Applet help

[Candy Bortniker]

I am just learning Java and I found this site while searching for help. I am so glad I found you. I am taking a course in college to learn Java. My instructor has given us an assignment to write an applet and to change the code of one of our projects to work with the applet. The first applet is suppose to pass any arguments. It sounded really simple but I find myself completely lost. Can you offer any suggestions that would help?
Here is the applet:
<applet code="BallProject.class" width = "800" height = "400">
</applet>
Here is the code:

import java.awt.* ;
import java.awt.geom.* ;
import java.awt.font.* ;
import java.awt.event.* ;
import javax.swing.* ;
 
public class BallProject extends JApplet
{
  public void init()
  {
    double topX ; //top corner value of X
    double topY ; //top corner value of Y
    Color c1 ; //color YELLLOW
    Color c2 ; //color BLACK
    
    topX = 100 ;
    topY = 100 ;
    c1 = Color.YELLOW ; //instance of color yellow
    c2 = Color.BLACK ; //instance of color black
    addMouseMotionListener( new MouseMotionHandler() ) ;
    addMouseListener( new MouseHandler() ) ;
    
    Container contentPane = getContentPane() ;
    contentPane.setLayout( new GridLayout( 0 , 2 ) ) ;
  }
}
 
/**
 A frame that contains a panel with drawings
 */
class BallFrame
{
  public BallFrame()
  {
    // add panel to frame
    //BallPanel panel = new BallPanel();
    //BallPanel panel2 = new BallPanel(75, 75, Color.BLUE, Color.RED);
    panel.setBackground( Color.WHITE ) ;
    contentPane.add( panel ) ;
    contentPane.add( panel2 ) ;
  }
}
 
class BallPanel extends JPanel
{
  double width = 200 ; //width of frame of ball
  double height = 200 ; //height of frame of ball
  double deltaX ;
  double deltaY ;
  
  boolean c_flag = true ; //double click flag
  boolean p_flag ; //pointer in ball flag
  Ellipse2D circle ; //ball
  
  //four args constructor
  //public BallPanel(int left, int top, Color color1, Color color2)
  //{
  // topX = left;
  // topY = top;
  // c1 = color1;
  // c2 = color2;
  // addMouseMotionListener(new MouseMotionHandler());
  // addMouseListener(new MouseHandler());
  //}
  
  public void paintComponent( Graphics g )
  {
    super.paintComponent( g ) ;
    Graphics2D g2 = ( Graphics2D ) g ;
    
    //draw a circle
    circle = new Ellipse2D.Double( topX , topY , width , height ) ;
    g2.setPaint( c1 ) ;
    g2.fill( circle ) ;
    
    //create the message
    String message = "Click and Drag the Circle!" ;
    Font f = new Font( "Serif" , Font.BOLD , 24 ) ;
    g2.setFont( f ) ;
    
    FontRenderContext context = g2.getFontRenderContext() ;
    Rectangle2D bounds = f.getStringBounds( message , context ) ;
    
    // draw the message
    FontMetrics fm = g2.getFontMetrics( f ) ; //gets size of font
    int stringLength = fm.stringWidth( message ) ; //computes size of message
    int panelWidth = this.getWidth() ; //gets the width of the ball panel
    int begX = ( panelWidth - stringLength ) / 2 ; //computes first X where message 
                                                   //should start
    g2.setPaint( Color.BLUE ) ;
    g2.drawString( message , begX , 352 ) ;
    
    if ( p_flag )
    {
      if ( c_flag )
      {
        g2.setPaint( c1 ) ;
        g2.fill( circle ) ;
      }
      else
      {
        g2.setPaint( c2 ) ;
        g2.fill( circle ) ;
      }
    }
    repaint() ;
  }
  
  private class MouseMotionHandler implements MouseMotionListener
  {
    public void mouseMoved( MouseEvent event )
    {
    }
    
