0

好的，所以我得到了一个 ArrayIndexOutofBoundsException。我不知道为什么。

这是我的代码：

/**
Tile Generator
Programmer: Dan J.
Thanks to: g00se, pbl.
Started May 23, 2010
**/

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class tileGen extends Applet implements KeyListener  {


    Image[] tiles; // tile arrays
    Image player; // player image
    int x, y, px, py, tx, ty; // x tile - y tile // player x - player y // tile x - tile y
    boolean left, right, down, up, canMove; // is true?
    int[][] board; // row tiles for ultimate mapping experience!
    final int NUM_TILES = 33; // how many tiles are we implementing?
    Label lx, ly; // to see where we are!
    private static int BLOCKED = 28;

    int lastX, lastY, row, col;

  public void init() {

    board = loadBoard();

    tiles = new Image[NUM_TILES];
    for(int i = 0;i < NUM_TILES;i++) {
        tiles[i] = getImage(getClass().getResource(String.format("tiles/t%d.png", i)));
    }
        board[2][2] = BLOCKED;
        player = getImage(getClass().getResource("player.png")); // our player
        addKeyListener(this);
        canMove = true;
        px = 0;
        py = 0;
        lastX = 0;
        lastY= 0;
    }

    public void keyPressed(KeyEvent e) {

if (blocked(lastX,lastY) == true) {
    System.out.println("You were JUST on a BLOCKED tile!");
}

int x1 = lastX = lastX + 1;
int y1 = lastY;
       System.out.println("++++++++++++++++++++++++\n(" +x1+","+y1+") " + blocked(x1,y1) + "\n++++++++++++++++++++++++");

        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            left = true;
            px = px - 32;
            lastX = lastX - 1;
        }
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
            right = true;
            px = px + 32;
            lastX = lastX + 1;
        }
        if (e.getKeyCode() == KeyEvent.VK_DOWN) {
            down = true;
            py = py + 32;
            lastY = lastY + 1;
        }
        if (e.getKeyCode() == KeyEvent.VK_UP) {
            up = true;
            py = py - 32;
            lastY = lastY - 1;
        }



        repaint();
    }
public void keyReleased(KeyEvent e){} // ignore
public void keyTyped(KeyEvent e){} // ignore

  public void paint(Graphics g) {


        for (row = 0; row < board.length; row++) {
            for (col = 0; col < board[row].length; col++) {
                int index = board[row][col];
                g.drawImage(tiles[index], 32 * col, 32 * row, this);

            }
        }
        System.out.println("X: " + lastX + "\nY: " + lastY + "\n=============================\n");

System.out.println("Blocked tile?: " +blocked(lastX,lastY) + " ("+lastX + ","+lastY+")");
        g.drawImage(player, px, py, this);
    } // end paint method

     public void update(Graphics g)
     {
          paint(g);
     }

    public int[][] loadBoard() {
        int[][] board = {
                { 2,2,24,24,24,24,24,1,3,0,0,0 },
                { 2,2,24,23,23,23,24,1,3,0,0,0 },
                { 1,1,24,23,23,23,24,1,3,3,3,3 },
                { 1,1,24,24,23,24,24,1,1,1,1,1 },
                { 1,1,1,1,7,1,1,1,1,1,3,3 },
                { 5,1,1,1,7,7,7,7,7,1,3,3 },
                { 6,1,3,1,1,1,1,1,7,7,7,3 },
                { 6,1,3,1,3,1,3,1,1,1,7,3 }
            };
    return board;
    }

    public boolean blocked(int tx, int ty) {

            return board[tx][ty] == BLOCKED;
        }

} // end whole thing

问题是当我去红砖时board[2][2]......我去那里。然后我上去......然后我尝试退后，但弹出该错误。另外，当我走到右边的 8 个方格时……我也得到了那个错误。

另外，假设我的 2d 地图被分成四个正方形......好吧，第一个正方形是左上角......如果我去任何其他地方......我得到那个错误。

我究竟做错了什么？谢谢。

更新：我找到了罪魁祸首！当我按下键时，它是 lastX 和 lastY 更新！但我仍然无法解决这个数组越界！:(

这是错误： Exception in thread "AWT-EventQueue-1" java.lang.ArrayIndexOutOfBoundsException: 8 at tileGen.blocked(tileGen.java:111) at tileGen.paint(tileGen.java:86) at tileGen.update(tileGen.java:92) at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239) at sun.awt.RepaintArea.paint(RepaintArea.java:216) at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:306) at java.awt.Component.dispatchEventImpl(Component.java:4706) at java.awt.Container.dispatchEventImpl(Container.java:2099) at java.awt.Component.dispatchEvent(Component.java:4460) at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre ad.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread. java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre ad.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)

    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)

    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)</code>
4

1 回答 1

2

一般来说，ArrayIndexOutOfBoundsException当尝试访问超出范围的索引处的数组元素时，会抛出 an 。

ArrayIndexOutOfBoundsException以下代码段显示了一些抛出的场景（彼此独立） ：

    // 1
    int[] x = new int[5];
    x[-1] = 0; // ArrayIndexOutOfBoundsException: -1

    // 2
    int[] x = new int[5];
    x[5] = 0; // ArrayIndexOutOfBoundsException: 5

    // 3
    int[][] table = new int[3][3];
    table[0][10] = 0; // ArrayIndexOutOfBoundsException: 10

    // 4
    int[][] table = new int[3][3];
    table[-10][10] = 0; // ArrayIndexOutOfBoundsException: -10

    // 5
    int[][][][] whoa = new int[0][0][0][0];
    whoa[0][-1][-2][-3] = 42; // ArrayIndexOutOfBoundsException: 0

    // 6
    int[][][][] whoa = new int[1][2][3][4];
    whoa[0][1][2][-1] = 42; // ArrayIndexOutOfBoundsException: -1

这在您的小程序中发生的位置和方式尚不清楚，但请放心，它发生的原因是正确的：您非法尝试访问无效索引处的数组元素，并且由于数组在 Java 中的运行时进行了绑定检查，引发运行时异常。

您可能想调出调试器来查看无效索引是如何评估的，但如果没有别的，System.out.println那么在您更改索引的任何地方以及您将要访问数组元素的任何地方都可以帮助定位错误。

附加提示：

代替：

lastX = lastX + 1;
lastY = lastY - 1;

你可以做：

lastX++;
lastY--;

这称为“后增量”和“后减量”运算符。明智地使用它可以提高可读性。

参考

于 2010-05-30T05:57:44.137 回答