c# - 在 Unity 中使用 getComponent 从附加到游戏对象的脚本中获取图像

Question

我正在尝试引入雷达扫描功能，以便在单击按钮时雷达上的图像会根据对象的标签更新为新图像。我在雷达扫描脚本的 Enemy.GetComponent 行收到“NullReferenceException:对象引用未设置为对象的实例”。但我有图像集？我现在将在下面显示的点 1

我是不是访问错了？这是我的 RadarScan 脚本

public class RadarScan : MonoBehaviour
{
GameObject Enemy;
Image RadarImageToChange;

void Start()
{
    Enemy = GameObject.Find("Enemy");
}

public void ChangeImage(Image UpdateImage)
{
    if (Enemy.tag == "Enemy")
    {
        RadarImageToChange = Enemy.GetComponent<MakeRadarObject>().image;
        UpdateImage = RadarImageToChange;
    }

}
}

这是我的雷达脚本

public class RadarObject
{
    public Image icon { get; set; }
    public GameObject owner { get; set; }
}

public class Radar : MonoBehaviour {

public Transform playerPos; //position of player
float mapScale = 0.1f; //scale radar size

public static List<RadarObject> radObjects = new List<RadarObject>();

//Registers Object to the radar
public static void RegisterRadarObject(GameObject o, Image i)
{
    Image image = Instantiate(i);
    radObjects.Add(new RadarObject() { owner = o, icon = image }); //adds to List
}

//It loops through the list looking for the owner existing in the list, when it finds the owner is detroys the icon
public static void RemoveRadarObject(GameObject o)
{
    //New list for destroyed objects
    List<RadarObject> newList = new List<RadarObject>();
    for (int i = 0; i < radObjects.Count; i++)
    {
        if (radObjects[i].owner == o)
        {
            Destroy(radObjects[i].icon);
            continue;
        }
         else
            newList.Add(radObjects[i]);
        }
    radObjects.RemoveRange(0, radObjects.Count);
    radObjects.AddRange(newList);
}


void DrawRadarDots()
{
    //loops through the list and for each Object it gets the owners transform position and determins the difference between it's
    //position and the players position, does calculations on the angle and distance and position on a circle using polar equations.
    foreach (RadarObject ro in radObjects)
    {
        Vector3 radarPos = (ro.owner.transform.position - playerPos.position);
        float distToObject = Vector3.Distance(playerPos.position, ro.owner.transform.position) * mapScale;
        float deltay = Mathf.Atan2(radarPos.x, radarPos.z) * Mathf.Rad2Deg - 270 - playerPos.eulerAngles.y;
        radarPos.x = distToObject * Mathf.Cos(deltay * Mathf.Deg2Rad) * -1;
        radarPos.z = distToObject * Mathf.Sin(deltay * Mathf.Deg2Rad);

        //grabs icon of players objects and make it a child of panel and set it's postion based on radarPos.x and radarPos.z
        ro.icon.transform.SetParent(this.transform);
        ro.icon.transform.position = new Vector3(radarPos.x, radarPos.z, 0) + this.transform.position;
    }
}

    //Update is called once per frame
    void Update ()
    {
        DrawRadarDots();
    }
 }

这是我的堆栈跟踪

Answer 1

but I have a image set

不是真的。您对变量成员资格和/或如何 GetComponent() 有误解有效。

GetComponent()方法(及其变体)用于获取 Component附加到 GameObject 直接。它不会识别/查找组件的成员(包括变量)；只有组件本身； 即使这些成员属于 Type Component .

这意味着 null你在 Enemy.GetComponent<Image>();没有被扔在 Image 上引用。正如您所说，那个已经设置好了。

---

问题出自GetComponent本身:

图像组件未附加到 GameObject ;相反，它的reference 被设置为 MakeRadarObject 中的member 组件。

因此， GetComponent没有找到任何 Image附加到 GameObject 的组件, 所以它返回 null ;正如它应该的那样。