I don't understand what's wrong, and how i can call "isCollision" method. In addition i have a bug because i didn't have PLAYER matrix, that i had to get in the part 16.(I coppied ENEMY matrix and renamed it as PLAYER 😅 )

Question about the task

Space Invaders (Part 17/34)

Games, Level 0, Lesson 6

Resolved

Why the 2nd task don't accept this part of code? :

if(bullets.isEmpty()) {
            return;
        }

What's wrong in this part of code ? :

else if(isAlive == true) {
        // for(Bullet a : bullets) {
        //     a.isCollision(ship);
        // }
        }

We'll give the PlayerShip class a method that checks whether enemy projectiles have hit the player's ship (the isCollision() method in the GameObject class).
If there is a hit, it will "kill" the ship and the projectile. We'll also add the player's ship to the class. We'll draw it and add the collision check in the appropriate method.

Requirements:

The PlayerShip class must have a public void checkHit(List<Bullet> bullets) method.
The checkHit(List<Bullet> bullets) method must not do anything if there are no projectiles in the bullets list (the list is empty).
In the checkHit(List<Bullet> bullets) method, if the player is alive, you need to check whether the player has collided with any of the live projectiles in the bullets list (use the isCollision(GameObject) method).
If the check returns true, you need to call the kill() method.
If the check returns true, you need to call the kill() method on the colliding projectile.
The SpaceInvadersGame class must have a private PlayerShip playerShip field.
The playerShip field must be initialized with a new PlayerShip object in the createGame() method before the call to the drawScene() method.
In the drawScene() method, the draw(Game) method must be called on the playerShip object after the call to the drawField() method. Pass "this" to the method.
In the SpaceInvadersGame class's check() method, you need to call the checkHit(List<Bullet>) method with enemyBullets as the argument on the playerShip object before the call to the removeDeadBullets() method.

package com.codegym.games.spaceinvaders; public class ShapeMatrix { public static final int[][] ENEMY = new int[][]{ {7, 0, 7}, {7, 7, 7}, {0, 7, 0} }; public static final int[][] BULLET = new int[][]{ {2}, {2} }; public static final int[][] PLAYER = new int[][]{ {7, 0, 7}, {7, 7, 7}, {0, 7, 0} }; }

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Artem Divertitto Senior Android Developer at United Tech

11 September 2020, 07:24

solution

Why did you remove this methods from GameObject?

public boolean isCollision(GameObject gameObject) {
      for (int gameObjectX = 0; gameObjectX < gameObject.width; gameObjectX++) {
          for (int gameObjectY = 0; gameObjectY < gameObject.height; gameObjectY++) {
              if (gameObject.matrix[gameObjectY][gameObjectX] > 0) {
                  if (isCollision(gameObjectX + gameObject.x, gameObjectY + gameObject.y)) {
                      return true;
                  }
              }
          }
      }
      return false;
  }
  private boolean isCollision(double x, double y) {
      for (int matrixX = 0; matrixX < width; matrixX++) {
          for (int matrixY = 0; matrixY < height; matrixY++) {
              if (matrix[matrixY][matrixX] > 0
                      && matrixX + (int) this.x == (int) x
                      && matrixY + (int) this.y == (int) y) {
                  return true;
              }
          }
      }
      return false;
  }

Inside method checkHit do not forget check is isCollision(a) return true and bullet is alive, use method kill and a.kill()

Pavlo Plynko Java Developer at CodeGym

11 September 2020, 06:44

Try to use:

isCollision(a);

instead:

a.isCollision(ship);

Dave Andrea

Level 41 , Canada

11 September 2020, 01:04

if(bullets.isEmpty()) {
            return;
        }

You could try if (bullets.size() == 0)

else if(isAlive == true) {
        // for(Bullet a : bullets) {
        //     a.isCollision(ship);
        // }
        }

You're on the right track here, but you need to use a conditional so you can make the function do something depending on whether there was a collision or not. if isCollision is true then... Look at requirements 4 and 5.