初始化2D对象数组时，空指针异常[Java]

Question

我正在尝试制作2D切片游戏，当制作包含切片的阵列时，我得到了NullPointerException，这是一些代码。抱歉，如果格式不正确，请第一时间

公共类世界{

//holds data for where to place images and rectangles
int[][] worldDat = new int[25][25]; 
//hold rectangles for checking interaction with player
Rectangle[][] blocks = new Rectangle[25][25];
//holds block's images to be painted
Image[][] blockImage = new Image[25][25];
//holds position to be pained on screen
int[][] location = new int[25][25];
//enumeration holding block's images and other things of the sort
EWorldBlocks eBlocks;

//sets all of the arrays listed above
public void setupAll(){

    for(int i = 0; i < 24; i++){

        for(int e = 0; e < 24; e++){                    
            blocks[i][e].setBounds(e * 20, i * 20, 20, 20);
            blocks[i][e].setLocation(e*20, i*20);

            if(worldDat[i][e] == 6){
                blockImage[i][e] = getRandomGrass();
            }else if(worldDat[i][e] == 0){
                blockImage[i][e] = null;
            }else{
            blockImage[i][e] = eBlocks.intToImage(worldDat[i][e]);
            }
        }
    }
}

//used to get a random block
private Image getRandomGrass()
{
    Random rand = new Random();

    int r = rand.nextInt(2);
    r++;

    return eBlocks.intToImage(r);
}


public World(int[][] worldDat) {
    this.worldDat = worldDat;
}

}

然后在本课程中被称为（我相信这是问题的一部分）

公共类worldDraw {

//ALSO if there is a better way to do this, do tell
levels levels = new levels();
static levels sLevels = new levels();
World level1;
static World sLevel1 = new World(sLevels.getLevel1());

//called in paint method for panel
public void draw(Graphics2D g2){
    sLevel1.setupAll();
    for(int i = 0; i < 24; i++){
        for(int e = 0; i < 24; i++){
            g2.drawImage(level1.blockImage[i][e], e*25, i*25, null);
        }
    }

}

//holds levels
public worldDraw() {        
    level1 = new World(levels.getLevel1());
}
}

Answer 1

创建对象数组时，将创建引用数组，但未分配引用。在尝试使用它们之前，必须先执行此操作。认为它类似于创建鸡蛋纸箱。在先将鸡蛋装满纸箱之前，您不能使用任何鸡蛋。因此，例如您的blocks数组，首先需要将Rectangle对象分配给数组中的每个项目，然后才能对其调用方法。这通常在for循环中完成。例如，

for(int i = 0; i < 24; i++){
    for(int e = 0; e < 24; e++){       
        blocks[i][e] = new Rectangle(....); //...             
        blocks[i][e].setBounds(e * 20, i * 20, 20, 20);
        blocks[i][e].setLocation(e*20, i*20);