Thread: drawLine problem, lines not connected

So I'm having an issue with drawLine; my program tracks the mouses movement when moving and when dragged and displays it on the screen, I also want a little drawing function as to have a visual representation of what they did. I used drawLine and for some reason the lines aren't really connected, the faster the mouse moves, the more dotted and broken the line is!

Heres MouseMotionEventDemo.java

 
package events;
 
/*
 * MouseMotionEventDemo.java
 *
 */
 
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.*;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
 
 
public class MouseMotionEventDemo extends JPanel
        implements MouseMotionListener {
    BlankArea blankArea;
    JTextArea textArea;
    int lastX=0, lastY=0;
    static final String NEWLINE = System.getProperty("line.separator");
 
    public static void main(String[] args) {
        /* Use an appropriate Look and Feel */
        try {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
            UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } catch (UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
        } catch (IllegalAccessException ex) {
            ex.printStackTrace();
        } catch (InstantiationException ex) {
 
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }
        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);
 
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("MouseMotionEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Create and set up the content pane.
        JComponent newContentPane = new MouseMotionEventDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);
 
 
    }
 
    public MouseMotionEventDemo() {
        super(new GridLayout(0,1));
        blankArea = new BlankArea(Color.WHITE);
        add(blankArea);
 
        textArea = new JTextArea();
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setPreferredSize(new Dimension(200, 75));
 
        add(scrollPane);
 
        //Register for mouse events on blankArea and panel.
        blankArea.addMouseMotionListener(this);
        addMouseMotionListener(this);
 
 
        setPreferredSize(new Dimension(450, 450));
        /*setBorder(BorderFactory.createEmptyBorder(20,20,20,20)); */
 
    }
 
    void eventOutput(String eventDescription, MouseEvent e) {
        textArea.append(eventDescription
                + " (" + e.getX() + "," + e.getY() + ")"
                + " detected on "
                + e.getComponent().getClass().getName()
                + NEWLINE);
        lastX = e.getX();
        lastY = e.getY();
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }
 
   public void mouseMoved(MouseEvent e) {
        eventOutput("Mouse moved", e);
    }
 
    @Override
   public boolean mouseDown(Event e, int x, int y){
       return(record(x,y));
               }
 
    @Override
   public boolean mouseEnter(Event e, int x, int y) {
        return(record(x, y));
        }
 
   public void mouseDragged(MouseEvent e) {
        eventOutput("Mouse dragged", e);
        Graphics g = getGraphics();
        g.drawLine(lastX, lastY, e.getX(), e.getY());
        record(e.getX(), e.getY());
    }
 
    @Override
   public void paintComponent(Graphics g) {
            super.paintComponent(g);
          /*  g.drawLine(lastX, lastY, newX, newY);
            repaint(lastX, lastY, newX, newY); */
        }
   protected boolean record(int x, int y){
        lastX = x;
        lastY = y;
        return(true);
    }
}

BlankArea.java is this

/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 
 
package events;
 
/*
 * BlankArea.java is used by:
 *    MouseEventDemo.java.
 *    MouseMotionEventDemo.java
 */
 
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.*;
 
 
 
public class BlankArea extends JLabel {
    Dimension minSize = new Dimension(100, 50);
 
    public BlankArea(Color color) {
        setBackground(color);
        setOpaque(false);
        setBorder(BorderFactory.createLineBorder(Color.black));  
 
    }
 
  }

Where should the current x and y be recorded? I can't use e.getX() in the paintcomponent since it doesn't recognize e

See Norm's post #2:

The other methods should define where the lines are to be drawn and save that data in a collection and then call repaint().

Now I'm just getting confused as to where to record all of the coordinates, as in, the current xy and the previous xy

 
package events;
 
/*
 * MouseMotionEventDemo.java
 *
 */
 
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.*;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.util.*;
 
 
public class MouseMotionEventDemo extends JPanel
        implements MouseMotionListener {
    BlankArea blankArea;
    JTextArea textArea;
    int lastX=0, lastY=0, currX=0, currY=0;
    ArrayList al = new ArrayList();
    Object ia[] = al.toArray();
    static final String NEWLINE = System.getProperty("line.separator");
 
    public static void main(String[] args) {
        /* Use an appropriate Look and Feel */
        try {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
            UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } catch (UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
        } catch (IllegalAccessException ex) {
            ex.printStackTrace();
        } catch (InstantiationException ex) {
 
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }
        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);
 
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("MouseMotionEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Create and set up the content pane.
        JComponent newContentPane = new MouseMotionEventDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);
 
