Unity 2D health bar

Question

I am new to coding and Unity

I have the health bar appearing on my screen, but I am not sure how to link the Health script of the health bar to my player script and my player's health script. Simply, I want to make it so when my player gets shot my health bar will lose a heart

my health bar script

using UnityEngine;
using System.Collections;

public class Health : MonoBehaviour {

    public int startHealth;
    public int healthPerHeart;

    private int maxHealth;
    private int currentHealth;

    public Texture[] heartImages;
    public GUITexture heartGUI;

    private ArrayList hearts = new ArrayList();

    // Spacing:
    public float maxHeartsOnRow;
    private float spacingX;
    private float spacingY;


    void Start () {
        spacingX = heartGUI.pixelInset.width;
        spacingY = -heartGUI.pixelInset.height;

        AddHearts(startHealth/healthPerHeart);
    }

    public void AddHearts(int n) {
        for (int i = 0; i <n; i ++) { 
            Transform newHeart = ((GameObject)Instantiate(heartGUI.gameObject,this.transform.position,Quaternion.identity)).transform; // Creates a new heart
            newHeart.parent = transform;

            int y = (int)(Mathf.FloorToInt(hearts.Count / maxHeartsOnRow));
            int x = (int)(hearts.Count - y * maxHeartsOnRow);

            newHeart.GetComponent<GUITexture>().pixelInset = new Rect(x * spacingX,y * spacingY,58,58);
            newHeart.GetComponent<GUITexture>().texture = heartImages[0];
            hearts.Add(newHeart);

        }
        maxHealth += n * healthPerHeart;
        currentHealth = maxHealth;
        UpdateHearts();
    }


    public void modifyHealth(int amount) {
        currentHealth += amount;
        currentHealth = Mathf.Clamp(currentHealth,0,maxHealth);
        UpdateHearts();
    }

    void UpdateHearts() {
        bool restAreEmpty = false;
        int i =0;

        foreach (Transform heart in hearts) {

            if (restAreEmpty) {
                heart.guiTexture.texture = heartImages[0]; // heart is empty
            }
            else {
                i += 1; // current iteration
                if (currentHealth >= i * healthPerHeart) {
                    heart.guiTexture.texture = heartImages[heartImages.Length-1]; // health of current heart is full
                }
                else {
                    int currentHeartHealth = (int)(healthPerHeart - (healthPerHeart * i - currentHealth));
                    int healthPerImage = healthPerHeart / heartImages.Length; // how much health is there per image
                    int imageIndex = currentHeartHealth / healthPerImage;


                    if (imageIndex == 0 && currentHeartHealth > 0) {
                        imageIndex = 1;
                    }

                    heart.guiTexture.texture = heartImages[imageIndex];
                    restAreEmpty = true;
                }
            }

        }
    }
}

my player script

/// <summary>
/// Player controller and behavior
/// </summary>
public class PlayerScript : MonoBehaviour
{
    public Health health;
    /// <summary>
    /// 1 - The speed of the ship
    /// </summary>
    public Vector2 speed = new Vector2(50, 50);

    // 2 - Store the movement
    private Vector2 movement;

    void OnCollisionEnter2D(Collision2D collision)
    {
        bool damagePlayer = false;

        // Collision with enemy
        EnemyScript enemy = collision.gameObject.GetComponent<EnemyScript>();
        if (enemy != null)
        {
            // Kill the enemy
            HealthScript enemyHealth = enemy.GetComponent<HealthScript>();
            if (enemyHealth != null) enemyHealth.Damage(enemyHealth.hp);

            damagePlayer = true;

        }

        // Damage the player
        if (damagePlayer)
        {
            HealthScript playerHealth = this.GetComponent<HealthScript>();
            if (playerHealth != null) playerHealth.Damage(1);

        }
    }



    void Update()
    {
        // 3 - Retrieve axis information
        float inputX = Input.GetAxis("Horizontal");
        float inputY = Input.GetAxis("Vertical");

        // 4 - Movement per direction
        movement = new Vector2(
            speed.x * inputX,
            speed.y * inputY);

        // 5 - Shooting
        bool shoot = Input.GetButtonDown("Fire1");
        shoot |= Input.GetButtonDown("Fire2");
        // Careful: For Mac users, ctrl + arrow is a bad idea

        if (shoot)
        {
            WeaponScript weapon = GetComponent<WeaponScript>();
            if (weapon != null)
            {
                // false because the player is not an enemy
                weapon.Attack(false);
            }
        }
        // 6 - Make sure we are not outside the camera bounds
        var dist = (transform.position - Camera.main.transform.position).z;

        var leftBorder = Camera.main.ViewportToWorldPoint(
            new Vector3(0, 0, dist)
            ).x;

        var rightBorder = Camera.main.ViewportToWorldPoint(
            new Vector3(1, 0, dist)
            ).x;

        var topBorder = Camera.main.ViewportToWorldPoint(
            new Vector3(0, 0, dist)
            ).y;

        var bottomBorder = Camera.main.ViewportToWorldPoint(
            new Vector3(0, 1, dist)
            ).y;

        transform.position = new Vector3(
            Mathf.Clamp(transform.position.x, leftBorder, rightBorder),
            Mathf.Clamp(transform.position.y, topBorder, bottomBorder),
            transform.position.z
            );

    }

    void FixedUpdate()
    {
        // 5 - Move the game object
        rigidbody2D.velocity = movement;
    }

    void OnDestroy() 
    {
        Application.LoadLevel("gameOver"); 
    } 

}

and my player's health script

using UnityEngine;

/// <summary>
/// Handle hitpoints and damages
/// </summary>
public class HealthScript : MonoBehaviour
{   
    /// <summary>
    /// Total hitpoints
    /// </summary>
    public int hp = 1;

    /// <summary>
    /// Enemy or player?
    /// </summary>
    public bool isEnemy = true;

    /// <summary>
    /// Inflicts damage and check if the object should be destroyed
    /// </summary>
    /// <param name="damageCount"></param>
    public void Damage(int damageCount)
    {
        hp -= damageCount;

        if (hp <= 0)
        {
            // 'Splosion!
            SpecialEffectsHelper.Instance.Explosion(transform.position);

            // Dead!
            Destroy(gameObject);
        }
    }

    void OnTriggerEnter2D(Collider2D otherCollider)
    {
        // Is this a shot?
        ShotScript shot = otherCollider.gameObject.GetComponent<ShotScript>();
        if (shot != null)
        {
            // Avoid friendly fire
            if (shot.isEnemyShot != isEnemy)
            {
                Damage(shot.damage);

                // Destroy the shot
                Destroy(shot.gameObject); // Remember to always target the game object, otherwise you will just remove the script
            }
        }
    }
}

Answer 1

With new UI system in Unity 4.6 it is really easy to create a health bar.

• GameObject->UI->Image
• Put your health bar sprite in image.
• Change the Image type to Filled. Then you can play with Fill amount property and also control in through code