NullReferenceException：开始动画时未将对象引用设置为对象的实例[重复]

有一个类player包含停止( stopPlayerAnim) 和启动( startPlayerAnim) 播放器动画的功能，以及启动Joystic它们的类。但是当我按下操纵杆时，游戏崩溃并出现以下错误：

NullReferenceException：对象引用未设置为对象的实例 player.startPlayerAnim ()（位于 Assets/scripts/player.cs:46）Joystic.OnDrag (UnityEngine.EventSystems.PointerEventData eventData)（位于 Assets/scripts/Joystic.cs： 13) UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IDragHandler handler, UnityEngine.EventSystems.BaseEventData eventData) (在Library/PackageCache/com.unity.ugui@1.0.0/Runtime/EventSystem/ExecuteEvents.cs:71) UnityEngine.EventSystems.ExecuteEvents.Execute[T]（UnityEngine.GameObject 目标，UnityEngine.EventSystems.BaseEventData eventData，UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] 函子）（在 Library/PackageCache/com.unity.ugui@1.0 .0/Runtime/EventSystem/ExecuteEvents.cs:262) UnityEngine.EventSystems.EventSystem:Update()（在 Library/PackageCache/com.unity.ugui@1.0。0/运行时/EventSystem/EventSystem.cs:385)>

错误指的是这一行：player1.GetComponent<Animator>().SetBool("ball_anim", true);

是什么原因造成的，如何消除？上述脚本的代码如下：

播放器.cs：

public class player : MonoBehaviour
{
  
    public static GameObject player1;
    
    void Start()
    {
     
    }
    
    public static void startPlayerAnim()
    {

        player1.GetComponent<Animator>().SetBool("ball_anim", true);
        player1.GetComponent<Animator>().SetBool("inverted_ball_anim", false);
    }

    public static void stopPlayerAnim()
    {

        player1.GetComponent<Animator>().SetBool("ball_anim", false);
        player1.GetComponent<Animator>().SetBool("inverted_ball_anim", false);
    }

    public static void startInvertedPlayerAnim()
    {
        player1.GetComponent<Animator>().SetBool("inverted_ball_anim", true);
        player1.GetComponent<Animator>().SetBool("ball_anim", false);

    }
   
    

  
    

   

    
}