Applet problems

[Jamie Wool]

I'm in the middle of creating my first applet, but it's doing some strange things. Ihaving problems mainly with the painting not quite working and the panels aren't working properly

  
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
 
public class jframe1 extends JApplet{
 
private JPanel ControlPanel;
private Image image;

public void init(){

image = getImage(getDocumentBase(), "images/skin1.gif");
JLabel label = new JLabel("Push Count = : 0");
label.setSize(400,25);
getContentPane().add(label, BorderLayout.NORTH);

getContentPane().setLayout(new FlowLayout());
JButton StartButton = new JButton();
StartButton.setText("Start");
StartButton.setPreferredSize(new java.awt.Dimension(100, 20));
        StartButton.setBorder(new SoftBevelBorder(BevelBorder.RAISED));

JButton StopButton = new JButton();
StopButton.setText("Stop");
StopButton.setPreferredSize(new java.awt.Dimension(100, 20));
        StopButton.setBorder(new SoftBevelBorder(BevelBorder.RAISED));
        JPanel ControlPanel = new JPanel();
ControlPanel.add(StartButton);
ControlPanel.add(StopButton);

ControlPanel.setSize(400,150);
getContentPane().add(ControlPanel, BorderLayout.SOUTH);

 
JFrame f = new JFrame("New Frame");
f.getContentPane().add(this, BorderLayout.CENTER);
f.setSize(500,200);
f.setVisible(true);
}
public void paint(Graphics g){
 g.drawImage(image,0,0,ControlPanel);
}
 
public void update(Graphics g){
paint(g);
}
 
}
 

[Ryan McGuire]

I didn't go through your code with the proverbial fine toothed comb, but...

I notice that you're adding components to the content pane with BorderLayout position constants, but you set the layout manager to a new FlowLayout.

Also you should set the layout first and then start adding components.

Ryan

[Jamie Wool]

Ok, been through the code and sorted that out, thx. But how do i control the painting as it seems to altenate between painting the buttons and the image??

[Craig Wood]

Using the paint method in an Applet or JApplet is tricky because it will draw on top of everything, including your components (see api). An easier way to get started is to use a separate image component as the content pane, set its layout and add the components to it. The image will be in the background. In Swing ('J' prefix on the components) we usually do not need to override the update method though it is common to do so for different uses in the AWT. Loading images inside an applet that has a main method is also tricky: you need an applet method, which you have above, for applet context and an application method, as in Toolkit with MediaTracker or ImageIcon, for the application context. You can avoid this with an inner or outer class that loads its own image (or with the newer ImageIO class - j2se 1.4).

/*  <applet code="JF1" width="300" height="200"></applet>
 *  use: >appletviewer JF1.java
 */
import ...
 
public class JF1 extends JApplet{
    ...
    public void init(){
        ...
        setContentPane(new AnImageComponent());
        getContentPane().setLayout(new BorderLayout());
        ...
    }
 
    public static void main(String[] args)
    {
        JApplet applet = new JF1();
        JFrame f = new JFrame("New Frame");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(applet, BorderLayout.CENTER);
        f.setSize(300,200);
        f.setLocation(200,200);
        applet.init();
        f.setVisible(true);
    }
}
 
class AnImageComponent extends JPanel{
    private Image image;
 
    public AnImageComponent(){
        image = new ImageIcon("images/dukeWaveRed.gif").getImage();  // j2se 1.2+
        setOpaque(true);  // for certain look and feels in j2se 1.4+
    }
 
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawImage(image,0,0,this);
    }
}

[Jamie Wool]

Thanks for that, but that seems to have brought on securtiy exceptions when loading the applet.


java.security.AccessControlException: access denied (java.io.FilePermission images/skin1.gif read)
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkRead(Unknown Source)
at sun.awt.SunToolkit.getImageFromHash(Unknown Source)
at sun.awt.SunToolkit.getImage(Unknown Source)
at javax.swing.ImageIcon.<init>(Unknown Source)
at javax.swing.ImageIcon.<init>(Unknown Source)
at AnImageComponent.<init>(JF1.java:42)
at JF1.init(JF1.java:15)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

[Jamie Wool]

Ok, i've figurd out the permissions problem, but still having problems with the code. With your example i no longer get the applet pop-up in a frame and it doesn't seem to add the background or the burttons?

[Jamie Wool]

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
 
 
public class JF1 extends JApplet{
 
private JPanel ControlPanel;
 

public void init(){
        setContentPane(new AnImageComponent());
        getContentPane().setLayout(new BorderLayout());

JPanel ControlPanel = new JPanel();
ControlPanel.setSize(400,50);

JButton StartButton = new JButton();
StartButton.setText("Start");
StartButton.setPreferredSize(new Dimension(100, 20));
        StartButton.setBorder(new SoftBevelBorder(BevelBorder.RAISED));

JButton StopButton = new JButton();
StopButton.setText("Stop");
StopButton.setPreferredSize(new Dimension(100, 20));
        StopButton.setBorder(new SoftBevelBorder(BevelBorder.RAISED));
        

getContentPane().add(ControlPanel, BorderLayout.SOUTH);
ControlPanel.add(StartButton);
ControlPanel.add(StopButton);

 
}
 
public static void main(String[] args)
{
        JApplet applet = new JF1();
        JFrame f = new JFrame("New Frame");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(applet, BorderLayout.CENTER);
        f.setSize(300,200);
        f.setLocation(200,200);
        applet.init();
        f.setVisible(true);
  }
}
 
class AnImageComponent extends JPanel{
    private Image image;
 
    public AnImageComponent(){
        image = new ImageIcon("images/skin1.gif").getImage();  // j2se 1.2+
setOpaque(true);  // for certain look and feels in j2se 1.4+
    }
 
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawImage(image,0,0,this);
    }
}

[Craig Wood]

The code in your last post runs okay in j2se 1.5. You might try another image file. The JFrame was meant to be a pop-up? I suggest you consider using a JOptionPane or JDialog for a pop-up container. You can launch it in your event code, say in the ActionListener of a JButton. If it must be launched during construction, ie, in init, I would opt for a JOptionPane.