B5RmoteCanvas extends Panel {
    
    private static boolean isentered = false;
    private static int curx = 0;
    private static int cury = 0;
    private static int xmax = 0;
    private static int xcntr = 0;
    private static int ymax = 0;
    private static int ycntr = 0;
    private static int[][] thearray = null;
    
    public B5RmoteCanvas() {
        addMouseListener(new TitikusHandler());
        addMouseMotionListener(new TitikusMotionHandler());
    }
    
    private class TitikusHandler extends MouseAdapter {
        
        public void mouseReleased(MouseEvent e) {
            curx = e.getX();
            cury = e.getY();
            repaint();
            e.consume();
        }
        
        public void mouseEntered(MouseEvent e) {
            isentered = true;
            e.consume();
        }
        
        public void mouseExited(MouseEvent e) {
            isentered = false;
            e.consume();
        }
    
    }
    
    private class TitikusMotionHandler implements MouseMotionListener {
        
        public void mouseDragged(MouseEvent e) {
            curx = e.getX();
            cury = e.getY();
            repaint();
            e.consume();
        }
        
    }
 
    /* THE PROBLEM METHOD! */
    public void doPlots(int[][] thearray) {
        System.out.println("updating thearray....");
        this.thearray = thearray;
 
        /* THIS repaint() METHOD IS IGNORED?! */
        repaint();
    }
    
    public void drawLayout(Graphics g) {
        /* Drawing panel's border. */
        /* Drawing panel's center mark.*/
        /* Drawing X axis. */
        /* Drawing Y axis. */
    }
    
    /* ACTUALLY WANT TO PLOT thearray[][] AFTER UPDATING ITS VALUE! */
    public void drawPlots(Graphics g) {
        /* Plotting thearray */
        for(int i = 0; i < 681; i++) {
            g.drawOval((thearray[0][I] / 6) + xcntr, (thearray[1][i] / 6) + ycntr, 1, 1);
        }
    }
    
    public void drawMouse(Graphics g) {
        /* Draw the line from center. */
    }
    
    public void update(Graphics g) {
        paint(g);
    }
    
    public void paint(Graphics g) {
        System.out.println("repainting....");
        /* Getting draw parameters. */
        Dimension d = getSize();
        xmax = d.width - 1;
        xcntr = xmax / 2;
        ymax = d.height -1;
        ycntr = ymax / 2;
        drawLayout(g);
        if(thearray != null) drawPlots(g);
        /* Action for Mouse Listener. */
        if(isentered) {
            drawMouse(g);
        }
    }
    
}

What I want to do is regularly update the thearray[][] value using doPlots(int[][] thearray) method and directly display it in the panel.

Originally I am planning to use repaint() method to manually redraw the panel. But nothing happens. same with validate() method.

Is this problems is connected to the thread, because I use threads to keep changing the thearray[][] value?

Hopes this information helps.

Thank you and please help me.

[Mike Guze]

Hi,

did you check your values passed to "drawOval()"?

I use a Thread to set values and repaint a JPanel and there isn't problem. Are you sure what the oval with width=1 and height=1 isn't there?

[Ashok Mor]

Hi Aji Tanaka,

Please change your "g.drawOval((thearray[0] / 6) + xcntr, (thearray[1][i] / 6) + ycntr, 1, 1);"

statement to "g.drawOval((thearray[0][i] / 6) + xcntr, (thearray[1][i] / 6) + ycntr, 1, 1);"




Ashok Mor
Ness Technology.

[Michael Dunn]

it does work, as you can see from this
(after stripping most of it - the stated problem being repaint() not called from doPlots())

    
import java.awt.*;
import java.awt.event.*;
class Testing
{
  public void buildGUI()
  {
    Frame f = new Frame();
    f.add(new B5RmoteCanvas());
    f.setSize(600,400);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
    f.addWindowListener(new WindowAdapter(){
      public void windowClosing(WindowEvent we){
        System.exit(0);
      }
    });
  }
  public static void main(String[] args)
  {
    EventQueue.invokeLater(new Runnable(){
      public void run(){
        new Testing().buildGUI();
      }
    });
  }
}
class B5RmoteCanvas extends Panel {
    private static int curx = 0;
    private static int cury = 0;
    public B5RmoteCanvas() {
        addMouseMotionListener(new TitikusMotionHandler());
    }
    private class TitikusMotionHandler extends MouseMotionAdapter {
        public void mouseMoved(MouseEvent e) {
          curx = e.getX();
          cury = e.getY();
          doPlots();
        }
    }
 
    /* THE PROBLEM METHOD! */
    //public void doPlots(int[][] thearray) {
    public void doPlots() {
        //System.out.println("updating thearray....");
        //this.thearray = thearray;
 
        /* THIS repaint() METHOD IS IGNORED?! */
        repaint();
    }
    public void paint(Graphics g) {
      super.paint(g);
      g.drawOval(curx-25,cury-25,50,50);
    }
}

you may notice you can copy/paste then click compile, click run and see it working.
I could not do the same with what you posted.

