Problem drawing a graph in Java2D

Question

I am trying to draw a graph using Java2D, onto a JPanel. I works sort of ok, but i have 2 problems;
1. I don't know how to get it "linked" to the paint() method, so everytime someone resizez the window/window looses focus, the drawing is removed.
2. The graphing becomes unacurate when passing more than 25-30 values, I think the problem might be the "hvorPaAkse" (whereOnAksis) or the "okY" (increaseY) value, that for some rasen appear to add too much, so that the error gradually increases for every loop in the for(), or something like that.
I know reading the code and understanding the problem itselv is a challenge, but I if there's anybody out there who can help, I would be thankful for any help!
CODE:
//The draw axis method
public void tegnAkser(JComponent comp, int antX, int antY, int okX, int okY) {
Graphics g = comp.getGraphics();
Graphics2D g2 = (Graphics2D) g;
g2.setStroke(akseStrek);
g2.draw(new Line2D.Double(origo.x, origo.y, origo.x, comp.getHeight()-((antY*okY)+(comp.getHeight()/yOffset))));
g2.draw(new Line2D.Double(origo.x, origo.y, origo.x+(antX*okX), origo.y));
int hvorPaAkse = origo.x;
System.out.println(comp.getHeight()/antY);
int gangeverdi = 1;
if(comp.getHeight()/antY < 16) {
gangeverdi = 5;
for(int i=0; i<antX; i++) {
g2.draw(new Line2D.Double(hvorPaAkse, origo.y - 2, hvorPaAkse,
origo.y + 2));
g2.drawString("" + i, hvorPaAkse, origo.y + 15);
hvorPaAkse += okX;
hvorPaAkse = origo.y;
for(int i=0; i<antY; i++) {
if(i%gangeverdi == 0) {
g2.draw(new Line2D.Double(origo.x - 2, hvorPaAkse, origo.x + 2,
hvorPaAkse));
g2.drawString("" + i, origo.x - 15, hvorPaAkse);
hvorPaAkse -= okY;
//the drawGraf method
public void tegnGraf(int[] verdier, JComponent comp) {
Graphics g = comp.getGraphics();
Graphics2D g2 = (Graphics2D) g;
int xLengde = comp.getWidth();
int yLengde = comp.getHeight();
origo = new Punkt(xLengde - 9 * (xLengde / xOffset),
yLengde - (yLengde / yOffset));
int ant = verdier.length;
int maxVerdi = 0;
for (int i = 0; i < verdier.length; i++) {
if (verdier[i] > maxVerdi)
maxVerdi = verdier;
tegnAkser(comp, ant+1, maxVerdi+1, (xLengde - (xLengde / xOffset)) / ant,
( (yLengde / yOffset) - yLengde) * -1 / maxVerdi);
g2.setColor(Color.BLUE);
g2.setStroke(grafStrek);
ArrayList punkter = new ArrayList();
for (int i = 0; i < verdier.length; i++) {
g2.drawString("x", origo.x-2 + (i * (xLengde - (xLengde / xOffset)) / ant),
origo.y +3 -
(verdier[i] * ( (yLengde / yOffset) - yLengde) * -1 /
maxVerdi));
punkter.add(new Point2D.Double(origo.x +
(i * (xLengde - (xLengde / xOffset)) / ant),
origo.y -
(verdier[i] *
( (yLengde / yOffset) - yLengde) * -1 /
maxVerdi)
//g2.draw(new Line2D.Double(origo.x,origo.y,origo.x+1,origo.y+1));
for(int i=1; i<punkter.size(); i++) {
Point2D.Double forrige = (Point2D.Double)punkter.get(i-1);
Point2D.Double denne = (Point2D.Double)punkter.get(i);
Line2D.Double linje = new Line2D.Double(forrige,denne);
g2.draw(linje);
Thanks
CJ

Answer 1

I couldn't do much with the code that you posted. It looks like you are plotting integers. Maybe you can use this.
/* Plots plus/minus int values for ordinate for
* evenly-distributed, positive int values on abcissa
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
public class PlottingIntegers
    public static void main(String[] args)
        int[] data = {
            100, 220, 12, 65, 47, 175, 190, 18
        IntegerPlotter plotter = new IntegerPlotter();
        for(int i = 0; i < 8; i++)
            plotter.plot(data);
JFrame f = new JFrame("Plotting Integers");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(plotter);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
class IntegerPlotter extends JPanel
final int PAD = 25;
List dataList;
public IntegerPlotter()
dataList = new ArrayList();
setBackground(Color.white);
setPreferredSize(new Dimension(400,300));
public void paintComponent(Graphics g)
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
int width = getWidth();
int height = getHeight();
int xStep = (width - 2*PAD)/(dataList.size() - 1);
int x = PAD;
int y;
// scale data
int max = ((Integer)Collections.max(dataList)).intValue();
int min = ((Integer)Collections.min(dataList)).intValue();
int vertSpace = height - 2*PAD;
int yOffset = height - PAD;
int yDataOffset = (min >= 0 ? min : max > 0 ? 0 : max);
double scale = (double)vertSpace/(max - min);
int yOrigin = yOffset + (int)(min > 0 ? 0 : max > 0 ? scale*min : - vertSpace);
// draw ordinate
g2.draw(new Line2D.Float(PAD, PAD, PAD, yOffset));
// draw abcissa
g2.draw(new Line2D.Float(PAD, yOrigin, width - PAD, yOrigin));
// label ordinate limits
g2.drawString(String.valueOf(max), 10, PAD - 10);
g2.drawString(String.valueOf(min), 10, yOffset + PAD/2);
g2.setStroke(new BasicStroke(4f));
g2.setPaint(Color.red);
for(int i = 0; i < dataList.size(); i++)
y = yOrigin -
(int)(scale * (((Integer)dataList.get(i)).intValue() - yDataOffset));
g2.draw(new Line2D.Float(x, y, x, y));
x += xStep;
protected void plot(int input)
dataList.add(new Integer(input));
repaint();