NullReferenceExceptionのエラーメッセージに困っています。

前提・実現したいこと

マインスイーパーを作っているのですが空白のセルを押すと以下のエラーメッセージが出ました。

発生している問題・エラーメッセージ

NullReferenceException: Object reference not set to an instance of an object
Cell.OnclickThis () (at Assets/Cell.cs:64)
UnityEngine.Events.InvokableCall.Invoke () (at <480508088aee40cab70818ff164a29d5>:0)
UnityEngine.Events.UnityEvent.Invoke () (at <480508088aee40cab70818ff164a29d5>:0)
UnityEngine.UI.Button.Press () (at C:/Program Files/Unity/Hub/Editor/2019.3.13f1/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Button.cs:68)
UnityEngine.UI.Button.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) (at C:/Program Files/Unity/Hub/Editor/2019.3.13f1/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/UI/Core/Button.cs:110)
UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (at C:/Program Files/Unity/Hub/Editor/2019.3.13f1/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/EventSystem/ExecuteEvents.cs:50)
UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) (at C:/Program Files/Unity/Hub/Editor/2019.3.13f1/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/EventSystem/ExecuteEvents.cs:261)
UnityEngine.EventSystems.EventSystem:Update() (at C:/Program Files/Unity/Hub/Editor/2019.3.13f1/Editor/Data/Resources/PackageManager/BuiltInPackages/com.unity.ugui/Runtime/EventSystem/EventSystem.cs:377)

該当のソースコード

C#
1using UnityEngine;
2using UnityEngine.UI;
3
4public class Cell : MonoBehaviour
5{
6    public Minesweeper minesweeper;
7    public Vector2Int positionCell;
8    public bool Open;
9
10    [SerializeField]
11    public GameObject m_button = null;
12
13    [SerializeField]
14    private Text _view = null;
15
16    [SerializeField]
17    private CellState _cellState = CellState.None;
18    public CellState CellState
19    {
20        get => _cellState;
21        set
22        {
23            _cellState = value;
24            OnCellStateChanged();
25        }
26    }
27
28    private void OnValidate()
29    {
30        OnCellStateChanged();
31    }
32
33    private void OnCellStateChanged()
34    {
35        if (_view == null) { return; }
36
37        if (_cellState == CellState.None)
38        {
39            _view.text = "";
40        }
41        else if (_cellState == CellState.Mine)
42        {
43            _view.text = "X";
44            _view.color = Color.red;
45        }
46        else
47        {
48            _view.text = ((int)_cellState).ToString();
49            _view.color = Color.blue;
50        }
51    }
52
53    public void CellOpen()
54    {
55        m_button.SetActive(false);
56        Open = true;
57    }
58    public void OnclickThis()
59    {
60        if (_cellState == CellState.None)
61        {
62            m_button.SetActive(false);
63            Open = true;
64            minesweeper.OpenCell(this);
65        }
66        else if (_cellState != CellState.Mine)
67        {
68            m_button.SetActive(false);
69            Open = true;
70        }
71        else
72        {
73            m_button.SetActive(false);
74            Open = true;
75        }
76    }
77}
78public enum CellState
79{
80    None = 0,
81    One = 1,
82    Two = 2,
83    Three = 3,
84    Four = 4,
85    Five = 5,
86    Six = 6,
87    Seven = 7,
88    Eight = 8,
89
90    Mine = -1,
91}

