Developing User Interfaces (DUI) Chris North cs3724: HCI

GUI Development: Goals 1.Learn general GUI programming concepts GUI components Layout Event-based programming Graphics Animation 2.Learn Java Swing Layout managers Listerners 2D graphics Threads Then: can learn other languages quickly VB, C#, Xwin, Java 49

Intro to Java

Why Java?

Java materials Java 2 = sdk 1.2 or better Documentation: Tutorials, reference, API Borland JBuilder 6 Free! Cross between VB and VC++

Java differences Basic statements identical to C++ Object-oriented only! No.h files main() is inside a class No global variables No pointers (object references only) No delete: automatic garbage collection Single inheritance only, “interfaces” Applet/application GUI: AWT, Swing Packaging Error Handling, exceptions (try, catch) E.g. Array bounds checking Security Components: beans

Java compiling Code: hello.java (text file) Compile: javac hello.java Creates: hello.class(byte code) Run: java hello Java virtual machine, interpets/compiles (machine code) Packaging: jar Or use JBuilder, like VC++

Java Applications Run from command line hello.java: class hello { public static void main(String[] args){ System.out.println(“Hello World!”); } javac hello.java java hello Hello World!

Typically create objects hello.java: class hello { public static void main(String[] args){ // Create and use objects hello h = new hello(); … } public hello(){ // Constructor … } … }

Many Classes Compile each separately Can be main( ) in any/all classes hello.java: class hello { goodbye g; public static void main(String[] args){ … } goodbye.java: class goodbye { public static void main(String[] args){ … }

Hmmm… dir hello.class goodbye.class blah.class foo.class bar.class areyouawakein.class Java ??? RunMe.bat: java hello

JBuilder

Java Applets Run in a web browser hello.java: import javax.swing.*; class hello extends JApplet { public void init(){ getContentPane().add( new JLabel(“Hello World!”) ); } javac hello.java appletviewer hello Hello World!

Java Applets in HTML hello.html: <applet code=“hello.class” height=100 width=200> Need java. Put hello.html and hello.class on website Java plug-in Hello World! hello.html

Applet Methods init( ) - initialization start( ) - resume processing (e.g. animations) stop( )- pause destroy( )- cleanup paint( )- redraw stuff (‘expose’ event)

Applet Security No read/write on client machine Can’t execute programs on client machine Communicate only with server “Java applet window” Warning Certificates

Upcoming Java Topics GUIs: Swing, AWT, MVC Event handling, listeners Graphics Animation, threads Components, JavaBeans Databases, JDBC