Thread: problem with coordinates (GUI)

Hi everybody
i have written a java code (GUI) , which a red marker (red point) should follow a line between 2 positions, the program works good but the red point is not exact on the line (it just moves one t edge of the line). now i need some help to change x and y coordinate to be one the line not on the edge..
thanks

import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.*;

public class JavaGrafikPanel1 extends JPanel
{
public boolean animation;
public animcircle mc;
JavaGrafikPanel1()
{
Color mycolor = new Color(10,50,100);
setBackground(mycolor);
this.animation = false;
mc = new animcircle();
mc.firstPoint = new Position(0, 0);
mc.lastPoint = new Position(0, 0);
}
private LinkedList points;
public LinkedList getPoints()
{
return points;
}
public void setPoints(LinkedList points)
{
this.points = points;
}
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
ListIterator li = points.listIterator();
Position p = new Position(0, 0);
Position q = new Position(0, 0);
while(li.hasNext())
{
p = (Position)li.next();
g.setColor(Color.pink);
g.drawOval((int)p.getX(), (int)p.getY(),3,3);
if(li.hasNext())
{
q = (Position)li.next();
g.setColor(Color.white);
g.drawLine((int)p.getX(), (int)p.getY(), (int)q.getX(), (int)q.getY());
li.previous();
}
else
break;
}
if(this.animation)
{
Position cr = new Position(0,0);
int index = 0;
if((cr = mc.getNextPosition()) == null)
{
index = points.indexOf(mc.lastPoint);
mc.firstPoint = mc.lastPoint;
if(points.size() > index+1)
mc.lastPoint = (Position)points.get(index+1);
else // stop animation
{
animation = false;
return;
}
mc.step = 0;
if((cr = mc.getNextPosition()) == null)
{
animation = false;
return;
}
}
g.drawOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
g.setColor(Color.red);
g.fillOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
}
}
}

[AnimPos]
import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.event.*;


public class AnimPos extends JFrame
{
private JavaGrafikPanel1 jpnl;
public static void main(String args[]) throws Exception
{
AnimPos p = new AnimPos();

p.jpnl = new JavaGrafikPanel1();
p.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
p.setContentPane(p.jpnl);
p.setSize(400,300);
p.setVisible(true);
LinkedList pos = new LinkedList();
p.jpnl.setPoints(pos);
pos = p.loadPoints();
double dist = 0;
ListIterator itr = pos.listIterator(0);
Position fpoint;
Position lpoint;
if(itr.hasNext())
{
fpoint = (Position)itr.next();
itr.previous();
}
while(itr.hasNext())
{
lpoint = (Position)itr.next();
fpoint = lpoint;
dist += fpoint.distance(lpoint);
}
System.out.print(dist);
}
public AnimPos()
{
ActionListener timerListener = new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
if(jpnl.animation)
{
jpnl.repaint();
}
else
{
}
}
};
Timer t = new Timer(100, timerListener);
t.start();
}

public LinkedList loadPoints() throws Exception
{
java.io.BufferedReader in_reader = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
System.out.println("How many positions?: \n");
String str = in_reader.readLine();
int antal = Integer.parseInt(str);
System.out.println("Write positions in each line seperated by comma. Ex. \nX1,Y1\nX2,Y2\n");
String[] doubles;
LinkedList poser = new LinkedList();
for(int i=0;i<antal;i++)
{
str= in_reader.readLine();
doubles = str.split(",");
double a = Double.parseDouble(doubles[0]);
double b = Double.parseDouble(doubles[1]);
poser.add(new Position(a, b));
this.jpnl.setPoints(poser);
this.repaint();
}
System.out.println("\nShow Animation?(Y/N)\n");
this.jpnl.mc.firstPoint = new Position(0,0);
this.jpnl.mc.lastPoint = (Position)poser.getFirst();
str = in_reader.readLine();
if(str.equals("Y") || str.equals("y"))
{
this.moveIt();
}
return poser;
}
public void moveIt()
{
this.jpnl.animation = true;
}
}[/AnimPos]
[JavaGrafikPanel1 ]
import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.*;