 
    }
 
    public MouseMotionEventDemo() {
        super(new GridLayout(0,1));
        blankArea = new BlankArea(Color.WHITE);
        add(blankArea);
 
        textArea = new JTextArea();
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setPreferredSize(new Dimension(200, 75));
 
        add(scrollPane);
 
        //Register for mouse events on blankArea and panel.
        blankArea.addMouseMotionListener(this);
        addMouseMotionListener(this);
 
 
        setPreferredSize(new Dimension(450, 450));
        /*setBorder(BorderFactory.createEmptyBorder(20,20,20,20)); */
 
    }
 
    void eventOutput(String eventDescription, MouseEvent e) {
        textArea.append(eventDescription
                + " (" + e.getX() + "," + e.getY() + ")"
                + " detected on "
                + e.getComponent().getClass().getName()
                + NEWLINE);
        lastX = e.getX();
        lastY = e.getY();
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }
 
   public void mouseMoved(MouseEvent e) {
      currX = e.getX();
      currY = e.getY();
       eventOutput("Mouse moved", e);
       record(currX, currY);
   }
 
    @Override
   public boolean mouseDown(Event e, int x, int y){
        return(record(x,y));
        }
 
    @Override
   public boolean mouseEnter(Event e, int x, int y) {
        return(record(x, y));
        }
 
   public void mouseDragged(MouseEvent e) {
        eventOutput("Mouse dragged", e);
    }
 
    @Override
   public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawLine(lastX, lastY, currX, currY);
            record(lastX,lastY);
            repaint();
        }
   protected boolean record(int x, int y){
        lastX = x;
        lastY = y;
        return(true);
    }
}

All it's doing is keeping the first point concrete and changing the current xy, so all moving the mouse does when clicked is pivot the line around a point

But I don't want it to draw "lines" i just want it to draw where the mouse is, as it's being dragged, like you'd do in MS paint

I've tried looking up things, like i said i'm REALLY new at java and am just overwhelmed with this right now.
I just wanted a simple click, move mouse and have it paint where you move the mouse.

package events;
 
/*
 * MouseMotionEventDemo.java
 *
 */
 
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.*;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.util.*;
 
 
public class MouseMotionEventDemo extends JPanel
        implements MouseMotionListener {
    BlankArea blankArea;
    JTextArea textArea;
    int lastX=0, lastY=0, currX=0, currY=0;
    ArrayList al = new ArrayList();
    Object ia[] = al.toArray();
    static final String NEWLINE = System.getProperty("line.separator");
 
    public static void main(String[] args) {
        /* Use an appropriate Look and Feel */
        try {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
            UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } catch (UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
        } catch (IllegalAccessException ex) {
            ex.printStackTrace();
        } catch (InstantiationException ex) {
 
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }
        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);
 
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("MouseMotionEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Create and set up the content pane.
        JComponent newContentPane = new MouseMotionEventDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);
 
 
    }
 
    public MouseMotionEventDemo() {
        super(new GridLayout(0,1));
        blankArea = new BlankArea(Color.WHITE);
        add(blankArea);
 
        textArea = new JTextArea();
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setPreferredSize(new Dimension(200, 75));
 
        add(scrollPane);
 
        //Register for mouse events on blankArea and panel.
        blankArea.addMouseMotionListener(this);
        addMouseMotionListener(this);
 
 
        setPreferredSize(new Dimension(450, 450));
        /*setBorder(BorderFactory.createEmptyBorder(20,20,20,20)); */
 
    }
 
    void eventOutput(String eventDescription, MouseEvent e) {
        textArea.append(eventDescription
                + " (" + e.getX() + "," + e.getY() + ")"
                + " detected on "
                + e.getComponent().getClass().getName()
                + NEWLINE);
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }
 
   public void mouseMoved(MouseEvent e) {
       eventOutput("Mouse moved", e);
       currX = e.getX();
       currY = e.getY();
       record(e.getX(),e.getY());
       repaint();
   }
 
   public boolean mouseDown(Event e, int x, int y){
       return(record(x,y));
   }
 
    @Override
   public boolean mouseEnter(Event e, int x, int y) {
        return(record(x, y));
    }
 
   public void mouseDragged(MouseEvent e) {
        eventOutput("Mouse dragged", e);
        currX = e.getX();
        currY = e.getY();
        repaint();
    }
 
    @Override
   public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawLine(lastX, lastY, currX, currY);
 
   }
 
   protected boolean record(int x, int y){
        lastX = x;
        lastY = y;
        return(true);
    }
}

could you test this and see what works for you?

