Writing Mouse Events

[George Jacobs]

Since my previous post has gotten much action I figured I would ask a more broad question.

How do I create a GUI that can have 2 mouse events on different "panes" and keep track of these? Is this doable?

For example, I have a JFrame with a mouse event and a JPanel with mouse events. Do I need to make one a keyboard event and keep the other as a mouse event?

Thanks!

[Randall Twede]

no, that is not a problem just set them both to have the same mouseListener. then in your mouse handling code determine where the event came from. e.getsource(). or let the JFrame handle its and let the JPanel handle its. that might be the best way.

[George Jacobs]

Randall Twede wrote:no, that is not a problem just set them both to have the same mouseListener. then in your mouse handling code determine where the event came from. e.getsource(). or let the JFrame handle its and let the JPanel handle its. that might be the best way.

Thanks Randall!

I have created a class to attempt to try this, but I am having trouble getting a box to draw.

Here is my code associated with what I have done.

public class JPanelExample extends JPanel implements MouseListener{

    int currentX, currentY, startX, startY;
    boolean dragMode = false;

    // if in drag mode, paint the current rectangle
    public void paint(Graphics g) {
        int beginX, beginY, width, height;
        if (dragMode == true) {
            beginX = Math.min(startX, currentX);
            beginY = Math.min(startY, currentY);
            width = Math.abs(currentX - startX);
            height = Math.abs(currentY - startY);
            g.drawRect(beginX, beginY, width, height);
	}
        else {
            g.drawString("Draw a box by dragging the mouse", 10, 25);
        }
    }

    // mouse down starts drag
    public boolean mouseDown(MouseEvent event, int x, int y) {
        dragMode = true;
        startX = x;
        startY = y;
        return true;
    }

    // mouse up ends drag
    public boolean mouseUp(MouseEvent event, int x, int y) {
        dragMode = false;
        return true;
    }

    // mouse drag, calculate new rectangle
    public boolean mouseDrag(MouseEvent event, int x, int y) {
        if (dragMode == true) {
            currentX = x;
            currentY = y;
            repaint();
	}
	return true;
    } 
        
    public static void main (String[]args){
        JFrame frame = new JFrame(); 
        frame.setPreferredSize(new Dimension(600, 400));
        JPanelExample p = new JPanelExample();
        p.setBackground(Color.BLUE);
        p.setBounds(0, 0, 600, 400);
        p.setOpaque(true);
        frame.add(p);
        frame.pack();
        frame.setVisible(true);
   }

I had to implement all abstract methods, but the goal is to draw a rectangle with the mouselistener in the jpanel. I open the program and I get nothing besides the "Draw a box by dragging the mouse" message. What am I doing wrong?

[Michael Dunn]

there's a bunch of things you have wrong, using old depecated methods, using paint() etc

here's a framework for you to play around with.

run it, click anywhere in the panel, drag the mouse sideways, then release it and check the console messages.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class JPanelExample extends JPanel{

    public JPanelExample()
    {
      addMouseListener(new MouseAdapter(){
        public void mousePressed(MouseEvent me){
          System.out.println("pressed/mouse down");
        }
         public void mouseReleased(MouseEvent me){
          System.out.println("released/mouse up");
        }
      });
      addMouseMotionListener(new MouseMotionAdapter(){
        public void mouseDragged(MouseEvent me){
          System.out.println("dragging...");
        }
      });
    }
    protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      g.drawRect(50, 50, 50, 50);
    }
    public static void main (String[]args){
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setPreferredSize(new Dimension(600, 400));
        JPanelExample p = new JPanelExample();
        p.setBackground(Color.BLUE);
        p.setBounds(0, 0, 600, 400);
        p.setOpaque(true);
        frame.add(p);
        frame.pack();
        frame.setVisible(true);
   }
}

[George Jacobs]

Michael Dunn wrote:there's a bunch of things you have wrong, using old depecated methods, using paint() etc

here's a framework for you to play around with.

run it, click anywhere in the panel, drag the mouse sideways, then release it and check the console messages.

Michael, thank you so much for the help. I got the rectangle to draw, but I am not sure if it is the best way because of the repaint method. Are there any problems with repaint

 addMouseListener(new MouseAdapter(){  
        public void mousePressed(MouseEvent me){  
            dragMode=true;
            startX=me.getX();
            startY=me.getY();
            System.out.println("pressed/mouse down");  
        }  
         public void mouseReleased(MouseEvent me){  
          System.out.println("released/mouse up");
          dragMode=false;
        }  
      });  
      addMouseMotionListener(new MouseMotionAdapter(){  
        public void mouseDragged(MouseEvent me){  
          System.out.println("dragging...");  
          if (dragMode == true) {  
            currentX = me.getX();  
            currentY = me.getY();  
            System.out.println(currentX);
            System.out.println(currentY);
          }
          repaint();
        }  
      });  
    }  
    protected void paintComponent(Graphics g) {  
      super.paintComponent(g);
      int beginX, beginY, width, height; 
      if (dragMode == true) {  
            beginX = Math.min(startX, currentX);  
            beginY = Math.min(startY, currentY);  
            width = Math.abs(currentX - startX);  
            height = Math.abs(currentY - startY);  
            g.drawRect(beginX, beginY, width, height);  
      }  
    }

[Randall Twede]

repaint is the way you do it. never call paintComponent() directly. here i have some code that will help you.