    public void mouseDragged( MouseEvent event )
    {
      if ( p_flag )
      {
        int currentX = event.getX() ;
        int currentY = event.getY() ;
        topX = currentX - deltaX ; //new topX
        topY = currentY - deltaY ; //new topX
      }
      repaint() ;
    }
  }
  
  private class MouseHandler extends MouseAdapter
  {
    public void mouseClicked( MouseEvent event )
    {
      Point n = new Point( event.getPoint() ) ;
      if ( event.getClickCount() == 2 )
      { //did a double click occur??
        if ( circle.contains( event.getX() , event.getY() ) )
        { //if you double clicked inside of the circle
          c_flag = !c_flag ; //reverse the color flag to use the other color
          repaint() ; //make a call to repaint to visualize the change in color
        }
      }
    }
    
    public void mousePressed( MouseEvent event )
    {
      //determine if mouse is in the ball
      if ( circle.contains( event.getX() , event.getY() ) )
        p_flag = true ;
        
      //get values for X & Y where mouse is at
      int currentX = event.getX() ;
      int currentY = event.getY() ;
      
      //calculate the movement of the mouse
      deltaX = currentX - topX ; //find the relative distance between the top
      deltaY = currentY - topY ; //corner and the place where the mouse was pressed.
      topX = currentX - deltaX ; //new topX
      topY = currentY - deltaY ; //new topX
    }
    
    public void mouseReleased( MouseEvent event )
    {
      if ( !circle.contains( event.getX() , event.getY() ) )
        p_flag = false ;
    }
  }
}

[ edited to preserve formatting using the [code] and [/code] UBB tags -ds ]
[ March 20, 2003: Message edited by: Dirk Schreckmann ]

[Layne Lund]

You have quite a bit of code there. What exactly are you lost about? It seems that you've put most of it together. I can't compile the code currently, but if you explain what happens when you do, and what happens when you run it, there are many people here that will be willing to help you out.
Good luck!
Layne

[Michael Morris]

Hi Candy,
First off please don't post the same topic in multiple forums.
Now to your code. You have quite a few problems here. For one thing, in the BallProject class you are calling addMouseMotionListener(new MouseMotionHandler()); MouseMotionHandler is a private inner class of the package level class BallPanel. BallProject does not have access to that class. I think you have gotten confused as to what needs to be done here. Just looking at the code it looks like you need to create a BallFrame (which BTW should extend JPanel or some other component or you won't be able to add it to your content pane) in the BallProject constructor and add that to its content pane. In the BallFrame constructor you need to create one (or two, it isn't clear from your code) BallPanels and add it (them) to the BallFrame's layout. Try doing that and if you need more help, just post back.
Michael Morris

[Candy Bortniker]

Where should addMouseMotionListener(new MouseMotionHandler()); addMouseListener(new MouseHandler()); be?

[Michael Morris]

Well, since MouseMotionHandler and MouseHandler are private member classes of BallPanel, I should assume it would go there.
[ March 19, 2003: Message edited by: Michael Morris ]

[Candy Bortniker]

Thank you for your help. I've gotten to where the panel will show with the ball but I can't drag it. Any suggestions?

public class BallProject extends JApplet
{
  //declare variables
  Container contentPane ;
  BallPanel panel ;
  double topX ; //top corner value of X
  double topY ; //top corner value of Y
  Ellipse2D circle ; //ball
  boolean c_flag = true ; //double click flag
  boolean p_flag ; //pointer in ball flag
  double deltaX ;
  double deltaY ;
  
  public void init()
  {
    topX = 100 ;
    topY = 100 ;
  }
  
  public BallProject()
  {
    contentPane = getContentPane() ;
    contentPane.setLayout( new GridLayout( 0 , 2 ) ) ;
    panel = new BallPanel() ;
    panel.setBackground( Color.WHITE ) ;
    contentPane.add( panel ) ; // add panel to frame
    
    addMouseMotionListener( new MouseMotionHandler() ) ;
    addMouseListener( new MouseHandler() ) ;
  }
  
  private class MouseHandler extends MouseAdapter
  {
    public void mouseClicked( MouseEvent event )
    {
      Point n = new Point( event.getPoint() ) ;
      if ( event.getClickCount() == 2 )
      {
        //did a double click occur??
        if ( circle.contains( event.getX() , event.getY() ) )
        { //if you double clicked inside of the circle
          c_flag = !c_flag ; //reverse the color flag to use the other color
          repaint() ; //make a call to repaint to visualize the change in color
        }
      }
    }
    
    public void mousePressed( MouseEvent event )
    {
      //determine if mouse is in the ball
      if ( circle.contains( event.getX() , event.getY() ) )
        p_flag = true ;
        
