Java Video Tutorial 57
In this video I continue making a Java Asteroids game while teaching about OOP design principles. In previous videos I showed how to make a Java UML class diagram and then we turned the UML class diagram into a class.
Here I finish up the class so that you can now fly your ship in any direction. You’ll also be able to keep it on the game board and use life like velocity that accelerates.
All of the code is below and is heavily commented to help you learn.
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Code From the Video
SpaceShip.java
import java.awt.*;
@SuppressWarnings("serial")
public class SpaceShip extends Polygon{
// Determines the speed the ship moves
private double xVelocity = 0, yVelocity = 0;
// Get the board width and height
int gBWidth = GameBoard.boardWidth;
int gBHeight = GameBoard.boardHeight;
// Center of space ship
private double centerX = gBWidth/2, centerY = gBHeight/2;
// Will hold the x & y coordinates for the ship
// Everything is based on coordinates from the center
// It is done this way so that rotation works properly
public static int[] polyXArray = {-13,14,-13,-5,-13};
public static int[] polyYArray = {-15,0,15,0,-15};
// Width and height of ship
private int shipWidth = 27, shipHeight = 30;
// Upper left hand corner of space ship
private double uLeftXPos = getXCenter() + this.polyXArray[0];
private double uLeftYPos = getYCenter() + this.polyYArray[0];
// Defines if the ship should rotate
private double rotationAngle = 0, movingAngle = 0;
// Creates a new space ship
public SpaceShip(){
// Creates a Polygon by calling the super or parent class Polygon
super(polyXArray, polyYArray, 5);
}
// Gets & sets the values for the x & y center of ship
public double getXCenter(){ return centerX; }
public double getYCenter(){ return centerY; }
public void setXCenter(double xCent){ this.centerX = xCent; }
public void setYCenter(double yCent){ this.centerY = yCent; }
public void increaseXPos(double incAmt) { this.centerX += incAmt; }
public void increaseYPos(double incAmt) { this.centerY += incAmt; }
// Gets & sets the x & y for upper left hand corner of ship
public double getuLeftXPos(){ return uLeftXPos; }
public double getuLeftYPos(){ return uLeftYPos; }
public void setuLeftXPos(double xULPos){ this.uLeftXPos = xULPos; }
public void setuLeftYPos(double yULPos){ this.uLeftYPos = yULPos; }
// Gets & sets the x & y for upper left hand corner of ship
public int getShipWidth(){ return shipWidth; }
public int getShipHeight(){ return shipHeight; }
// Gets, sets, increases and decreases the ship velocity
public double getXVelocity(){ return xVelocity; }
public double getYVelocity(){ return yVelocity; }
public void setXVelocity(double xVel){ this.xVelocity = xVel; }
public void setYVelocity(double yVel){ this.yVelocity = yVel; }
public void increaseXVelocity(double xVelInc){ this.xVelocity += xVelInc; }
public void increaseYVelocity(double yVelInc){ this.yVelocity += yVelInc; }
public void decreaseXVelocity(double xVelDec){ this.xVelocity -= xVelDec; }
public void decreaseYVelocity(double yVelDec){ this.yVelocity -= yVelDec; }
// Set and increase the ship movement angle
public void setMovingAngle(double moveAngle){ this.movingAngle = moveAngle; }
public double getMovingAngle(){ return movingAngle; }
public void increaseMovingAngle(double moveAngle){ this.movingAngle += moveAngle; }
// Calculate the ship angle of movement
// This is trigonometry at work
// By taking the cos of the angle I get the adjacent value of x
// Angle * Math.PI / 180 converts degrees into radians
public double shipXMoveAngle(double xMoveAngle){
return (double) (Math.cos(xMoveAngle * Math.PI / 180));
}
// By taking the sin of the angle I get the opposite value of y
// Angle * Math.PI / 180 converts degrees into radians
public double shipYMoveAngle(double yMoveAngle){
return (double) (Math.sin(yMoveAngle * Math.PI / 180));
}
// Gets & increases or decreases the rotation angle of the ship
// Increase the rotation angle by 5, but don't let it go above 360
public double getRotationAngle(){ return rotationAngle; }
public void increaseRotationAngle(){
if(getRotationAngle() >= 355) { rotationAngle = 0; }
else { rotationAngle += 5; }
}
// Decrease the rotation angle by 5, but don't let it go below 0
public void decreaseRotationAngle(){
if(getRotationAngle() < 0) { rotationAngle = 355; }
else { rotationAngle -= 5; }
}
// Artificial rectangle that is used for collision detection
public Rectangle getBounds(){
return new Rectangle(getShipWidth() - 14, getShipHeight() - 15, getShipWidth(), getShipHeight());
}
public void move(){
// Increase the x origin value based on current velocity
this.increaseXPos(this.getXVelocity());
// If the ship goes off the board flip it to the other side of the board
if(this.getXCenter() < 0){
this.setXCenter(gBWidth);
} else
if (this.getXCenter() > gBWidth){
this.setXCenter(0);
}
// Increase the x origin value based on current velocity
this.increaseYPos(this.getYVelocity());
// If the ship goes off the board flip it to the other side of the board
if(this.getYCenter() < 0){
this.setYCenter(gBHeight);
} else
if (this.getYCenter() > gBHeight){
this.setYCenter(0);
}
}
}