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Object Oriented Programming with JAVA Graphical User Interface GUI Lecture 6. GUI: Creating Simple Drawings. • Java Coordinate system. • Coordinate units are measured in pixels (picture element);. GUI.

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Object Oriented ProgrammingwithJAVA

Graphical User Interface


Lecture 6

gui creating simple drawings
GUI: Creating Simple Drawings

• Java Coordinate system.

• Coordinate units are measured in pixels (picture element);

  • The original graphical user interface (GUI) for Java was called the Abstract Windowing Toolkit (AWT(
  • A new GUI interface, known as Swing. Swing provides replacements for most of the AWT components
swing vs awt
Swing vs. AWT

• Abstract Window Toolkit (AWT)

  • AWT components are:
    • called heavyweight components.
    • They must rely on the local platform's windowing system to determine their functionality and their look and feel.
    • Every graphical units it will invoke native methods

• Swing components are :

    • called lightweight components.
    • They don’t rely on the local platform's windowing system
    • Most Swing components are pure Java components which means they are written completely in Java [It doesn't invoke native methods]
    • Complete

import java.awt.*;

import javax.swing.*;

import java.awt.FlowLayout; // specifies how components are arranged

import java.awt.Graphics;

import javax.swing.JFrame; // provides basic window features

import javax.swing.JLabel; // displays text and images

import javax.swing.ImageIcon; // loads images

import javax.swing.JApplet;

import javax.swing.JPanel;

swing components
Swing Components

• JLabel

– Displays uneditable text or icons.

• JTextField

– Enables user to enter data from the keyboard. Can also be used to display editable or uneditable text.

• JButton

– Triggers an event when clicked with the mouse.

• JCheckBox

– Specifies an option that can be selected or not selected.

• JComboBox

– Provides a drop-down list of items from which the user can make a selection by clicking an item or possibly by typing into the box.

swing components cont
Swing Components , cont…

• JList

– Provides a list of items from which the user can make a selection by clicking on any item in the list. Multiple elements can be selected.

• JPanel

– Provides an area in which components can be placed and organized. Can also be used as a drawing area for graphics.

creating simple drawing
Creating simple drawing

class DrawPanel extends JPanel{

// draws an X from the corners of the panel

public void paintComponent( Graphics g ){ // g is created by render device (screen)

// call paintComponent to ensure the panel displays correctly

super.paintComponent( g ); // Typical Swing approach that paint background

int width = getWidth(); // get width of JPanel component.

int height = getHeight(); // total height of current JPanel component

// draw a line from the upper-left to the lower-right

g.drawLine( 0, 0, width, height );

// draw a line from the lower-left to the upper-right

g.drawLine( 0, height, width, 0 );

} // end method paintComponent

} // end class DrawPanel

creating simple drawing cont
Creating simple drawing – cont.

import java.awt.Graphics;

import javax.swing.*;

public class DrawPanelTest{

public static void main( String args[ ] ){

// create a panel that contains our drawing

DrawPanel panel = new DrawPanel();

// create a new frame to hold the panel

JFrame application = new JFrame();

// set the frame to exit when it is closed

application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

application.add( panel ); // add the panel to the frame

application.setSize( 250, 250 ); // set the size of the frame

application.setVisible( true ); // make the frame visible

} // end main

} // end class DrawPanelTest

drawing rectangles and ovals
Drawing Rectangles and Ovals

public class ShapesTest{

public static void main(String[] args){

JFrame mf=new JFrame("Test Shapes");

mf.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );


Shapes ms=new Shapes(2);





import javax.swing.*;

import java.awt.*;

class Shapes extends JPanel{

private int choice=0;

public Shapes(int choice){



public void paintComponent(Graphics g)




case 1:

for(int i=0;i<5;i++)



case 2:

for(int i=0;i<10;i++)





drawrect drawoval
drawRect & drawOval

• drawRect & drawOval takes four arguments, the first two are for the left top position coordinate, the other two are for the width and height respectively.

colors and filled shapes
Colors and Filled Shapes

• Colors displayed on computer screens are defined by their red, green, and blue components. These components, called RGB values, have integer values from 0 to 255. The higher the value of a particular component, the brighter the particular shade will be in the final color.

