BSc Computing GRAPHICS PROGRAMMING: JAVA

GRAPHICS PROGRAMMING

Section A – Java 1 - Introduction 2 - Installation & First Programs 3 - GUI: Swing & Input Dialog Box 4 - GUI: JFrame 5 - GUI: JButton 6 - GUI: Look and Feel 7 - GUI: JList 8 - GUI: Layout Managers 9 - GUI: JMenu

Gary Hill

December 2003

Java 1 of 1

GRAPHICS PROGRAMMING

1 Introduction Syllabus, Teaching & Learning Strategy, Assessment Schedule, Resources. Integrated Development Environments (IDE's) In theory, it is easiest to use an IDE, even 'Sun strongly encourages the use of a professional Integrated Development Environment (IDE)'. Although these will be mentioned below, this course will initially use the JDK via the command line.

Borland http://www.borland.com/jbuilder/personal/ JBUILDER PERSONAL •

JBuilder 9 Personal

If you already have the JBuilder Personal software and need your activation key, get your activation key here What is JBuilder 9 Personal? Speed coding and debugging with an integrated, extensible source code editor, graphical debugger, compiler, visual designers, timesaving wizards, sample applications, and support for Java standards. Get started quickly using the included tutorials. Develop on the Windows,® Linux,® and Solaris® platforms. Rapidly build Java applications using the Borland AppBrowser™ integrated development environment, refactorings, build and configuration management tools, CVS version control, and Two-Way-Tools.™ Easily create JavaBeans® with BeansExpress.™ Speed coding and reduce syntax errors with CodeInsight™ and ErrorInsight™ technologies. JBuilder Personal is a fully functional, entry-level version of JBuilder for personal, noncommercial use. The JBuilder Personal license does not expire. To install the latest jdk within JBuilder you will need to go to: Project - Default project properties - Paths - jdk -..... change jdk etc.. Also Java 3D will need to be set up following the instructions from the Borland Developer Network.

Sun One Studio 4 The Sun[tm] ONE Studio 4 (formerly Forte™ for Java™ ) software is available for immediate download so you can quickly begin taking advantage of this robust integrated development environment to boost your productivity. Choose from versions for the Solaris™, Linux, or Windows platforms, available in both English and Japanese languages.

Before You Download •

Read the Getting Started Guide for installation and configuration information: o Community Edition (PDF)

Gary Hill

December 2003

Java 2 of 2

GRAPHICS PROGRAMMING Enterprise Edition for Java (PDF) Mobile Edition (PDF) Read the product family Release Notes and the Mobile Edition Release Notes for the latest information on the product. The Sun ONE Studio product requires additional software products, which are available on the Sun ONE Studio product CD, or from the following downloads: o Java™ 2 Platform, Standard Edition, v. 1.4 (J2SE™ 1.4) software If you are an Early Access customer planning to upgrade to the released product, please read our FAQ on moving from Early Access software to the released version. o o

• •

•

Gary Hill

December 2003

Java 3 of 3

GRAPHICS PROGRAMMING

2 Installation & First Program Installation The course will be using the latest version of Java 2 (SDK 1.4.2). Download this and the accompanying documentation from Sun: • •

Java[tm] 2 Platform, Standard Edition, v. 1.4.2 (J2SE[tm]1.4.2) software filename: j2sdk-1_4_2-windows-i586.exe Documentation j2sdk-1_4_2-doc.zip

Install in a directory: C:\j2sdk1.4

2003/2004 Install Recommendations Java SDK Step 1: Install j2sdk-1_4_2-windows-i586.exe in the directory c:\j2sdk1.4 Step 2: Install j2sdk-1_4_2-doc.zip in the directory c:\j2sdk1.4 Forte IDE Step 3: Install j2sdk-1_4_0-forte_ce-4-bin-windows.exe in the recommended directory e.g. c:\forte_jdk. forte should locate the previously installed sdk in c:\j2sdk1.4 Java3D Step 4: Install java3d-1_3_1-windows-i586-opengl-sdk.exe in c:\j2sdk1.4 Step 5: Install java3d-1_3_1-doc.zip in the directory c:\j2sdk1.4

For Win 95/98 Edit your 'autoexec.bat' file to include the following: PATH c:\j2sdk1.4\bin; Gary Hill

December 2003

Java 4 of 4

GRAPHICS PROGRAMMING

For Win NT/2000 Edit the 'Systems Variables' PATH (Control Panel>System> Environment) to include: PATH c:\j2sdk1.4\bin;

