I am working on creating a game using the 2D rouge-like tutorial provided by unity. Everything works as expected thus far apart from movement. When the game runs a single error appears.
"NullReferenceException: object reference not set to an instance of an object completed.player.start () (at Assets/Completed/Scripts/Player.cs:39) "
This is the line of code causing the error:
healthText.text = "Health: " + health;
The code for the entire script is below:
using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;
using UnityEngine.UI; //Allows us to use UI.
namespace Completed
{
//Player inherits from MovingObject, our base class for objects that can move, Enemy also inherits from this.
public class Player : MovingObject
{
public float restartLevelDelay = 1f; //Delay time in seconds to restart level.
public int pointsPerGoodFood = 10; //Number of points to add to player health points when picking up a GoodFood object.
public int pointsPerOkayFood = 20; //Number of points to add to player health points when picking up a OkayFood object.
public int wallDamage = 1; //How much damage a player does to a wall when attacking it.
public Text healthText; //UI Text to display current player health total.
public AudioClip moveSound1; //1 of 2 Audio clips to play when player moves.
public AudioClip moveSound2; //2 of 2 Audio clips to play when player moves.
public AudioClip eatSound1; //1 of 4 Audio clips to play when player collects a GoodFood object.
public AudioClip eatSound2; //2 of 4 Audio clips to play when player collects a GoodFood object.
public AudioClip eatSound3; //3 of 4 Audio clips to play when player collects a OkayFood object.
public AudioClip eatSound4; //4 of 4 Audio clips to play when player collects a OkayFood object.
public AudioClip gameOverSound; //Audio clip to play when player dies.
private Animator animator; //Used to store a reference to the Player's animator component.
private int health; //Used to store player health points total during level.
//Start overrides the Start function of MovingObject
protected override void Start ()
{
//Get a component reference to the Player's animator component
animator = GetComponent<Animator>();
//Get the current health point total stored in GameManager.instance between levels.
health = GameManager.instance.playerHealthPoints;
//Set the foodText to reflect the current player health total.
healthText.text = "Health: " + health;
//Call the Start function of the MovingObject base class.
base.Start ();
}
//This function is called when the behaviour becomes disabled or inactive.
private void OnDisable ()
{
//When Player object is disabled, store the current local health total in the GameManager so it can be re-loaded in next level.
GameManager.instance.playerHealthPoints = health;
}
private void Update ()
{
//If it's not the player's turn, exit the function.
if(!GameManager.instance.playersTurn) return;
int horizontal = 0; //Used to store the horizontal move direction.
int vertical = 0; //Used to store the vertical move direction.
//Check if we are running either in the Unity editor or in a standalone build.
#if UNITY_STANDALONE || UNITY_WEBPLAYER
//Get input from the input manager, round it to an integer and store in horizontal to set x axis move direction
horizontal = (int) (Input.GetAxisRaw ("Horizontal"));
//Get input from the input manager, round it to an integer and store in vertical to set y axis move direction
vertical = (int) (Input.GetAxisRaw ("Vertical"));
//Check if moving horizontally, if so set vertical to zero.
if(horizontal != 0)
{
vertical = 0;
}
//Check if we have a non-zero value for horizontal or vertical
if (horizontal != 0 || vertical != 0)
{
//Call AttemptMove passing in the generic parameter Wall, since that is what Player may interact with if they encounter one (by attacking it)
//Pass in horizontal and vertical as parameters to specify the direction to move Player in.
AttemptMove<Wall> (horizontal, vertical);
}
}
//AttemptMove overrides the AttemptMove function in the base class MovingObject
//AttemptMove takes a generic parameter T which for Player will be of the type Wall, it also takes integers for x and y direction to move in.
protected override void AttemptMove <T> (int xDir, int yDir)
{
//Every time player moves, subtract from health points total.
health--;
//Update health text display to reflect current score.
healthText.text = "Health: " + health;
//Call the AttemptMove method of the base class, passing in the component T (in this case Wall) and x and y direction to move.
base.AttemptMove <T> (xDir, yDir);
//Hit allows us to reference the result of the Linecast done in Move.
