玩家可以跳两次。 | Unity C＃

Question

在我的代码中，玩家只应该跳一次。但是玩家跳了起来，并且“IsGrounded”我仍然是真的，直到玩家再次跳起来。有人可以帮忙吗？

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class player_controller : MonoBehaviour {

    public int speed = 5;

    public Vector3 jump;
    public int jumpForce = 2;

    public bool isGrounded;
    Rigidbody rb;

    private string JumpButton = "Jump";

    // Use this for initialization
    void Start ()
    {
        rb = GetComponent<Rigidbody>();
        jump = new Vector3(0.0f, 2.0f, 0.0f);
    }

    void OnCollisionStay()
    {
        isGrounded = true;
    }

    // Update is called once per frame
    void Update () {
       transform.Translate(speed * Input.GetAxis("Vertical") * Time.deltaTime, 0f, speed * Input.GetAxis("Horizontal") * Time.deltaTime);

        if (Input.GetKeyDown(KeyCode.Space) && isGrounded)
        {
            isGrounded = false;
            rb.AddForce(jump * jumpForce, ForceMode.Impulse);

        }
    }
}