For Win XP Edit the 'Systems Variables' PATH (Control Panel>System>Advanced>Environment Variables) to include: PATH C:\win....; .... C:\jdk1.4\bin; ... To check the above works type javac and java in a command window. If correct various help information will be displayed. Hopefully, the above should work. For further details consult Cadenhead & Lemay (2000) or www.sun.com. Text Editor Notepad is a useful text editor, but has the limitation that the code syntax is not highlighted. All IDE's use colour-coded syntax highlighting, which assists programming. One such editor available under the GNU license which is 'freeware' is Jext (Java Text Editor) at www.jext.org Jext does not just syntax highlight for java, but many more languages such as ASP, C, C++, Eiffel, Java, JSP, Perl, PHP3, HTML, TeX, XML... The latest Jext version was 3.1 is 2.2MB download size. There will be other editors available with syntax highlighting, but this is just one that will be suitable for java programming. File Administration Before writing your first application and applet, make a directory for your Java files (md c:\java (Win) or mkdir java (Unix/Linux)). Remember to always make a safe copy of your work on floppy disk, you may need it at a later date! Coding Conventions public class HelloApplication

Class names start with an uppercase letter and each successive word. private int age; private int initialAmount;

Variable names start with a lowercase letter, but each successive word should be an uppercase letter. public void showSquares()

Methodnames start with a lowercase letter, but each successive word should be an uppercase letter. static final int MILES_PER_KILOMETER

Constant are all uppercase letters with each word separated by an underscore.. For further details regarding Java Code Conventions see thefollowing Sun: Java Code Gary Hill

December 2003

Java 5 of 5

GRAPHICS PROGRAMMING Conventions ( JavaCodeConventions.pdf 82 KB ) or http://java.sun.com/docs/codeconv/html/CodeConvTOC.doc.html First Program (Using the JDK) Follow the notes from the Your First Cup of Java: to write your first 'application' and 'applet'. Comments There are three ways to identify comments. The first two are the same as those used in C/C++. Single line comments use: // prints ‘Hello, world!’ to the screen with a line break. Multiple line comments use: /* It is important to carefully work through each line of source code and enter verbose comments. Use a reference book or the web to help you understand and comment the code. Good programing practice dictates that you should include a block of header information that gives a summary of all the key program information. As a minimum include those in 'HelloApplication.java' below. */ The third type of comment /**...............*/ can be used to assist in the generation of Java Documentation. HTML code can also be embedded within these comments. To generate the documentation type 'C:\java>javadoc -author -version HelloApplication.java' and an HTML file will be produced 'Generating HelloApplication.html'. This is a useful way of documenting a large program. /** Program: Application to say 'Hello World' Filename: HelloApplication.java @author: © Gary Hill (200WXYZ) Course: BSc Computing Module: CSY3019 Graphics Programming Tutor: Gary Hill @version: 2.0 Incorporates name and age! Date: 20/09/02 */ public class HelloApplication { public HelloApplication() { int age = 21; String name = new String(); // default constructor to create empty string name = "Gary"; // assignment operator, assigns "Gary" to name {

Gary Hill

December 2003

Java 6 of 6

GRAPHICS PROGRAMMING System.out.println("Hello World,\nMy name is "+name+" and I am "+age+" years old."); } } public static void main(String[] args) { HelloApplication hello1 = new HelloApplication(); } }

new: The new operator is a 'dynamic memory allocation operator' and is used to 'create an instance' or 'instantiate an object' (See Appendix: Definitions in Object-Oriented Java Programming). First Application (Forte for Java) This description relates to the use of Forte for Java, Community Edition v4.0. Forte is a complex Integrated development environment IDE. The simplest way to run your first java application is as follows: Open Forte Select File, Open then your HelloApplication.java file from your java directory. Forte will ask you whether this file should be in the default package. Accept this and continue. This will mean that your java directory is used as the default directory for all your remaining projects i.e. your *.java & *.class files are saved in this directory.

Linux On Linux Red Hat (Gnome desktop) in MY22, 20 & 32 Sun One is installed in the usr/local directory. It is useful to add a 'launcher' to your lower toolbar as follows: Start/Foot>Panel>Add to panel>Launcher Gary Hill

December 2003

Java 7 of 7

GRAPHICS PROGRAMMING In the 'Create launcher applet' fill in the following details: Name: Sun One Comment: Forte Community Edition 4 Command: /usr/local/forte_4j/bin/runide.sh Type: Application Icon: /usr/local/forte_4j/bin/icons/ide.ico Applets To view your applet you can use a java enabled browser, butit is simpler to use the JDK's 'appletviewer. A novel way to run your applet without writing a separate HTML file, is to embed your code at the headof your java source code. This enables you to quickly develop and test your applets: /** Program: Filename: @author: Course: Module: Tutor: @version: Date: */

Applet to say 'Hello World' HelloApplet.java ©Gary Hill (200WXYZ) BSc Computing CSY3018 Graphics Programming Gary Hill 2.0 commented 05/07/02











import java.applet.*; //enables access to the java.applet.Applet class import java.awt.*; //enables access to the java.awt.Graphics class /* */ // the applet size is 200 pixels wide by 60 pixels high public class HelloApplet extends Applet { public void init()// paint method (others are init, start) { } public void paint(Graphics g) // Display "Hello World!" { g.drawString("Hello world!", 50, 25); } }

