LibGDX渲染方法的问题******固定*******

Question

Attempt to read from field 'com.badlogic.gdx.utils.Array com.rocketdefender.GameWorld.GameWorld.rockets' on a null object reference 

我一直在尝试渲染一个火箭阵列并更新它们，以便它们向下移动屏幕，但它只是想出来这个错误，当我在移动运行。在我运行程序之前没有错误。我试图修复，但不知道为什么该数组首先是空的。

public class GameWorld { 

    public Array<Rocket> rockets; 
    private long lastDropTime = 0; 
    private Rocket rocket; 
    private SpriteBatch batch; 

    public GameWorld(){ 
     rockets = new Array<Rocket>(); 
    } 

    public void update(float delta){ 

     Iterator<Rocket> iter = rockets.iterator(); 
     while(iter.hasNext()) { 
      Rocket nextRocket = iter.next(); 
      nextRocket.y -= 200 * delta; 
      if (nextRocket.y + 64 < 0) iter.remove(); 
     } 
     if(TimeUtils.nanoTime() - lastDropTime > 1000000000) spawnRocket(); 

    } 

    public void spawnRocket(){ 
     rocket = new Rocket(20, 30); 
     rockets.add(rocket); 
     lastDropTime = TimeUtils.nanoTime(); 
    } 
    ... 
} 

---

public Rocket(int width, int height) { 
    rocket = new Rectangle(); 
    rocket.x = MathUtils.random(0, 800- (width * 2)); 
    rocket.y = 100; 
    rocket.width = width; 
    rocket.height = height; 
} 

---

GameRenderer类

public class GameRenderer { 

    private GameWorld myWorld; 

    private OrthographicCamera cam; 
    private SpriteBatch batch; 

    private int GameHeight; 

    public GameRenderer(GameWorld world, float GameHeight) { 
     myWorld = world; 
     this.GameHeight = (int) GameHeight; 

     cam = new OrthographicCamera(); 
    cam.setToOrtho(false, 136, 204); 

    batch = new SpriteBatch(); 
    // Attach batch to camera 
    batch.setProjectionMatrix(cam.combined); 
} 


    public void render(){ 
     cam.update(); 

     Gdx.gl.glClearColor(0, 0, 0, 1); 
     Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 

     batch.begin(); 
     for(Rocket nextRocket: myWorld.rockets) { 
       batch.draw(AssetLoader.rocket, nextRocket.x, nextRocket.y); 
     } 
     batch.end(); 
    } 
} 

Answer 1

的anwser是，我根本没有正确initiliaze一个变量在我的一半是错误的。