This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 2 years ago.
I'm in search of problem solution for a game I'm making.
There is a player that needs to evade obstacles and I want to make my Score to stop when player collides with obstacle and also further I want to make a highscore count.
But for now I'm getting an error when the player collides with an obstacle.
the code for the player is
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;
public class Player : MonoBehaviour
{
public GameObject deathcanvas;
public float moveSpeed = 600f;
public Text scoreText;
float movement = 0f;
private bool isDead = false;
// Update is called once per frame
void Update()
{
movement = Input.GetAxisRaw("Horizontal");
}
private void FixedUpdate()
{
if (isDead)
return;
transform.RotateAround(Vector3.zero, Vector3.forward, movement * Time.fixedDeltaTime * -moveSpeed);
}
private void OnTriggerEnter2D(Collider2D collision)
{
Death();
}
private void Death()
{
isDead = true;
GetComponent<Score> ().OnDeath();
deathcanvas.SetActive(true);
}
}
also there is a code for score counter that is
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using UnityEngine;
using UnityEngine.UI;
public class Score : MonoBehaviour
{
public int Player_Score;
public Text txt;
private float clock;
private bool isDead = false;
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
if (isDead)
return;
txt.text = "Score: " + Player_Score;
clock += 1 * Time.deltaTime;
if (clock > 1)
{
Player_Score += 1;
clock = 0;
}
}
public void OnDeath()
{
isDead = true;
}
}
and there is also a code for obstacle spawner, but i don't think that it is needed.
And the error for when the player collides with an obstacle is
NullReferenceException: Object reference not set to an instance of an object
Player.Death () (at Assets/scripts/Player.cs:36)
Player.OnTriggerEnter2D (UnityEngine.Collider2D collision) (at Assets/scripts/Player.cs:31)
What should i do?
There are some strange things here, why do you have 2 functions of death and 2 book of death? It's useful, since Score is on player like the other script you can put everything inside the Player script and access to the canvas and score text without using public functions and a lot of variables. If it's still an error then we can see something else
Related
I have a Script Coin-Counter connected with a Text. Every time the Player and the Coin are colliding the coinScore decreases by 1. If I want to display the coinScore in Update() this doesn't work. Why?
using UnityEngine.UI;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class CoinScore : MonoBehaviour
{
[SerializeField] private Text coinScorer;
private int coinScore;
private int oldCoinScore;
void Update()
{
coinScorer.text = coinScore.ToString(); // This doesn't work.
oldCoinScore = coinScore;
}
private void OnTriggerEnter2D(Collider2D other)
{
if (other.gameObject.CompareTag("Player"))
{
coinScore += 1;
Destroy(gameObject);
//coinScorer.text = coinScore.ToString(); //This works.
}
}
Your collision method is destroying this game object.
There is no update to run after that.
Hey guys I want to make a sword attack. But I get the error of:
NullReferenceException: Object reference not set to an instance of an
object
These are my codes:
My weaponattack script:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Weaponattack : MonoBehaviour
{
Enemy Enemy;
public float power;
// Use this for initialization
void Start () {
}
// Update is called once per frame
void Update () {
}
public void OnTriggerEnter(Collider col)
{
if(col.tag == "Enemy")
{
var kılıc = GetComponent<Enemy>();
Enemy.currentHealt -= 10;
Enemy.TakeDamage();
Debug.Log("Düşman Vuruldu");
}
}
}
This is my Enemy Health scrpt:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Enemy : MonoBehaviour {
public float currentHealt;
public float maxHealth;
// Use this for initialization
void Start () {
currentHealt = maxHealth;
}
// Update is called once per frame
void Update () {
}
public void TakeDamage()
{
currentHealt -= 10;
if(currentHealt < 0)
{
die();
}
}
void die()
{
Destroy(gameObject);
}
}
Can you helo em I couldnt understan why these codes are not working why am I getting that error.