Originally Posted by Norm

How many lines do you want drawn?
Enough to show where the mouse has moved
Or just one from the click point to the current mouse position

Enough to show where the mouse has moved, just like if you opened MS Paint and used the pencil function

That was my original thought was that I was going to save the end points as the mouse moves, but i couldn't figure out where exactly to put the code for current xy and previous xy.

You sort of hinted at it, but like I said I'm a newbie at Java so I have no idea where to do that stuff

you mentioned paintcomponent and I tried to throw something in there but all I ever got was one endpoint not moving, and the other just following the cursor instead of painting. I just don't know how to set everything up

EDIT: All in all I think i just need to know how paintComponent is set up and how the function that repaints is set up

Oh wow that clears a few things up! ok I understand a bit more now.

So I tweaked things and, if you run this code you'll see that there is just a small trail behind the cursor instead of it actually drawing the WHOLE line, it just draws from the last xy to the current, and keeps doing that without "saving" it. What do I need to move around?

package events;
 
/*
 * MouseMotionEventDemo.java
 *
 */
 
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.*;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.util.*;
 
 
public class MouseMotionEventDemo extends JPanel
        implements MouseMotionListener {
    BlankArea blankArea;
    JTextArea textArea;
    int lastX=0, lastY=0, currX=0, currY=0;
    ArrayList al = new ArrayList();
    Object ia[] = al.toArray();
    static final String NEWLINE = System.getProperty("line.separator");
 
    public static void main(String[] args) {
        /* Use an appropriate Look and Feel */
        try {
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
            UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
        } catch (UnsupportedLookAndFeelException ex) {
            ex.printStackTrace();
        } catch (IllegalAccessException ex) {
            ex.printStackTrace();
        } catch (InstantiationException ex) {
 
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        }
        /* Turn off metal's use of bold fonts */
        UIManager.put("swing.boldMetal", Boolean.FALSE);
 
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("MouseMotionEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Create and set up the content pane.
        JComponent newContentPane = new MouseMotionEventDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);
 
        //Display the window.
        frame.pack();
        frame.setVisible(true);
 
 
    }
 
    public MouseMotionEventDemo() {
        super(new GridLayout(0,1));
        blankArea = new BlankArea(Color.WHITE);
        add(blankArea);
 
        textArea = new JTextArea();
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        scrollPane.setPreferredSize(new Dimension(200, 75));
 
        add(scrollPane);
 
        //Register for mouse events on blankArea and panel.
        blankArea.addMouseMotionListener(this);
        addMouseMotionListener(this);
 
 
        setPreferredSize(new Dimension(450, 450));
        /*setBorder(BorderFactory.createEmptyBorder(20,20,20,20)); */
 
    }
 
    void eventOutput(String eventDescription, MouseEvent e) {
        textArea.append(eventDescription
                + " (" + e.getX() + "," + e.getY() + ")"
                + " detected on "
                + e.getComponent().getClass().getName()
                + NEWLINE);
        textArea.setCaretPosition(textArea.getDocument().getLength());
    }
 
   public void mouseMoved(MouseEvent e) {
       eventOutput("Mouse moved", e);
       currX = e.getX();
       currY = e.getY();
       record(e.getX(),e.getY());
   }
 
   public boolean mouseDown(Event e, int x, int y){
       return(record(x,y));
   }
 
   public boolean mouseEnter(Event e, int x, int y) {
        return(record(x, y));
    }
 
   public void mouseDragged(MouseEvent e) {
        eventOutput("Mouse dragged", e);
        currX = e.getX();
        currY = e.getY();
        repaint();
    }
 
    @Override
   public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawLine(lastX, lastY, currX, currY);
        record(currX,currY);
   }
 
   protected boolean record(int x, int y){
        lastX = x;
        lastY = y;
        return(true);
    }
}

Not even sure where to start with that.

I'll just figure this out tomorrow or something, because I don't have a clue whats going wrong.

Yeah it draws a line between the last two mouse positions, but I want that to save on the screen.
like i said, it's like going into Microsoft Paint and using the Pen feature. hm

I've never had to use arraylist before though. I made a basic whiteboard app without any frames or windows or mouse tracking or anything, and it didn't use arrayList.



Here's my issue; go to paintComponent and comment out "super.paintComponent(g); " and tell me what you get.
for me I am able to draw JUST like I want, but the mouse tracking text extends into the drawing screen?