How do I rework my Java applet code to use a JPane

问题:

I'm a .net programmer just learning Java. I've been working on this issue for the past 2 weeks...

Here is my code to show my security system webcams and update the images in a JFrame running in an applet: (I need to convert this code to work in a JPanel instead!)

public class Streamer extends JApplet {
String PATH = "C:/Security/CamCap/";
Integer UPDATE_INTERVAL = 100;
String CAM1FILE = "current1.png";
String CAM2FILE = "current2.png";
String CAM3FILE = "current3.png";
String CAM4FILE = "current4.png";
String CAM5FILE = "current5.png";
String CAM6FILE = "current6.png";
String CAM7FILE = "current7.png";
String CAM8FILE = "current8.png";
String LOGOFILE = "logo.png";

private String path1 = PATH + CAM1FILE;
private String path2 = PATH + CAM2FILE;
private String path3 = PATH + CAM3FILE;
private String path4 = PATH + CAM4FILE;
private String path5 = PATH + CAM5FILE;
private String path6 = PATH + CAM6FILE;
private String path7 = PATH + CAM7FILE;
private String path8 = PATH + CAM8FILE;
private String pathLogo = PATH + LOGOFILE;

JFrame frame = new JFrame("@Home - Live Video");
boolean loaded = false;

JLabel label1, label2, label3, label4, label5, label6, label7, label8, labelLogo;


public void init()
{
    frame.getContentPane().setBackground(Color.BLACK);
    frame.setMinimumSize(new Dimension(1087, 777));
    frame.setLayout(new GridLayout(3, 3, 2, 2));
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(1090,780);
    frame.getContentPane().setSize(1087, 777);
    frame.setLocationRelativeTo ( null );
    frame.setVisible(true); 


    //INITIALIZE CAMERA 1
ImageIcon icon1 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon1 = new ImageIcon(ImageIO.read(new File(path1)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label1 = new JLabel(icon1);
    frame.add(label1);


    //INITIALIZE CAMERA 2
ImageIcon icon2 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon2 = new ImageIcon(ImageIO.read(new File(path2)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label2 = new JLabel(icon2);
    frame.add(label2);


    //INITIALIZE CAMERA 3
ImageIcon icon3 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon3 = new ImageIcon(ImageIO.read(new File(path3)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label3 = new JLabel(icon3);
    frame.add(label3);



    //INITIALIZE CAMERA 4
ImageIcon icon4 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon4 = new ImageIcon(ImageIO.read(new File(path4)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label4 = new JLabel(icon4);
    frame.add(label4);


    //INITIALIZE CAMERA 5
ImageIcon icon5 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon5 = new ImageIcon(ImageIO.read(new File(path5)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label5 = new JLabel(icon5);
    frame.add(label5);


    //INITIALIZE CAMERA 6
ImageIcon icon6 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon6 = new ImageIcon(ImageIO.read(new File(path6)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label6 = new JLabel(icon6);
    frame.add(label6);


    //INITIALIZE CAMERA 7
ImageIcon icon7 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon7 = new ImageIcon(ImageIO.read(new File(path7)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label7 = new JLabel(icon7);
    frame.add(label7);


    //INITIALIZE CAMERA 8
ImageIcon icon8 = new ImageIcon();
    loaded = false;
    while(!loaded)
    {
        try {
            icon8 = new ImageIcon(ImageIO.read(new File(path8)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }
    }

    label8 = new JLabel(icon8);
    frame.add(label8);


    //INITIALIZE LOGO
ImageIcon iconLogo = new ImageIcon();
        try {
            iconLogo = new ImageIcon(ImageIO.read(new File(pathLogo)));
            loaded = true;
        } catch (Exception ex) { loaded = false; }

    labelLogo = new JLabel(iconLogo);
    frame.add(labelLogo);

    frame.setVisible(true);
    run();
}

public void run()
{
    while(true)
    {
        try {
            ImageIcon icon1 = new ImageIcon(ImageIO.read(new File(path1)));
            label1.setIcon(icon1);
            label1.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon2 = new ImageIcon(ImageIO.read(new File(path2)));
            label2.setIcon(icon2);
            label2.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon3 = new ImageIcon(ImageIO.read(new File(path3)));
            label3.setIcon(icon3);
            label3.repaint();
         } catch (Exception ex) {}

        try {
            ImageIcon icon4 = new ImageIcon(ImageIO.read(new File(path4)));
            label4.setIcon(icon4);
            label4.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon5 = new ImageIcon(ImageIO.read(new File(path5)));
            label5.setIcon(icon5);
            label5.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon6 = new ImageIcon(ImageIO.read(new File(path6)));
            label6.setIcon(icon6);
            label6.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon7 = new ImageIcon(ImageIO.read(new File(path7)));
            label7.setIcon(icon7);
            label7.repaint();
        } catch (Exception ex) {}

        try {
            ImageIcon icon8 = new ImageIcon(ImageIO.read(new File(path8)));
            label8.setIcon(icon8);
            label8.repaint();
        } catch (Exception ex) {}

        try {            
            Thread.sleep(UPDATE_INTERVAL);
        } catch (Exception ex) {}
        }
    }
}

I've tried everything, and I can't find a way to convert this code to work inside a JPanel. I need to use a JPanel in my applet so that my cameras don't show up in a new, separate window (JFrame).