[Aji Prasetyo]

Dear guys,

First of all, thank you for all of your effort to direct my problem.

But, sorry to tell you that the same problem still occurs.

This time, I have paste in this post the very program that causing the problem. If it is not too much of a problem, please take a look at those code. Feel free to copy-paste and Run the codes as it is.

This time I added 2 buttons on the left side of frame, one is for changing the background color into red and the other is for changing the background color into blue. This function also do not work. Maybe the problem is somehow has connection to the won't-repaint() problem.

Thank you so much for your time and efforts. Help me, please.

package testingrepaint;
 
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Random;
 
public class TestingRepaint extends Applet {
    
    private static final String AITEPC = "localhost";
    private static final int PORT = 8020;
    private static final int DELAY = 500;
    private static final int WIDTH = 1015;
    private static final int HEIGHT = 675;
    
    public void init() {
        /* Seting the frame. */
        setSize(WIDTH, HEIGHT);
        setLayout(new BorderLayout(10, 10));
        Panel ttle = new Panel();
        ttle.add(new Label("<< Testing repaint() >>"));
        add(ttle, BorderLayout.NORTH);
        TRPanel pnlGUI = new TRPanel();
        add(pnlGUI, BorderLayout.WEST);
        TRCanvas knvGUI = new TRCanvas();
        add(knvGUI, BorderLayout.CENTER);
    }
    
    public void start() {
        /* Creating thread I client's object. */
        Runnable runabelCli = new TRRunCli(PORT);
        Thread thredCli = new Thread(runabelCli);
        thredCli.start();
        try {
            /* Main thread sleep for awhile. */
            Thread.sleep(DELAY);
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
        /* Creating thread I server's object. */
        Runnable runabelSer = new TRRunSer(AITEPC, PORT);
        Thread thredSer = new Thread(runabelSer);
        thredSer.start();
    }
}
/* TestingRepaint class ends here.
 
 * TRPanel class starts here. */
class TRPanel extends Panel {
    
    private void makeButon(String nama, final Color bgcolor) {
        Button tmbol = new Button(nama);
        add(tmbol);
        tmbol.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                TRCanvas kanvas = new TRCanvas();
                kanvas.setBGColor(bgcolor);
            }
        });
    }
    
    public TRPanel() {
        setLayout(new GridLayout(0, 1, 10, 10));
        makeButon("Red", Color.RED);
        makeButon("Blue", Color.BLUE);
    }
}
/* TRPanel class ends here.
 
 * TRCanvas class starts here. */
class TRCanvas extends Panel {
    
    private static boolean isentered = false;
    private static int xmax = 0;
    private static int xcntr = 0;
    private static int ymax = 0;
    private static int ycntr = 0;
    private static int curx = 0;
    private static int cury = 0;
    private static int[][] thearray = null;
    
    public TRCanvas() {
        addMouseListener(new TikusHndler());
        addMouseMotionListener(new TikusMtionHndler());
    }
    
    public void doPlots(int[][] thearray) {
        System.out.println("Updating thearray....");
        this.thearray = thearray;
        repaint();
    }
    
    public void setBGColor(Color bgcolor) {
        System.out.println("Changing background color....");
        setBackground(bgcolor);
    }
    
    private class TikusHndler implements MouseListener {
        
        public void mouseClicked(MouseEvent e) {
        }
        
        public void mousePressed(MouseEvent e) {
        }
        
        public void mouseReleased(MouseEvent e) {
            curx = e.getX();
            cury = e.getY();
            repaint();
            e.consume();
        }
        
        public void mouseEntered(MouseEvent e) {
            isentered = true;
            e.consume();
        }
        
        public void mouseExited(MouseEvent e) {
            isentered = false;
            e.consume();
        }
    }
    
    private class TikusMtionHndler implements MouseMotionListener {
        
        public void mouseDragged(MouseEvent e) {
            curx = e.getX();
            cury = e.getY();
            repaint();
            e.consume();
        }
 
