c# - Unity NullReferenceException 是 Die Im 类的对象，实际上是 Null，我该如何解决这个问题？

Question

我是统一的新手，并且对我遇到问题的一段代码有疑问。当我在主脚本中声明对象时，它会正确呈现空白精灵，但是当我尝试调用 PlaceMultiplier 函数时，它会抛出 NullReferenceException。我希望得到修复并从解释中学习，谢谢！

使用 UnityEngine；使用 System.Collections；

公共类死：MonoBehaviour {

public Sprite Dice1;
public Sprite Blank;
public Sprite Multiplier1;
public Sprite Multiplier2;
public Sprite Multiplier3;
public Sprite Multiplier4;
public Sprite Multiplier5;
public Sprite Multiplier6;
public Sprite Multiplier7;
public Sprite Multiplier8;


// Use this for initialization
void Start () {

    if ((this != null)) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Blank;
    }

}

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

}

public void PlaceMultiplier(int multiple){


    if (multiple == 2) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier1;
    }

    if (multiple == 3) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier2;
    }

    if (multiple == 7) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier3;
    }

    if (multiple == 8) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier4;
    }

    if (multiple == 9) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier5;
    }

    if (multiple == 10) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier6;
    }

    if (multiple == 15) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier7;
    }

    if (multiple == 25) {
        this.gameObject.GetComponent<SpriteRenderer> ().sprite = Multiplier8;
    }

}

}