public class JavaGrafikPanel1 extends JPanel
{
public boolean animation;
public animcircle mc;
JavaGrafikPanel1()
{
Color mycolor = new Color(10,50,100);
setBackground(mycolor);
this.animation = false;
mc = new animcircle();
mc.firstPoint = new Position(0, 0);
mc.lastPoint = new Position(0, 0);
}
private LinkedList points;
public LinkedList getPoints()
{
return points;
}
public void setPoints(LinkedList points)
{
this.points = points;
}
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
ListIterator li = points.listIterator();
Position p = new Position(0, 0);
Position q = new Position(0, 0);
while(li.hasNext())
{
p = (Position)li.next();
g.setColor(Color.pink);
g.drawOval((int)p.getX(), (int)p.getY(),3,3);
if(li.hasNext())
{
q = (Position)li.next();
g.setColor(Color.white);
g.drawLine((int)p.getX(), (int)p.getY(), (int)q.getX(), (int)q.getY());
li.previous();
}
else
break;
}
if(this.animation)
{
Position cr = new Position(0,0);
int index = 0;
if((cr = mc.getNextPosition()) == null)
{
index = points.indexOf(mc.lastPoint);
mc.firstPoint = mc.lastPoint;
if(points.size() > index+1)
mc.lastPoint = (Position)points.get(index+1);
else // stop animation
{
animation = false;
return;
}
mc.step = 0;
if((cr = mc.getNextPosition()) == null)
{
animation = false;
return;
}
}
g.drawOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
g.setColor(Color.red);
g.fillOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
}
}
}
[/JavaGrafikPanel1 ]

------------------------------
[Position]

public class Position
{
public Position(double x, double y)
{
this.X = x;
this.Y = y;
}
private double X;
private double Y;
public String toString()
{
return "(" + Double.toString(X) + "," + Double.toString(Y) + ")";
}
public void SetPosition(double x,double y)
{
this.X = x;
this.Y = y;
}
public double getX()
{
return this.X;
}
public double getY()
{
return this.Y;
}
public double distance(Position q)
{
return java.lang.Math.sqrt(java.lang.Math.pow(this.X - q.getX(),2) + java.lang.Math.pow(this.Y - q.getY(),2));
}
public double direction(Position q)
{
return (this.Y - q.getY())/(this.X - q.getX()) ;
}
}
[/Position]

-----------------------------
[animcircle]
public class animcircle
{

public Position firstPoint;
public Position lastPoint;
public int step;
public int pixeljumper;
public animcircle()
{
this.firstPoint = new Position(0, 0);
this.lastPoint = new Position(0, 0);
this.step = 0; //in order to begin from 0 at the main program;
pixeljumper = 1;
}

public Position getNextPosition()
{
step++;
Position p = new Position(0, 0);
double m = this.firstPoint.direction(lastPoint);
double y = 0;
double x = 0;
if(firstPoint.getX() - lastPoint.getX() == 0)
{
if(firstPoint.getY() - lastPoint.getY() == 0)
{

return null;
}

int totstep = (int)(firstPoint.getY() - lastPoint.getY())/pixeljumper + 1;

if(step< Math.abs(totstep))
{
if(firstPoint.getY() > lastPoint.getY())
y = firstPoint.getY() - (step-1)*pixeljumper;
else
y = firstPoint.getY() + (step-1)*pixeljumper;
x = (y-firstPoint.getY())/m +firstPoint.getX();
p.SetPosition(x, y);
}
else
{
return null;
}
}
else
{

int totstep = (int)(firstPoint.getX() - lastPoint.getX())/pixeljumper + 1;

if(step< Math.abs(totstep))
{
if(firstPoint.getX() > lastPoint.getX())
x = firstPoint.getX() - (step-1)*pixeljumper;
else
x = firstPoint.getX() + (step-1)*pixeljumper;
y = (x-firstPoint.getX())*m +firstPoint.getY();
p.SetPosition(x, y);
}
else
{
return null;
}

}
return p;
}
}
[/animcircle]

Hi
i have written a java code (GUI) , which a red marker (red point) should follow a line between 2 positions, the program works good but the red point is not exact on the line (it just moves one t edge of the line). now i need some help to change x and y coordinate to be one the line not on the edge..
thanks
Here is all the classes and code

import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.event.*;
 
 
public class AnimPos extends JFrame
{
        private JavaGrafikPanel1 jpnl;
	public static void main(String args[]) throws Exception
        {
            AnimPos p = new AnimPos();
 
            p.jpnl = new JavaGrafikPanel1();
            p.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            p.setContentPane(p.jpnl);
            p.setSize(400,300);
            p.setVisible(true);
            LinkedList pos = new LinkedList();
            p.jpnl.setPoints(pos);
            pos = p.loadPoints();            
            double dist = 0;
            ListIterator itr = pos.listIterator(0);
            Position fpoint;
            Position lpoint;
            if(itr.hasNext())
                {
                    fpoint = (Position)itr.next();
                    itr.previous();
                }
            while(itr.hasNext())
            {
                lpoint = (Position)itr.next();
                fpoint = lpoint;
                dist += fpoint.distance(lpoint);
            }
            System.out.print(dist);
	}
        public AnimPos()
        {
            ActionListener timerListener = new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    if(jpnl.animation)
                    {
                        jpnl.repaint();
                    }
                    else
                    {
                    }
                }
            };
            Timer t = new Timer(100, timerListener);
            t.start();
        }
 
