How do you make a 2D Rigidbody "Jump" Once in Unity?

I’m currently developing a simple 2d game, and of course do to the fact that unity’s fricken awesome, I’ve selected this to make a game rather than just hard coding it or using gamemaker. My character currently can walk right and left, but,

HOW can I make the character jump? All the ways that I’ve tried make the player just rise continually. People say to create a boolean object like “isGrounded” and it is controlled by “Physics.Raycast” and a long line with transform.position and stuff. The problem was however, that isGrounded won’t change.

I’m using Unity 4.6.0f. The character has an animator with an idle animation, a Box Collider 2d, Rigidbody 2D, and PlayerScript.

This is the Code:

using UnityEngine;
using System.Collections;

public class Player : MonoBehaviour {

	public float speed = 10f;
	public Vector2 maxVelocity = new Vector2(3, 5);
	public bool standing;
	public float jumpHeight = 12f;
	public float airSpeedMuiltiplier = 0.3f;
	public RaycastHit hit;

	public Transform tran;

	public bool isGrounded;

	void Start () {
		tran = transform;
	}

	void Update () {
		var forceX = 0f;
		var forceY = 0f;

		var absVelX = Mathf.Abs(rigidbody2D.velocity.x);
		var absVelY = Mathf.Abs(rigidbody2D.velocity.y);

		if(Physics.Raycast (tran.position, -tran.up, 7777f)) {
			isGrounded = true;
			if(hit.transform.tag == "Terrain") {
				isGrounded = true;
			} else {
				isGrounded = false;
			}
		} else {
			isGrounded = false;
		}

		if(Input.GetKey ("right") || Input.GetKey (KeyCode.D)) {
			if(absVelX < maxVelocity.x) {
				forceX = speed;
			}

			transform.localScale = new Vector3(1, 1, 1);
		} else if(Input.GetKey ("left") || Input.GetKey (KeyCode.A)) {
			if(absVelX < maxVelocity.x) {
				forceX = -speed;
			}
			transform.localScale = new Vector3(-1, 1, 1);
		} else if((Input.GetKeyDown ("up") || Input.GetKey (KeyCode.W)) && isGrounded) {
			rigidbody2D.AddForce(new Vector2(0, 54f));
		}

		rigidbody2D.AddForce(new Vector2(forceX, forceY));

	}

}

Thanks in Advance!

First of all this is how I would do the ground check

float isGroundedRayLength =0.1f;
LayerMask layerMaskForGrounded;
public bool isGrounded {
				get {
						Vector3 position = transform.position;
						position.y = GetComponent<Collider2D> ().bounds.min.y + 0.1f;
						float length = isGroundedRayLength + 0.1f;
						Debug.DrawRay (position, Vector3.down * length);
						bool grounded = Physics2D.Raycast (position, Vector3.down, length, layerMaskForGrounded.value);
						return grounded;
				}
		}

This enables checking of the very lowest part of your collider and also has a layer mask which if you make public gives you a drop down list of what physics layers to collide with.

Aswell I would caution restraint on using hard coded values and addforce as they are generally bad practice when making something with the requirement to have precise control over your speed as stopping when using addforce is not simple.

The more common way I’ve seen it done and also used many times is similar to this

		float speed =5f;
void Update(){
                rigidbod2D = GetComponent<Rigidbody2D> ();
                Vector2 move = rigidbod2D.velocity;
		float hor = Input.GetAxis ("Horizontal");

		move.x = hor * speed;
		if (Input.GetButtonDown ("Jump")&&isGrounded) {
			move.y = jumpSpeed;
		}
		rigidbod2D.velocity = move;
}

this gives a lot more control is very clean and allows for multiple different types of input natively(keyboard(wasd and arrows) and controllers) if that matters to you. Hope this was helpful

if(Input.GetButtonDown(“Jump”) && Mathf.Approximately(rigid.velocity.y,0))
{
rigid.AddForce(new Vector2(0, jumpSpeed) * movementSpeed * Time.deltaTime, ForceMode2D.Impulse);
}