I think your problem is in this line here GetComponent<Enemy>(); This needs a game object to get the component of
Enemy = col.GetComponent<Enemy>();
Should be what you're doing
You also may have issue calling your variable Enemy exactly the same as your class Enemy, I would change this to Enemy enemy; and
enemy = col.GetComponent<Enemy>();
respectivley
It seems pretty straightforward. You don't assign an Enemy to Weaponattack and so it's barfing when you first reference Enemy (Enemy.currentHealt). Either make Enemy public or a SerializedField so you can assign it in the Inspector, or however else you want to get an Enemy into Weaponattack.
Also don't name your property the same name as your script (Enemy Enemy). Surprised you didn't get a compile error.
EDIT Based on comments:
Enemy enemy;
public void OnTriggerEnter(Collider col)
{
if(col.tag == "Enemy")
{
var kılıc = GetComponent<Enemy>();
kilic.currentHealt -= 10;
kilic.TakeDamage();
Debug.Log("Düşman Vuruldu");
}
}
This also assumes you have an Enemy attached to your Weaponattack (GetComponent)
I have a script that makes the camera do a shake by putting a button because
It is a public access function, if I do it that way when placing a button it works well but what I cannot achieve is to call the function so that every time my player collides with an enemy he makes the shake. I hope you can help me.
The shake code in camera is:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class ScreenShaker : MonoBehaviour {
private float shakeAmount = 0.5f;
private float shakeTime = 0.0f;
private Vector3 initialPosition;
private bool isScreenShaking = false;
void Update () {
if(shakeTime > 0)
{
this.transform.position = Random.insideUnitSphere * shakeAmount + initialPosition;
shakeTime -= Time.deltaTime;
}
else if(isScreenShaking)
{
isScreenShaking = false;
shakeTime = 0.0f;
this.transform.position = initialPosition;
}
}
public void ScreenShakeForTime(float time)
{
initialPosition = this.transform.position;
shakeTime = time;
isScreenShaking = true;
}
}
The enemy code is:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class ControladorEnemigoCirculoMediano : MonoBehaviour
{
void OnTriggerEnter2D(Collider2D other)
{
if (other.tag == "Player")
{
Here I don't know what to call the public void function ScreenShakeForTime (float time);
I already tried many things online but when my character comes into contact with the character, I don't do the shake in the camera.
}
}
}
You can create Unity-singleton in your ScreenShaker class like:
class ScreenShaker
{
public static ScreenShaker Instance {private set; get;};
void Awake() {
Instance = this;
}
}
And than from any place to call like:
ScreenShaker.Instance.ScreenShakeForTime(2f);
This is the easiest way, but maybe it's better to create standard singeleton(it's up to you).
And also don;t forget to destroy it on OnDestroy()
can you tell me in enemy game object collider isTrigger is enable or not
if it is not enable then use OnColliderEnter2D(Collision2D other){} for collision detection
My problem is that when all the enemies are killed the scene that should be loaded is not loading. I did add the scene to the Build setting (it has an index of 3) but it is still not loading. The script I created is attached to an empty object and not directly to the sprite (is that okay?). Can someone tell me why the scene isn't loading? Thank you.