Does anyone know how to convert (just a small portion of) this code to draw and refresh my images in a JPanel?

Thanks (in advance)!

回答1:

An example of using a GUI in a JLabel that uses a Swing Timer for animation, and which is displayed in a JApplet:

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.*;

@SuppressWarnings("serial")
public class SpriteAnimationApplet extends JApplet {
   private static final String SPRITE_SHEET_SPEC = "http://www.funorb.com/img/images/game/"
         + "central/dev_diary/sprite_sheet_full.gif";
   private static final int SPRITE_ROWS = 8; // an 8 x 8 sprite sheet

   @Override
   public void init() {
      try {
         final Icon[] icons = SpriteIO.getSprites(SPRITE_SHEET_SPEC, SPRITE_ROWS);
         SwingUtilities.invokeAndWait(new Runnable() {
            public void run() {
               SpriteAnimationPanel spritePanel = new SpriteAnimationPanel(icons);
               getContentPane().add(spritePanel);
               spritePanel.startAnimation();
            }
         });
      } catch (InvocationTargetException e) {
         e.printStackTrace();
         System.exit(-1);
      } catch (InterruptedException e) {
         e.printStackTrace();
         System.exit(-1);
      } catch (MalformedURLException e) {
         e.printStackTrace();
         System.exit(-1);
      } catch (IOException e) {
         e.printStackTrace();
         System.exit(-1);
      }
   }

}

class SpriteIO {
   public static Icon[] getSprites(String spriteSheetSpec, int spriteRows)
         throws MalformedURLException, IOException {
      Icon[] icons = new Icon[spriteRows * spriteRows];
      URL spriteSheetUrl = new URL(spriteSheetSpec);
      BufferedImage spriteSheet = ImageIO.read(spriteSheetUrl);
      double wD = (double) spriteSheet.getWidth() / spriteRows;
      double hD = (double) spriteSheet.getHeight() / spriteRows;
      int w = (int) wD;
      int h = (int) hD;
      for (int i = 0; i < spriteRows; i++) {
         for (int j = 0; j < spriteRows; j++) {
            int x = (int) (i * wD);
            int y = (int) (j * hD);
            BufferedImage img = spriteSheet.getSubimage(x, y, w, h);

            icons[j * spriteRows + i] = new ImageIcon(img);
         }
      }
      return icons;
   }
}

@SuppressWarnings("serial")
class SpriteAnimationPanel extends JPanel {
   private static final int TIMER_DELAY = 200;
   private Icon[] icons;
   private JLabel animationLabel = new JLabel();

   public SpriteAnimationPanel(Icon[] icons) {
      this.icons = icons;
      setLayout(new BorderLayout());
      add(animationLabel );
   }

   public void startAnimation() {
      Timer spriteTimer = new Timer(TIMER_DELAY, new ActionListener() {
         private int iconIndex = 0;

         @Override
         public void actionPerformed(ActionEvent arg0) {
            animationLabel.setIcon(icons[iconIndex]);
            iconIndex++;
            iconIndex %= icons.length;
         }
      });
      spriteTimer.start();
   }
}

回答2:

ImageIcon icon5 = new ImageIcon(ImageIO.read(new File(path5)));

Applet resources are typically loaded from the run-time class-path or home server of the applet. Avoid using File objects in an applet unless they are provided by the user from a JFileChooser (not the case here).

ImageIcon icon5 = new ImageIcon(this.getClass().getResource(href5));

URLs to resources can be formed relative to the document or code base of the applet.

Tips

When in doubt, print out!

For every catch dump the stack trace.

} catch (Exception ex) {
    ex.printStackTrace();
    //..

Watch for output

Ensure the Java Console is shown when the browser launches an applet.

Perform animation using a Swing Timer

As discussed/shown by HFoE.

Image caching

Images in applets are typically cached. It seems the applet is loading an image multiple times, expecting it to be different each time (the last frame of the security camera). To get around that, load the image as a byte[] and put it into a ByteArrayInputStream. Then load the image from the stream using ImageIO.

Since the JRE cannot map the byte[] of the image to a File path or URL, it cannot be cached.