无法修复Unity中的单行为脚本问题

Question

我刚开始使用Unity并使用它的Standard Assets库。我使用了它的rollerball对象，但是它的Ball和BallUserControl脚本都给了我以下错误：

  

文件中没有Monobehaviour脚本，或者名称与文件名不匹配。

我没有更改任何脚本，并且我的环境中没有其他对象或脚本。类名与文件名匹配。我确定我缺少明显的东西（太新了）。有哪些可能的错误？ 我正在Windows 10上运行最新版本的unity。

这是BallUserControl脚本，根据要求：

using System;
using UnityEngine;
using UnityStandardAssets.CrossPlatformInput;

namespace UnityStandardAssets.Vehicles.Ball
{
    public class BallUserControl : MonoBehaviour
    {
        private Ball ball; // Reference to the ball controller.

        private Vector3 move;
        // the world-relative desired move direction, calculated from the camForward and user input.

        private Transform cam; // A reference to the main camera in the scenes transform
        private Vector3 camForward; // The current forward direction of the camera
        private bool jump; // whether the jump button is currently pressed


        private void Awake()
        {
            // Set up the reference.
            ball = GetComponent<Ball>();


            // get the transform of the main camera
            if (Camera.main != null)
            {
                cam = Camera.main.transform;
            }
            else
            {
                Debug.LogWarning(
                    "Warning: no main camera found. Ball needs a Camera tagged \"MainCamera\", for camera-relative controls.");
                // we use world-relative controls in this case, which may not be what the user wants, but hey, we warned them!
            }
        }


        private void Update()
        {
            // Get the axis and jump input.

            float h = CrossPlatformInputManager.GetAxis("Horizontal");
            float v = CrossPlatformInputManager.GetAxis("Vertical");
            jump = CrossPlatformInputManager.GetButton("Jump");

            // calculate move direction
            if (cam != null)
            {
                // calculate camera relative direction to move:
                camForward = Vector3.Scale(cam.forward, new Vector3(1, 0, 1)).normalized;
                move = (v*camForward + h*cam.right).normalized;
            }
            else
            {
                // we use world-relative directions in the case of no main camera
                move = (v*Vector3.forward + h*Vector3.right).normalized;
            }
        }


        private void FixedUpdate()
        {
            // Call the Move function of the ball controller
            ball.Move(move, jump);
            jump = false;
        }
    }
}