如何查找网格实例化位置？解决GetRandomRoadPoint返回null问题

我正在搭建一个用于程序化生成城镇的行人AI系统，初始采用Pack Publishing提供的Grid系统进行开发，以下是该系统的初始化代码：

public class Point
{
    public int X { get; set; }
    public int Y { get; set; }

    public Point(int x, int y)
    {
        this.X = x;
        this.Y = y;
    }

    public override bool Equals(object obj)
    {
        if (obj == null)
        {
            return false;
        }
        if (obj is Point)
        {
            Point p = obj as Point;
            return this.X == p.X && this.Y == p.Y;
        }
        return false;
    }

    public override int GetHashCode()
    {
        unchecked
        {
            int hash = 6949;
            hash = hash * 7907 + X.GetHashCode();
            hash = hash * 7907 + Y.GetHashCode();
            return hash;
        }
    }

    public override string ToString()
    {
        return "P(" + this.X + ", " + this.Y + ")";
    }
}

public enum CellType
{
    Empty,
    Road,
    Structure,
    SpecialStructure,
    None
}

public class Grid
{
    private CellType[,] _grid;
    private int _width;
    public int Width { get { return _width; } }
    private int _height;
    public int Height { get { return _height; } }

    private List<Point> _roadList = new List<Point>();
    private List<Point> _specialStructure = new List<Point>();
    private List<Point> _houseStructure = new List<Point>();

    public Grid(int width, int height)
    {
        _width = width;
        _height = height;
        _grid = new CellType[width, height];
    }

// 代码存在重复定义问题：重复声明了CellType和Grid类
public enum CellType
{
    Empty,
    Road,
    Structure,
    SpecialStructure,
    None
}

public class Grid
{
    private CellType[,] _grid;
    private int _width;
    public int Width { get { return _width; } }
    private int _height;
    public int Height { get { return _height; } }

    private List<Point> _roadList = new List<Point>();
    private List<Point> _specialStructure = new List<Point>();
    private List<Point> _houseStructure = new List<Point>();

    public Grid(int width, int height)
    {
        _width = width;
        _height = height;
        _grid = new CellType[width, height];
    }

    public void Update()
    {
        Console.Write("GRID IS RUNNING");
    }

    // 索引器：通过grid[i,j]访问单元格
    public CellType this[int i, int j]
    {
        get
        {
            return _grid[i, j];
        }
        set
        {
            if (value == CellType.Road)
            {
                _roadList.Add(new Point(i, j));
            }
            if (value == CellType.SpecialStructure)
            {
                _specialStructure.Add(new Point(i, j));
            }
            if (value == CellType.Structure)
            {
                _houseStructure.Add(new Point(i, j));
            }
            _grid[i, j] = value;
        }
    }

    // 获取随机道路点方法
    public Point GetRandomRoadPoint()
    {
        if (_roadList.Count == 0)
        {
            return null;
        }
        return _roadList[UnityEngine.Random.Range(0, _roadList.Count)];
    }
}

初始化后调用网格的代码：

public int width, height;
Grid placementGrid;

private void Start()
{
    placementGrid = new Grid(width, height);
    Debug.Log(placementGrid.GetRandomRoadPoint());
}

问题分析与解决方案 #

1. GetRandomRoadPoint返回null的直接原因

_roadList为空列表，说明没有任何道路类型的单元格被添加到网格中：

• 检查width和height变量：如果未赋值，默认值为0，会创建一个宽高为0的空网格，无法添加任何单元格。
• 当前Start方法仅初始化网格，未通过索引器placementGrid[i,j] = CellType.Road添加道路单元格，自然_roadList无数据。

2. 代码语法错误修复

提供的初始化代码存在重复定义类的问题：删除重复的CellType枚举和Grid类声明，保留包含索引器、Update方法及GetRandomRoadPoint方法的完整版本。

3. 查找网格实例化位置的方法

• 如果Grid是MonoBehaviour子类：在Unity Hierarchy窗口搜索Grid组件，或用FindObjectsOfType<Grid>()在代码中获取所有实例。
• 如果是普通C#类：在Grid构造函数中添加日志追踪调用位置：

  public Grid(int width, int height)
  {
      _width = width;
      _height = height;
      _grid = new CellType[width, height];
      // 输出调用构造函数的方法信息
      Debug.Log($"Grid实例化于：{new System.Diagnostics.StackTrace().GetFrame(1).GetMethod().Name}");
  }
  

修复后的示例调用代码 #

public int width = 10, height = 10; // 给宽高赋值
Grid placementGrid;

private void Start()
{
    placementGrid = new Grid(width, height);
    // 添加一行道路单元格
    for (int i = 0; i < width; i++)
    {
        placementGrid[i, 5] = CellType.Road;
    }
    Point randomRoad = placementGrid.GetRandomRoadPoint();
    Debug.Log(randomRoad?.ToString() ?? "无可用道路点");
}

内容的提问来源于stack exchange，提问作者VChuckShunA