Question

我正在尝试制作基于磁贴的游戏。我制作了一个Tile课程，并为每个人提供了Rectangle用于碰撞的课程。一旦我渲染并更新它们，我将它们全部存储到ArrayList中。那部分工作正常，但是当我尝试通过getter从另一个类访问同一个ArrayList时，我没有得到任何元素。我用我的控制台检查大小，它给了我正确的数字，但是当我尝试实际获得一个元素时即rect.get(0)，我收到了这些错误：

Exception in thread "Thread-3" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.rangeCheck(Unknown Source)
    at java.util.ArrayList.get(Unknown Source)

我认为这是一个线程安全问题，但我已经尝试了使用synchronize关键字到Collections所能想到的一切，但没有运气。任何帮助都会非常感激。

使用代码编辑。很抱歉没有提前发布

public class Launcher extends JFrame implements Runnable {

    private static final long serialVersionUID = 1L;

    private static final int WIDTH = 1500;
    private static final int HEIGHT = 900;

    private static final String title = ("Game Alpha");

    volatile boolean running;

    Thread CT;

    Canvas canvas = new Canvas();
    Dimension size = new Dimension(WIDTH, HEIGHT);

    Camera camera;

    Controls controls;

    PlayerTest pt;

    BufferStrategy BS;

    Graphics graphics;

    //I'm declaring the arrayList here
    public  ArrayList<Rectangle> bounded = new ArrayList<Rectangle>();

    public Launcher() {

        Sprites.resources();
        controls = new Controls();
        GUI();
        //The camera class is the one in which I'm trying to access the list
        //It's there right now just to test, I plan on changing it later
        camera = new Camera(this, controls, 0, 0);

        pt = new PlayerTest(this, canvas.getWidth() / 2, canvas.getHeight() / 2);

        Tiles.tileSets();

        CT = new Thread(this);
        START();

    }

    public void GUI() {
        setTitle(title);
        setPreferredSize(size);
        setResizable(false);
        pack();
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        addKeyListener(controls);

        canvas.setPreferredSize(size);
        canvas.setMaximumSize(size);
        canvas.setMinimumSize(size);
        canvas.setFocusable(false);
        add(canvas);

        setVisible(true);
    }

    public void render() {
        BS = canvas.getBufferStrategy();

        if(BS == null) {
            canvas.createBufferStrategy(3);
            return;
        }


        graphics = BS.getDrawGraphics();
        graphics.setColor(Color.ORANGE);

        graphics.fillRect(0, 0, WIDTH, HEIGHT);

        Rectangle cam = new Rectangle((int)camera.getX(), 
                (int)camera.getY(), 
                camera.getWidth(), 
                camera.getHeight());

        //Here I'm looping to get my tiles
        for(int x = 0; x < 64; x++) {
            for(int y = 0; y < 64; y++) {
                Tiles.getTile(LevelCode.code[y][x]).setBounds( x * 50 - (int)camera.getXof(),  y * 50 - (int)camera.getYof());

                //Here I'm adding the rectangles from each tile into the array
                bounded.add(new Rectangle(Tiles.getTile(code[y][x]).getBounds()));

            }   
        }

        pt.render(graphics);

        BS.show();
        graphics.dispose();
//Here after I render the tiles I clear the list, for my updates, then //repopulate
        bounded.clear();

    }

    public ArrayList<Rectangle> getList() {
        return bounded;
    }

}

Answer 1

同步（如果操作正确）意味着这不是线程安全问题，尽管您还没有发布实际代码，因此您可能做错了。

这里最可能的情况是，实际上有多个ArrayList并且您访问了错误的toString。尝试检查ID（当你forEach时＃之后的数字），并确保两个地方的ID相同。

需要帮助使用ArrayList Synchronizing

1 个答案: