Drawing a Line in JAVA

Well Ive got my program to draw a line, but when I drag the mouse across the screen I'd like it to show its actual progress. Ill try to explain this better, if I click my mouse on one point on the screen and drag it to the enxt the line doesnt show up untill I reach my final spot when i release my mouse. What Id like for it to do is to be able to start the line and then have it show the lines progress while Im dragging it. I dont want it to hide the line or whatever. Can anyone give me some help with this? Heres both my java and HTML code.
Java:
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Lab11 extends Applet implements MouseListener {
 int x0, y0, x1, y1;
 public void init() {
 addMouseListener(this);
 public void mouseClicked(MouseEvent e) { }
 public void mouseEntered(MouseEvent e) { }
 public void mouseExited (MouseEvent e) { }
 public void mousePressed(MouseEvent e) {
 x0 = e.getX();
 y0 = e.getY();
 System.out.println("Mouse pressed at: (" +
 x0 + ", " + y0 + ")" );
 public void mouseReleased(MouseEvent e) {
 x1 = e.getX();
 y1 = e.getY();
 System.out.println("Mouse released at: (" +
 x1 + ", " + y1 + ")" );
 this.repaint();
 public void paint(Graphics g) {
 g.drawLine(x0, y0, x1, y1);
}HTML:
<html>
<head>
 <title>Lab 11 Applets</title>
</head>
<body bgcolor=white>
 <applet code="Lab11.class" width=300 height=300>
 </applet>
</body>
</html>Thanks guys!

You forgot to add this to your paint() code ...
g.setColor(Color.BLACK)
You'll never see anything drawn unless you set a color different thatn background.
This works, I added code so you can run it in a frame too because I don't want to be bothered with dealing with applets and html files;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Lab11 extends Applet implements MouseListener, MouseMotionListener {
    int x0, y0, x1, y1;
    //public void init() {
         public Lab11() {
         addMouseListener(this);
         addMouseMotionListener(this);
    public void mouseDragged(MouseEvent e)
         x1 = e.getX();
         y1 = e.getY();
         repaint();
    public void mouseMoved(MouseEvent e) { }
    public void mouseClicked(MouseEvent e) { }
    public void mouseEntered(MouseEvent e) { }
    public void mouseExited (MouseEvent e) { }
    public void mousePressed(MouseEvent e) {
     x0 = e.getX();
     y0 = e.getY();
     System.out.println("Mouse pressed at: (" +
                  x0 + ", " + y0 + ")" );
    public void mouseReleased(MouseEvent e) {
     x1 = e.getX();
     y1 = e.getY();
     System.out.println("Mouse released at: (" +
                  x1 + ", " + y1 + ")" );
     this.repaint();
   public void paint(Graphics g) {
        g.setColor(Color.BLACK);
     g.drawLine(x0, y0, x1, y1);
    public static void main(String[] argv)
         JFrame f = new JFrame("Test");
         f.getContentPane().add(new Lab11());
         f.setVisible(true);
         f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

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This code is incomplete. The program is compiled and Ran. I am unable to see the Line.
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mjava

I have no idea what JTutor is, but if it tells you to override paint() in Swing, it's not worth its disk space.
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You forgot to add this to your paint() code ...
g.setColor(Color.BLACK)
You'll never see anything drawn unless you set a color different thatn background.
This works, I added code so you can run it in a frame too because I don't want to be bothered with dealing with applets and html files;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Lab11 extends Applet implements MouseListener, MouseMotionListener {
    int x0, y0, x1, y1;
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         y1 = e.getY();
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    public void mouseExited (MouseEvent e) { }
    public void mousePressed(MouseEvent e) {
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     y0 = e.getY();
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    public void mouseReleased(MouseEvent e) {
     x1 = e.getX();
     y1 = e.getY();
     System.out.println("Mouse released at: (" +
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}

How to Draw a line Graph using x,y Cordinates in Java ?

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There's a number of sample applications in one of the packages of freechart, one of which should do the trick.
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Here are my last 3 duke dollars. Can someone please help me draw a line?