To view the above applet type: C:/java> javac HelloApplet.java [to compile the source code HelloApplet.java into the byte code HelloApplet.class] C:/java> appletviewer HelloApplet.java

Gary Hill

December 2003

Java 8 of 8

GRAPHICS PROGRAMMING

To run your applet (HellApplet.java) in a java enabled browser an HTML file is required (HelloApplet.html) as follows:

To view the above applet: Select the HTML file (HelloApplet.html) from the browser, or type C:/java> appletviewer HelloApplet.html First Applet (Forte for Java) This description relates to the use of Forte for Java, Community Edition v4.0. Forte is a complex Integrated development environment IDE. The simplest way to run your first java applet is as follows: Right click the mouse on the Java applet Select properties from the popup menu Select the Execution tab from the properties popup Click on Default Debugging and select Applet Debugging Click on External Execution and selct Applet Execution

Applet imports

Gary Hill

December 2003

Java 9 of 9

GRAPHICS PROGRAMMING import java.awt.*; //enables access to the java.awt.Graphics class AWT is the Abstract Window Toolkit, which provides the Java graphical user interface (GUI), in this case access to the Graphics class for the drawString() method. import java.applet.*;//enables access to the java.applet.Applet class which are required to run applets. Alternatively Swing could be used by using the following import: import javax.swing.*// or import javax.swing.JApplet. Note: Ensure that you have compiled and run your first 'application' and 'applet' from above and named and commented your programs carefully. Work through Sun's Java Tutorial Getting Started paying particular attention to the:

Lesson: A Closer Look at HelloWorld Java applets are covered in Sun's Java Tutorial - Lesson: The Anatomy of an Applet . Exercise Write a java application that extends HelloApplication.java, called SquaresApplication.java that provides the following: Prints the program name and your name etc. as a title screen which outputs the squares of all the numbers between 0 and 100 in the format: square of 0 is 0 square of 1 is 1 sqaure of 2 is 4

Gary Hill

December 2003

Java 10 of 10

GRAPHICS PROGRAMMING

Gary Hill

December 2003

Java 11 of 11

GRAPHICS PROGRAMMING

3 - Graphical User Interface (GUI) Input Dialog Box & Numerical Output Swing Swing which is part of the Java Foundation Classes (JFC) was introduced to further enhance support for and extend the Graphical User Interface (GUI) components with a pluggable look and feel (Macintosh, Microsoft, Solaris). Swing improved numerous Abstract Window Toolkit (AWT) components such as Button, Scrollbar, Label, etc. which became JButton, JScrollbar, JLabel respectively. New components were also introduced e.g. tree view, list box, and tabbed panes etc. Using Swing contents pane and formating numerical output. The Applet ( JTempApplet.java ) converts a fahrenheit input value as a String then converts the input to a double before using formula to calculate centigrade from fahrenheit c = ( 5.0 / 9.0 ) * ( f - 32 ) The output is then formatted to produce two decimal places (similar to the use of placeholder in 'C' where %6.2d would be used). /** Program: JApplet to display the output of Fahrenheir to Centigrade conversion Filename: JTempApplet.java @author: © Gary Hill (200WXYZ) Course: BSc Computing Module: CSY3019 Graphics Programming Tutor: Gary Hill @version: 1.0 Date: 20/09/02 */ import javax.swing.*; //enables access to the javax.swing.JApplet class import java.awt.*; //enables access to the java.awt.Graphics class import java.text.DecimalFormat; //enables access to DecimalFormat /* */ public class JTempApplet extends JApplet { double centNumber; //declare global Centigrade variable double fahNumber; //declare global Fahrenheit variable public void init()

Gary Hill

// initialize applet by obtaining

December 2003

Java 12 of 12

GRAPHICS PROGRAMMING fahrenheit value { String fahrenheit; // string for fahrenheit entered by user fahrenheit = JOptionPane.showInputDialog("Enter your Fahrenheit temperature" ); fahNumber = Double.parseDouble(fahrenheit); //convert from type String to type double centNumber = ( 5.0 / 9.0 ) * ( fahNumber - 32 ); //conversion calculation on doubles } public void paint( Graphics g ) //draw result on the applet { super.paint( g ); // call inherited version of method paint

g.drawRect( 15, 10, 270, 20 ); // draw rectangle starting at (15, 10) which is 270 // pixels wide and 20 pixels high DecimalFormat twoDecPlaces = new DecimalFormat("0.00"); //two decim g.drawString(twoDecPlaces.format(fahNumber)+" Fahrenheit is " +twoDecPlaces.format(centNumber)+" Centigrade", 25, 25 ); } // end method paint } // end class JTempApplet

In an Application, the result could have been shown using a 'Message Dialog' box as follows: JOptionPane.showMessageDialog(null, twoDecPlaces.format(fahNumber)+" Fahrenheit is " +twoDecPlaces.format(centNumber)+" Centigrade", "Results", JOptionPane.PLAIN_MESSAGE);