This image is for to show you the EnemySpawner empty object inspector
EnemySpawner Script :
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class EnemySpawner : MonoBehaviour {
[SerializeField] GameObject EnemyPreFab;
[SerializeField] int MaxEnemies = 30;
[SerializeField] float EnemySpawnTime = 1.00001f;
[SerializeField] GameObject FirstWaypoint;
int CurrentNumOfEnemies = 0;
public LevelManager myLevelManager;
public int maximumnumberofhits = 0;
int timesEnemyHit;
IEnumerator SpawningEnemies()
{
while(CurrentNumOfEnemies <= MaxEnemies)
{
GameObject Enemy = Instantiate(EnemyPreFab, this.transform.position, Quaternion.identity);
CurrentNumOfEnemies++;
yield return new WaitForSeconds(EnemySpawnTime);
}
}
void Start()
{
StartCoroutine(SpawningEnemies());
timesEnemyHit = 0;
if (this.gameObject.tag == "EnemyHit")
{
CurrentNumOfEnemies++;
}
}
void OnCollisionEnter2D()
{
timesEnemyHit++;
if (timesEnemyHit == maximumnumberofhits)
{
CurrentNumOfEnemies--;
Destroy(this.gameObject);
}
if (CurrentNumOfEnemies == 0)
{
myLevelManager.LoadLevel("NextLevelMenu");
Debug.Log("LevelLoaded");
}
}
}
LevelManger script:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
public class LevelManager : MonoBehaviour {
public void LoadLevel(string name)
{
print("Level loading requested for" + name);
SceneManager.LoadScene(name);
}
}
EnemyShooting Script :
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class EnemyShooting : MonoBehaviour {
[SerializeField] float EnemyLaserSpeed = 10f;
[SerializeField] float EnemyLaserFireTime;
[SerializeField] GameObject LaserBulletEnemyPreFab;
[SerializeField] int MaxNumberOfHits = 1;
int CurrentNumberOfHits = 0;
Coroutine FireCoroutine;
void OnTriggerEnter2D(Collider2D collider)
{
if(collider.gameObject.tag == "PlayerLaser")
{
if(CurrentNumberOfHits < MaxNumberOfHits)
{
CurrentNumberOfHits++;
Destroy(collider.gameObject);
Score.ScoreValue += 2;//The user will be rewarded 1 point
}
}
}
void DestroyEnemy()
{
if(CurrentNumberOfHits >= MaxNumberOfHits)
{
Destroy(gameObject);
}
}
private void Fire()
{
FireCoroutine = StartCoroutine(ShootContinuously());
}
void BecomeVisible()
{
Fire();
}
IEnumerator ShootContinuously()
{
while (true)
{
GameObject LaserBulletEnemy = Instantiate(LaserBulletEnemyPreFab, this.transform.position, Quaternion.identity) as GameObject;
LaserBulletEnemy.GetComponent<Rigidbody2D>().velocity = new Vector2(0, EnemyLaserSpeed);
EnemyLaserFireTime = Random.Range(0.5f, 0.9f);
yield return new WaitForSeconds(EnemyLaserFireTime);
}
}
// Use this for initialization
void Start () {
BecomeVisible();
}
// Update is called once per frame
void Update () {
DestroyEnemy();
}
}
EnemyPathing script:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class EnemyPathing : MonoBehaviour {
[SerializeField] List<Transform> WayPoints;
[SerializeField] float EnemyMovingSpeed = 5f;
int WayPointIndex = 0;
void EnemyMoving()
{
if (WayPointIndex <= WayPoints.Count - 1)
{
var TargetedPosition = WayPoints[WayPointIndex].transform.position; //The position of where the enemy needs to go
TargetedPosition.z = 0f;
var MoveThisFrame = EnemyMovingSpeed * Time.deltaTime;
transform.position = Vector2.MoveTowards(this.transform.position, TargetedPosition, MoveThisFrame);
if(transform.position == TargetedPosition)
{
WayPointIndex++;
}
}
else
{
Destroy(gameObject);
}
}
// Use this for initialization
void Start () {
transform.position = WayPoints[WayPointIndex].transform.position;
}
// Update is called once per frame
void Update () {
EnemyMoving();
}
}
Problem
You're checking for collisions on the SPAWNER; when someone hits the Spawner it counts down enemies. But the Spawner doesn't have a collision box in the screenshot so it can never be hit. The Scene changing code can never be called.
So the game, based on the code, looks like this:
Spawn X enemies,
Hit the Spawner X times,
(Removed: Destroy the Spawner,)
Change scene.
I'm guessing this is conceptually incorrect and you actually want to check collisions on the spawned enemies, which will then count up the amount of destroyed enemies, and change the scene when they are all dead.
Solution
Conceptually, what you want is:
Spawn X enemies
Count up variable for every enemy
On Enemy death, count it down
When 0, change scene
So how do we code this?