I have been BEATING my head on this for well over a week now. I'm new to Java2D and I cannot find even one example of this simple little thing that I am trying to do. Not one.
All I want to do is draw an image, zoom that image, then draw some lines on that image, and then zoom it and have those lines show up where they should.
For example, we have an image which has been zoomed. No lines are yet drawn on it.
A line is added.
The image is then zoomed in or out one more time.
How do we get the line to remap to the newly zoomed image?
What I am doing is:
0) Load up an image from a file.
1) Create a zoomed image by using the Image.getScaledInstance() method.
2) Create a BufferedImage with the width and height of the image AFTER the zoom has taken place.
3) Create a Graphics2D object by the createGraphics from this BufferedImage.
4) Place the image into the BufferedImage by doing a BufferedImage.drawImage
5) Select two points to be the start and end of the line.
6) Draw the line using Graphics2D.drawLine(start.x, start.y, end.x, end.y).
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8) Create a new ImageIcon using the image from above and override its paintIcon method like this:
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public void paintIcon(Component c, Graphics g, int x, int y)
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zoom(); //<---- ZOOM call
Now in the zoom routine, what do I need to do to get the lines to draw at the proper location and size?
Remember, the points of the lines (stored in a list as home grown line objects) are in screen coordinates, not image coordinates since they are just click points
Note that when I use these points to draw a line, all is well (the line gets drawn where it should), but I have problems when I zoom the image.
Thanks!

Below is the documentation and method signature of
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So basically your visual data is located in an offscreen image. You can draw a line on that. Then create a new image, get it's graphics and call drawImage(original_image, co-ordinates that cause it to scale how you like).
Then you can draw lines on the 2nd image, create a 3rd, ...etc
 * Draws as much of the specified area of the specified image as is
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 * 
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 * for the current output device.
 * If the current output representation is not yet complete then
 * <code>drawImage</code> returns <code>false</code>. As more of
 * the image becomes available, the process that draws the image notifies
 * the specified image observer.
 * 
 * This method always uses the unscaled version of the image
 * to render the scaled rectangle and performs the required
 * scaling on the fly. It does not use a cached, scaled version
 * of the image for this operation. Scaling of the image from source
 * to destination is performed such that the first coordinate
 * of the source rectangle is mapped to the first coordinate of
 * the destination rectangle, and the second source coordinate is
 * mapped to the second destination coordinate. The subimage is
 * scaled and flipped as needed to preserve those mappings.
 * @param img the specified image to be drawn
 * @param dx1 the x coordinate of the first corner of the
 * destination rectangle.
 * @param dy1 the y coordinate of the first corner of the
 * destination rectangle.
 * @param dx2 the x coordinate of the second corner of the
 * destination rectangle.
 * @param dy2 the y coordinate of the second corner of the
 * destination rectangle.
 * @param sx1 the x coordinate of the first corner of the
 * source rectangle.
 * @param sy1 the y coordinate of the first corner of the
 * source rectangle.
 * @param sx2 the x coordinate of the second corner of the
 * source rectangle.
 * @param sy2 the y coordinate of the second corner of the
 * source rectangle.
 * @param observer object to be notified as more of the image is
 * scaled and converted.
 * @return <code>true</code> if the current output representation
 * is complete; <code>false</code> otherwise.
 * @see java.awt.Image
 * @see java.awt.image.ImageObserver
 * @see java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
 * @since JDK1.1
 public abstract boolean drawImage(Image img,
 int dx1, int dy1, int dx2, int dy2,
 int sx1, int sy1, int sx2, int sy2,
 ImageObserver observer);

Drawing fading line

Hello everyone!
I am trying to draw a fading line on a desktop. For example: we have a JFrame instance on the screen, when we press right mouse button over the frame and drag the mouse across the screen, I want to draw a line, fading through time. I don't want to restrict the line in the JFrame bounds, instead I want to draw it on the desktop screen.
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If you don't want to restrict the line to a single JFrame, I believe the JLayeredPane is for you. It allows you to have a transparent pane which overlays multiple Swing components.
http://java.sun.com/j2se/1.4.2/docs/api/javax/swing/JLayeredPane.html

Draw a line after zoom in

Hi All,
I want to draw a line after zooming in/out the image. If the image is not scaled, then ever thing is fine. But once I scaled the image and draw the line, the position is not coming correctly. Can you correct me, what's my mistake?
package imagetest;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
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 private double translateY = 0.0;
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 if (dragging)
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 else
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 public static void main(String[] args)
 JFrame frame = new JFrame();
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 ZoomAndDraw zoomAndDraw = new ZoomAndDraw();
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 frame.add(zoomAndDraw);
 frame.setPreferredSize(new Dimension(640, 480));
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 frame.setVisible(true);
}Thanks and Regards
Raja.