        public LinkedList loadPoints() throws Exception
        {
            java.io.BufferedReader in_reader = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
            System.out.println("How many positions?: \n");
            String str = in_reader.readLine();
            int antal = Integer.parseInt(str);
            System.out.println("Write positions in each line seperated by comma. Ex. \nX1,Y1\nX2,Y2\n");
            String[] doubles;
            LinkedList poser = new LinkedList();
            for(int i=0;i<antal;i++)
            {
                    str= in_reader.readLine(); 
                    doubles = str.split(",");
                    double a = Double.parseDouble(doubles[0]);
                    double b = Double.parseDouble(doubles[1]);
                    poser.add(new Position(a, b));
                    this.jpnl.setPoints(poser);
                    this.repaint();
            }
            System.out.println("\nShow Animation?(Y/N)\n");
            this.jpnl.mc.firstPoint = new Position(0,0);
            this.jpnl.mc.lastPoint = (Position)poser.getFirst();
            str = in_reader.readLine();
            if(str.equals("Y") || str.equals("y"))
            {
                this.moveIt();
            }
            return poser;
        }
        public void moveIt()
        {
            this.jpnl.animation = true;
        }
}

import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.*;
 
public class JavaGrafikPanel1 extends JPanel
{
    public boolean animation;
    public animcircle mc;
    JavaGrafikPanel1()
    {
        Color mycolor = new Color(10,50,100);
        setBackground(mycolor);
        this.animation = false;
        mc = new animcircle();
        mc.firstPoint = new Position(0, 0);
        mc.lastPoint = new Position(0, 0);
    }
    private LinkedList points;
    public LinkedList getPoints()
    {
        return points;
    }
    public void setPoints(LinkedList points)
    {
        this.points = points;
    }
    protected void paintComponent(Graphics g)
    {
	super.paintComponent(g);
        ListIterator li = points.listIterator();
        Position p = new Position(0, 0);
        Position q = new Position(0, 0);
        while(li.hasNext())
        {
            p = (Position)li.next();
            g.setColor(Color.pink);
            g.drawOval((int)p.getX(), (int)p.getY(),3,3);
            if(li.hasNext())
            {
                q = (Position)li.next();
                g.setColor(Color.white);
                g.drawLine((int)p.getX(), (int)p.getY(), (int)q.getX(), (int)q.getY());
                li.previous();
            }
            else
                break;
        }
        if(this.animation)
        {
            Position cr = new Position(0,0);
            int index = 0;
            if((cr = mc.getNextPosition()) == null)
            {
                index = points.indexOf(mc.lastPoint);
                mc.firstPoint = mc.lastPoint;
                if(points.size() > index+1)
                    mc.lastPoint = (Position)points.get(index+1);
                else    // stop animation
                {
                    animation = false;
                    return;
                }
                mc.step = 0;
                if((cr = mc.getNextPosition()) == null)
                {
                    animation = false;
                    return;                    
                }
            }
            g.drawOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
            g.setColor(Color.red);
            g.fillOval(((int)cr.getX())/2,((int)cr.getY())/2,8,8);
        }
    }
}

 
public class Position
{
       public Position(double x, double y)
        {
            this.X = x;
            this.Y = y;
        }
        private double X;
        private double Y;
        public String toString()
        {
            return "(" + Double.toString(X) + "," + Double.toString(Y) + ")";
        }
        public void SetPosition(double x,double y)
        {
            this.X = x;
            this.Y = y;
        }
        public double getX()
        {
            return this.X;
        }
        public double getY()
        {
            return this.Y;
        }
        public double distance(Position q)
        {
            return java.lang.Math.sqrt(java.lang.Math.pow(this.X - q.getX(),2) + java.lang.Math.pow(this.Y - q.getY(),2));
        }
        public double direction(Position q)
        {
            return (this.Y - q.getY())/(this.X - q.getX())  ;
        }
}

public class animcircle
{
 
    public Position firstPoint;
    public Position lastPoint;
    public int step;
    public int pixeljumper;
    public animcircle()
    {
        this.firstPoint = new Position(0, 0);
        this.lastPoint = new Position(0, 0);
        this.step = 0; //in order to begin from 0 at the main program;
        pixeljumper = 1;
    }
 
    public Position getNextPosition()
    {
        step++;
        Position p = new Position(0, 0);
        double m = this.firstPoint.direction(lastPoint);
        double y = 0;
        double x = 0;
        if(firstPoint.getX() - lastPoint.getX() == 0)
        {
            if(firstPoint.getY() - lastPoint.getY() == 0)
            {
 