C#
1using System.Collections.Generic;
2using UnityEngine;
3using UnityEngine.UI;
4
5public class Minesweeper : MonoBehaviour
6{
7    [SerializeField]
8    private int _rows = 1;
9
10    [SerializeField]
11    private int _columns = 1;
12
13    [SerializeField]
14    private int _mineCount = 1;
15
16    [SerializeField]
17    private GridLayoutGroup _gridLayoutGroup = null;
18
19    [SerializeField]
20    private Cell _cellPrefab = null;
21
22    [SerializeField]
23    private Cell[,] _cells;
24
25    void Start()
26    {
27        var parent = _gridLayoutGroup.gameObject.transform;
28        if (_columns < _rows)
29        {
30            _gridLayoutGroup.constraint = GridLayoutGroup.Constraint.FixedColumnCount;
31            _gridLayoutGroup.constraintCount = _columns;
32        }
33        else
34        {
35            _gridLayoutGroup.constraint = GridLayoutGroup.Constraint.FixedRowCount;
36            _gridLayoutGroup.constraintCount = _rows;
37        }
38
39        _cells = new Cell[_rows, _columns];
40        for (var r = 0; r < _rows; r++)
41        {
42            for (var c = 0; c < _columns; c++)
43            {
44                var cell = Instantiate(_cellPrefab);
45                cell.transform.SetParent(parent);
46                _cells[r, c] = cell;
47            }
48        }
49
50        for (var i = 0; i < _mineCount;)
51        {
52            var r = Random.Range(0, _rows);
53            var c = Random.Range(0, _columns);
54            var cell = _cells[r, c];
55            if (cell.CellState != CellState.Mine)
56            {
57                cell.CellState = CellState.Mine;
58                i++;
59            }
60        }
61        for (var r = 0; r < _rows; r++)
62        {
63            for (var c = 0; c < _columns; c++)
64            {
65                if (_cells[r, c].CellState == CellState.Mine)
66                {
67                    AddMine(r, c);
68                }
69            }
70        }
71
72        //for (var r = 0; r < _rows; r++)
73        //{
74        //    for (var c = 0; c < _columns; c++)
75        //    {
76        //        // 周辺の地雷数を設定したいセル
77        //        var cell = _cells[r, c];
78        //        Debug.Log($"Cell[{r}, {c}]={cell.CellState}");
79
80        //        if (cell.CellState == CellState.Mine)
81        //        {
82        //            continue; // 地雷なら無視する
83        //        }
84
85        //        // 以下、泥臭く周辺のセルが地雷かどうか調べるコード
86        //        // ただしそのままだと不正なインデックスになるので注意
87        //        var count = 0;
88        //        if (_cells[r - 1, c - 1].CellState == CellState.Mine)
89        //        {
90        //            count++;
91        //        }
92        //        if (_cells[r - 1, c].CellState == CellState.Mine)
93        //        {
94        //            count++;
95        //        }
96        //        // etc...
97
98        //        // 最後に count をセルに設定する
99        //    }
100        //}
101    }
102
103    public void AddMine(int r, int c)
104    {
105        var left = c - 1;
106        var right = c + 1;
107        var top = r - 1;
108        var bottom = r + 1;
109
110        if (top >= 0)
111        {
112            if (left >= 0 && _cells[top, left].CellState != CellState.Mine) { _cells[top, left].CellState++; }
113            if (_cells[top, c].CellState != CellState.Mine) { _cells[top, c].CellState++; }
114            if (right < _columns && _cells[top, right].CellState != CellState.Mine) { _cells[top, right].CellState++; }
115        }
116        if (left >= 0 && _cells[r, left].CellState != CellState.Mine) { _cells[r, left].CellState++; }
117        if (right < _columns && _cells[r, right].CellState != CellState.Mine) { _cells[r, right].CellState++; }
118        if (bottom < _rows)
119        {
120            if (left >= 0 && _cells[bottom, left].CellState != CellState.Mine) { _cells[bottom, left].CellState++; }
121            if (_cells[bottom, c].CellState != CellState.Mine) { _cells[bottom, c].CellState++; }
122            if (right < _columns && _cells[bottom, right].CellState != CellState.Mine) { _cells[bottom, right].CellState++; }
123        }
124    }
125    public int GetMineCount(int r, int c)
126    {
127        var left = c - 1;
128        var right = c + 1;
129        var top = r - 1;
130        var bottom = r + 1;
131
132        var count = 0;
133        if (top >= 0)
134        {
135            if (left >= 0 && _cells[top, left].CellState == CellState.Mine) { count++; }
136            if (_cells[top, c].CellState == CellState.Mine) { count++; }
137            if (right < _columns && _cells[top, right].CellState == CellState.Mine) { count++; }
138        }
139        if (left >= 0 && _cells[r, left].CellState == CellState.Mine) { count++; }
140        if (right < _columns && _cells[r, right].CellState == CellState.Mine) { count++; }
141        if (bottom < _rows)
142        {
143            if (left >= 0 && _cells[bottom, left].CellState == CellState.Mine) { count++; }
144            if (_cells[bottom, c].CellState == CellState.Mine) { count++; }
145            if (right < _columns && _cells[bottom, right].CellState == CellState.Mine) { count++; }
146        }
147        return count;
148    }
149    private Cell[] SearchCell(int r, int c)
150    {
151        var list = new List<Cell>();
152
153        var left = c - 1;
154        var right = c + 1;
155        var top = r - 1;
156        var bottom = r + 1;
157
158        if (top >= 0)
159        {
160            if (left >= 0) { list.Add(_cells[top, left]); }
161            list.Add(_cells[top, c]);
162            if (right < _columns) { list.Add(_cells[top, right]); }
163        }
164        if (left >= 0) { list.Add(_cells[r, left]); }
165        if (right < _columns) { list.Add(_cells[r, right]); }
166        if (bottom < _rows)
167        {
168            if (left >= 0) { list.Add(_cells[bottom, left]); }
169            list.Add(_cells[bottom, c]);
170            if (right < _columns) { list.Add(_cells[bottom, right]); }
171        }
172
173        return list.ToArray();
174    }
175
176    public void OpenCell(Cell target)
177    {
178        //自分の座標を記憶
179        var x = target.positionCell.x;
180        var y = target.positionCell.y;
181
182        foreach (var item in SearchCell(x, y))
183        {
184            if (item.Open) //既にあいてたら次のセルへ
185            {
186                continue;
187            }
188            item.CellOpen(); //セルをあけてフラグをtrueにする
189            if (item.CellState == CellState.None)
190            {
191                OpenCell(item); //Noneなら再帰でNoneを探してあけていく
192            }
193        }
194    }
195}

試したこと

ここに問題に対して試したことを記載してください。

補足情報（FW/ツールのバージョンなど）

2019.3.13f1

行動規範の内容に同意します

回答2件

そいつはNullの変数を参照してるときに出ます
そこに出てるとこらへんで実行を止め、片っ端から変数のナカミをチェックしてみよう

投稿2021/06/14 21:33

y_waiwai

総合スコア87774

自己解決

c#
1for (var r = 0; r < _rows; r++)
2        {
3            for (var c = 0; c < _columns; c++)
4            {
5                var cell = Instantiate(_cellPrefab);
6                cell.positionCell = new Vector2Int(r, c);
7                //cell.minesweeper = this;
8                cell.transform.SetParent(parent);
9                _cells[r, c] = cell;
10            }
11        }