/*
 * DrawingArea.java
 * Class for drawing shapes
 * Created on February 4, 2004, 12:03 PM
 */

/**
 *
 * Randall Twede
 */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Vector;

public class DrawingArea extends JPanel implements MouseListener, MouseMotionListener
{
   private Vector shapes = new Vector();
   private Point start = new Point();
   private Point end = new Point();
   private Paint parent;    // Reference to the JFrame containing this Panel
   private Shape current;
   private int x1 = 0;
   private int x2 = 0;
   private int y1 = 0;
   private int y2 = 0;
   private int w = 0;
   private int h = 0;
    
    /** Creates a new instance of DrawingArea */
    public DrawingArea(Paint p)
    {
        parent = p;
        setBorder( BorderFactory.createTitledBorder( "Drawing Area" ) );
        addMouseListener(this);
	addMouseMotionListener(this);
    }
    
    // Draws all the shapes stored in the vector
    public void paintComponent(Graphics g)
    {
        Shape shape;
        
        super.paintComponent(g);
        setBackground(parent.getBack());    // Set the background color
        if(parent.image != null)
	{
            g.drawImage(parent.image, 0, 0, null);
	}
        // Loop through the vector
        for(int i = 0; i < shapes.size(); i++)
        {
            shape = (Shape)shapes.elementAt(i);
            shape.draw(g);
        }
	  if(current != null)
	  {
	      current.draw(g);
	  }
    }
 
    public void undo()
    {
        shapes.removeElementAt(shapes.size() - 1);
        current = null;
        repaint();
    }
   
    // Clears the drawing area
    public void clear()
    {
        parent.image = null;
        shapes.clear();
	current = null;
        repaint();
    }
    
    // Gets the starting point
    public void mousePressed(java.awt.event.MouseEvent mouseEvent)
    {
        start = mouseEvent.getPoint();
    }

    public void mouseReleased(java.awt.event.MouseEvent mouseEvent)
    {
        //Stores the Shape in a Vector
        shapes.add(current);
    }
    
    public void mouseClicked(java.awt.event.MouseEvent mouseEvent)
    {
    }
    
    public void mouseEntered(java.awt.event.MouseEvent mouseEvent)
    {
    }
    
    public void mouseExited(java.awt.event.MouseEvent mouseEvent)
    {
    }
    
    public void mouseDragged(java.awt.event.MouseEvent mouseEvent)
    {
        JRadioButton shape;
        String type;
        Color color;
        // Gets the ending point
        end = mouseEvent.getPoint();
        // Calls a private method
        setParameters();
        // Retrieves a referenced to the selected JRadioButton
        shape = parent.getSelected();
        // Sets the type of shape to draw
        type = shape.getText();
        // Sets the drawing color
        color = parent.getFore();
        // Creates a Shape object
	if (type == "Draw Line")
	{
	    current = new Shape(start.x, start.y, end.x, end.y, type, color);
	}
	else
	{
            current = new Shape(x1, y1, w, h, type, color);
	}
        // Call paintComponent()
        repaint();
    }

    public void mouseMoved(java.awt.event.MouseEvent mouseEvent)
    {
    }

    // Determines top left coordinates, width, and height
    private void setParameters()
    {
        x1 = start.x;
        y1 = start.y;
        x2 = end.x;
        y2 = end.y;
        int temp = 0;
        // Swap if necessary
        if (x1 > x2)
        {
            temp = x1;
            x1 = x2;
            x2 = temp;
        }
        // Swap if necessary
        if (y1 > y2)
        {
            temp = y1;
            y1 = y2;
            y2 = temp;
        }
        w = x2 - x1;
        h = y2 - y1;
    }
}

there are 3 other classes in this program but the code i posted should help.

[Rob Camick]

if (type == "Draw Line")  

Don't use "==".

Use the equals() method.

[George Jacobs]

Thanks for the code. Haven't tried to implement yet, but will try soon.

My next question is how do I now calculate the coordinates of the rectangle after it is drawn. For example, I would like to know center x, y coordinates of rectangle, the four corner coordinates, and the width/height which could be derived by these listed.

[Randall Twede]

rob is correct the equals method is better.