The 'showMessageDialog' requires four arguments: argument 1 is the screen position (null = centre of screen), argument 2 is the message argument 3 is the title bar label for the dialog box argument 4 is the type of dialog box (.PLAIN_MESSAGE = plain message without an icon to the left of the message). Other 'types' include ERROR_MESSAGE, INFORMATION_MESSAGE, QUESTION_MESSAGE & WARNING_MESSAGE Gary Hill

December 2003

Java 13 of 13

GRAPHICS PROGRAMMING Note: The html code is embedded within the *.java source, but using the Sun One IDE will not work. You will either need to run appletviewer JTempApplet.java within a command window or creat a html file (JTempApplet.html) and run from within a java enabled browser:

Exercise: Write a java program, JDayCounter.java, that uses an input dialog box (JOptionPane.showInputDialog) and an applet for the output (g.drawString) to improve the command-line version shown below:

Gary Hill

December 2003

Java 14 of 14

GRAPHICS PROGRAMMING

4 - GUI: JFrame Swing and JFrames are covered in Sun's Java Tutorial - Trail: Creating a GUI with JFC/Swing and Lesson: User Interfaces that Swing: A Quick Start Guide

Figure 11.1 The JFrame Containment Hierarchy (java.sun.com) JFrames will be used here to introduce a number of the Swing component. The first example, as usual, will be a JFrame 'Hello World" application (HelloJFrame.java). /** Program: Filename: @author: Course: Module: Tutor: @version: Date: */

Swing JFrame to say 'Hello World' HelloJFrame.java © Gary Hill (200WXYZ) BSc Computing CSY3019 Graphics Programming Gary Hill 1.0 14/10/03

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











//enables access to the java.awt.Graphics //enables access to the javax.swing.JFrame

public class HelloJFrame extends JFrame { public HelloJFrame()//could use (String title) to declare title, instead of .. { super ("HelloJFrame Frame"); //..set the JFrame title Container yourContainer = getContentPane(); // get content pane and name it JLabel yourJLabelText = new JLabel("Hello World"); yourContainer.add(yourJLabelText);

Gary Hill

December 2003

Java 15 of 15

GRAPHICS PROGRAMMING pack(); //sets the frame size to preferred size of its contents/components setSize(250, 150); //set size of JFrame to width=250 height=150 setVisible(true); //display the JFrame } public static void main(String[] args) { HelloJFrame test = new HelloJFrame(); //HelloJFrame("Hello JFrame Frame"); test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //close frame the Swing way } }// end class HelloJFrame

Exercise: Convert the above two Applet/Option Pane programs ( JDayCounter.java, JTempApplet) to Applications (JTempApplication.java & JDayApplication.java) using 'inputMessageDialog & the JLabel &/or showMessageDialog. JDayApplication.java:

.. and even ...

Gary Hill

December 2003

Java 16 of 16

GRAPHICS PROGRAMMING

Gary Hill

December 2003

Java 17 of 17

GRAPHICS PROGRAMMING

5 - GUI: JButton The first Swing example JFrame 'Hello World" application (HelloJFrame.java) introduced a number of the Swing components. The next application (HelloJButton.java) will introduce: Button (JButton) Button Handler (ButtonHandler) Action Listener (ActionListener) Background Colour (setBackground) Text Labels (JLabel) Text Field (JTextField) Tool Tip Text (setToolTipText)

Figure 12.1 The JButton & JLabel Component Hierarchy (java.sun.com)

The Button Class (see: Introduction to Programming Using Java, V3.0, Summer 2000, David J. Eck) An object of class Button is a push button. Buttons use components, events, and listeners described below: Constructors The Button class has a constructor that takes a string as a parameter. This string becomes the label displayed on the button. For example: stopGoButton = new Button("Go") Events When the user clicks on a button, the button generates an event of type ActionEvent. This event is sent to any listener that has been registered with the button. Listeners An object that wants to handle events generated by buttons must implement the ActionListener interface. This interface defines just one method, "pubic void actionPerformed(ActionEvent event)", which is called to notify the object of an action event. Registration of Listeners Gary Hill

December 2003

Java 18 of 18

GRAPHICS PROGRAMMING In order to actually receive notification of an event from a button, an ActionListener must be registered with the button. This is done with the button's addActionListener() method. For example: stopGoButton.addActionListener(buttonHandler) Event methods When actionPerformed(event) is called by the button, the parameter, event, contains information about the event. This information can be retrieved by calling methods in the ActionEvent class. In particular, event.getActionCommand() returns a String giving the command associated with the button. By default, this command is the label that is displayed on the button. Component methods There are several useful methods in the Button class. For example, stopGoButton.setLabel("Stop") changes the label displayed on the button to "Stop". And stopGoButton.setActionCommand("sgb") changes the action command associated to this button for action events. Of course, Buttons alsohave all the general Component methods, such as setEnabled() and setFont(). The setEnabled() and setLabel() methods of a button are particularly usefulfor giving the user information about what is going on in the program. A disabled button is better than a button that gives an obnoxious error message such as "Sorry, you can't click on me now!"