Hi,
I'm having one more doubt. Just assume, after calling the ZoomIn(), I am drawing a line.
Subsequent ZoomIn() calls (let's say 5 times), changed the actual line position. How do I synchronize the zoom in call with the line coordinates?
public void FireZoomIn()
 new Thread(new Runnable()
 public void run()
 try
 Thread.sleep(3000);
 catch (InterruptedException iex)
 int count = 0;
 while (count++ < 5)
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 }).start();
public void mouseReleased(MouseEvent e)
 if (dragging)
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 dragging = false;
 }Thanks and Regards
Raja.

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Personally I wouldn't work with Swing for this functionality,
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Look for the java.awt.Shape interface and to the java.awt.geom.* implementations of such shapes.
It contains already most of the functionality required for painting and hit-detection of a shape on the
screen.
kind regards,

Displaying Lines in java Qusetion?

hi,
i was wondering is there a way to display thick 2d lines in java swing when drawing lines with paintComponent(). the default is very thin but i was wondering is there a method to display wider lines!!
cheers in advance

You can define line width using setStroke(Stroke myStroke) of Graphics2D class.
Cheers
DB

Draw a line on a JFrame

I have 2 panels inside a JFrame and I want to separate the 2 panels using a visible line. How can I draw this line?

You will need to over ride the paint(Graphics g) method.
From there you can use the g.drawLine(startX,startY,endX,endY). So for instance if you had two panels next to each other and the line is a vertical line then you would do something similar to this.
public void paint(Graphics g){
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http://java.sun.com/docs/books/tutorial/2d/basic2d/index.html

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Hello there:
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          y0 = e.getY();
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thanks n regards...
Dev

You can implement the listeners on any class, even one that (implicitly) extends Object. What matters is that the listener is added to the component that needs to use it.
That said, why do you want to extend JFrame? Are you adding functionality to the JFrame to justify extending the JFC class? Note that extending JFrame allows the users of your class to access the functionality of a JFrame, is that really indicated here?
one class that extends JFrame, and one can draw a line on JLabel, embedded within JFrame!So you still have to override paintComponent of the JLabel, which implies using an anonymous inner class.
Starting with the example already posted, that would be:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
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JLabel label;
int x0, y0, x1, y1;
private void makeUI() {
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    label.addMouseListener(this);
    label.addMouseMotionListener(this);
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public void mousePressed(MouseEvent e) {
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    y0 = e.getY();
public void mouseReleased(MouseEvent e) {
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    y1 = e.getY();
public void mouseDragged(MouseEvent e) {
    x1 = e.getX();
    y1 = e.getY();
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public void mouseMoved(MouseEvent e) { }
public void mouseClicked(MouseEvent e){ }
public void mouseEntered(MouseEvent e) { }
public void mouseExited (MouseEvent e) { }
}Better spend more time with the tutorials, there's a separate section on writing event listeners.
db

Drawing dotted lines

Hey
I've already figured out how to draw dotted lines so that's not the questions
the thing is I only need to draw some lines as dotted, some as dashed and all others just normal..
I figured I could make radiobox to select which line.. then I save that to an array of some sort and then in the paintComponent thing I should make an if to check for array value and change the stoke according to that
so far I've just made my lines dotted like this
http://www.jguru.com/faq/view.jsp?EID=114099
but now everything is dotted.. even the borders around my buttons..
ni my applet I have some buttons which are connected with a line.. I want that line dotted or dashed when the users wants it to.. and only then otherwise just normal lines
I couldn't find anything about that on the google =(

