Where is the error in my script causing my player to not be able to jump after jumping into a wall?

Question

I have been coding a game for about an hour now and I have run into an error with my script that I can't seem to fix. What I mainly seem to be focusing on is the isGrounded update part of my script:

    private void OnCollisionExit2D(Collision2D collision)
    {
        isGrounded = false;

    }
    private void OnCollisionEnter2D(Collision2D collision2)
    {
        isGrounded = true;
    }

But I am concerned it might be a different part of my script because I don't think anything is wrong with this part. Here is the full script:

using UnityEngine;
using System.Collections;

public class move : MonoBehaviour
{

    public float speed;
    float moveVelocity;

    public float jumpPower = 300.0f;
    private bool isGrounded = false;
    private bool facingEast = false;

    void Update()
    {

        moveVelocity = 0;

        //Left Right Movement
        if (Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A))
        {
            moveVelocity = -speed;
            facingEast = false;
        }
        if (Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D))
        {
            moveVelocity = speed;
            facingEast = true;
        }

        GetComponent<Rigidbody2D>().velocity = new Vector2(moveVelocity, GetComponent<Rigidbody2D>().velocity.y);

        Rigidbody2D rb = GetComponent<Rigidbody2D>();
        if (Input.GetKeyDown(KeyCode.UpArrow) || Input.GetKeyDown(KeyCode.Space))
        {
            if (isGrounded == true)
            {
                rb.AddForce(Vector2.up * jumpPower);
            }
        }

    }
    private void OnCollisionExit2D(Collision2D collision)
    {
        isGrounded = false;

    }
    private void OnCollisionEnter2D(Collision2D collision2)
    {
        isGrounded = true;
    }
}

Sorry if this is a bad question or if there is an obvious answer and I am just being stupid. I am still fairly new to C#

Answer 1

In general in OnCollisionEnter2D and OnCollisionExit2D you should check what you are colliding with!

e.g. using Tags and CompareTag like

private void OnCollisionExit2D(Collision2D collision)
{
    if(!collision.transform.CompareTag("Ground")) return;

    // only do this if the thing you don't collide 
    // anymore is actually the ground
    isGrounded = false;
}

private void OnCollisionEnter2D(Collision2D collision2)
{
    if(!collision.transform.CompareTag("Ground")) return;

    // only do this if the thing you collided with is actually the ground
    isGrounded = true;
}

otherwise what happens when you collide with a wall is a OnCollisionEnter2D followed by a OnCollisionExit2D => isGrounded = false;

---

Also in general: Don't use GetComponent in Update and especially not for getting the same reference in 3 different places!

Rather get it once in Awake or already assign it via the Inspector

// already assign via the Inspector by drag&drop
[SerializeField] private Rigidbody2D _rigidbody;

// as fallback assign ONCE in the beginning
private void Awake()
{
    if(!_rigidbody) _rigidbody = GetComponent<Rigidbody2D>();
}

and later reuse it

void Update()
{
    moveVelocity = 0;

    //Left Right Movement
    if (Input.GetKey(KeyCode.LeftArrow) || Input.GetKey(KeyCode.A))
    {
        // I would use -= and += here so when pressing both buttons
        // you simply stay at 0. But that's only my opinion of course
        // Alternatively I would use 'else if' in order to make the blocks exclusive
        moveVelocity -= speed;
        facingEast = false;
    }
    if (Input.GetKey(KeyCode.RightArrow) || Input.GetKey(KeyCode.D))
    {
        moveVelocity += speed;
        facingEast = true;
    }

    _rigidbody.velocity = new Vector2(moveVelocity, _rigidbody.velocity.y);

    // here it is cheeper to first check the isGrounded flag
    // and only if it is true get the input
    if (isGrounded && (Input.GetKeyDown(KeyCode.UpArrow) || Input.GetKeyDown(KeyCode.Space)))
    {
        _rigidbody.AddForce(Vector2.up * jumpPower);
    }
}