Java Video Tutorial 52
In this part of my Java video tutorial, I create the spaceship object and a keyboard listener. I will use the keyboard listener to move the ship around the screen.
It is so easy to randomly add objects to the game we started making here Make a Java Video Game. I slowed things down a bit here, just to make sure you completely get the process.
All of the code is available under the video. Please feel free to ask questions.
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Code From the Video
GAMEBOARD.JAVA
// Layout used by the JPanel
import java.awt.BorderLayout;
// Define color of shapes
import java.awt.Color;
// Allows me to draw and render shapes on components
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
// Will hold all of my Rock objects
import java.util.ArrayList;
// Runs commands after a given delay
import java.util.concurrent.ScheduledThreadPoolExecutor;
// Defines time units. In this case TimeUnit.MILLISECONDS
import java.util.concurrent.TimeUnit;
import javax.swing.JComponent;
import javax.swing.JFrame;
public class GameBoard extends JFrame{
// Height and width of the game board
public static int boardWidth = 1000;
public static int boardHeight = 800;
public static void main(String [] args)
{
new GameBoard();
}
public GameBoard()
{
// Define the defaults for the JFrame
this.setSize(boardWidth, boardHeight);
this.setTitle("Java Asteroids");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addKeyListener(new KeyListener() {
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyReleased(KeyEvent e) {
if (e.getKeyCode()==87)
{
System.out.println("Forward");
} else if (e.getKeyCode()==83){
System.out.println("Backward");
}
}
});
GameDrawingPanel gamePanel = new GameDrawingPanel();
// Make the drawing area take up the rest of the frame
this.add(gamePanel, BorderLayout.CENTER);
// Used to execute code after a given delay
// The attribute is corePoolSize - the number of threads to keep in
// the pool, even if they are idle
ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(5);
// Method to execute, initial delay, subsequent delay, time unit
executor.scheduleAtFixedRate(new RepaintTheBoard(this), 0L, 20L, TimeUnit.MILLISECONDS);
// Show the frame
this.setVisible(true);
}
}
// Class implements the runnable interface
// By creating this thread we can continually redraw the screen
// while other code continues to execute
class RepaintTheBoard implements Runnable{
GameBoard theBoard;
public RepaintTheBoard(GameBoard theBoard){
this.theBoard = theBoard;
}
@Override
public void run() {
// Redraws the game board
theBoard.repaint();
}
}
@SuppressWarnings("serial")
// GameDrawingPanel is what we are drawing on
class GameDrawingPanel extends JComponent {
// Holds every Rock I create
public static ArrayList<Rock> rocks = new ArrayList<Rock>();
// Get the original x & y points for the polygon
int[] polyXArray = Rock.sPolyXArray;
int[] polyYArray = Rock.sPolyYArray;
// Create a SpaceShip
SpaceShip theShip = new SpaceShip();
// Gets the game board height and weight
int width = Lesson50.boardWidth;
int height = Lesson50.boardHeight;
// Creates 50 Rock objects and stores them in the ArrayList
public GameDrawingPanel() {
for(int i = 0; i < 10; i++){
// Find a random x & y starting point
// The -40 part is on there to keep the Rock on the screen
int randomStartXPos = (int) (Math.random() * (Lesson50.boardWidth - 40) + 1);
int randomStartYPos = (int) (Math.random() * (Lesson50.boardHeight - 40) + 1);
// Add the Rock object to the ArrayList based on the attributes sent
rocks.add(new Rock(Rock.getpolyXArray(randomStartXPos), Rock.getpolyYArray(randomStartYPos), 13, randomStartXPos, randomStartYPos));
}
}
public void paint(Graphics g) {
// Allows me to make many settings changes in regards to graphics
Graphics2D graphicSettings = (Graphics2D)g;
// Draw a black background that is as big as the game board
graphicSettings.setColor(Color.BLACK);
graphicSettings.fillRect(0, 0, getWidth(), getHeight());
// Set rendering rules
graphicSettings.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// Set the drawing color to white
graphicSettings.setPaint( Color.WHITE);
// Cycle through all of the Rock objects
for(Rock rock : rocks){
// Move the Rock polygon
rock.move();
// Stroke the polygon Rock on the screen
graphicSettings.draw(rock);
}
theShip.move();
graphicSettings.draw(theShip);
}
}
SPACESHIP.JAVA
import java.awt.Polygon;
@SuppressWarnings("serial")
public class SpaceShip extends Polygon{
// Upper left hand corner of space ship
int uLeftXPos = 500, uLeftYPos = 400;
// Determines the direction the ship moves
int xDirection = 0;
int yDirection = 0;
// Get the board width and height
int width = GameBoard.boardWidth;
int height = GameBoard.boardHeight;
// Will hold the x & y coordinates for the ship
public static int[] polyXArray = {500,527,500,508,500};
public static int[] polyYArray = {400,415,430,415,400};
// Creates a new space ship
