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Memory leak in image display

Posted on 1997-07-31
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Last Modified: 2006-11-17
I have slideshow application that displays numerous images. However, after each image display more memory is taken by the program till after about 40 images the program runs out of memory and crashes.  I need to be able to clear the memory used by each previously displayed image.  I have tried g.dispose() and image.flush() with no results.  How do I reclaim the used memory?
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Question by:faust073197
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Expert Comment

by:mann061997
ID: 1224227
Remember that MediaTracker will maintain a reference to registered images - they can't be garbage collected until they are released or the Tracker object goes out of scope.
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Author Comment

by:faust073197
ID: 1224228
I have tried it with elimination of the MediaTracker, with no effect... still how would one release a reference to a image in MediaTracker... just set it to null?
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Author Comment

by:faust073197
ID: 1224229
Actually, here is a simple example of a program that illustrates my problem.  Each mouse click displays a new image, but each previous image still exists in memory.  After 40 or so the program runs out of memory and crashes.


import java.awt.*;
import java.util.*;
import java.io.*;

public class java_app extends Frame
{
      Image image;
      int x = 10;
      String simage = "back.jpg";
      Toolkit tk = Toolkit.getDefaultToolkit();
        
      public java_app(String title)
      {
            super(title);
      }

      public void main (String args[])
      {
        
            java_app application = new java_app("java_app");
            application.resize(300, 300);
            application.show();
      }
      public void paint(Graphics g)
      {
                 String simage =  "img00" + x + ".jpg";
             image =  tk.getImage(simage);
            g.drawImage(image, 0 , 0, this);
            Runtime info = Runtime.getRuntime();
            System.out.println("total memory= " + info.totalMemory());

            
      }

      public boolean mouseDown(Event evt, int xx, int yy)
{
            if (image != null)
            {image.flush();}
             repaint();
             System.out.println(simage + x);

             x++;
             repaint();
                 return true;
      }

}


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Expert Comment

by:mann061997
ID: 1224230
flush() only marks the image for deletion; it doesn't get removed until the next gc cycle. Try calling System.gc() after flush(). Does it make any difference?
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Expert Comment

by:arktur
ID: 1224231
If you use Sun's JVM try to run your application with by calling "java -verbosegc your_application_class". You will be able to see when gc runs.
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Author Comment

by:faust073197
ID: 1224232
i've tried running System.gc() right after the image.flush() with no result
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Expert Comment

by:aleshka
ID: 1224233
Try to run System.gc() after 'image = null'.
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Accepted Solution

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adrianr091197 earned 150 total points
ID: 1224234
This question has been answered, see the query "Images and flushing memory", answered by keisha on 09/09
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