/** Program: Filename: @author: Course: Module: Tutor: @version: Date: */

Swing JFrame with JButtons HelloJButton.java © Gary Hill (200WXYZ) BSc Computing CSY3019 Graphics Programming Gary Hill 1.0 15/01/02

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











//enables access to the java.awt.Graphics //enables access to the javax.swing.JFrame //for button clicks and mouse movement

public class HelloJButton extends JFrame { JTextField helloTextField; //declare JTextField JButton helloButton; //declare JButton JLabel yourJLabelText; //declare JLabel public HelloJButton()//could use (String title) then super(title) and declare title. { super ("HelloJButton Frame"); //set the JFrame title Container yourContainer = getContentPane(); // get content pane and

Gary Hill

December 2003

Java 19 of 19

GRAPHICS PROGRAMMING name it yourContainer.setLayout(new FlowLayout(FlowLayout.CENTER)); // center components yourContainer.setBackground(Color.yellow); //set the background colour to yellow helloButton = new JButton("Press"); helloButton.setToolTipText("Press me"); / tip. yourContainer.add(helloButton);

// create button // gives a mouse over help

// create an instance of inner class ButtonHandler to use for button event handling ButtonHandler bHandler = new ButtonHandler(); helloButton.addActionListener( bHandler ); yourJLabelText = new JLabel("Press the above button for response:"); yourContainer.add(yourJLabelText); //add label to container helloTextField = new JTextField("", 12 ); display button response helloTextField.setEditable( false ); editing yourContainer.add( helloTextField ); container

//create text field to //prevent text field //add text field to

pack(); //helps determine the window's size from the added components preferred sizes setSize(200, 150); //set size of JFrame to width=200 height=150 setVisible(true); //display the JFrame } private class ButtonHandler implements ActionListener // inner class for button event handling { // handle button event int noPress = 1; //integer variable to keep account of button presses public void actionPerformed( ActionEvent event ) { if (event.getSource() == helloButton) //(event.getActionCommand()=="Press")could also be used { helloTextField.setText(" Press " + noPress); //set the text to this.. noPress++; //increment } } } // end private inner class ButtonHandler public static void main(String[] args) { HelloJButton testHelloJButton = new HelloJButton(); //HelloJFrame("Hello JFrame Frame"); testHelloJButton.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //close frame the Swing } }// end class HelloJButton

Gary Hill

December 2003

Java 20 of 20

GRAPHICS PROGRAMMING

Note: Instead of using a private abstract inner class for handling the button events, as above, the actionPerformed() method can be included within the class and the class modified so that it implements ActionListener. See HelloJButton2.java. Note: Layout Managers will be covered in a later section, but one way of maintaning the layout and look of your application is to restrict a user resizing your JFrame. To do this a method inherited from class java.awt.Frame, setResizable(boolean). Therefore above the main method could be altered to include a third line: testHelloJButton.setResizable(false);//prevents resizing of the JFrame Example Write an application similar to above (HelloJButton.java) that includes three button (Red, Green and Blue) which when pressed indicate which button has been pressed by showing Red, Green or Blue in the text field and also changing the background to the appropriate colour (RGBJButton.java).

Gary Hill

December 2003

Java 21 of 21

GRAPHICS PROGRAMMING

6 - GUI: Look and Feel Java allow the programmer to set the look and feel of any graphical user interface (GUI) bythe use of the UIManager's method setLookAndFeel as follows: Cross Platform - the default Java GUI look and feel (UIManager.getCrossPlatformLookAndFeelClassName()) System - the look and feel set for the current operating system / desktop (UIManager.getSystemLookAndFeelClassName()) Metal - the Java GUI look and feel ("javax.swing.plaf.metal.MetalLookAndFeel") Windows - Microsoft look and feel ("com.sun.java.swing.plaf.windows.WindowsLookAndFeel") Motif - Sun and Unix look and feel ("com.sun.java.swing.plaf.motif.MotifLookAndFeel") Macintosh - Apple look and feel ("javax.swing.plaf.mac.MacLookAndFeel") (See: Sun's Java Tutorial: How to Set the Look and Feel) For each of the looks and feels the programmer would need to incorporate the following code (unless you except the default): Cross Platform public static void main(String[] args) { try { UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName()) ; } catch (Exception e) { System.err.println("Couldn't use the system "+ "look and feel: " + e); } HelloJButton testHelloJButton = new HelloJButton(); //HelloJFrame("Hello JFrame Frame"); testHelloJButton.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //close frame the Swing } }// end class HelloJButton

System try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception e) { System.err.println("Couldn't use the system "+"look and feel:

