Unit 4: Object Oriented Programming

What is JOptionPane

A class enabling programmers to use dialog boxes to recieve user input

4 Key Components of a JOptionPane

Parent Component: Determines the position of the dialog box (set to null to center it)

Message: The object you want ot apepar in the dialog box

Title: The string you want to appear

Message Type: Icon that you want to be displayed

Syntax:

• JOptionPane.showInputDialog(null, “Message”, “Title”, Message Type);

5 Different types of Messages

1. Error_Message

2. Information_Message

3. Warning_Message

4. Question_Message

5. Plain_Message

What is polymorphism?

Fuck you nigger Richard

Difference between scanner and JOptionPane

JOptionPane only takes in STRING values and OBJECTS while Scanner can read all datatypes

Difference between showMessageDialog() and showInputDialog()

showMessageDialog() - Does not return or input anything

showInputDialog() - Can read user input

In a showConfirmDialog() what values would be returned based on the button you pressed?

It is very similar to an array, as the first button from the left will be assigned the value 0, the following would be 1 and so on.

How to import custom images in java

Declare and initialize an ImageIcon object

private ImageIcon img;

img = new ImageIcon (“file name“);

How to add buttons to the JOptionPane

Declare an array and fill in the buttons/dialog for each button

String[] buttons = new String[4] {“Yes”, “Yes to all”, “No”, “Cancel”};

JOptionPane.showOptionDialog(null, “Question ?”, “Buttons”, JOptionPane. WARNING_MESSAGE, 0, null, buttons, null);

What is SWING

A package allowing programmers to create applications in the GUI

What is JFrame

The main window where components like labels, buttons, textfields are added to create a GUI

Where do you set the properties of the frame?

In the constructor

What does setting null to setLocatioNrelativeTo(null); do

It sets the JFrame to the center of the users screens

Difference between private, protected, and public modifiers

Private: Makes data fields accessible in a singular class

Public: Makes data fields accessible in all classes within the project folder

Protected: Makes data fields accessible in all classes or subclasses

What JFrame method must always be used

seteVisible(true);

What must be written in main after setting the properties in the constructor?

new [class name](); —> This calls on the constructor

What 2 methods do you need to change the background colour of the frame

getContentPane() and setBackground()

/

getContentPane().setBackground(Color.BLUE);

What is the difference between Graphics and Graphics2D

Graphics: It is used for simple drawings

Graphics2D: Used for more complex and high-quality graphics rendering.

How does drawing strings work in the paint method?

g2.drawString(“message”, x, y);

How to instantiate a font

Font f = new Font(“Papyrus”, Font.BOLD, 18);

How to instantiate a FontMetrics and what is FontMetrics

FontMetrics fm = getFontMetrics(f);

It is used to measure the size of characters, strings, and other text elements in a specific font

How to write custom fonts

Font f = Font.createFont(Font.TRUETYPE_FONT, new FILE(“file”)).deriveFont(30f)

How to draw images?

g2.drawImage(img.getImage(), xPos, yPos, this);

How to draw lines and rectangles?

g2.draw(new Line2D.Double(Origin X, Origin Y, Width, Height);

g2.draw(new Rectangle2D.Double(Origin X, Origin Y, Width, Height);

How to set colours of the shape drawn

g2.setColor(Color.COLOR);

g2.draw(new Rectangle2D.Double(Origin X, Origin Y, Width, Height);

How to import JPanel to a class

After the class name write “extends JPanel” and import the package

public class Example extends JPanel {

}

Is JFrame the same as JPanel?

JFrame represents a framed window and a JPanel represents some area in which controls

Where does JFrame go when using JPanel

Instead of writing Extends JFrame at the top, JFrame will be instantiated in side the constructor, and the name given must be used to set the JFrame properties

Ex:

JFrame jf = new JFrame();

jf. setSize(100, 500);

Biggest change in the JFrame when using JPanel

the setContentPane(this);

When the keyword this is set inside the parameters, it tells JFrame to add all components of JPane to the JFrame so we can see it.

What’s the difference between a method and a constructor?

A constructor instantiates field, named after the class, and has no return type

A method is named everything but the class name and has a return type, either void or a datatype

What makes up a method header

public int max(int num1, int num2){}

Visibility: Public

Return Type: int

Method Name: move

Parameters: int num1, int num2

What are the 3 keywords that a class containss?

Fields: Defines the global variables

Constructors: Initializes the fields

Methods: Defines the methods of the class and returns the data type

How to access another class in main

[Class name] [name] = new [Class name]();

[name].[method in class]();

Ex: Dice dice = new Dice();

dice.getRoll();

What is a Unified Modelling Language (UML) Diagram

A diagram used to help programmers organize their code to help non-programmers understand.

What is a UML made up of

Class Name

Fields

Constructors and Methods

How are the components of a UML denoted?

Fields: field name: Data Type

Constructor: [Constructor Name](Parameters)

Methods: [Method Name](Parameter): [Data Type]

Which symbols indicate the visibility?

Public: +

Private: -

Protected: #

What is an accessor and mutator?

Accessor: An accessor method, or getter, is used to retrieve the value of an instance variable. It typically follows a naming convention where the method name starts with "get" followed by the name of the variable with the first letter capitalized.

Mutator: A mutator method, or setter, is used to set or update the value of an instance variable. It typically follows a naming convention where the method name starts with "set" followed by the name of the variable with the first letter capitalized.

How does the RGB Color work?

