unity c# script with 2 rigid bodies. jumping not working when one rigid body has been onto of the other

Question

second rigid body uses the same script as the first one but with "& player number == 1" in the if-instances.

problem is if the first rigid body jumps on top of the other and then jumps off, the second one will not be able to jump at all. (and vice versa)

what would be a simple solution for this?

using UnityEngine;

using System.Collections;

public class PlayerController : MonoBehaviour 
{

//Movement
public float speed;
public float jump;
float moveVelocity;

//Grounded Vars
bool grounded = true;

int playernumber;


void Update () 
{
    if (Input.GetKeyDown (KeyCode.Alpha1)) {
        playernumber = 1;
    }

    if (Input.GetKeyDown (KeyCode.Alpha2)) {
        playernumber = 2;
    }

    if (Input.GetKeyDown (KeyCode.Alpha3)) {
        playernumber = 3;
    }
    //Jumping   
    if ((Input.GetKeyDown (KeyCode.Space) || Input.GetKeyDown (KeyCode.UpArrow) || Input.GetKeyDown (KeyCode.Z) || Input.GetKeyDown (KeyCode.W))  & playernumber == 1  ) 
    {
        if(grounded)
        {
            GetComponent<Rigidbody2D> ().velocity = new Vector2 (GetComponent<Rigidbody2D> ().velocity.x, jump);
        }
    }



    moveVelocity = 0;

    //Left Right Movement
    if ((Input.GetKey (KeyCode.LeftArrow) || Input.GetKey (KeyCode.A)) & playernumber == 1 ) 
    {
        moveVelocity = -speed;
    }
    if ((Input.GetKey (KeyCode.RightArrow) || Input.GetKey (KeyCode.D)) & playernumber == 1 ) 
    {
        moveVelocity = speed;
    }

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

}

//Check if on the ground
void OnTriggerEnter2D()
{
    grounded = true;
}
void OnTriggerExit2D()
{
    grounded = false;
}
}

Answer 1

These trigger events are fired once when the actual events occur and thus:

1. player1 and player2 spawn and touch the floor or smt. along thosel lines => the onTriggerEnter event is fired for both and they are both grounded
2. player1 jumps on player2
   • player1 jumps => onTriggerExit - not grounded
   • player1 lands on player2 => onTriggerEnter fires for both players and they are both grounded
3. player1 jumps off of player2 => onTriggerExit fires for both - both are not grounded
   • player1 then hits the floor and triggers onTriggerEnter, so he's grounded, but player2 doesn't meaning he's not grounded and thus cannot jump

You could quite simply just set the grounded to false when the user jumps and only reset it to true using the onTriggerEnter and scrap the onTriggerExit:

if(grounded){
    GetComponent<Rigidbody2D> ().velocity = new Vector2 (GetComponent<Rigidbody2D> ().velocity.x, jump);
    grounded = false;
}

Edit: I failed to notice that both trigger methods don't match their appropriate signatures in your code as they miss a Collider2D parameter.

void OnTriggerEnter2D(Collider2D collider) {
    grounded = true;
}