處理圖形錯誤

Question

我做了一個使用二維數組繪製網格的程序，但是我得到一個空指針異常。這裏是我的代碼：

Cell[][] Cells; 
void setup(){ 
    size(500,500); 
    background(255); 
    for (int x = 0; x < 50; x++) { 
    for (int y = 0; y < 50; y++) { 
     Cells[x][y] = new Cell(round(random(255)),x * 10,y * 10,10,10); 
    } 
    } 
} 
void draw(){ 
    for (int x = 0; x < 50; x++) { 
    for (int y = 0; y < 50; y++) { 
     Cells[x][y].Draw(); 
    } 
    } 
} 
class Cell{ 
    int X; 
    int Y; 
    int Width; 
    int Height; 
    int Color; 
    Cell(int C,int X,int Y,int Width,int Height){ 
    Color = C; 
    X = X; 
    Y = Y; 
    Width = Width; 
    Height = Height; 
    } 
    void Draw(){ 
    fill(Color); 
    rect(X,Y,Width,Height); 
    } 
} 

，這裏是錯誤消息：

Exception in thread "Animation Thread" java.lang.NullPointerException 
    at Grid.setup(Grid.java:27) 
    at processing.core.PApplet.handleDraw(PApplet.java:2103) 
    at processing.core.PGraphicsJava2D.requestDraw(PGraphicsJava2D.java:190) 
    at processing.core.PApplet.run(PApplet.java:2006) 
    at java.lang.Thread.run(Thread.java:662) 

我究竟做錯了什麼？

Answer 1

你錯過了創建磁盤陣列：

Cell[][] cells = new Cell[50][50];