Graphics Methods

Java Exercises

Graphics Methods

This exercise should be carried out after reading the Graphics Methods Tutorial

You can choose to do one or both of the exercises listed below.

The tutorial walked you though the creation of a house using some graphics methods. In one exercise, a moon shape was drawn above the house and in another exercise a sun shape was drawn.

How about creating an Applet that displays the house with a moon which changes to house with a sun when the user clicks anywhere on the applet window, and vice-versa.

You could also add the text "House at night - click to see House in the day" and "House in the day - click to see House at night" as appropriate. You could also change the color of the house depending on whether it is day or night.

Here is my House applet.

I would suggest you first create two different classes; HouseAtNight and HouseInDay and play with the fill colors until you are satisfied. Make sure you keep the positioning of the two houses the same

Once you are completely happy with both your applets, change the code as follows:-

HouseAtNight:

Change the line

public class HouseAtNight extends applet{

to

public class HouseAtNight {

This makes a stand-alone class instead of a class that extends and inherits from applet.

Also remove the line:- import java.applet.*;

HouseInDay:

Change the line

public class HouseInDay extends applet {

to

public class HouseInDay {

This makes a stand-alone class instead of a class that extends and inherits from applet.

Also remove the line:- import java.applet.*;

HouseApplet:

Now create a new class called HouseApplet as shown below:-

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

public class HouseApplet extends Applet implements MouseListener {

boolean isDay = true; //boolean to know which house is currently being displayed

    HouseInDay dayHouse = new HouseInDay(); // create an instance of HouseInDay
    HouseAtNight nightHouse = new HouseAtNight(); // create an instance of HouseAtNight

    public void init() {

        addMouseListener(this); // add a mouse listener so we can catch mouse click events
    }

   public void paint (Graphics g) {

        if (isDay == true) { // if house displayed is day house
            dayHouse.paint(g); // paint the day house
        }

        else {
            nightHouse.paint(g); // paint the night house
        }
    }

    public void mouseClicked(MouseEvent e) {   //method that runs when user clicks with mouse

        if (isDay == true) {   //if boolean isDay is true, day house is diplayed
            isDay = false;   //so set boolean isDay to false
            repaint();   //repaint so paint method runs and night house is displayed
        }
        else {
        isDay = true; //set boolean isDay to true
        repaint(); //repaint so paint method runs and day house is displayed
        }
    }

    public void mousePressed(MouseEvent e){
    }

    public void mouseReleased(MouseEvent e) {
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

}// end class

Compile this class and create a HTML file for it. Now run the applet in the browser or using appletviewer and see what you get

Exercise 2: Face Applet

Create an applet that displays a face using Graphics methods. Let your imagination run riot. I am not going to give you any help on this, it can be any sort of face you choose.

Have fun!