Graphical User Interface Programming

Graphical User Interface Programming Dr. Susan McKeever (not me) Email: richard.lawlor@dit.ie www.comp.dit.e/rlawlor

UI Programming • At the end of the course you will be able to: • Develop GUI applications • Use standard UI components • Develop custom UI components • And… Program in Java • And.. Be a better programmer

Admin… • Assessment: • 1 formal exam = 50% • 1 assignment + in class test = 35% • Lab marks = 15%

Admin • Contact Hours: • 1 hour lecture • 2 hour lab session • 1 hour tutorial

Admin • Tutorial/Lecture/Lab • Lecture • Provide new material • Usually new Lab exercises • Lab • Work on latest Lab Sheet • Lab content will be a week behind the lecture.. • Tutorial • Discuss issues from last Lab Sheet • Review Broken Code/error messages

Course.. • Topics • Java Language Basics • Hello World • Operators/Reference Types • OO Basics • Packages • Abstractions • Exceptions • Connecting to Databases JDBC • “Good” programming practices • GUIs (Java Swing) • Layout Managers • Event Handing • Graphics • Applets • GUI Design • Class structures and Model View Controller (MVC)

Resources… • Resources • Web, web, web, web, web, web,……………… • JAVA API http://download.oracle.com/javase/6/docs/api/ • Textbook: UI Programming: Paul Fischer, An Intro to GUIs with Java SwingGeneral Reference: Java in a Nutshell, O’Reilly Java Swing, O’Reilly 2nd Ed. • Webcourses– www.comp.dit.ie/smckeever • CHECK YOU CAN ACCESS.. IF NOT EMAIL ME • Lecture notes • Lab Assignments & eventually Solutions • Assignments (Details and Submission) • Links to Useful References • Past Exam Papers.. Just 1 set..

Important • Lecture notes are my guide to structuring lectures • They do not contain all material covered • Will do plenty of work/examples etc on the board

Introduction toJava Programming

Java Editions Java 2 Platform Java2 Standard Edition (J2SE™) Java2 Enterprise Edition (J2EE™) Java2 Micro Edition (J2ME™) Standard desktop & workstation applications; applets Heavy duty server Systems – mediumto large companies Small & memory constrained devices

Key Benefits of Java • Java is “write once, run anywhere” • architecture neutral • portable across different platforms • Due to Java Virtual Machine (JVM) • Security features • highly configurable security levels prevent any piece of Java code doing harm to the host system

Key Benefits of Java • Network-centric platform • easy to work with resources across a network and to create network based applications • Object Oriented • an interacting collection of independent software components • dynamic extensible programs

Key Benefits of Java • Internationalisation • uses 16 bit Unicode characters that represents the phonetic and ideographic character sets of the entire world • Performance • although an interpreted language Java programs run almost as fast as native C, C++ programs • Simple and easy to develop • powerful & well designed set of APIs • http://download.oracle.com/javase/6/docs/api/

1001100101001 … … Interpreted by JVM class myCode { … … … …} Bytecode myCode.class myCode.java JVM Compiled by Java compiler Source Code Application runs

JVM • JVM provides the run time environment for the bytecode(Java Runtime Environment JRE) • executes the bytecode and causes native machine code instructions to execute on the CPU that the JVM is on  each target platform needs an implementation of the JVM

The Simplest Java Program public class HelloWorld{ // no fields // main method public static void main (String [] args){ System.out.println("Hello World.."); }}

Basic Program structure • Basic class definition - remember from OO programming last year?class className { // field declarations … // method declarations … }

Class versus Object?

The Simplest Java Program public class HelloWorld{ // no fields // main method public static void main (String [] args){ System.out.println("Hello World.."); }} To run a java program, you need a special methods called the main method to tell the program where to start executing

accessible to all classes(info hiding) Simple Java Program public class HelloWorld{ // no fields // main method public static void main (String [] args){ System.out.println("Hello World.."); }} command line args indicates class method returns nothing invoking a member Not much point in creating an object out of this class.. It doesn’t describe anything.. It just “runs”

Objects • An object includes state (fields) and behaviour (methods) • A class object is the blueprint for the instance objects • All code must be included in a class • no inline functions like C++

An Example Class • Want to create a class that represents a student. • Want to store a “name” for the student. • How? • Want to the class to have a way to print out the student name • How?