Well, every enemy needs a reference to the object that holds the count. You can do this in several ways, when I personally do it I usually have just one spawner that is responsible for everyone so I make that one a Singleton, that can be references from anywhere:
EnemySpawner
public class EnemySpawner : MonoBehaviour
{
public static Spawner Instance = null;
int CurrentNumOfEnemies = 0;
// ... etc
void Start()
{
if (Instance == null)
Instance = this;
// Spawn enemies like you do already, CurrentNumOfEnemies++ for every spawned
}
public OnEnemyDeath() {
CurrentNumOfEnemies--;
if (CurrentNumOfEnemies < 1)
{
// You killed everyone, change scene:
LevelManager.LoadLevel("Your Level");
}
}
}
Enemy script (I don't know how your current code looks, but here's a minimal solution based on how I THINK your code looks):
void OnDestroy()
{
// This will run automatically when you run Destroy() on this gameObject
EnemySpawner.Instance.OnEnemyDeath(); // Tell the EnemySpawner that someone died
}
This will only work if you have exactly only ONE spawner. If you have multiple ones you will have to send a reference to the instance of its spawner to every spawned enemy. I can show you how to do ths too, if you wish.
Bonus content
LevelManager doesn't need to be on a GameObject, it can be static instead:
Remove the LevelManager script from any GameObject
Change your LevelManager code to this:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
public static class LevelManager
{
public static void LoadLevel(string name)
{
Debug.Log("Level loading requested for" + name);
SceneManager.LoadScene(name);
}
}
Now you can use it from ANYWHERE, without needing to initialize a reference to any script or GameObject:
LevelManager.LoadLevel("My Level");
myLevelManager.LoadLevel("NextLevelMenu"); is never executed, because you destroy the object in the if-test above.
This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 3 years ago.
Hello I am new to coding in unity and i was trying to make the health bar go down when the player hits an object. When i use a debug.log it prints what i want it to print when it collides with the object however when i try to make the health go down when it hits the object it gives me this error
NullReferenceException:
Object reference not set to an instance of an object
DamagePlayer.OnCollisionEnter2D (UnityEngine.Collision2D collision)
(at Assets/Scripts/DamagePlayer.cs:30)
here is my code.
My Damage class
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class DamagePlayer : MonoBehaviour
{
public BarScript bar;
public int playerHealth = 100;
int damage = 10;
// Start is called before the first frame update
void Start()
{
print(playerHealth);
}
// Update is called once per frame
void Update()
{
}
private void OnCollisionEnter2D(Collision2D collision)
{
if(collision.collider.tag =="enemy")
{
Debug.Log("enemy");
bar.math(damage);
}
}
}
Health Bar class
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class BarScript : MonoBehaviour
{
private float fillAmount;
[SerializeField]
private Image content;
// Start is called before the first frame update
void Start()
{
fillAmount = 1f;
}
// Update is called once per frame
void Update()
{
content.fillAmount = fillAmount;
}
public float math(float value)
{
return fillAmount =(value / 100);
}
}
My Player class
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Player : MonoBehaviour
{
private Rigidbody2D rb;
[SerializeField]
private float speed = 300f;
private float jump = 400f;
// Start is called before the first frame update
void Start()
{
rb = GetComponent<Rigidbody2D>();
}
// Update is called once per frame
void Update()
{
Movement();
}
void Movement()
{
if (Input.GetKeyDown("d")){
rb.velocity = new Vector2(speed * Time.fixedDeltaTime, rb.velocity.y);
}else if (Input.GetKeyDown("a"))
{
rb.velocity = new Vector2(-speed * Time.fixedDeltaTime, rb.velocity.y);
}else if (Input.GetKeyDown("space"))
{
rb.velocity = new Vector2(rb.velocity.x, jump * Time.fixedDeltaTime);
}
}
}
You haven't create an instance of BarScript in DamagePlayer, that's why this is creating problem.
Without instance you can't access member method of a class, you can use static to make that accessible by anyone. If it is just for Player then you can do that (Single-player), But it won't be so nice.
If you it's multi-player or you want do the same for enemy, then create prefab with both script, then instantiate or use pooling. Finally use findGameobjectsWithTag (not findGameobjectWithTag) and access those scripts, members and use their member methods.