Making a diagram interactive???

[Constanze Michaelis]

Hi @ll,

I'm programming a complicated Applet with a lot of functions. Because of just a bit experiences with java several problems occure.
I'm showing a graph with the paint(Graphics g) Method. Thats why I paint the graph with g.drawPolyline(...) . Now I would like to
know, if there is any possibility to add a Listener, because I would like to show the exact values in a textfield, after the user clicked
the graph.

bye

Constanze

[Craig Wood]

Here's one way to approach this. Written for j2se 1.5

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
 
public class GraphTest
{
    GraphTestPanel testPanel = new GraphTestPanel();
    PathSeeker seeker = new PathSeeker(this);
    Label label;
 
    public GraphTest()
    {
        label = new Label();
        label.setAlignment(Label.CENTER);
        Dimension d = label.getPreferredSize();
        d.height = 25;
        label.setPreferredSize(d);
        testPanel.addMouseListener(seeker);
        Frame f = new Frame();
        f.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
        f.add(testPanel);
        f.add(label, "South");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    public static void main(String[] args)
    {
        new GraphTest();
    }
}
 
class GraphTestPanel extends Panel
{
    int[][] points = {
        { 40,  80, 150, 225, 230, 250, 340, 400 },  // x
        { 40, 125, 325, 300, 100,  40, 300, 400 }   // y
    };
    GeneralPath path;
 
    public GraphTestPanel()
    {
        initPath();
    }
 
    public void paint(Graphics g)
    {
        super.paint(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.draw(path);
    }
 
    private void initPath()
    {
        path = new GeneralPath();
        path.moveTo(points[0][0], points[1][0]);
        for(int j = 1; j < points[0].length; j++)
            path.lineTo(points[0][j], points[1][j]);
    }
}
 
class PathSeeker extends MouseAdapter
{
    public GraphTest test;
    double layer;  // max allowable distance from line segment for detection
 
    public PathSeeker(GraphTest gt)
    {
        test = gt;
        layer = 0.40;
    }
 
    public void mousePressed(MouseEvent e)
    {
        Point p = e.getPoint();
        GeneralPath path = test.testPanel.path;
        PathIterator iterator = path.getPathIterator(null);
        double[] coords = new double[6];
        double startX = 0, startY = 0, nextX, nextY;
        boolean lineFound = false;
        while(!iterator.isDone())
        {
            if(iterator.currentSegment(coords) == PathIterator.SEG_MOVETO)
            {
                startX = coords[0];
                startY = coords[1];
            }
            if(iterator.currentSegment(coords) == PathIterator.SEG_LINETO)
            {
                  nextX = coords[0];
                  nextY = coords[1];
                  if(Line2D.ptLineDist(startX, startY, nextX, nextY,
                                       p.x, p.y) < layer)
                  {
                      test.label.setText("x = " + p.x + ",  y = " + p.y);
                      lineFound = true;
                      System.out.printf("distance from line is %.4f%n",
                                    Line2D.ptLineDist(startX, startY, nextX,
                                                      nextY, p.x, p.y));
                  }
                  startX = nextX;
                  startY = nextY;
            }
            if(!lineFound)
                test.label.setText("");
            iterator.next();
        }
    }
}