Thread: Simple Balloon Applet [Help!!!]

The bottom of the balloons string is supposed to stick to the bottom center (which it does). When you click a button, the balloon moves in that direction, simple. Problem is, for some reason, the balloon isn't stopping when it hits the east or south boundaries, but west and north work fine. Any reason why? Thank you!

package Balloon_Applet;
 
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
 
public class Balloon_Applet extends Applet
 
implements ActionListener{  
 
    private static final long serialVersionUID = 1L; 
 
    Button north, west, south, east, northeast, northwest, southeast, southwest, center;
 
    public static final int DISPLAY_WIDTH = 600;
    public static final int DISPLAY_HEIGHT = 600;
 
    public int startX = DISPLAY_WIDTH/2;
    public int startY = DISPLAY_HEIGHT/2;
 
    public int boundX = DISPLAY_WIDTH;
    public int boundY = DISPLAY_HEIGHT;
 
    public static final boolean CONSOLE_LOGGING = true;
 
    public void init(){
 
        west = new Button ("West");
        add (west);
        west.addActionListener (this); 
 
        northwest = new Button ("Northwest");
        add (northwest);
        northwest.addActionListener (this); 
 
        northeast = new Button ("Northeast");
        add (northeast);
        northeast.addActionListener (this); 
 
        north = new Button ("North");
        add (north);
        north.addActionListener (this); 
 
        center = new Button ("Center");
        add (center);
        center.addActionListener (this);
 
        south = new Button ("South");
        add (south);
        south.addActionListener (this); 
 
        southwest = new Button ("Southwest");
        add (southwest);
        southwest.addActionListener (this);
 
        southeast = new Button ("Southeast");
        add (southeast);
        southeast.addActionListener (this); 
 
        east = new Button ("East");
        add (east);
        east.addActionListener (this);  
 
    } // end Init 
 
    public void paint(Graphics g){
 
            resize(DISPLAY_WIDTH, DISPLAY_HEIGHT);
        setBackground(Color.CYAN);
        g.setColor(Color.BLACK);
        g.fillOval(startX,startY,50,70);
        g.drawLine(startX+25,startY+70,boundX-275,boundY);
 
    } //end Paint
 
    public void actionPerformed(ActionEvent clic){
 
                    if (clic.getSource()== west)
            doWest();
            else if (clic.getSource()== northwest)
            doNorthwest();
            else if (clic.getSource()== northeast)
            doNortheast();
            else if (clic.getSource()== north)
            doNorth();
            else if (clic.getSource()== center)
            doCenter();
            else if (clic.getSource()== south)
            doSouth();
            else if (clic.getSource()== southwest)
            doSouthwest();
            else if (clic.getSource()== southeast)
            doSoutheast();
            else if (clic.getSource()== east)
            doEast();
 
                    repaint();
 
                    if (CONSOLE_LOGGING)
                System.out.println(startX + " " + startY);
 
    } //end ActionPerformed
 
    public void doWest(){
 
                if (startX-10 >= 0)
                    startX-=10;
            else
                startX -= Math.abs(0+startX);
    }
    public void doNorthwest(){
 
            doNorth();
            doWest();
    }
    public void doNortheast(){
 
            doNorth();
            doEast();
    }
    public void doNorth(){
 
            if (startY-10 >= 0)
                    startY-=10;
            else
                startY -= Math.abs(0+startY);
    }
    public void doCenter(){
 
            startX=boundX/2;
            startY=boundY/2;
    }
    public void doSouth(){
 
            if (startY+10 <= boundY)
                    startY+=10;
            else
               startY += Math.abs(boundY-startY);
    }
    public void doSouthwest(){
 
            doSouth();
            doWest();
    }
    public void doSoutheast(){
 
            doSouth();
            doEast();
    }
    public void doEast(){
 
            if (startX+10 <= boundX)
                    startX+=10;
            else
               startX += Math.abs(boundX-startX);
    }
} //end ActionListener

You should have been put an eye on the fact that the coordinates you are specifying in drawing an object are its top-left corner coordinates.
So if you intended that the balloon should stop when its right edge just reach the end of the frame, you should say in condition that if startX<=boundX-balloonWidth.

public void doEast(){
 
            if (startX+10 <= boundX-50/*balloonWidth*/)
                    startX+=10;
//            else
//               startX += Math.abs(boundX-startX);
    }

the same to south since for there, y is also increasing.
Hope this will help.

Originally Posted by aba muhammad

You should have been put an eye on the fact that the coordinates you are specifying in drawing an object are its top-left corner coordinates.
So if you intended that the balloon should stop when its right edge just reach the end of the frame, you should say in condition that if startX<=boundX-balloonWidth.

public void doEast(){
 
            if (startX+10 <= boundX-50/*balloonWidth*/)
                    startX+=10;
//            else
//               startX += Math.abs(boundX-startX);
    }

the same to south since for there, y is also increasing.
Hope this will help.

I changed the South and east (the two that aren't working):

public void doSouth(){
 
            if (startY+10 <= boundY-70)
                    startY+=10;
            else
               startY += Math.abs(boundY - startY);
    }

 public void doEast(){
 
            if (startX+10 <= boundX-50)
                    startX+=10;
            else
               startX += Math.abs(boundX-startX);
    }

What happens now is as soon as it hits the edge, it sort of "snaps" outside of the screen. I'm just curious as to why North and West look so different and work:

public void doNorth(){
 
            if (startY-10 >= 0)
                    startY-=10;
            else
                startY -= Math.abs(0+startY);
    }

public void doWest(){
 
                if (startX-10 >= 0)
                    startX-=10;
            else
                startX -= Math.abs(0+startX);
    }

Not sure why they use 0's and the others don't, but I can't seem to get it working right.

sorry for being late!!!
If you have a closer look at the code segment I posted, I commented "else".
so it should be:

public void doEast(){
 
            if (startX+10 <= boundX-50/*balloonWidth*/)
                    startX+=10;
//            else
//               startX += Math.abs(boundX-startX);
    }