Une zone dessinable de type paint en ligne

/*
 */

import java.awt.event.*;
import java.awt.*;
import java.applet.*;

import java.util.Vector;

public class DrawTest extends Applet{
    DrawPanel panel;
    DrawControls controls;

    public void init() {
        setLayout(new BorderLayout());
        panel = new DrawPanel();
        controls = new DrawControls(panel);
        add("Center", panel);
        add("South",controls);
    }

    public void destroy() {
        remove(panel);
        remove(controls);
    }

    public static void main(String args[]) {
        Frame f = new Frame("DrawTest");
        DrawTest drawTest = new DrawTest();
        drawTest.init();
        drawTest.start();

        f.add("Center", drawTest);
        f.setSize(300, 300);
        f.show();
    }
    public String getAppletInfo() {
        return "A simple drawing program.";
    }
}

class DrawPanel extends Panel implements MouseListener, MouseMotionListener {
    public static final int LINES = 0;
    public static final int POINTS = 1;
    int    mode = LINES;
    Vector lines = new Vector();
    Vector colors = new Vector();
    int x1,y1;
    int x2,y2;

    public DrawPanel() {
        setBackground(Color.white);
        addMouseMotionListener(this);
        addMouseListener(this);
    }

    public void setDrawMode(int mode) {
        switch (mode) {
          case LINES:
          case POINTS:
            this.mode = mode;
            break;
          default:
            throw new IllegalArgumentException();
        }
    }


    public void mouseDragged(MouseEvent e) {
        e.consume();
        switch (mode) {
            case LINES:
                x2 = e.getX();
                y2 = e.getY();
                break;
            case POINTS:
            default:
                colors.addElement(getForeground());
                lines.addElement(new Rectangle(x1, y1, e.getX(), e.getY()));
                x1 = e.getX();
                y1 = e.getY();
                break;
        }
        repaint();
    }

    public void mouseMoved(MouseEvent e) {
    }

    public void mousePressed(MouseEvent e) {
        e.consume();
        switch (mode) {
            case LINES:
                x1 = e.getX();
                y1 = e.getY();
                x2 = -1;
                break;
            case POINTS:
            default:
                colors.addElement(getForeground());
                lines.addElement(new Rectangle(e.getX(), e.getY(), -1, -1));
                x1 = e.getX();
                y1 = e.getY();
                repaint();
                break;
        }
    }

    public void mouseReleased(MouseEvent e) {
        e.consume();
        switch (mode) {
            case LINES:
                colors.addElement(getForeground());
                lines.addElement(new Rectangle(x1, y1, e.getX(), e.getY()));
                x2 = -1;
                break;
            case POINTS:
            default:
                break;
        }
        repaint();
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

    public void mouseClicked(MouseEvent e) {
    }

    public void paint(Graphics g) {
        int np = lines.size();

        /* draw the current lines */
        g.setColor(getForeground());
        for (int i=0; i < np; i++) {
            Rectangle p = (Rectangle)lines.elementAt(i);
            g.setColor((Color)colors.elementAt(i));
            if (p.width != -1) {
                g.drawLine(p.x, p.y, p.width, p.height);
            } else {
                g.drawLine(p.x, p.y, p.x, p.y);
            }
        }
        if (mode == LINES) {
            g.setColor(getForeground());
            if (x2 != -1) {
                g.drawLine(x1, y1, x2, y2);
            }
        }
    }
}


class DrawControls extends Panel implements ItemListener {
    DrawPanel target;

    public DrawControls(DrawPanel target) {
        this.target = target;
        setLayout(new FlowLayout());
        setBackground(Color.lightGray);
        target.setForeground(Color.red);
        CheckboxGroup group = new CheckboxGroup();
        Checkbox b;
        add(b = new Checkbox(null, group, false));
        b.addItemListener(this);
        b.setForeground(Color.red);
        add(b = new Checkbox(null, group, false));
        b.addItemListener(this);
        b.setForeground(Color.green);
        add(b = new Checkbox(null, group, false));
        b.addItemListener(this);
        b.setForeground(Color.blue);
        add(b = new Checkbox(null, group, false));
        b.addItemListener(this);
        b.setForeground(Color.pink);
        add(b = new Checkbox(null, group, false));
        b.addItemListener(this);
        b.setForeground(Color.orange);
        add(b = new Checkbox(null, group, true));
        b.addItemListener(this);
        b.setForeground(Color.black);
        target.setForeground(b.getForeground());
        Choice shapes = new Choice();
        shapes.addItemListener(this);
        shapes.addItem("Lines");
        shapes.addItem("Points");
        shapes.setBackground(Color.lightGray);
        add(shapes);
    }

    public void paint(Graphics g) {
        Rectangle r = getBounds();
        g.setColor(Color.lightGray);
        g.draw3DRect(0, 0, r.width, r.height, false);

        int n = getComponentCount();
        for(int i=0; i<n; i++) {
            Component comp = getComponent(i);
            if (comp instanceof Checkbox) {
                Point loc = comp.getLocation();
                Dimension d = comp.getSize();
                g.setColor(comp.getForeground());
                g.drawRect(loc.x-1, loc.y-1, d.width+1, d.height+1);
            }
        }
    }

  public void itemStateChanged(ItemEvent e) {
    if (e.getSource() instanceof Checkbox) {
      target.setForeground(((Component)e.getSource()).getForeground());
    } else if (e.getSource() instanceof Choice) {
      String choice = (String) e.getItem();
      if (choice.equals("Lines")) {
        target.setDrawMode(DrawPanel.LINES);
      } else if (choice.equals("Points")) {
        target.setDrawMode(DrawPanel.POINTS);
      }
    }
  }
}