java - 设置对象数组值时出错

Question

package net.gfx;

public class TileSet {

    public final int TILES = 627;

    class Tiles {
        int x = 0, y = 0;
        int w = 0, h = 0;

    }

    public Tiles tiles[] = new Tiles[TILES];

    public TileSet() {
        for (int i = 0, y = 0; i < TILES; i++) {
            for (int x = 0; x < 1280; x =+ 25) {
                if (x > 1280) {
                    x = 0;
                    y += 40;

                }
                else {
                    tiles[i].x = x; //ERROR CAUSED HERE
                    tiles[i].y = y; //TO HERE *Unknown reason*
                    tiles[i].w = 40;
                    tiles[i].h = 40;

                }

            }

        }

    }

}

我收到的错误:

Exception in thread "main" java.lang.ExceptionInInitializerError
    at net.jump.Jump.<clinit>(Jump.java:8)
Caused by: java.lang.NullPointerException
    at net.gfx.TileSet.<init>(TileSet.java:24)
    at net.gfx.Graphics.<clinit>(Graphics.java:10)
    ... 1 more

我想做的基本上是在屏幕上创建一个图 block 数组。除了设置对象数组值之外，其他一切都有效。

我几乎找遍了所有地方，但一无所获。我敢打赌这可能是我错过的一些简单的事情。

Answer 1

您必须先创建一个 Tiles 实例，然后才能对其执行任何操作。

 for (int i = 0, y = 0; i < TILES; i++) {
    for (int x = 0; x < 1280; x =+ 25) {
        if (x > 1280) {
            x = 0;
            y += 40;

        }
        else {
            tiles[i] = new Tiles(); //instance created here.
            tiles[i].x = x; 
            tiles[i].y = y; 
            tiles[i].w = 40;
            tiles[i].h = 40;

        }

    }

}