1. Java Programming: From Problem Analysis to Program Design, 3e Chapter 6 Graphical User Interface (GUI) and Object-Oriented Design (OOD)

2. 2Java Programming: From Problem Analysis to Program Design, 3e Chapter Objectives Learn about basic GUI components Explore how the GUI components JFrame, JLabel, JTextField, and JButton work Become familiar with the concept of event- driven programming

3. 3Java Programming: From Problem Analysis to Program Design, 3e Chapter Objectives Discover events and event handlers Explore object-oriented design Learn how to identify objects, classes, and members of a class

4. 4Java Programming: From Problem Analysis to Program Design, 3e Graphical User Interface (GUI) Components View inputs and outputs simultaneously One graphical window Input values in any order Change input values in window Click on buttons to get output

5. 5Java Programming: From Problem Analysis to Program Design, 3e Java GUI Components

6. 6Java Programming: From Problem Analysis to Program Design, 3e Graphical User Interface (GUI) Components (continued) GUI components placed in content pane GUI components –Windows –Labels –Text areas –Buttons

7. 7Java Programming: From Problem Analysis to Program Design, 3e GUI Components Added to content pane of window Not added to window itself Pixel: picture element

8. 8Java Programming: From Problem Analysis to Program Design, 3e Windows Can be created using a JFrame object The class JFrame provides various methods to control attributes of a window Measured in pixels of height and width Attributes associated with windows –Title –Width –Height

9. 9Java Programming: From Problem Analysis to Program Design, 3e class JFrame GUI window instance created as instance of JFrame Provides various methods to control window attributes

10. 10Java Programming: From Problem Analysis to Program Design, 3e Methods Provided by the class JFrame

11. 11Java Programming: From Problem Analysis to Program Design, 3e Methods Provided by the class Jframe (continued)

12. 12Java Programming: From Problem Analysis to Program Design, 3e Two Ways to Create a Window First way –Declare object of type JFrame –Instantiate object –Use various methods to manipulate window Second way –Create class containing application program by extending definition of class JFrame –Utilizes mechanism of inheritance

13. 13Java Programming: From Problem Analysis to Program Design, 3e Content Pane Inner area of GUI window (below title bar, inside border) To access content pane –Declare reference variable of type Container –Use method getContentPane of class JFrame

14. 14Java Programming: From Problem Analysis to Program Design, 3e Methods Provided by the class Container

15. 15Java Programming: From Problem Analysis to Program Design, 3e class JLabel Labels: objects of particular class type class JLabel : used to create labels Label attributes –Title –Width –Height To create a label –Instantiate object of type JLabel –Modify attributes to control display of labels

16. 16Java Programming: From Problem Analysis to Program Design, 3e class Jlabel (continued)

17. 17Java Programming: From Problem Analysis to Program Design, 3e class JTextField Text fields: objects belonging to class JTextField To create text field –Declare reference variable of type JTextField –Instantiate object

18. 18Java Programming: From Problem Analysis to Program Design, 3e class JTextField (continued)

19. 19Java Programming: From Problem Analysis to Program Design, 3e class JTextField (continued)

20. 20Java Programming: From Problem Analysis to Program Design, 3e class JButton Provided to create buttons in Java To create button –Same technique as creating JLabel and JTextField

21. 21Java Programming: From Problem Analysis to Program Design, 3e class Jbutton (continued)

22. 22Java Programming: From Problem Analysis to Program Design, 3e Handling an Event Action event: event created when JButton is clicked Event listener: object that receives message when JButton is clicked In Java, you must register the listener

23. 23Java Programming: From Problem Analysis to Program Design, 3e Handling an Event (continued) class ActionListener –Handles action event –Part of package java.awt.Event –The class ActionListener is a special type of class (interface) –Must contain actionPerformed method

24. 24Java Programming: From Problem Analysis to Program Design, 3e Rectangle Program: Sample Run

25. 25Java Programming: From Problem Analysis to Program Design, 3e Programming Example: Temperature Conversion Input: temperature in Fahrenheit or Celsius Output: temperature in Celsius if input is Fahrenheit; temperature in Fahrenheit if input is Celsius

26. 26Java Programming: From Problem Analysis to Program Design, 3e Programming Example: Temperature Conversion (continued) Solution –Create the appropriate JLabels, JTextFields, JButtons –Add them to the created content pane –Calculate the appropriate conversions when the buttons are clicked and an event is triggered

27. 27Java Programming: From Problem Analysis to Program Design, 3e Sample Run for TempConversion

28. 28Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Simplified methodology 1. Write down detailed description of problem 2. Identify all (relevant) nouns and verbs 3. From list of nouns, select objects 4. Identify data components of each object 5. From list of verbs, select operations

29. 29Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Example 1 Problem Statement –Write a program to input the length and width of a rectangle, and calculate and print the perimeter and area of the rectangle Nouns –Length, width, rectangle, perimeter, area

30. 30Java Programming: From Problem Analysis to Program Design, 3e class Rectangle with Data Members and Operations

31. 31Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Example 2 An inoperable candy machine has a cash register and four dispensers to hold and release items sold by the machine The machine sells: candies, chips, gum, and cookies Write a program for this candy machine so that it can be put into operation

32. 32Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Example 2 (continued) The program should do the following: –Show the customer the different products sold by the candy machine –Let the customer make the selection –Show the customer the cost of the item selected –Accept money from the customer –Return change –Release the item; that is, make the sale

33. 33Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Example 2 (continued)

34. 34Java Programming: From Problem Analysis to Program Design, 3e Object-Oriented Design Example 2 (continued)

35. 35Java Programming: From Problem Analysis to Program Design, 3e Implementing Classes and Operations Algorithms are used to implement operations Construct and implement your own methods classes Integer, Double, Character, Long, Float –Known as wrapper classes –Provided so that values of primitive data types can be treated as objects –Have limitations (cannot change value stored in objects)

36. 36Java Programming: From Problem Analysis to Program Design, 3e The class Integer

37. 37Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued)

38. 38Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued)

39. 39Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued) Integer num; num = new Integer(86)

40. 40Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued) int x; Integer num; num = 25; For the most part, this statement is similar to the statement: num = new Integer(25); The expression: num = 25; is referred to as autoboxing of the int type

41. 41Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued) int x; Integer num; The statement: x = num; This statement is equivalent to the statement: x = num.intValue(); This statement is referred to as auto unboxing of the int type

42. 42Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued) To compare the values of two Integer objects, you can use the method compareTo If you want to compare the values of two Integer objects only for equality, then you can use the method equals

43. 43Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued)

44. 44Java Programming: From Problem Analysis to Program Design, 3e The class Integer (continued)

45. 45Java Programming: From Problem Analysis to Program Design, 3e Chapter Summary Every GUI contains a window Various components are added to content pane of window class JFrame is used to create windows JLabel is used to label GUI components and display information to user JTextFiled is used for input/output JButton generates action event Action event is sent to action listener

46. 46Java Programming: From Problem Analysis to Program Design, 3e Chapter Summary (continued) Action listener must have method called actionPerformed class: collection of data members and methods associated with those members Object-Oriented Design (OOD) –Starts with a problem statement –Identifies classes required with nouns in problem statement –Identifies methods required with verbs in problem specification