        public void mouseMoved(MouseEvent e) {
        }
    }
    
    public void drawLayout(Graphics g) {
        /* Drawing panel's border. */
        g.drawRect(0, 0, xmax, ymax);
        /* Drawing panel's center mark.*/
        g.drawRect(xcntr - 5, ycntr - 5, 10, 10);
        g.drawLine(xcntr - 5, ycntr - 5, xcntr, ycntr - 10);
        g.drawLine(xcntr + 5, ycntr - 5, xcntr, ycntr - 10);
        /* Drawing X axis. */
        g.drawLine(0 + 9, ymax - 9, xmax - 9, ymax - 9);
        g.drawString("2500", xcntr + (2500 / 6), ymax - 10);
        g.drawLine(xcntr + (2500 / 6), ymax - 10, xcntr + (2500 / 6), ymax - 5);
        g.drawString("2000", xcntr + (2000 / 6), ymax - 10);
        g.drawLine(xcntr + (2000 / 6), ymax - 10, xcntr + (2000 / 6), ymax - 5);
        g.drawString("1500", xcntr + (1500 / 6), ymax - 10);
        g.drawLine(xcntr + (1500 / 6), ymax - 10, xcntr + (1500 / 6), ymax - 5);
        g.drawString("1000", xcntr + (1000 / 6), ymax - 10);
        g.drawLine(xcntr + (1000 / 6), ymax - 10, xcntr + (1000 / 6), ymax - 5);
        g.drawString("500", xcntr + (500 / 6), ymax - 10);
        g.drawLine(xcntr + (500 / 6), ymax - 10, xcntr + (500 / 6), ymax - 5);
        g.drawString("0", xcntr, ymax - 10);
        g.drawLine(xcntr, ymax - 10, xcntr, ymax - 5);
        g.drawString("-500", xcntr - (500 / 6), ymax - 10);
        g.drawLine(xcntr - (500 / 6), ymax - 10, xcntr - (500 / 6), ymax - 5);
        g.drawString("-1000", xcntr - (1000 / 6), ymax - 10);
        g.drawLine(xcntr - (1000 / 6), ymax - 10, xcntr - (1000 / 6), ymax - 5);
        g.drawString("-1500", xcntr - (1500 / 6), ymax - 10);
        g.drawLine(xcntr - (1500 / 6), ymax - 10, xcntr - (1500 / 6), ymax - 5);
        g.drawString("-2000", xcntr - (2000 / 6), ymax - 10);
        g.drawLine(xcntr - (2000 / 6), ymax - 10, xcntr - (2000 / 6), ymax - 5);
        g.drawString("-2500", xcntr - (2500 / 6), ymax - 10);
        g.drawLine(xcntr - (2500 / 6), ymax - 10, xcntr - (2500 / 6), ymax - 5);
        /* Drawing Y axis. */
        g.drawLine(0 + 9, 0 + 9, 0 + 9, ymax - 9);
        g.drawString("1500", 0 + 10, ycntr + (1500 / 6));
        g.drawLine(0 + 10, ycntr + (1500 / 6), 0 + 5, ycntr + (1500 / 6));
        g.drawString("1000", 0 + 10, ycntr + (1000 / 6));
        g.drawLine(0 + 10, ycntr + (1000 / 6), 0 + 5, ycntr + (1000 / 6));
        g.drawString("500", 0 + 10, ycntr + (500 / 6));
        g.drawLine(0 + 10, ycntr + (500 / 6), 0 + 5, ycntr + (500 / 6));
        g.drawString("0", 0 + 10, ycntr);
        g.drawLine(0 + 10, ycntr, 0 + 5, ycntr);
        g.drawString("-500", 0 + 10, ycntr - (500 / 6));
        g.drawLine(0 + 10, ycntr - (500 / 6), 0 + 5, ycntr - (500 / 6));
        g.drawString("-1000", 0 + 10, ycntr - (1000 / 6));
        g.drawLine(0 + 10, ycntr - (1000 / 6), 0 + 5, ycntr - (1000 / 6));
        g.drawString("-1500", 0 + 10, ycntr - (1500 / 6));
        g.drawLine(0 + 10, ycntr - (1500 / 6), 0 + 5, ycntr - (1500 / 6));
    }
    
    public void drawPlots(Graphics g) {
        /* Plotting thearray */
        for(int i = 0; i < 681; i++) {
            g.drawOval((thearray[0][i] / 6) + xcntr, (thearray[1][i] / 6) + ycntr, 1, 1);
        }
    }
    