Gary Hill

December 2003

Java 22 of 22

GRAPHICS PROGRAMMING "+e); }

Metal try { UIManager.setLookAndFeel(("javax.swing.plaf.metal.MetalLookAndFeel")); } catch (Exception e) { System.err.println("Couldn't use the system "+"look and feel: " + e); }

Windows try { UIManager.setLookAndFeel(("com.sun.java.swing.plaf.windows.WindowsLookAndF eel")); } catch (Exception e) { System.err.println("Couldn't use the system "+"look and feel: " + e); }

Motif try { UIManager.setLookAndFeel( ("com.sun.java.swing.plaf.motif.MotifLookAndFeel")); } catch (Exception e) { System.err.println("Couldn't use the system " + "look and feel: " + e); }

Macintosh try {

Gary Hill

December 2003

Java 23 of 23

GRAPHICS PROGRAMMING UIManager.setLookAndFeel( ("javax.swing.plaf.mac.MacLookAndFeel")); } catch (Exception e) { System.err.println("Couldn't use the system " + "look and feel: " + e); }

Example Adapt your Red, Green and Blue application to use the above look and feel types (RGBJButton.java) to see the difference, if any.

Gary Hill

December 2003

Java 24 of 24

GRAPHICS PROGRAMMING

7 - GUI: JList /** Program: Filename: @author: Course: Module: Tutor: @version: Date: */

Swing JList Application RGBJList.java © Gary Hill (200WXYZ) BSC Computing CSY3019 Graphics Programming Gary Hill 1.0 22/09/02

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











//enables access to the java.awt.Graphics //enables access to the javax.swing.JFrame //enables access to the

public class RGBJList extends JFrame { JTextField helloTextField; //declare JTextField JList colorList; //declare JList for colour selection Container yourContainer; String colorNames[] = { "Black", "Blue", "Cyan","Dark Gray", "Gray", "Green", "Light Gray", "Magenta", "Orange", "Pink", "Red", "White", "Yellow" }; Color colors[] = { Color.black, Color.blue, Color.cyan, Color.darkGray, Color.gray, Color.green, Color.lightGray, Color.magenta, Color.orange, Color.pink, Color.red, Color.white, Color.yellow }; public RGBJList() //could use (String title) then super(title) and declare title. { super ("RGBJList Application"); //set the JFrame title yourContainer = getContentPane(); //get content pane and name it yourContainer.setLayout(new FlowLayout(FlowLayout.CENTER)); // center components yourContainer.setBackground(Color.yellow); //set the background colour to yellow colorList = new JList( colorNames ); //create a list with items in colorNames array colorList.setVisibleRowCount( 6 ); colorList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION ); //do not allow multiple selections yourContainer.add( new JScrollPane( colorList ) );//add a JScrollPane containing JList to content pane colorList.addListSelectionListener( // set up event handler new ListSelectionListener() { // anonymous inner class for list selection events

Gary Hill

December 2003

Java 25 of 25

GRAPHICS PROGRAMMING public void valueChanged( ListSelectionEvent event ) handle list selection events { yourContainer.setBackground(colors[ colorList.getSelectedIndex()]);

//

helloTextField.setText(colorNames[colorList.getSelectedIndex()]); } } // end anonymous inner class ); // end call to addListSelectionListener JLabel yourJLabelText = new JLabel("Select a background 'colour' from the list above:"); yourContainer.add(yourJLabelText); //add label to container helloTextField = new JTextField("", 12 ); display button response helloTextField.setEditable( false ); editing yourContainer.add( helloTextField ); container pack(); setSize(350, 250); height=250 setVisible(true); }

//create text field to //prevent text field //add text field to

//set size of JFrame to width=350 //display the JFrame

public static void main(String[] args) { RGBJList testRGBJList = new RGBJList(); //RGBJList("RGBJList Application"); testRGBJList.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //close frame the Swing way //JDK1.3 version of addWindowListener } }// end class RGBJList

Note: Instead of using an annonymous abstract inner class for handling the list selection events, as above, the valueChanged() method can be included within the class and the class modified so that it implements ListSelectionListener . See RGBList2.java. Example Stage 1: Write an application similar to above that includes includes a list of at least ten currencies which when selected indicate the currency choice in the text field Gary Hill

December 2003

Java 26 of 26

GRAPHICS PROGRAMMING (CurrencyJList.java). Stage 2: Adapt the Currency application to show another text field that includes the exchange rate for the selected currency.

Gary Hill

December 2003

Java 27 of 27

GRAPHICS PROGRAMMING

8 - GUI: Layout Managers In Java there are a numberof layout manager that enable you to place components onto a container (JFrame etc.). These include: • • • • • •

FlowLayout GridLayout BorderLayout CardLayout GridBagLayout BoxLayout

(See: Sun's Java Tutorial Lesson: Laying Out Components Within a Container) For simple applications only one layout manager may be required, but for a complicated GUI it is necessary to combine any number of layout managers to create the desired GUI. This is achieved by adding a number of JPanels to one the main Container (or a JPanel before adding to the main Container). The JPanels can use any of the layout managers to enable the components to be added to it. The JPanels can then be added to the main Container. The example below illustrates the use of 5 JPanels added to the Container. The JPanels use the FlowLayout layout manager and the JPanels are added to the Container using BorderLayout.

