网络摄像头未运行时无法获取像素

当我将协程 TakePhoto 附加到按钮时，出现以下错误，有人可以帮忙吗？ 错误：

网络摄像头未运行时无法获取像素
UnityEngine.WebCamTexture:GetPixels()
GetCam/d__6:MoveNext ()（位于 Assets/GetCam.cs:52）
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)

Code我把它从

```
using UnityEngine;
using System.Collections;
using System.IO;
using UnityEngine.UI;


public class GetCam: MonoBehaviour 
{
    WebCamTexture webCam;
    string your_path = "C:\\Users\\Jay\\Desktop";
    public RawImage display;
    public AspectRatioFitter fit;

    public void Start() 
    {
         webCam = new WebCamTexture();
         webCam.Play();
         StartCoroutine(TakePhoto());
         display.texture = webCam;
         
    }
 
    public void Update(){


        float ratio = (float)webCam.width / (float)webCam.height;
        fit.aspectRatio = ratio;


        float ScaleY = webCam.videoVerticallyMirrored ? -1f: 1f;
        display.rectTransform.localScale = new Vector3(1f,ScaleY, 1f);

        int orient = -webCam.videoRotationAngle;
        display.rectTransform.localEulerAngles = new Vector3(0,0,orient);


        
    }

    IEnumerator TakePhoto()  // Start this Coroutine on some button click
    {

    // NOTE - you almost certainly have to do this here:

     yield return new WaitForEndOfFrame(); 

    // it's a rare case where the Unity doco is pretty clear,
    // http://docs.unity3d.com/ScriptReference/WaitForEndOfFrame.html
    // be sure to scroll down to the SECOND long example on that doco page 

        Texture2D photo = new Texture2D(webCam.width, webCam.height);
        photo.SetPixels(webCam.GetPixels());
        photo.Apply();

        //Encode to a PNG
        byte[] bytes = photo.EncodeToPNG();
        //Write out the PNG. Of course you have to substitute your_path for something sensible
        File.WriteAllBytes(your_path + "photo.png", bytes);
        //lol
    }
}