ccannon94/spaceinvaders.md

## spaceinvaders.md

      
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    javafx-space-invaders

JavaFX Space Invaders game developed as an assignment for high school students.
Created by Chris Cannon
Overview

This is a basic JavaFX space invaders game. The code is split into three primary areas. Datatypes holds the underlying data that is used to run the game, this is basic code that holds information and provides it to the program. Framework is the code that is used to interface between the program and the computer. GUI is the graphical user interface, the code that the user interacts with directly.
Getting Started

To work on this assignment, open the JavaFX SpaceInvaders project in IntelliJ on your computer. Open each class and look for the TODO tags. Then, look for that same class in the instructions below for helpful hints.
Data Types

Game


Accessor methods: accessor methods are used to get the value from a private variable. They should usually begin with "get" and return the private variable they are named after. For example public String getName() { return name;}

-Mutator methods: mutator methods are used to change the value of a private variable. Mutator methods should only be written when necessary, as they may lead to unexpected changes in the code. For example public void setName(String name) { this.name = name; }
GameConfigData


Arrays are data structures that hold values of a single type. In this case, our array will hold String variables. We must instantiate (create) an array to a given size and type. For example, an array that would hold 20 integers called "myInts" would be instantiated like this: myInts = new String[20];.

PlayerProfile


Constructors are special methods that are used to create instances of an object. Unlike most other methods, they do not have a return type. They often have arguments with the same name as the variables of the class. For example, if we have a class called "Book" that has the String variables "title" and "author", one constructor that takes an argument for each variable would look like this:

public Book(String title, String author) {
  this.title = title;
  this.author = author;
}


Additionally, there can be multiple constructors for a single class. For example, a no-argument constructor initializes all variables to their default value, but has no arguments. The no-arg constructor for Book would look like this:

public Book() {
  this.title = "";
  this.author = "";
}


Every single Java class has a toString() method, because all Java classes inherit from the Object class. With many classes that we write, we may want to override this method with our own, custom toString(). This is especially useful for saving data to a file, or displaying information to a user. A toString() method returns a string representation of the object, which basically just means the text that represents the data of your object. A very common format of toString() methods is comma-separated values, or csv. Lets say we have a Student object with three properties, firstName, lastName, and studentID. The toString() method would look like this:

@Override
public String toString() {
  return firstName + ", " + lastName + ", " + studentID;
}


Notice that the toString() method above does not take any arguments, and it uses String concatenation (using the "+" sign to combine Strings) to insert commas between the properties.

PlayerProfileCollection


An ArrayList is a data structure that holds multiple variables of a specific type, but does not have a set size, like an array does. It grows and shrinks as needed as items are added and removed. One of the most important parts of programming is Encapsulation, which involves protecting data from being used improperly. For a data structure like an ArrayList, it is important to allow access to certain operations without allowing complete access. Lets say we had a private ArrayList called "widgets" that holds Widget objects, we would set up the following public methods to access and mutate the ArrayList:

public int getNumWidgets() {
  return widgets.getSize();
}

public void addWidget(Widget object) {
  widgets.add(object);
}

public void setWidget(int index, Widget other) {
  widgets.set(index, other);
}

public Widget getWidget(int index) {
  return widgets.get(index);
}

public Widget removeWidget(int index) {
  return widgets.remove(index);
}


To update the high score, you must iterate through the ArrayList profiles, and compare each high score to the current highScore. You will want to use a for loop to perform this search.

Framework

SpaceInvadersIO


To write to a file, you will want to use the PrintWriter class, and the print() method. An example is below

try{
  PrintWriter pw = new PrintWriter(new File("filename"));
  pw.println("This will print to the file");
  pw.close();
}catch(java.io.FileNotFoundException ex) {
  System.err.println("Could not find file for printing");
}


The GameConfigData method will read the input file called gameConfigData.txt and populate the imagePaths array. You will use the Scanner class and the nextLine method. You should use a for loop or a while loop to read in the 4 image paths. An example of reading one image path is below

try{
  Scanner reader = new Scanner(new File("filename"));
  imagePaths[0] = reader.nextLine();
}catch(java.io.FileNotFoundException ex) {
  System.err.println("Could not find file to read")''
}


As you can see, there are try/catch blocks surrounding the Scanner and PrintWriter code blocks. This is because when dealing with files, it is possible to run into errors if the file isn't found by the program. Therefore, we must tell Java how to handle these errors if they occur.

GUI

BadGuyCraft


To make a class a subclass, you must extend the superclass. For example, to make Student a subclass of Person we would say public class Student extends Person.


Using the constructors of superclasses is a very useful tool that can keep a developer from rewriting code. To call a constructor of a superclass, simply use the super(); keyword.


Craft


Software development is all about math. Computers themselves are nothing but complex mathematical machines that use numbers to perform calculations and interact with users! Here, we are going to use an algorithm, or problem-solving template, to move the Craft. Hint, you may want to use the Math.cos() and Math.sin() method, as well as the Math.PI constant, to solve this problem*.


To move the craft:

x = x + speed * cos(direction * (2 * pi) / 360)
y = y + speed * sin(direction * (2 * pi) / 360)


You will have to convert the algorithm above to java code to complete the move method.


GamePane


This class extends Pane, which is a JavaFX class that is used to arrange nodes on a screen. To add something like a Level object, use the this.getChildren().add() method.


Pane also has a method to set the preferred height and width of a Pane. Try using IntelliJ's autocomplete feature to find the right methods. Type this. and scroll through the list of suggested methods.


StartMenu


StartMenu is the main class for this program, which means that it has the main() method. The main() method is the first method called in any Java program. Java programs can be launched from the command line, with specific arguments that are stored in the array args. To access the first command line argument, you would use args[0], for the second command line argument, args[1], and so on.


To set the visible property of UI components, use the setVisible() method. true means the component is visible and false means it is invisible.


To validate the GamerID, see if it contains a space " ". There is a method for String that can help with this. Try doing gamerID. and looking through the suggested methods. Then, iterate through the playerProfiles to see if one matches gamerID. If either one of these things are true, return false.