done!
now I want to be able to use diffrent line style combinations but it doesn't work
currently it only uses the linestyle that you selected for the first line and then uses that for every line after that too
this is my code
 public void paintComponent(Graphics g) {
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 Graphics2D g2d = (Graphics2D)g;
 g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
 g2d.setColor(lijnKleur);
 for (int i = 0; i < Main.XList.size(); i++) {
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 int k = (i + 1);
 int aantal = 0;
 if ((k % 2 == 0) && (i != 0)) {
 if (Main.lijnstyleList.get(aantal) == 1){
 g2d.setStroke(normaal);
 else if (Main.lijnstyleList.get(aantal) == 2){
 g2d.setStroke(gestippeld);
 else if (Main.lijnstyleList.get(aantal) == 3){
 g2d.setStroke(gestreept);
 else{
 g2d.setStroke(normaal);
 int tmpX_oud = Main.XList.get(j) + (Main.breedte / 2);
 int tmpY_oud = Main.YList.get(j) + (Main.hoogte / 2);
 int tmpX = Main.XList.get(i) + (Main.breedte / 2);
 int tmpY = Main.YList.get(i) + (Main.hoogte / 2);
 aantal++;
 if (tmpY_oud > tmpY){
 tmpY = tmpY + (Main.hoogte / 2);
 int half = tmpY + (Main.spacing / 2);
 if ((tmpY_oud != tmpY) && (tmpX_oud != tmpX)) {
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX_oud, half);
 g2d.drawLine(tmpX_oud, half, tmpX, half);
 g2d.drawLine(tmpX, half, tmpX, tmpY);
 else{
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX, tmpY);
 g2d.drawLine(tmpX, tmpY, tmpX - 5, tmpY + 8);
 g2d.drawLine(tmpX, tmpY, tmpX + 5, tmpY + 8);
 else if (tmpY_oud < tmpY){
 tmpY = tmpY - (Main.hoogte / 2);
 int half = tmpY - (Main.spacing / 2);
 if ((tmpY_oud != tmpY) && (tmpX_oud != tmpX)) {
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX_oud, half);
 g2d.drawLine(tmpX_oud, half, tmpX, half);
 g2d.drawLine(tmpX, half, tmpX, tmpY);
 else{
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX, tmpY);
 g2d.drawLine(tmpX, tmpY, tmpX - 5, tmpY - 8);
 g2d.drawLine(tmpX, tmpY, tmpX + 5, tmpY - 8);
 else {
 if (tmpX_oud > tmpX){
 tmpX = tmpX + (Main.breedte / 2);
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX, tmpY);
 g2d.drawLine(tmpX, tmpY, tmpX + 8, tmpY - 5);
 g2d.drawLine(tmpX, tmpY, tmpX + 8, tmpY + 5);
 else{
 tmpX = tmpX - (Main.breedte / 2);
 g2d.drawLine(tmpX_oud, tmpY_oud, tmpX, tmpY);
 g2d.drawLine(tmpX, tmpY, tmpX - 8, tmpY - 5);
 g2d.drawLine(tmpX, tmpY, tmpX - 8, tmpY + 5);
 g2d.setStroke(normaal);
 }**EDIT**
according to this it can be done..
http://java.sun.com/developer/JDCTechTips/2003/tt0520.htm
no clue why mine doesn't work then
Edited by: Nizzle on Sep 13, 2007 10:15 AM

Draw a line smoothed

How can I draw a line smoothed with awt.graphics???
I use this class and not Java 2D because i need use it with I.E. without Java Plugin.

there are quite a few line antialiasing algorithms out there. try for example http://graphics.lcs.mit.edu/classes/6.837/F01/Lecture05/Slide12h.html
but any good computer graphics book will help.

"I want to draw a line, and it will highlight when I click it."

I am currently working on a project right now. My project is a structural analysis software for civil engineers. Our project is already at it's infant
stage of development. I am having trouble with how to implement drawing on a canvas. Heres the specs:
-There are nodes on the drawing board illustrated by dots.
-Lines must be drawn connecting the nodes.
-Nodes must be a separate object where it could respond to mouse
events.
-Lines must also be a separate object where it could respond to mouse
events.
-Nodes and lines contain mathematical attributes, color information.
-I can instantly delete a line, or change its attributes by selecting
it.
Heres what I have imagined:
-I am going to draw my Nodes in a JPanel which implements a
mouseListener.
-Whenever I want to add nodes to the drawing board, I only have to add
the Node objects i created.
No problem with the nodes. Problem is in the lines i will be drawingconnecting one node to another.
-I tried manual live drawing of the lines as the mouse moves. Now its
flat on the drawing board. It can't be touched!
-I still don't have any idea how to implement the line that it could
respond to mouse events.
-If I try to draw it in a JPanel with mouseListener, a JPanel is square
so if I move my mouse to point in to the line drawn on the JPanel, it
will already respond before the mouse could reach the line image. One
thing also, it could overlap other JPanels.
-The JPanel idea came up to my mind coz I thought these objects could
be
selectable custom components.
-Now I realized JPanel is not the ANSWER!
In simple saying:
"I want to draw a line, and it will highlight when I click it."
Stubborn Newbie,
Edgar

