ObjectEditor

1. ObjectEditor Prasun Dewan Comp 114

2. ObjectEditor • Automatic user-interface generation. • You only write computation code • Separate object to do I/O • Main just instantiates it • Can replace it with own UI later. • Serves as training wheels • Serves to separate UI from computation

3. Example Class package bmi; publicclass ABMICalculator implements BMICalculator { publicdouble calculateBMI (double weight, double height) { return weight/(height*height); } }

4. Example Main Class package main; import bus.uigen.ObjectEditor; import bmi.ABMICalculator; public class ABMIDisplayer { publicstaticvoidmain(String[] args) { ObjectEditor.edit(new ABMICalculator()); } }

5. ABMICalculator UI

6. ABMICalculator UI

7. Adding a library in JBuilder

8. Adding a library in JBuilder

9. Adding a library in JBuilder

10. Adding a library in JBuilder

11. Adding a library in JBuilder

12. Adding a library in JBuilder

13. Adding a library in JBuilder

14. Location of Libraries • http://www.cs.unc.edu/~dewan/oe • Use Internet explorer (not Netscape) to download files • Library names • oe.jar • shapes.jar • oe2.jar version 2 of oe.jar • Try oe2 first and in case of bugs use oe.jar • oe.jar used by comp14 students • oe has lots of bugs! • Send me mail for workarounds bugs.

15. Location of Libraries

16. Unchanging value retyped What-if BMI Calculations

17. State: Data Remembered by an Object between computations BMI Spreadsheet

18. accesses accesses Belong to a single method Belong to all methods of an instance Instance Variables ABMICalculator Instance ABMISpreadsheet Instance calculateBMI getBMI Body Body Instance Variables Parameters local variable global variable

19. Identical Instances Different Instances State-less Vs State-ful Objects ~ car radios without presets ~ car radios with presets

20. ABMISpreadsheet publicclass ABMISpreadsheet { double height, weight; publicdouble getHeight() { return height; } publicvoid setHeight(double newHeight) { height = newHeight; } publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return weight/(height*height); } } Height Weight BMI

21. Name: P publicclass C { Type: T Editable publicvoid setP(T newValue) { ... } Getter method Setter method } newP Violates Bean Conventions obtainP Read-Only and Editable Properties Typed, Named Unit of Exported Object State Bean public T getP() { ... } Readonly • Conventions for • humans • tools

22. Read-Only Editable Independent Editable Independent Read-only Dependent Properties Classification • publicclass ABMISpreadsheet { • double height; • publicdouble getHeight() { • return height; • } • publicvoid setHeight(double newHeight) { • height = newHeight; • } • double weight; • publicdouble getWeight() { • return weight; • } • publicvoid setWeight(double newWeight) { • weight = newWeight; • } • publicdouble getBMI() { • return weight/(height*height); • } • … Height Weight BMI

23. Calling Getter and Setter Methods • When ObjectEditor window is created • Getter method of each property called to display initial value of property • When property is changed to a new value • Setter method of property is called with new value as actual parameter • Getter method of each property is called to refresh display

24. Calling Getter and Setter Methods publicclass ABMISpreadsheet { double height = 1.77; publicdouble getHeight() { return height; } publicvoid setHeight(double newHeight) { height = newHeight; } double weight = 77; publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return weight/(height*height); } }

25. publicclass ABMISpreadsheet { double height = 1.77; publicdouble getHeight() { System.out.println (“getHeight Called”); return height; } publicvoid setHeight(double newHeight) { System.out.println (“setWeight Called”); height = newHeight; } double weight = 77; publicdouble getWeight() { System.out.println (“getWeight Called”); return weight; } publicvoid setWeight(double newWeight) { System.out.println (“setWeight Called”); weight = newWeight; } publicdouble getBMI() { System.out.println (“getBMI Called”); return weight/(height*height); } } Tracing Method Calls

26. Actual Trace

27. How will above UI change? publicclass ABMISpreadsheet { double height, weight; publicdouble getHeight() { return height; } publicvoid setHeight(double newHeight) { height = newHeight; } publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return calculateBMI(weight, height); } publicdouble calculateBMI(double weight, double height) { return weight / (height*height); | } Modified ABMISpreadsheet

28. Properties + Class Menu

29. Editing in slow motion : Initial value

30. Editing in slow motion: text string edited

31. Editing in slow motion: return triggers setter and getter calls

32. publicclass ABMISpreadsheet { double height, weight; publicdouble height() { return height; } publicvoid setHeight(double newHeight) { height = newHeight; } publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return calculateBMI(weight, height); } publicdouble calculateBMI(double weight, double height) { return weight / (height*height); | } Renaming getter method

33. ObjectEditor does not know it is getter

34. publicclass ABMISpreadsheet { double height, weight; double getHeight() { return height; } publicvoid setHeight(double newHeight) { height = newHeight; } publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return calculateBMI(weight, height); } publicdouble calculateBMI(double weight, double height) { return weight / (height*height); | } Reducing Access

35. Height is not a readable property

36. Changing setter publicclass ABMISpreadsheet { double height, weight; publicdouble getHeight() { return height; } publicint setHeight(double newHeight) { height = newHeight; return height; } publicdouble getWeight() { return weight; } publicvoid setWeight(double newWeight) { weight = newWeight; } publicdouble getBMI() { return calculateBMI(weight, height); } publicdouble calculateBMI(double weight, double height) { return weight / (height*height); | }

37. Height is not a writeable property

38. An alternative class • public class AStringHistory implements StringHistory { • public staticfinalint MAX_SIZE = 50; • String[] contents = new String[MAX_SIZE]; • int size = 0; • publicint size() { return size;} • public String elementAt (int index) { return contents[index]; } • boolean isFull() { return size == MAX_SIZE; } • publicvoid addElement(String element) { • if (isFull()) • System.out.println("Adding item to a full history"); • else { • contents[size] = element; • size++; • } • } • } Variable number of dynamically created indexed properties

39. Write method (name does not matter to OE) Arbitrary Type (Must be Object Type to be recognized by ObjectEditor) Read methods ObjectEditor Conventions for Variable-Sized Collection • publicinterface I { • publicvoid addElement (T t); • public T elementAt (int index); • publicint size(); • }

40. Initial State

41. Adding an element Name does not matter to ObjectEditor

42. Adding an element

43. Adding an element ObjectEditor calls all elementAt () and getter() methods after each method call

44. Adding another element

45. Adding another element

46. Public Class Constants

47. Public Class Constants

48. Non Public Class Constant • public class AStringHistory implements StringHistory { • staticfinalint MAX_SIZE = 50; • String[] contents = new String[MAX_SIZE]; • int size = 0; • publicint size() { return size;} • public String elementAt (int index) { return contents[index]; } • boolean isFull() { return size == MAX_SIZE; } • publicvoid addElement(String element) { • if (isFull()) • System.out.println("Adding item to a full history"); • else { • contents[size] = element; • size++; • } • } • }

49. Non-Public Class Constant Non constants menu

50. Public Instance Constant • public class AStringHistory implements StringHistory { • publicfinalint MAX_SIZE = 50; • String[] contents = new String[MAX_SIZE]; • int size = 0; • publicint size() { return size;} • public String elementAt (int index) { return contents[index]; } • boolean isFull() { return size == MAX_SIZE; } • publicvoid addElement(String element) { • if (isFull()) • System.out.println("Adding item to a full history"); • else { • contents[size] = element; • size++; • } • } • }