Gary Hill

December 2003

Java 28 of 28

GRAPHICS PROGRAMMING

Gary Hill

December 2003

Java 29 of 29

GRAPHICS PROGRAMMING

Example Use the resources available (see: Indicative Reading and Other Resources) to experiment with each type of Layout Manager. Use your Currency Application (CurrencyJList.java) from above. Alternatively, a good exercise is to attempt to emulate the Calualtor GUI available within all Windows Operating Systems as the XP version below:

Gary Hill

December 2003

Java 30 of 30

GRAPHICS PROGRAMMING

9 - GUI: JMenu To create the familiar 'Windows' GUI menu bar in an application (also applets) the stages are as follows: Create an object of the JMenuBar class. Call the window's setJMenuBar( ) method to give the menu bar to the window. Create objects of the JMenu class for each menu you want in the menu bar. Call the JMenuBar object's add( ) method to add each menu object to the menu bar. Create objects of the JMenuItem (or JCheckboxMenuItem) classe/s for each item you want to appear in the menus. Call the menus' add( ) methods in order to add each item to its appropriate menu. Remember to addActionListener to each JMenuItem. Note: Variations on JMenuItem include: JCheckBoxMenuItem, JRadioButtonMenuItem. There is also another type of JMenu is the JPopupMenu.

Figure 16.1 The Menu Component Hierarchy (java.sun.com) Each of the above steps is covered in the application (GraphicsJFrame.java) below:

Gary Hill

December 2003

Java 31 of 31

GRAPHICS PROGRAMMING

/** Program: Filename: @author: Course: Module: Tutor: @version: Notes Date: */

Java Graphics Screen Application GraphicsJFrame.java © Gary Hill (200WXYZ) BSC Computing Graphics Programming Gary Hill 1.1 1.1 Added centreWindow method 28/10/03

import java.awt.*; BorderLayout import javax.swing.*; JPanel class












//enables access to the

Container &

//enables access to the javax.swing.JFrame &

public class GraphicsJFrame extends JFrame implements ActionListener//ActionListener for menu only { Container yourContainer; //declare container DrawingArea drawingArea; //declare JPanel for drawing JScrollPane scrollsVH; //declare vertical & horizontal scrolling JMenuBar topMenuBar; //declare Menu Bar JMenu fileMenu, editMenu, searchMenu, helpMenu; //declare sub-Menus JMenuItem exitItem, fontItem, foreColor, backColor, helpItem, aboutItem; String aboutBoxString = (" Application written by\n © Gary Hill BSc(Hons) MSc MPhil PGCE\n" + " Principal Lecturer - Computer Systems,\n School of Technology & Design,\n" + " University College Northampton\n St Georges Avenue,\n " + " Northampton, NN2 6JD,\n United Kingdom\n E-Mail: [email protected]\n" + " Tel.(Work) +44 (0)1604 735500 Ext. 3077\n http://www.eng.nene.ac.uk/~gary/\n" + " Fax.(Work) +44 (0)1604) 792650/717813.") ; JLabel statusBar = new JLabel(" Example - DrawingArea JPanel");

Gary Hill

December 2003

Java 32 of 32

GRAPHICS PROGRAMMING

public GraphicsJFrame() //could use (String title) then super(title) and declare title. { super ("Java 2D/3D Graphics Application"); //set the JFrame title yourContainer = getContentPane(); // get content pane and name it yourContainer.setLayout(new BorderLayout()); // use border layout drawingArea = new DrawingArea(); scrollsVH = new JScrollPane(drawingArea, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS); scrollsVH.setBackground(Color.white); //set background colour for the drawing area to white yourContainer.add(scrollsVH, BorderLayout.CENTER);//add V & H scrolling to container yourContainer.add(statusBar, BorderLayout.SOUTH); menuSetup(); //standard menu set up method - requires actionListener pack(); setSize(500, 350); //set default size of JFrame to width=500 height=350 centreWindow(); setVisible(true); //display the JFrame } public void menuSetup() { topMenuBar = new JMenuBar(); //create a menu bar setJMenuBar(topMenuBar); //set the menu bar to the JFrame fileMenu = new JMenu("File");

// File menu, with open, save,

exitItem = new JMenuItem("Exit"); fileMenu.add(exitItem); exitItem.addActionListener(this); topMenuBar.add(fileMenu);

//EXIT item //add the items to the menu //add the listener to the item //add the menu to the menu bar

editMenu = new JMenu("Edit");