public SpaceShip(){
// Creates a Polygon by calling the super or parent class of Rock Polygon
super(polyXArray, polyYArray, 5);
}
public void move(){
// Get the upper left and top most point for the Polygon
// This will be dynamic later on
int uLeftXPos = super.xpoints[0];
int uLeftYPos = super.ypoints[0];
// If the ship hits a wall it will go in the opposite direction
if (uLeftXPos < 0 || (uLeftXPos + 25) > width) xDirection = -xDirection;
if (uLeftYPos < 0 || (uLeftYPos + 50) > height) yDirection = -yDirection;
// Change the values of the points for the Polygon
for (int i = 0; i < super.xpoints.length; i++){
super.xpoints[i] += xDirection;
super.ypoints[i] += yDirection;
}
}
}
ROCK.JAVA
import java.awt.Polygon;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
// Extending the Polygon class because I'm drawing Polygons
class Rock extends Polygon{
// Upper left hand corner of the Polygon
int uLeftXPos, uLeftYPos;
// Used to change the direction of the asteroid when
// it hits something and determines how fast it moves
int xDirection = 1;
int yDirection = 1;
// Define rock height and width
int rockWidth = 26;
int rockHeight = 31;
// Copy of the Rock ArrayList
// Holds every Rock I create
static ArrayList<Rock> rocks = new ArrayList<Rock>();
// For JApplet
// int width = ExampleBoard.WIDTH;
// int height = ExampleBoard.HEIGHT;
// Get the board width and height
int width = GameBoard.boardWidth;
int height = GameBoard.boardHeight;
// Will hold the x & y coordinates for the Polygons
int[] polyXArray, polyYArray;
// x & y positions available for other methods
// There will be more Polygon points available later
public static int[] sPolyXArray = {10,17,26,34,27,36,26,14,8,1,5,1,10};
public static int[] sPolyYArray = {0,5,1,8,13,20,31,28,31,22,16,7,0};
// Creates a new asteroid
public Rock(int[] polyXArray, int[] polyYArray, int pointsInPoly, int randomStartXPos, int randomStartYPos){
// Creates a Polygon by calling the super or parent class of Rock Polygon
super(polyXArray, polyYArray, pointsInPoly);
// Randomly generate a speed for the Polygon
this.xDirection = (int) (Math.random() * 4 + 1);
this.yDirection = (int) (Math.random() * 4 + 1);
// Holds the starting x & y position for the Rock
this.uLeftXPos = randomStartXPos;
this.uLeftYPos = randomStartYPos;
}
public void move(){
// Get the upper left and top most point for the Polygon
// This will be dynamic later on
int uLeftXPos = super.xpoints[0];
int uLeftYPos = super.ypoints[0];
// If the Rock hits a wall it will go in the opposite direction
if (uLeftXPos < 0 || (uLeftXPos + 25) > width) xDirection = -xDirection;
if (uLeftYPos < 0 || (uLeftYPos + 50) > height) yDirection = -yDirection;
// Change the values of the points for the Polygon
for (int i = 0; i < super.xpoints.length; i++){
super.xpoints[i] += xDirection;
super.ypoints[i] += yDirection;
}
}
// public method available for creating Polygon x point arrays
public static int[] getpolyXArray(int randomStartXPos){
// Clones the array so that the original shape isn't changed for the asteroid
int[] tempPolyXArray = (int[])sPolyXArray.clone();
for (int i = 0; i < tempPolyXArray.length; i++){
tempPolyXArray[i] += randomStartXPos;
}
return tempPolyXArray;
}
// public method available for creating Polygon y point arrays
public static int[] getpolyYArray(int randomStartYPos){
// Clones the array so that the original shape isn't changed for the asteroid
int[] tempPolyYArray = (int[])sPolyYArray.clone();
for (int i = 0; i < tempPolyYArray.length; i++){
tempPolyYArray[i] += randomStartYPos;
}
return tempPolyYArray;
}
}
Could you list the key codes for us, or tell us how to know what number each key is, if there is a method for doing so (such as A = 1, so B = 2, C = 3, etc.)? Thank you, sir.
And thank you for the lessons. They are helping me pursue my dream career, despite being unable to afford to go to college. There is no price I could put on that, nor words to describe my gratitude.
Thank you 🙂 It is always great to hear that I helped so much!
Here are the key codes
backspace 8
tab 9
enter 13
shift 16
ctrl 17
alt 18
pause/break 19
caps lock 20
escape 27
page up 33
page down 34
end 35
home 36
left arrow 37
up arrow 38
right arrow 39
down arrow 40
insert 45
delete 46
0 48
1 49
2 50
3 51
4 52
5 53
6 54
7 55
8 56
9 57
a 65
b 66
c 67
d 68
e 69
f 70
g 71
h 72
i 73
j 74
k 75
l 76
m 77
n 78
o 79
p 80
q 81
r 82
s 83
t 84
u 85
v 86
w 87
x 88
y 89
z 90
left window key 91
right window key 92
select key 93
numpad 0 96
numpad 1 97
numpad 2 98
numpad 3 99
numpad 4 100
numpad 5 101
numpad 6 102
numpad 7 103
numpad 8 104
numpad 9 105
multiply 106
add 107
subtract 109
decimal point 110
divide 111
f1 112
f2 113
f3 114
f4 115
f5 116
f6 117
f7 118
f8 119
f9 120
f10 121
f11 122
f12 123
num lock 144
scroll lock 145
semi-colon 186
equal sign 187
comma 188
dash 189
period 190
forward slash 191
grave accent 192
open bracket 219
back slash 220
close braket 221
single quote 222