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class SelectingLines extends JPanel
 Line2D.Double[] lines;
 int selectedIndex = -1;
 protected void paintComponent(Graphics g)
 super.paintComponent(g);
 Graphics2D g2 = (Graphics2D)g;
 g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
 RenderingHints.VALUE_ANTIALIAS_ON);
 if(lines == null)
 initLines();
 for(int j = 0; j < lines.length; j++)
 Color color = Color.blue;
 if(j == selectedIndex)
 color = Color.green.darker();
 g2.setPaint(color);
 g2.draw(lines[j]);
 public void setSelection(int index)
 selectedIndex = index;
 repaint();
 private void initLines()
 lines = new Line2D.Double[3];
 int w = getWidth();
 int h = getHeight();
 lines[0] = new Line2D.Double(w/8, h/8, w/3, h/6);
 lines[1] = new Line2D.Double(w/3, h/6, w/2, h/2);
 lines[2] = new Line2D.Double(w/2, h/2, w*5/8, h*7/12);
 public static void main(String[] args)
 SelectingLines selectPanel = new SelectingLines();
 selectPanel.addMouseListener(new LineSelector(selectPanel));
 JFrame f = new JFrame();
 f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 f.getContentPane().add(selectPanel);
 f.setSize(400,400);
 f.setLocation(200,200);
 f.setVisible(true);
class LineSelector extends MouseAdapter
 SelectingLines selectingLines;
 Rectangle r;
 final int S = 4;
 public LineSelector(SelectingLines sl)
 selectingLines = sl;
 r = new Rectangle(S, S);
 public void mousePressed(MouseEvent e)
 Point p = e.getPoint();
 r.setLocation(p.x-S/2, p.y-S/2);
 Line2D.Double[] lines = selectingLines.lines;
 int index = -1;
 for(int j = 0; j < lines.length; j++)
 if(lines[j].intersects(r))
 index = j;
 break;
 if(index != selectingLines.selectedIndex)
 selectingLines.setSelection(index);
}

How to draw a line after i load a frame?

its simple to draw a line before i load the frame..
when i try to draw a line after i load the frame, i get a error in the last line of the lauchFrame method..
the error is "java.awt.Graphics is abstract; cannot be instantiated"
import java.awt.*;
class GraphArea extends Panel
    public void paint(Graphics g)
        g.setColor(Color.BLUE);
        g.drawLine(0,0,250,250);
    public void paint(Graphics g,int X1, int X2)
        g.drawLine(0,0,X1,X2);
class Grapherv1 {
private Frame f;
private GraphArea drawPanel;
public Grapherv1() {
    f = new Frame("Drawing Shapes:Lenin");
    drawPanel = new GraphArea();
public void launchFrame() {
      f.setLayout(new FlowLayout());
      drawPanel.setSize(950,550);
      drawPanel.setBackground(new Color(220,220,220));
      drawPanel.setLayout(null);
     f.setBackground(Color.white);
      f.add(drawPanel);
    f.pack();
    f.setSize(1000, 800);
    f.setVisible(true);
    drawPanel.paint(new Graphics(),100,100);
public static void main(String args[]) throws InterruptedException {
      Grapherv1 gui = new Grapherv1();
    gui.launchFrame();
}please tell me how to call this method ...
public void paint(Graphics g,int X1, int X2)
what argument i should pass for Graphics??
Edited by: Tall-Dude on Dec 3, 2007 4:33 PM
Edited by: Tall-Dude on Dec 3, 2007 4:33 PM

Tall-Dude wrote:
please tell me how to call this method ...
public void paint(Graphics g,int X1, int X2)just past the new x1 and x2 and repaint no need to pass the graphics.
e.g.
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
class Grapherv1 {
    private Frame f;
    private GraphArea drawPanel;
    public Grapherv1() {
        f = new Frame("Drawing Shapes:Lenin");
        drawPanel = new GraphArea();
    public void launchFrame() {
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
        f.setLayout(new BorderLayout());
        drawPanel.setSize(950,550);
        drawPanel.setBackground(new Color(220,220,220));
        drawPanel.setLayout(null);
        f.setBackground(Color.white);
        f.add(drawPanel);
        f.pack();
        f.setSize(1000, 800);
        f.setVisible(true);
        drawPanel.redraw(300,400);
    public static void main(String args[]) throws InterruptedException {
        Grapherv1 gui = new Grapherv1();
        gui.launchFrame();
    class GraphArea extends Panel {
        int x1, x2;
        public void paint(Graphics g) {
            g.setColor(Color.BLUE);
            g.drawLine(0,0,x1,x2);
        public void redraw(int X1, int X2) {
            x1 = X1;
            x2 = X2;
            repaint();
}

Drawing a Line in JAVA

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