Question

我正在尝试循环遍历卡片对象的2D数组并在Unity场景中实例化它们。但是，在尝试实例化它时，我得到一个Null引用异常。以下是实例化对象的代码：

//Setting up initial board
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 4; j++){
            //Checked with debug.log, this should work Debug.Log (board[j, i].name);
            Debug.Log(board[j, i].name);
            temp = Instantiate(board[j,i]) as GameObject;
            CardScript cs = temp.GetComponent<CardScript>();
            objectBoard[j, i] = cs;
            //Setting locations of the cards
            objectBoard[j, i].transform.position = new Vector3(30 * j + 20, 50 * i +   70, 0);
        }
    }

错误发生在'CardScript cs = new ....行中我最初在temp = Instantiate ...行中有错误，当代码是GameObject temp = Instantiate ....它修复了我做的时候在代码中临时一个私有的GameObject变量。我不认为我能用这个做到这一点，因为我需要引用我正在实例化的每个单独的对象。

完整代码：

public class MatchScript : MonoBehaviour {

public CardScript[] potentialCards;

private CardScript[,] board;
private CardScript[,] objectBoard;
private List<CardScript> entries;
private GameObject temp;


// Use this for initialization
void Start () {
    entries = new List<CardScript> ();
    objectBoard = new CardScript[4,3];
    board = new CardScript[4, 3];
    foreach (CardScript c in potentialCards)
        entries.Add (c);
    foreach (CardScript c in potentialCards)
        entries.Add (c);

    //Loading up the board
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 4; j++){
            int k = Random.Range(0, entries.Count);
            board[j, i] = entries[k];

            entries.RemoveAt(k);
        }
    }

    //Setting up initial board
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 4; j++){
            //Checked with debug.log, this should work Debug.Log (board[j, i].name);
            Debug.Log(board[j, i].name);
            temp = Instantiate(board[j,i]) as GameObject;
            CardScript cs = temp.GetComponent<CardScript>();
            objectBoard[j, i] = cs;
            //Setting locations of the cards
            objectBoard[j, i].transform.position = new Vector3(30 * j + 20, 50 * i + 70, 0);
        }
    }
}

// Update is called once per frame
void Update () {

}

Answer 1

我不确定为什么会这样。但你可以通过改变来解决这个问题

temp = Instantiate(board[j,i]) as GameObject;

到

temp = Instantiate(board[j,i].gameObject) as GameObject;

Answer 2

“expression as Type”子句将表达式强制转换为Type当且仅当实际类型的表达式派生自Type时，否则返回null。

Instantiate生成一个传递的对象的独立副本，当然，它具有CardScript类型。现在，存在一些可能的误解：GameObject是Unity场景中所有“实体”的基类，但不包括您自己创建的所有类。如果CardScript是您创建的类，并且它没有显式继承任何类，那么它将继承System.Object（它是所有 C＃类的基类）。

如果CardScript派生自GameObject，那么你也应该提供该类。

Unity - 实例化新对象时的Null引用

2 个答案: