OnTriggerEnter2D and OnTriggerExit2D are firing each frame of a collision and OnTriggerStay2D never fires

Question

So I'm basically making pong and lethal league combined, the paddles start with no collision until a certain key is pressed then the collider is enabled. OnTriggerEnter2D stops the ball, OnCollisionStay2D adds to an acceleration variable while the ball is still colliding, and OnTriggerExit2D flips the direction of the ball and applies the acceleration.

The problem I'm having right now is that Enter and Exit are being called every frame of the collision instead of the first frame and the frame after collision respectively, and Stay is never called at all, but that part is understandable.

Even if I comment out the OnTriggerExit2D function, which again applies the new speed and flips the direction, and essentially make the ball stop on collision, OnTriggerEnter2D will still fire each frame despite nothing moving.

I tried taking this to my professor but he wasn't of much help, I don't think I'll be able to get any help on this unless it's from here or I take my laptop to his office to show him what's going on. Please help

void OnTriggerStay2D(Collider2D c)
{
    if (c.gameObject.transform.tag.StartsWith("Paddle") && acceleration <= 1)
    {
        acceleration += 0.1f;
    }
}

void OnTriggerExit2D(Collider2D c)
{
    if (c.gameObject.CompareTag("PaddleLeft"))
    {
        dir.x = 1;
        speed = tempSpeed + acceleration;
    }

    if (c.gameObject.CompareTag("PaddleRight")
    {
        dir.x = -1;
        speed = tempSpeed + acceleration;
    }
}

void OnTriggerEnter2D(Collider2D c)
{
    if (c.gameObject.transform.tag.StartsWith("Paddle"))
    {
        tempSpeed = speed;
        speed = 0;
        acceleration = 0;
    }
 }

Answer 1

Always start by logging. If you try to infer which functions are being called based on the behavior you see in the game, you may misunderstand what is happening.

For example:

void OnTriggerStay2D(Collider2D c) {
    Debug.Log($"{this} OnTriggerStay2D N:{c.name} T:{c.tag}", this);
    if (c.gameObject.tag.StartsWith("Paddle") && acceleration <= 1) {
        acceleration += 0.1f;
    }
}

Then in the console, you'll see a message like

ball OnTriggerStay2D N:paddle T:PaddleLeft

Adding a similar log message for each trigger function will help you understand exactly what is happening.

I don't think it will affect functionality, but for consistency, you should access the tag from the same place. Right now you do c.gameObject.CompareTag() in some places and c.gameObject.transform.tag in other places. You can simplify the latter to c.gameObject.tag, or simplify even further and use c.tag and c.CompareTag().

Answer 2

My issue wasn’t the OnTrigger functions, aside from a few changes after the fix they behave as intended. My problem was actually cause from how I was enabling and disabling the colliders on the paddles. I was setting the colliders to false in the update function and then using Input.GetKey to detect if the key is pressed. So Unity thought it was a new collision each frame because it was. I fixed the issue by simply moving the lines of code that were disabling the colliders into else statements after the if statements containing the GetKey