ECE 462Object-Oriented Programmingj g g

using C++ and Java

Key Inputs in Java Games

Yung-Hsiang Lul @ d dyunglu@purdue.edu

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Handle Key EventsHandle Key Events

• have the focus of the keyboard inputs by calling y p y gsetFocusable(true)

• two types of events:– pressing and releasing– what key (Unicode) is pressed (such as 'A' or '<')

implement three functions• implement three functions– keyPressed(KeyEvent e) – keyReleased(KeyEvent e)keyReleased(KeyEvent e) – keyTyped(KeyEvent e)

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Handle Key Events in a Full Screen Game

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must be overriddenby derived classes

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by derived classes

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ECE 462Object-Oriented Programmingj g g

using C++ and Java

Mouse Inputs in Java Games

Yung-Hsiang Lul @ d dyunglu@purdue.edu

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Java Mouse ListenersJava Mouse Listeners

• MouseListener: handle clicks– mouseClicked(MouseEvent e) – mouseEntered(MouseEvent e) – mouseExited(MouseEvent e) – mousePressed(MouseEvent e)

( )– mouseReleased(MouseEvent e) • MouseMotionListener: handle motion

mouseDragged(MouseEvent e)– mouseDragged(MouseEvent e) – mouseMoved(MouseEvent e)

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ECE 462Object-Oriented Programmingj g g

using C++ and Java

Multiple Inheritance in C++

Yung-Hsiang Lul @ d dyunglu@purdue.edu

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Multiple InheritanceMultiple Inheritance

• One of the most (if not the most) controversial features ( )in C++.

• Not supported in Java. Java uses interfaces.• Most C++ books do not explain the concept and the

problems.• Understand the advantages and the problems and you• Understand the advantages and the problems and you

can decide whether to use it.

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Multiple InheritanceMultiple Inheritance

Student Teacher Car Truck

TeachingAssistant

Car Truck

SportUtilityVehicleSportUtilityVehicle

Person

EmployeeWoman Employee

FemaleEmployee

Woman

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FemaleEmployee

Design IssuesDesign Issues

• A class provides interface and pimplementation.

• Code reuse is good but a class, d l d i h d t h

Person

W P tonce declared, is hard to change because of the code depending on this class. Employee

Woman Parent

M th• If you have any doubt, do not

create a class.A id th lif ti f l

Mother

• Avoid the proliferation of classes because they make code reuse harder.

MomEmployee

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Too Many ClassesToo Many Classes

• In many payroll systems, a person's status (for example y p y y , p ( ptax withholding) depends on the person's role. If a person has children, the person's tax withholding is less.If l i l th d• If an employee is also a mother, a company may send a gift to the children on their birthdays.

• Should you create one class for each possible status ofShould you create one class for each possible status of employee?

• Or, use attributes to distinguish their status?

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What Does a Class Give You?What Does a Class Give You?

• interface (public inheritance) and implementation(p ) p• polymorphism• object creation

• If you are not using polymorphism, think twice (or more) before creating a classbefore creating a class.

• It is usually easier to change the behavior of an attribute (encapsulation) than changing the interface ( p ) g g(code reuse).

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Repeated InheritanceRepeated Inheritance

class Vehicle{

int v_engineSize; Vehicle

int v_numberWheel;}; Car Truck

Does SportUtilityVehicle have onev engineSize or two?

SportUtilityVehicle

v_engineSize or two?⇒ two, unless you use virtual inheritance⇒ ambiguous, compilation error

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⇒ ambiguous, compilation error

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Virtual InheritanceVirtual Inheritance

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Virtual Inheritance and Copy Constructor

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X

Y Tvirtual virtual

Z

U

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Virtual Inheritance and Assignment Operator

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ECE 462Object-Oriented Programmingj g g

using C++ and Java

Qt Layout

Yung-Hsiang Lul @ d dyunglu@purdue.edu

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Menubar and Vertical LayoutMenubar and Vertical Layout

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Horizontal LayoutHorizontal Layout

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Grid LayoutGrid Layout

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Combination of LayoutsCombination of Layouts

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