Applet initialization problem

[Zach Miller]

Hi, I am making an animation for my intro to Java class, and I seem to be having some problems with it. I believe I'm on the right track, but when I run the applet (it compiles fine) it says "applet not initialized." Obviously this has something to do with the init() part of the class, but I can't figure out what. I'm not too good with making GUI's in Java. Anyway, here's the code. (by the way it's purpose is to draw an ipod on the screen originally, then when the button is pushed, it will "grow" into an ipad)

  import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.RoundRectangle2D;

/**
*	@author Zachary Miller -- [e-mail]
*	@version 06/05/10
*	Applet animation
*
*
**/
public class ipod_VS_ipad extends JApplet
{
	//Variables
	private JFrame frame;
	private Container cp;
	private JButton button;
	private boolean firstPaint = true;
	private boolean buttonPushed = false;
	
	//Constants
	private final int APPLET_WIDTH = 500, APPLET_HEIGHT = 500;
	private int x3 = 50, x4 = 100;
	private int final_x3 = 240, final_x4 = 240;
	private int y3 = 40, y4 = 90;
	private int final_y3 = 230, final_y4 = 230;
	
	public void init()
	{
		frame = new JFrame("Ipod vs. Ipad");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		//panel
		cp = getContentPane();
		//add panel to frame
		frame.add(cp, BorderLayout.CENTER);
		//size of frame
		frame.pack();
		//Make visible
		frame.setVisible(true);
		//panel size
		cp.setPreferredSize(new Dimension(APPLET_WIDTH, APPLET_HEIGHT));
		//JButton
		button = new JButton("Push Me");
		button.addActionListener(new ButtonListener());
		//panel set up
		cp.setBackground(Color.white);
		cp.setLayout(new BorderLayout());
		//add button to frame
		frame.add(button, BorderLayout.SOUTH);
	}
	
	public void paintComponent(Graphics g)
	{
		if(firstPaint) {
		firstPaint = false;
		//draw ipod
		Graphics2D graphics2 = (Graphics2D) g;
		g.setColor(Color.black);
		RoundRectangle2D roundedRect = new RoundRectangle2D.Float(100, 100, x3, x4, 10, 10);
		graphics2.draw(roundedRect);
		Color myColor = new Color(205, 201, 201);
		g.setColor(myColor);
		RoundRectangle2D roundedRect2 = new RoundRectangle2D.Float(110, 110, y3, y4, 10, 10);
		graphics2.draw(roundedRect2);
		}
		if(buttonPushed) {
		buttonPushed = false;
		while(x3<final_x3 & x4<final_x4 & y3<final_y3 & y4<final_y4) {
		x3++;
		x4++;
		y3++;
		y4++;
		repaint(); }
		}
	}
	
	private class ButtonListener implements ActionListener
	{
		public void actionPerformed(ActionEvent event)
		{
			{
				buttonPushed = true;
			}
			
		}
	}
}  

[pete stein]

I'm no applet pro, but it appears to me that you are concentrating on building a JFrame when you should be building an applet. One major problem is that you have a paintComponent method present as if it is being overridden, but it's not. To prove this, place an @Override annotation above this method and you'll see a compiler error telling you this.

I suggest that you create your GUI in a JPanel -- that way the paintComponent method will work, and then place this JPanel into your JApplet's contentPane.

edit: also in this section here you desire to do animation (I'm guessing). If you want to see the image grow, you'll probably want to use a Swing Timer not the while loop, and you definitely don't want to have this program logic and a repaint call in the paintComponent method.

    if (buttonPushed) {
      buttonPushed = false;
      while (x3 < final_x3 & x4 < final_x4 & y3 < final_y3 & y4 < final_y4) {
        x3++;
        x4++;
        y3++;
        y4++;
        repaint();
      }
    }

[Zach Miller]

Ok thanks, I wasn't sure about the Swing Timer, that's what I was going to use, but I couldn't figure out how to implement it properly. I'll figure that out, and ill work on the JPanel. Thanks, I appreciate the advice.

[pete stein]

Zach Miller wrote:Ok thanks, I wasn't sure about the Swing Timer, that's what I was going to use, but I couldn't figure out how to implement it properly. I'll figure that out, and ill work on the JPanel. Thanks, I appreciate the advice.

No problem. Here's a general skeleton of code that has worked for me, and may work for you, but you'd have to supply the details.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.RoundRectangle2D;

@SuppressWarnings("serial")
public class AppletFoo extends JApplet {
  public void init() {
    try {
      javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
        public void run() {
          createGUI();
        }
      });
    } catch (Exception e) {
      System.err.println("createGUI didn't successfully complete");
    }
  }

  private void createGUI() {
    getContentPane().add(new MyPanel());
  }
}

@SuppressWarnings("serial")
class MyPanel extends JPanel {

  private JButton button;

  //.... more variables here

  public MyPanel() {
    button = new JButton("Push Me");
    //...
  }

  private class ButtonListener implements ActionListener {
    public void actionPerformed(ActionEvent event) {
      int timerDelay = 20;
      Timer sTimer = new Timer(timerDelay, new ActionListener() {

        public void actionPerformed(ActionEvent e) {
          boolean keepGoing = true;
          //.....  code to grow the image goes here
          //.....  when image stops growing, make keepGoing false
          if (!keepGoing) {
            ((Timer) e.getSource()).stop();
          }
          repaint();
        }
      });
      sTimer.start();
    }
  }

  @Override
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    // graphics code goes here
  }
}

[Zach Miller]

Yep.... that seems like basically exactly what I was attempting to do haha. I'll definitely make use of that. Thanks I appreciate it.

[Norm Radder]

When I run the applet I get this error:

java.security.AccessControlException: access denied (java.lang.RuntimePermission exitVM.0)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkExit(SecurityManager.java:744)
at javax.swing.JFrame.setDefaultCloseOperation(JFrame.java:377)
at ipod_VS_ipad.init(ipod_VS_ipad.java:45)
at sun.applet.AppletPanel.run(AppletPanel.java:418)
at java.lang.Thread.run(Thread.java:619)

Applets should NOT use System.exit(). Its probably buried in:

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);