    public void drawMouse(Graphics g) {
        g.drawLine(xcntr, ycntr, curx, cury);
    }
    
    public void update(Graphics g) {
        paint(g);
    }
    
    public void paint(Graphics g) {
        System.out.println("Repainting panel....");
        /* Getting parameters for drawing. */
        Dimension d = getSize();
        xmax = d.width - 1;
        xcntr = xmax / 2;
        ymax = d.height -1;
        ycntr = ymax / 2;
        drawLayout(g);
        if(thearray != null) drawPlots(g);
        /* Action for Mouse Listener. */
        if(isentered) {
            drawMouse(g);
        }
    }
}
/* TRCanvas class ends here.
 
   TRRunCli class starts here. */
class TRRunCli implements Runnable {
    
    private static int PORT = 0;
    private static ServerSocket servsoket = null;
    
    public TRRunCli(int PORT) {
        this.PORT = PORT;
    }
 
    public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
        try {
            servsoket = new ServerSocket(PORT);
            while(true) new TRRunServer(servsoket.accept()).start();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        try {
            servsoket.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}
/* TRRunCli class ends here.
 
   TRRunSer class starts here. */
class TRRunSer implements Runnable {
    
    private static String AITEPC = null;
    private static int PORT = 0;
    private static final int DELAY = 500;
    
    public TRRunSer(String AITEPC, int PORT) {
        this.AITEPC = AITEPC;
        this.PORT = PORT;
    }
 
    public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
        while(true) {
            int[][] thearray = TRNative.getArrayNtive();
            try {
                TRSocket goOut = new TRSocket(AITEPC, PORT);
                goOut.doSend(thearray);
                Thread.sleep(DELAY);
            } catch (IOException ex) {
                ex.printStackTrace();
            } catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
        }
    }
}
/* TRRunSer class ends here.
 
 * TRRunServer class starts here. */
class TRRunServer implements Runnable {
    
    private static int threadNum = 0;
    private static Socket soket = null;
    private static InputStream is = null;
    private static ObjectInputStream ois = null;
    private static int[][] thearray = null;
    
    public void start() {
        Thread thredSub = new Thread(this, Integer.toString(threadNum++));
        thredSub.start();
    }
    
    public TRRunServer(Socket soket) {
        this.soket = soket;
    }
 
    public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
        try {
            is = soket.getInputStream();
            ois = new ObjectInputStream(is);
            try {
                thearray = (int[][]) ois.readObject();
            } catch (ClassNotFoundException ex) {
                ex.printStackTrace();
            }
            /* Plot thearray into canvas. */
            TRCanvas cnvs = new TRCanvas();
            cnvs.doPlots(thearray);
            ois.close();
            is.close();
            soket.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}
/* TRRunServer class ends here.
 
   TRSocket class starts here. */
class TRSocket {
    
    private static Socket soket = null;
    private static OutputStream os = null;
    private static ObjectOutputStream oos = null;
    
    public void doSend(int[][] thearray) throws IOException {
        oos.writeObject(thearray);
        oos.flush();
        oos.close();
        os.close();
        soket.close();
    }
    
    public TRSocket(String AITEPC, int PORT) throws IOException {
        try {
            soket = new Socket(AITEPC, PORT);
        } catch (UnknownHostException ex) {
            System.out.println("ERROR: Unable to connect: " + AITEPC + " at port: " + PORT);
        }
        os = soket.getOutputStream();
        oos = new ObjectOutputStream(os);
    }
}
/* TRSocket class ends here.
 
   TRNative class starts here. */
class TRNative {
    
    public static int[][] getArrayNtive() {
        int[][] thearray = new int[2][681];
        Random rand = new Random();
        for(int i = 0; i < 681; i++) {
            thearray[0][i] = rand.nextInt() % 10000;
            thearray[1][i] = rand.nextInt() % 10000;
        }
        return thearray;
    }
}
/* TRNative class ends here. */

[Aji Prasetyo]

Hello again,

Sorry for the trouble, but in connection of the problem that I am asking, I want to consult a possible solution.

since the mouse listener can detect the mouse action and repaint() the panel properly, is it possible to put the object listener on the thearray[][] object. I mean, when thearray[][] object receive new value, the object listener catch it and repaint() the panel properly as if mouse listener do.

Is there anyone knows how to do this?

Thank you for your attention. Please assist me.