There are 3 numbers that represent Red, Green and Blue

• (0, 0, 0)

Timer Class

Has a Timer object that is used to time certain events in the program. For the case of Animation, the swing package is used and no the the util one (that brings your computer’s actual clock in).

Events

Objects created when something changes in the GUI of a program

Timer Object

Generates events at regular intervals and has a listener that listens when an “event” occurs → ActionListener

Methods

Timer Class Methods

Methods we Only Care About

.start() → starts the timer
.stop() → stops the timer

initializing a timer

• Declare timer as a field first

• The first parameter/argument is measured in milliseconds

• The second parameter is the ActionListener interface

interface

Similar to a class but contains abstract methods like actionPerformed().

Multiple Timers

The actionPerformed method will always the take the fast timer if e.getSource() is not used.

if (e.getSource() == exampleTimer)

Grabs the specified timer if there are multiple timers and runs the code below the if statement.

Thread Class

Creates sleep() method which stops the code from running for a specified amount of time. Ex: Code stops for half a second (measured in milliseconds)

interrupt()

method that is called within the thread class given an error. The error is the InterruptedException error.

repaint()

cleans the JFrame and rebuild it very quickly, placing each “component” in a new location on the screen.

Animation in Multiple Classes

For animation to happen in multiple classes, a few variables and methods must be used:

• Direction Variables: RIGHT, DOWN, LEFT, UP

• ImageIcon Variables: imgPlayer (imgPlayerLeft, imgPlayerRight, etc.)

• Mutator Methods: setDirection(), setX(), setY()

• Void Methods: move(int dir)

• Boundary Checking Method: (can be used in main or class)

KeyEvent Class

contains keyboard event objects or in other words, events that deal with the user inputting stuff via the keyboards.

keyboard event

generated everytime a user inputs something into the keyboard.

Registering an object for the KeyListener interface

component.addKeyListener(listener);
- Listener → Listens for the key events
- Component → object that generates the key events

KeyListener Interface

And objects that need to listen for key events must have the KeyListener interface implemented.

For the KeyEvent class to work, what code must be initialized in the constructor?

addKeyListener(this); → Tells Java to send key events to this object
setFocusable(true); → Ensures that the component can receive keyboard focus or understand what key is being typed
requestFocus(); → asks for the object to get the keyboard focus right now

Implementing KeyListener Methods

When implementing KeyListener, these three methods must be placed in the class (whether or not they are used).

getKeyChar() vs. getKeyCode() methods

getKeyChar() → returns the inputted character to the KeyEvent Class
getKeyCode() → returns constatns such as “VK_DOWN”

Some Constants

KeyPressed and KeyReleased methods

KeyPressed() example:
if (e.getKeycode == KeyEvent.VK_RIGHT)
right = true;

KeyReleased() Example:
if (e.getKeycode == KeyEvent.VK_RIGHT)
right = false;

The purpose of this is to prevent lag in the movement of the image/character that the programmer puts in place.

actionPerformed method

After adding the code to the KeyPressed and the KeyReleased methosd → it is time to increase or decrease xPos and increase or decrease yPos based on the direction

MouseEvent

A class where mouse object events belong to.

MouseListener & MouseMoveListener

Any objects that need to listen for mouse events must have the MouseListener and MouseMoveListener interface.

What do we initialize in the constructor to let the MouseListener listen to our key events?

addMouseListener(this);

addMouseMotionListener(this);

setFocusable(true);

requestFocus();

MouseListener Methods

MouseMotionListener Methods

Methods in the MouseMotionListener and MouseListener Methods?

Collision Detection

Used to see if shapes surrounding an object (masks/bounding boxes) collide with each other.

.intersects()

Method part of the rectangle class. At least one of the masks has to be a rectangle.

Ellipse2D vs. Rectangle2D

For images that fit a circle-like frame better. Ex:
// Ellipse variable + Rectangle2D variable
Ellipse2D circle = new Ellipse2D(player.getX(), player.getY(), img.getIconWidth(), img.getIconHeight());

Rectangle2D rect = new Rectangle2D(player.getX(), player.getY(), img.getIconWidth(), img.getIconHeight());

boolean collision = false;

// Checking for collision:
if (circle.intersects(rect))

{
collision = true;
}

ALWAYS PUT THE RECTANGLE 2D SECOND IF YOU WANT TO CHECK FOR COLLISION BETWEEN A CIRCLE AND A RECT MASK!

Projectiles

Steps:

• Set the x and y pos out of bounds initially for the image and the rect to prevent early collisions

• If player is playing → utilize a keyboard pressed event such as VK_SPACE

• When user presses VK_SPACE → set position of the projectile to the player’s x and y pos

• Used a boolean variable such as “IsFired” to prevent the user from firing prematurely

Adding Sounds in Java

Java Supports:

• MIDI

• WAV

• RMF

• AU

• AIFF

Packages Needed

java.io → FileInputStream class to get the needed audio

javax.sound → AudioInputStream and clip class

Starting and Stopping audio

// what ever your Clip file is

clip.start();
clip.stop();

Looping a song entirely

clip.loop(Clip.LOOP_CONTINUOUSLY);

Playing more than one sound

try
{
// Open an audio input stream.
File soundFile2 = new File("Music.wav");
AudioInputStream audioIn2 =
AudioSystem.getAudioInputStream(soundFile2);
clip2 = AudioSystem.getClip();
clip2.open(audioIn2);
clip2.start();
}
catch(Exception e)
{
JOptionPane.showMessageDialog(null, “File not Found”);
}

// Copy and paste this format into things such as keyPressed method to play it everytime there is a key event.