RaycastHit2D hit;
//If Move returns true, meaning Player was able to move into an empty space.
if (Move (xDir, yDir, out hit))
{
//Call RandomizeSfx of SoundManager to play the move sound, passing in two audio clips to choose from.
SoundManager.instance.RandomizeSfx (moveSound1, moveSound2);
}
//Since the player has moved and lost health points, check if the game has ended.
CheckIfGameOver ();
//Set the playersTurn boolean of GameManager to false now that players turn is over.
GameManager.instance.playersTurn = false;
}
//OnCantMove overrides the abstract function OnCantMove in MovingObject.
//It takes a generic parameter T which in the case of Player is a Wall which the player can attack and destroy.
protected override void OnCantMove <T> (T component)
{
//Set hitWall to equal the component passed in as a parameter.
Wall hitWall = component as Wall;
//Call the DamageWall function of the Wall we are hitting.
hitWall.DamageWall (wallDamage);
//Set the attack trigger of the player's animation controller in order to play the player's attack animation.
animator.SetTrigger ("playerAttack");
}
//OnTriggerEnter2D is sent when another object enters a trigger collider attached to this object (2D physics only).
private void OnTriggerEnter2D (Collider2D other)
{
//Check if the tag of the trigger collided with is Exit.
if(other.tag == "Exit")
{
//Invoke the Restart function to start the next level with a delay of restartLevelDelay (default 1 second).
Invoke ("Restart", restartLevelDelay);
//Disable the player object since level is over.
enabled = false;
}
//Check if the tag of the trigger collided with is GoodFood.
else if(other.tag == "GoodFood")
{
//Add pointsPerGoodFood to the players current health total.
health += pointsPerGoodFood;
//Update healthText to represent current total and notify player that they gained points
healthText.text = "+" + pointsPerGoodFood + " Health: " + health;
//Call the RandomizeSfx function of SoundManager and pass in two eating sounds to choose between to play the eating sound effect.
SoundManager.instance.RandomizeSfx (eatSound1, eatSound2);
//Disable the GoodFood object the player collided with.
other.gameObject.SetActive (false);
}
//Check if the tag of the trigger collided with is OkayFood.
else if(other.tag == "OkayFood")
{
//Add pointsPerOkayFood to players health points total
health += pointsPerOkayFood;
//Update healthText to represent current total and notify player that they gained points
healthText.text = "+" + pointsPerOkayFood + " Health: " + health;
//Call the RandomizeSfx function of SoundManager and pass in two eating sounds to choose between to play the eating sound effect.
SoundManager.instance.RandomizeSfx (eatSound3, eatSound4);
//Disable the OkayFood object the player collided with.
other.gameObject.SetActive (false);
}
}
//Restart reloads the scene when called.
private void Restart ()
{
//Load the last scene loaded, in this case Main, the only scene in the game.
SceneManager.LoadScene(0);
}
//LoseHealth is called when an enemy attacks the player.
//It takes a parameter loss which specifies how many points to lose.
public void LoseHealth (int loss)
{
//Set the trigger for the player animator to transition to the playerHit animation.
animator.SetTrigger ("playerHit");
//Subtract lost health points from the players total.
health -= loss;
//Update the health display with the new total.
healthText.text = "-"+ loss + " Health: " + health;
//Check to see if game has ended.
CheckIfGameOver ();
}
//CheckIfGameOver checks if the player is out of health points and if so, ends the game.
private void CheckIfGameOver ()
{
//Check if health point total is less than or equal to zero.
if (health <= 0)
{
//Call the PlaySingle function of SoundManager and pass it the gameOverSound as the audio clip to play.
SoundManager.instance.PlaySingle (gameOverSound);
//Stop the background music.
SoundManager.instance.musicSource.Stop();
//Call the GameOver function of GameManager.
GameManager.instance.GameOver ();
}
}
}
}