• Java uses class Color in package java.awtto represent colors using their RGB values.

For convenience, the Color object contains 13 predefined static Color objects:

Color.BLACK, Color.BLUE, Color.CYAN, Color.DARK_GRAY, Color.GRAY, Color.GREEN, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE, Color.PINK, Color.RED, Color.WHITE andColor.YELLOW.

Class Color also contains a constructor of the form:

public Color( int r, int g, int b )

• Filled rectangles and filled ovals are drawn using Graphics methods fillRect and fillOval , respectively.

filling example
Filling: Example

public class ColorsTest{

public static void main(String[] args){

JFrame mf=new JFrame("Test Colors");


mf.add(new UseColors());




import java.awt.*;

import javax.swing.*;

class UseColors extends JPanel{

public void paintComponent(Graphics g){



g.fillOval( 10, 10, 200, 200 );



g.fillOval( 55, 65, 30, 30 );

g.fillOval( 135, 65, 30, 30 );

//draw mouth

g.fillOval( 50, 110, 120, 60 );

g.setColor( Color.YELLOW );

g.fillRect( 50, 110, 120, 30 );

g.fillOval( 50, 120, 120, 40 );



example rainbow cont
Example – Rainbow cont…

import java.awt.*;

import javax.swing.*;

class DrawRainbow extends JPanel{

// Define indigo and violet

final Color VIOLET = new Color( 128, 0, 128 );

final Color INDIGO = new Color( 75, 0, 130 );

// colors to use in the rainbow, starting from the innermost

// The two white entries result in an empty arc in the center

private Color colors[] ={ Color.WHITE, Color.WHITE, VIOLET,

INDIGO, Color.BLUE, Color.GREEN, Color.YELLOW, Color.ORANGE, Color.RED };

// constructor

public DrawRainbow(){

setBackground( Color.WHITE ); // set the background to white

} // end DrawRainbow constructor

example rainbow
Example - Rainbow

// draws a rainbow using concentric circles

public void paintComponent( Graphics g ){

super.paintComponent( g );

int radius = 20; // radius of an arch

// draw the rainbow near the bottom-center

int centerX = getWidth() / 2;

int centerY = getHeight() - 10;

// draws filled arcs starting with the outermost

for ( int counter = colors.length; counter > 0; counter-- ){

// set the color for the current arc

g.setColor( colors[ counter - 1 ] );

// fill the arc from 0 to 180 degrees

g.fillArc( centerX - counter * radius, centerY - counter * radius,

counter * radius * 2, counter * radius * 2, 0, 180 );

} // end for

} // end method paintComponent

} // end class DrawRainbow

example rainbow cont1
Example – Rainbow cont…

public class DrawRainbowTest{

public static void main( String args[ ] ){

DrawRainbow panel = new DrawRainbow();

JFrame application = new JFrame();

application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

application.add( panel );

application.setSize( 400, 250 );

application.setVisible( true );

} // end main

} // end class DrawRainbowTest

example rainbow cont2
Example – Rainbow cont…

Method setBackground takes a single Color argument and sets the background of the component to that color.

• Method fillArc requires six parameters.

The first four represent the bounding rectangle in which the arc will be drawn. The first two specify the coordinates for the upper-left corner of the bounding rectangle, and the next two specify its width and height. The fifth parameter is the starting angle on the oval, and the sixth specifies the sweep, or the amount of arc to cover.

The starting angle and sweep are measured in degrees, with zero degrees pointing right. A positive sweep draws the arc counter-clockwise, while a negative sweep draws the arc clockwise.

A method similar to fillArc is drawArc it requires the same parameters as fillArc , but draws the edge of the arc rather than filling it.