League Invaders Pt. 10

Projectiles

1. Create a new class called Projectile. Have it extend GameObject the same as the Rocketship class.

2. Have the constructor of the Projectile class initialize the x, y, width, and height variables the same way that you did for the Rocketship class.

3. Create a member variable for the speed and initialize it to 10.

4. Add the same update and draw methods you did for the Rocketship class.

5. In the draw method, set the color to red and draw a rectangle around the x, y, width, and height of the projectile.

6. In the update method, decrement the y value by speed.

7. In the update method, do a check of the y position. If the y position becomes less than 0, set isAlive to false. This way, we will stop caring about the projectile when it goes off the screen.

8. Go to the ObjectManager class and create and initialize an ArrayList of Projectile objects.

9. Create a method called addProjectile that takes in a Projectile object. The method simply add this Projectile object to the list.

10. Add code to the ObjectManager's update method that iterates through the list of projectiles and calls their update method.

11. Add code to the ObjectManager's draw method that iterates through the list of projectiles and calls their draw method. Don't forget to pass in the Graphics object.

12. Go to your GamePanel class. When the SPACE key is pressed, add a new Projectile object to the ObjectManager. Use the Make the width and height of the projectile 10 by 10. Use the rocket's x and y position for the starting x and y position of the projectile.

        manager.addProjectile(new Projectile(rocket.x, rocket.y, 10, 10));

13. Run your program. Do you see projectiles fire when you press SPACE?

14. Adjust the starting x and y positions so that the projectile fires from the center of the rocket.