Mouse Input

There are two parts of a mouse - clicks and motion. They are treated as two seperate parts of input in Java.

In an applet (JApplet), it involves importing the following classes:

import java.awt.event.*;

then we need to added the line after our class declaration implements MouseListener This tells we will be listening for a mouse action.

Now we addMouseListener(this); to our init() method. This line is saying we are listening to a mouse action.

Now whenever we implement MouseListener, we need to declare the following methods (whether we use them or not)

public void mousePressed(MouseEvent e) { } //when someone presses the mouse button

public void mouseReleased(MouseEvent e) { } //when someone releases the mouse button

public void mouseEntered(MouseEvent e) { } // when the mouse enters the applet

public void mouseExited(MouseEvent e) { } //when the mouse leaves the applet

public void mouseClicked(MouseEvent e) {} //when the mouse button is clicked

To use one or all of these methods, put code in method.

When one of those methods are activated (ie when someone clicks somewhere in the applet, the method is called. We are given the coordinates of where they clicked. The coordinates are sent down as e.

They are:

e.getX() //for the x coordinate

e.getY() //for the y coordinate

For more on the difference between them, click here.

Heres is a sample:

 
/*
 * Test class to practice mouse inputs by drawing a circle where the user clicks.
 *
 * @author Jeff Borland
 * @date version 1.11
 */

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

public class OvalDraw extends JApplet implements MouseListener,ActionListener
{
   
    public void init()
    {
        Container screen = getContentPane();
        screen.setBackground(Color.white);
        screen.setLayout (new FlowLayout() );
        addMouseListener(this);
               
    }

    public void paint (Graphics g)
    {
        super.paint(g);      
        g.fillOval(0,0,25,25);   
    }

    //when someone presses the mouse button
    public void mousePressed(MouseEvent e)
    {       

    }

    //when someone releases the mouse button
    public void mouseReleased(MouseEvent e)
    {       

    }

    // when the mouse enters the applet
    public void mouseEntered(MouseEvent e)
    {       

    }

    //when the mouse leaves the applet
    public void mouseExited(MouseEvent e)
    {       

    }

    //when the mouse button is clicked
    public void mouseClicked(MouseEvent e)
    {
        // MouseEvent e is the variable, which we can get
        // the coordinates of where the mouse is, by
        // using the methods e.getX(); or e.getY();
        int x=e.getX();
        int y=e.getY();
        Graphics g = getGraphics();
        g.fillOval(x,y,25,25);   
    }

    public void actionPerformed(ActionEvent thisEvent)
    {
        Object source = thisEvent.getSource();

        //now have if statements seeing finding out where the action occured

    }
}

HWJ8:

Create these applets (start with the code above for each example):

If working alone - do 4. If working with a partner 5. If advanced - do atleast 1 more than required.

1. Create an applet FindLocation that will display the location of where the mouse clicks and it will display that in 2 textfields (one for x, one for y)
2. Create an applet SquareDraw with a textfield that will allow the user to put in a size of a square. When the user clicks, it will draw that size square centered around the cursor.
3. Create an applet LineDraw where a line will be drawn between where the user presses the button down to where they release the button.
4. Create an applet TopHalf that will change the applet to green if the mouse clicks on the top half and black if they click the bottom half. Use g.setColor and then g.fillRect to do that.
5. Create an applet RectangleDraw where an rectangle will be drawn between where the user presses the button down to where they release the button. (Advanced people - make it work from any direction)
6. Create an applet RectClicked that in the paint method add this rectangle g.fillRect(200,200,100,100) that will draw a rectangle in the middle of the screen. Then count the number of times the user clicks in the region and display this in a textfield
7. Create an applet DottedLine that when the user clicks it will draw a dotted lines from the center to where the user clicked. Advanced - display the distance of the line in the textfield, you will need the distance formula

Super advanced: Bring in timer and make a game out of it. (Like have an object appear and the user has to click it - keep tracker)