        //get values for X & Y where mouse is at
      int currentX = event.getX() ;
      int currentY = event.getY() ;
      
      //calculate the movement of the mouse
      deltaX = currentX - topX ; //find the relative distance between the top
      deltaY = currentY - topY ; //corner and the place where the mouse was pressed.
      topX = currentX - deltaX ; //new topX
      topY = currentY - deltaY ; //new topX
    }
    
    public void mouseReleased( MouseEvent event )
    {
      if ( !circle.contains( event.getX() , event.getY() ) )
        p_flag = false ;
    }
  }
  
  private class MouseMotionHandler implements MouseMotionListener
  {
    public void mouseMoved( MouseEvent event )
    {}
    
    public void mouseDragged( MouseEvent event )
    {
      if ( p_flag )
      {
        System.out.println( "I'm getting here." ) ;
        int currentX = event.getX() ;
        int currentY = event.getY() ;
        topX = currentX - deltaX ; //new topX
        topY = currentY - deltaY ; //new topX
      }
      repaint() ;
    }
  }
  
  /**
     A frame that contains a panel with drawings
   */
  class BallPanel extends JPanel
  {
    double width = 200 ; //width of frame of ball
    double height = 200 ; //height of frame of ball
    
    public void paintComponent( Graphics g )
    {
      super.paintComponent( g ) ;
      Graphics2D g2 = ( Graphics2D ) g ;
      
      //draw a circle
      
      circle = new Ellipse2D.Double( 100 , 100 , width , height ) ;
      g2.setPaint( Color.YELLOW ) ;
      g2.fill( circle ) ;
      
      //create the message
      String message = "Click and Drag the Circle!" ;
      Font f = new Font( "Serif" , Font.BOLD , 24 ) ;
      g2.setFont( f ) ;
      
      FontRenderContext context = g2.getFontRenderContext() ;
      Rectangle2D bounds = f.getStringBounds( message , context ) ;
      
      // draw the message
      FontMetrics fm = g2.getFontMetrics( f ) ; //gets size of font
      int stringLength = fm.stringWidth( message ) ; //computes size of message
      int panelWidth = this.getWidth() ; //gets the width of the ball panel
      int begX = ( panelWidth - stringLength ) / 2 ; //computes first X where 
                                                     //message should start
      g2.setPaint( Color.BLUE ) ;
      g2.drawString( message , begX , 352 ) ;
      
      if ( p_flag )
      {
        if ( c_flag )
        {
          g2.setPaint( Color.YELLOW ) ;
          g2.fill( circle ) ;
        }
        else
        {
          g2.setPaint( Color.BLACK ) ;
          g2.fill( circle ) ;
        }
      }
      repaint() ;
    }
  }
}

[ edited to preserve formatting using the [code] and [/code] UBB tags -ds ]
[ March 20, 2003: Message edited by: Dirk Schreckmann ]

[Dirk Schreckmann]

Candy,
When posting code, please be sure to surround the code with the [code] and [/code] UBB Tags. This will help to preserve the formatting of the code, thus making it easier to read and understand.

[Barry Gaunt]

        deltaX = currentX - topX; //find the relative distance between the top
        deltaY = currentY - topY; //corner and the place where the mouse was pressed.
        topX = currentX - deltaX; //new topX
        topY = currentY - deltaY; //new topX  

This looks to be the same as:

        topX = topX;
        topY = topY;

which does nowt to topX and topY.