An Example Class public class Student { // member fields private String name; // constructor public Student(String name) { this.name=name; } // methods public void printDetails(){ System.out.println("\nName: “ + name); } }

An Example Class a business class predefined Java class public class Student { // member fields private String name; // constructor public Student(String name) { this.name=name; } // methods public void printDetails(){ System.out.println("\nName: “ + name); } } accessibility no return type reference to the object itself String concatenation

Instantiation (i.e. creating objects out of a class) • Class definition used to create a “class object” at runtime • E.g. created a Student class.. Now want to create a “real” student object • To instantiate “instance objects” use new operator ClassNamemyInstance = new ClassName(); where ClassName() is a constructor Note: no need to allocate the memory for the object like in C++

Using a Class in a Program the program control class: Contains “main” source file called myProg.java public class myProg { public static void main(String args []){ // instantiate a Student object Student student1= new Student("Joe Bloggs"); Student student2= new Student(“Liz mckeever"); // invoke printDetails methodstudent1.printDetails(); student2.printDetails(); }}

Using the JDK • Each class is stored in a source file “xxx.java” • The name of source file should be the same as the name of class public class myCode { … … … …} myCode.java Source File

Compiling your source code • Compile each class source file into bytecode (class files) • In DOS To compile a java source file javac myCode.java • This creates a classfile called myCode.class BUT.. This year we’re going to use Eclipse 1001101001110101011 … … … … myCode.class Class File

Eclipse • An Integrated Development Environment (IDE) • Originally created by IBM (2001) • Open source community, free • Widely widely used in industry • Increases coding efficiency • Spots compile errors as you type • Allows quick fixes • Helps file organisations/packages • Imports are easy • Demo..

Eclipse • Free to download • Worth doing.. • http://www.eclipse.org/

To run your program • All so easy in Eclipse.. • Click the “RUN” command in Eclipse – full instructions at the lab

Using a Control Class // This is in a file call myControlClass.java public class myControlClass { public static void main(String args []){ // instantiate a Student object new StudentPrinter(); } }

Using a Control Class // This is in a file call StudentPrinter.java public class StudentPrinter { // Constructor - instantiate a Student object public StudentPrinter() { Student student1= new Student("Joe Bloggs"); Student student2= new Student(“Liz mckeeve"); // invoke printDetails method student1.printDetails(); student2.printDetails(); } }

Using a Control Class // This is in a file call Student.java public class Student { // member fields private String name; // constructor public Student(String name) { this.name=name; } // methods public void printDetails(){ System.out.println("\nName: " + name); } }

General points to note.. • 80% of the cost of software is on maintaining code • Typically not the original developer • “You cannot be good at s/w development if you don’t make it as easy as possible for someone else to maintain your code” • Dr. Susan McKeever Sept 2012

How? • ??

Common sense • Comment your code • Header at the top of your code • Every method explained • Use meaningful names for variables, classes, objects... • Use java conventions (see overleaf) • Many more.. To be covered.

Use Conventions.. • Java is Case sensitive • Use the conventions • Classes should be nouns, capitalised first letter e.g. Student, ImagePixel • Variables mixed case starting with lower. E.g. acctBalance, line • Constant are all upper case e.g. COLOR_RED • Methods are verbs, mixed case starting with lower e.g. getBalance()

Java Syntax part 1 Java Syntax Primitive data types Operators Control statements

Primitive data types • Using a variable in java.. You must declare what type of data can contain.. • int, char etc.. • A primitive type is predefined by the language and is named by a reserved keyword.... 8 of them in java

Primitive data types • char (16 bits) a Unicode character • byte (8 bits) • int(32 bits) a signed integer • short (16 bits) a short integer • long (64 bits) a long integer

Primitive data types • float (32 bits) a real number • double (64 bits) a large real number • boolean(8 bits) • values are true or false(keywords) • Used with control statements e.g. while, do , if • e.g.while (fileEmpty)

Operators • Additive+ - • Multiplicative* / % • Equality (tests)== != • Assignment operators= += -= *= /= %=

Operators • Relational operators< <= > >= • Increment operators (postfix and prefix)++ -- • Conditional operator (short cut for if/else ?: e.g. max = (a > b) ? a : b; • String concatenation +

Logical Operators • Not ! • Logical AND && • Logical OR ||

Control Statements • Similarto C/C++ syntax: • if statement if (x != n){ …}else if { … }else { … } • for statement for (int i=0; i<max; i++){ … };

Control Statements • while statement while (x==n ){ …}; • do statement do {…} while( x<=y && x!=0);

Control Statements • switch statement switch (n){ case 1: … break; case 2: case 3: … break; default: break;};

Java Syntax Part 2 Java Reference Types Classes Arrays

Reference Types • Classes and arrays are composite types • no standard size • contain other elements • Manipulated “by reference’’ to the object or array • Primitive data types manipulated “by value”

Graphical User Interface Programming