java 2d數組沒有正確填充

概述：我有一個「節點」的二維數組，它是一個簡單的對象，我有一個x和y座標並存儲一些基本值。java 2d數組沒有正確填充

網格是一個類，它將所有節點保存在其二維節點數組「節點」中。網格構造函數需要兩個參數：寬度和高度（x & y），然後使用座標（字段）與二維數組中的座標相匹配的節點填充二維數組，除了這樣做以外。出於某種原因，該陣列空物體填滿，並拋出一個NullPointerException每當我試圖全球化志願服務青年它們

public class Node { 

//fields 

public int x, y; //coordinates 
public int Fcost, Hcost; //values used for pathfinding. f is distance from user, h is distance from target. 
public boolean validity = false; 

//Constructors 
public Node(int x, int y) { 
    this.x = x; 
    this.y = y; 
} 

public Node(int x, int y, int F, int H) { 
    this.x = x; 
    this.y = y; 
    this.Fcost = F; 
    this.Hcost = H; 
} 

public Node(Node n) { 
    this.x = n.x; 
    this.y = n.y; 
    this.Fcost = n.Fcost; 
    this.Hcost = n.Hcost; 
} 



public boolean isValid() { 
    ////if out of bounds, return flase. 
    if (this.x >= Game.width) { 
     return false; 
    } 
    if (this.x < 0) { 
     return false; 
    } 
    if (this.y >= Game.height) { 
     return false; 
    } 
    if (this.y < 0) { 
     return false; 
    } 

    return true; 
} 

public void checkIfValid() { 
    this.validity = this.isValid(); 
}

public class Grid { 

public Node[][] nodes; 
private int length, height; 

///constructor 
//populates the grid with a new node for each coordinate 
public Grid(int x, int y) { 
    nodes = new Node[x + 1][y + 1]; 
    for (int i = 0; i < x; i++) { 
     for (int w = 0; w < y; w++) { 
      nodes[x][y] = new Node(x, y); 
      System.out.println("populating..."); 
     } 
    } 
    this.length = x; 
    this.height = y; 

    ////prints the number of nodes 
    int w = 0; 
    for (Node[] a : nodes) { 
     for (Node n : a) { 
      w++; 
     } 
    } 
    System.out.println("nodes " + w); 
} 

///methods 
public Node[] getNeighbors(Node in) { 
    ArrayList<Node> n = new ArrayList<>(); 

////NOT YET IMPLEMENTED 
    return (Node[]) n.toArray(); 
} 

///tells each node to check weather or not it is valid 
public void update() { 
    for (Node n[] : nodes) { 
     for (Node realNode : n) { 
      realNode.checkIfValid(); 
     } 
    } 
} 

}

編輯 - 這裏是打印出來。遊戲是爲其網格調用「更新」方法的類。

java.lang.NullPointerException 
at Pathfinding.Grid.update(Grid.java:55) 
at pkg2dgame.Game.tick(Game.java:62) 
at pkg2dgame.Game.run(Game.java:104) 
at java.lang.Thread.run(Thread.java:745)

來源

2016-09-22 joey101937

你能告訴我們的錯誤消息，從控制檯得到什麼？ –

你正在迭代我和w，但你總是分配給同一個節點（nodes [x] [y]應該是nodes [i] [w]？） – HomeIsWhereThePcIs

nodes[x][y] = new Node(x, y);應該nodes[i][w] = new Node(x, y);

您再植相同的索引所有的時間，由於所有的陣列桶是空的。您的代碼還有一個問題是，for循環不會循環到2d數組的末尾。

for (int i = 0; i < nodes.length; i++) { 
     for (int w = 0; w < nodes[i].length; w++) { 
      nodes[i][w] = new Node(x, y); 
      System.out.println("populating..."); 
     } 
}

正在對null值執行操作時拋出該錯誤。

來源

2016-09-22 00:07:46 Rishi

非常感謝你。完美的作品 – joey101937

填充節點正確

for (int i = 0; i < x; i++) { 
     for (int w = 0; w < y; w++) { 
      nodes[i][w] = new Node(i, w); 
      System.out.println("populating..."); 
     } 
    }

來源

2016-09-22 00:10:09 ravthiru

java 2d數組沒有正確填充

回答

相關問題