                return null;
            }
 
            int totstep = (int)(firstPoint.getY() - lastPoint.getY())/pixeljumper + 1;
 
            if(step< Math.abs(totstep))
            {
                if(firstPoint.getY() > lastPoint.getY())
                    y = firstPoint.getY() - (step-1)*pixeljumper;
                else
                    y = firstPoint.getY() + (step-1)*pixeljumper;
                x = (y-firstPoint.getY())/m +firstPoint.getX();
                p.SetPosition(x, y);
            }
            else
            {
                return null;
            }
        }
        else
        {
 
            int totstep = (int)(firstPoint.getX() - lastPoint.getX())/pixeljumper + 1;
 
            if(step< Math.abs(totstep))
            {
                if(firstPoint.getX() > lastPoint.getX())
                    x = firstPoint.getX() - (step-1)*pixeljumper;
                else
                    x = firstPoint.getX() + (step-1)*pixeljumper;
                y = (x-firstPoint.getX())*m +firstPoint.getY();                
                p.SetPosition(x, y);
            }
            else
            {
                return null;
            }
 
        }
        return p;
    }
}

Hi Norm,
thanks for reply,
there is no problem to execute the code, my question is when i run the code, in the animation part, should a red marker follow the line between to positions, but the red point is one edge of line not exact on the line, now i want it to be on line when it moves on line!!! hope that i clear with my explanation!
thanks

here is the input:
How many positions?:

5
Write positions in each line seperated by comma. Ex.
X1,Y1
X2,Y2

10,40
40,60
90,110
150,200
10,60

Show Animation?(Y/N)

y
0.0

this JavaGrafikPanel1 is correct code not the last one is posted

import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.*;
import java.awt.*;
 
public class JavaGrafikPanel1 extends JPanel
{
    public boolean animation;
    public animcircle mc;
    JavaGrafikPanel1()
    {
        Color mycolor = new Color(10,50,100);
        setBackground(mycolor);
        this.animation = false;
        mc = new animcircle();
        mc.firstPoint = new Position(0, 0);
        mc.lastPoint = new Position(0, 0);
    }
    private LinkedList points;
    public LinkedList getPoints()
    {
        return points;
    }
    public void setPoints(LinkedList points)
    {
        this.points = points;
    }
    protected void paintComponent(Graphics g)
    {
	super.paintComponent(g);
        ListIterator li = points.listIterator();
        Position p = new Position(0, 0);
        Position q = new Position(0, 0);
        while(li.hasNext())
        {
            p = (Position)li.next();
            g.setColor(Color.pink);
            g.drawOval((int)p.getX(), (int)p.getY(),3,3);
            if(li.hasNext())
            {
                q = (Position)li.next();
                g.setColor(Color.white);
                g.drawLine((int)p.getX(), (int)p.getY(), (int)q.getX(), (int)q.getY());
                li.previous();
            }
            else
                break;
        }
        if(this.animation)
        {
            Position cr = new Position(0,0);
            int index = 0;
            if((cr = mc.getNextPosition()) == null)
            {
                index = points.indexOf(mc.lastPoint);
                mc.firstPoint = mc.lastPoint;
                if(points.size() > index+1)
                    mc.lastPoint = (Position)points.get(index+1);
                else    // stop animation
                {
                    animation = false;
                    return;
                }
                mc.step = 0;
                if((cr = mc.getNextPosition()) == null)
                {
                    animation = false;
                    return;                    
                }
            }
            g.drawOval((int)cr.getX(),(int)cr.getY(),8,8);
            g.setColor(Color.red);
            g.fillOval((int)cr.getX(),(int)cr.getY(),8,8);
        }
    }
}

yes , the problem is the red ball moves on the edge of line and doesnt stay centered, for example try these new inputs, between 2 first point it is on the center of the line , but after that between the other positions , it goes on one side of the line, if u try this new input u will see what i mean, thank alot for helping
How many positions?:

4
Write positions in each line seperated by comma. Ex.
X1,Y1
X2,Y2

20,50
90,150
250,70
30,50

Show Animation?(Y/N)

y
0.0

that's the point, in post #9 stayed centered, but when i try for post #11 it doesnt work good. same code and no changes , but different input works insane.
can u do me a favor and tell me why is it so?

StringReader sr = new StringReader("4\n20,50\n90,150\n250,70\n30,50\nY\n");
java.io.BufferedReader in_reader = new java.io.BufferedReader(sr); //new java.io.InputStreamReader(System.in));

i will try, thanks anyway