refreshing 2D Graphics screen problem

From: edward hage (edha_at_xs4all.nl)
Date: 01/13/04

  • Next message: Silvio Bierman: "Re: refreshing 2D Graphics screen problem" 
    Date: Tue, 13 Jan 2004 23:38:26 +0100

    The following program is an applet that reads a number from a file 10
    times per second. It needs to be shown graphically.
    The file monitors a procesvariable and changes continuously. It is read
    okay, and also displays correct on screen (this in the form of a box
    that is filled with a certain % corresponding to the value in the file.)

    However, the screen only gets the initial value right. The problem I
    encounter is that the display is not updated. This is because the method
      paint is only performed at init, and for example when I drag the
    window (appletviewer) of the screen. That part of the screen is updated.

    My question: How can I make sure that every time a value is written,
    that the method paint is performed. Can I make a link in class
    RemindTask to paint. I tried some things but this did not work. I am a
    newbie at Java. Can somebody help me out?

    Thanks in advance, Edward Hage

    import java.awt.*;
    import java.awt.event.*;
    import java.awt.geom.*;
    import javax.swing.*;
    import java.io.*;
    import java.util.Timer;
    import java.util.TimerTask;

    public class Shapes extends JApplet {
         Timer timer;
         Double showvalue;
       // some more things //

         public void init() {
                 timer = new Timer();
            timer.schedule(new RemindTask(), 0, 100);
         }

         class RemindTask extends TimerTask {

            public void run() {
            String d;
            d = ReadTopLine();
            showvalue = Double.valueOf(d);
            }

            private String ReadTopLine() {
            File inputFile = new File("showfile.txt");
            // etc.
            return string read from file
            //
            }

           public void paint(Graphics g) {
            Graphics2D g2 = (Graphics2D)g;
            // etc. draw a box filled with
            value showvalue //
            }

         public static void main(String s[]) {
             JFrame f = new JFrame("Shapes");
             f.addWindowListener(new WindowAdapter() {
                 public void windowClosing(WindowEvent e) {System.exit(0);}
             });

            JApplet applet = new Shapes();
             f.getContentPane().add("Center", applet);
             applet.init();
            f.pack();
             f.setSize(new Dimension(550,100));
             f.show();
         }

    }

  • Next message: Silvio Bierman: "Re: refreshing 2D Graphics screen problem"

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