// edit menu, could have copy,

exit

paste foreColor = new JMenuItem("Foreground Colour"); //Foreground Colour item editMenu.add(foreColor); //add the items to the menu foreColor.addActionListener(this); //add the listener to the item backColor = new JMenuItem("Background Colour"); //Background Colour item editMenu.add(backColor); //add the items to the menu backColor.addActionListener(this); //add the listener to the item topMenuBar.add(editMenu ); searchMenu = new JMenu("Search"); topMenuBar.add(searchMenu); helpMenu = new JMenu("Help"); // help menu, with about application helpItem = new JMenuItem("Help Topics"); helpMenu.add(helpItem); helpItem.addActionListener(this); aboutItem = new JMenuItem("About..."); helpMenu.add(aboutItem);

Gary Hill

December 2003

help topics,

Java 33 of 33

GRAPHICS PROGRAMMING aboutItem.addActionListener(this); topMenuBar.add(helpMenu); } public void centreWindow() { //Center the window Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); Dimension frameSize = getSize(); if (frameSize.height > screenSize.height) { frameSize.height = screenSize.height; } if (frameSize.width > screenSize.width) { frameSize.width = screenSize.width; } setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2); } public void actionPerformed(ActionEvent e) { if (e.getSource() == exitItem) { System.exit(0); } if (e.getSource() == foreColor) { //Handle the "Foreground Color" menu item Color color = JColorChooser.showDialog(this,"Foreground Color", getForeground()); System.out.println("Foreground Color is Red = "+ color.getRed() +" G= "+color.getGreen()+" B= "+color.getBlue()); if (color != null) { drawingArea.setForeground(color); setForeground(color); } } if (e.getSource() == backColor) { //Handle the "Foreground Color" menu item Color color = JColorChooser.showDialog(this,"Background Color", getBackground()); if (color != null) { scrollsVH.setBackground(color); } drawingArea.setBackground(Color.white); System.out.println("Background Color is Red = " +color.getRed() +" G= "+color.getGreen()+" B= "+color.getBlue()); } if (e.getSource() == helpItem) JOptionPane.showMessageDialog(null, "Help Topics chosen."); if (e.getSource() == aboutItem) JOptionPane.showMessageDialog(null, aboutBoxString, "About the author", JOptionPane.INFORMATION_MESSAGE); this.repaint(); //repaints menu after item is selected }

Gary Hill

December 2003

Java 34 of 34

GRAPHICS PROGRAMMING public static void main(String[] args) { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception e) { System.err.println("Couldn't use the system look and feel: " + e); } GraphicsJFrame test = new GraphicsJFrame(); //GraphicsJFrame("Java 2D/3D Graphics Application"); test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //close frame Swing way } }// end class GraphicsJFrame /** Program: Filename: @author: Course: Module: Tutor: @version: Date: */

Java Graphics Screen Application
DrawingArea.java
© Gary Hill (200WXYZ)
BSC Computing
Graphics Programming
Gary Hill
1.1
28/10/03


import java.awt.*; BorderLayout import javax.swing.*; JPanel class

//enables access to the

Container &

//enables access to the javax.swing.JFrame &

class DrawingArea extends JPanel { public void paint(Graphics g) { g.drawString("A drawRect rectangle", 175, 100); position g.drawString("This 'DrawingArea' will be used for applications", 100, 200); g.setColor(Color.blue); //set colour to g.drawRect(25, 25, 425, 150); //Rectangle x , height } }// end class DrawingArea

Gary Hill

December 2003

//string & x, y our graphics blue y, width &

Java 35 of 35

GRAPHICS PROGRAMMING

Message Dialog The text editor application (GraphicsJFrame.java) above makes use of a 'Message Dialog' box to provide an About box as follows: if (e.getSource() == aboutItem) JOptionPane.showMessageDialog(null, " Application........"); The showMessageDialog method requires four arguments: argument 1 is the screen position (null = centre of screen), argument 2 is the message argument 3 is the title bar label for the dialog box argument 4 is the type of dialog box (.PLAIN_MESSAGE = plain message without an icon to the left of the message). Other 'types' include ERROR_MESSAGE, INFORMATION_MESSAGE, QUESTION_MESSAGE & WARNING_MESSAGE.

Gary Hill

December 2003

Java 36 of 36

GRAPHICS PROGRAMMING

Application Icon You may have noticed that the GraphicsJFrame application above has an application icon in the top left hand corner of the JFrame, instead of the default steaming cup of java coffee! Add your own application icon as follows using the setIconImage method inherited by JFrame from the java.awt.Frame class: setIconImage(Toolkit.getDefaultToolkit().createImage (GraphicsJFrame.class.getResource("rat_icon.gif")));//set application icon or Toolkit toolkit = Toolkit.getDefaultToolkit(); Image icon = toolkit.getImage(getClass().getResource("rat_icon.gif")); setIconImage(icon); //see here See the API Documentation for further details. Applications To incorporate text and styled text, even HTML, into an application see JTextPane and JEditorPane.

Gary Hill

December 2003

Java 37 of 37