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How to Make Enemy Attack When In Range of The Player? [duplicate]

This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 1 year ago.
So my game is a 2D top down movement game and my script does make my enemy attack but it constantly loops the attack animation because I obviously don't know what EXACTLY to put code wise to make the enemy attack when in range of the player to do damage instead of letting him constantly loop. Also i seem to be getting an error when i get close to my enemy as of right now it says
NullReferenceException: Object reference not set to an instance of an object
EnemyCombat.Attack () (at Assets/EnemyCombat.cs:36)
EnemyCombat.Update () (at Assets/EnemyCombat.cs:25)
Also, Here is the EnemyCombat script
enemy attausing System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class EnemyCombat : MonoBehaviour
{
public Animator animator;
public Transform AttackPoint;
public float attackRange = 0.5f;
public LayerMask enemyLayers;
public int attackDamage = 5;
public float attackRate = 2f;
float nextAttackTime = 0f;
// Update is called once per frame
void Update()
{
if (Time.time >= nextAttackTime)
{
Attack();
nextAttackTime = Time.time + 1f / attackRate;
}
}
void Attack()
{
animator.SetTrigger("Attack");
Collider2D[] hitEnemies = Physics2D.OverlapCircleAll(AttackPoint.position, attackRange, enemyLayers);
foreach (Collider2D enemy in hitEnemies)
{
enemy.GetComponent<Enemy>().TakeDamage(attackDamage);
}
}
void OnDrawGizmosSelected()
{
if (AttackPoint == null)
return;
Gizmos.DrawWireSphere(AttackPoint.position, attackRange);
}
}

To fix your endless attack loop:
// Update is called once per frame
void Update()
{
if (attackRate >= nextAttackTime) /* checks that nextAttackTime is less than or equal to the attackRate */
{
Attack();
nextAttackTime = Time.deltaTime * 5f; // adds 5 seconds to nextAttackTime
}
else
{
nextAttackTime -= Time.deltaTime; /* if nextAttackTime is greater than the attackRate, subtract one from nextAttackTime. this only happens once per second because you use Time.deltaTime */
}
}

From that NullReference Error it looks like the major problem you're having is that there is no actual point in the code or in the game hierarchy that you are telling your script which gameObject it is referring to.
Line 36 is trying to retrieve that information with .GetComponent<Enemy()>, so you need to provide that reference.
You could do this in the script fairly easily by creating a public variable that you can drag the enemy gameObject into in your hierarchy in Unity.
Try something like:
public GameObject enemyObject;
This will create a variable in the script visible in the hierarchy when you select the script which you can drag the appropriate gameObject into.
There might need to be some adjustments to it because I can't see the rest of your code, but this seems to be the issue.
Another option would be trying to manually adding it in:
void Start()
{
GameObject enemyObject = gameObject.GetComponent<Enemy>();
}
this is taken from Unity Scripting Documentation

Text is supposed to be displayed when childCount equals 0, but it doesn't

this should be a very simple answer. I'm following a Unity with C# tutorial for making a simple Space Invaders game, and at one point it is shown that when our enemyHolder object has no child objects left (when all enemies are destroyed) the attached text under the winText function should be displayed.
So we have
if (enemyHolder.childCount == 0)
{
winText.enabled = true;
}
When I run the code the text isn't displayed after the enemies are destroyed and no child object is left. It's like the code stops getting read at that point, although the character is still movable and you can generate new shots.
If I create two "Enemy" child objects and tell it to display the winText rather when the childCount reaches 1, it does work.
So why is it not working when the function calls for == 0?
EDIT: Complete class code:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class EnemyController : MonoBehaviour
{
private Transform enemyHolder;
public float speed;
public GameObject shot;
public Text winText;
public float fireRate = 0.997f;
// Start is called before the first frame update
void Start()
{
winText.enabled = false;
InvokeRepeating("MoveEnemy", 0.1f, 0.3f);
enemyHolder = GetComponent<Transform>();
}
void MoveEnemy()
{
enemyHolder.position += Vector3.right * speed;
foreach (Transform enemy in enemyHolder)
{
if (enemy.position.x < -10.5 || enemy.position.x > 10.5)
{
speed = -speed;
enemyHolder.position += Vector3.down * 0.5f;
return;
}
if (enemy.position.y <= -4)
{
GameOver.isPlayerDead = true;
Time.timeScale = 0;
}
if (enemyHolder.childCount == 1)
{
CancelInvoke();
InvokeRepeating("MoveEnemy", 0.1f, 0.25f);
}
if (enemyHolder.childCount == 0)
{
winText.enabled = true;
}
}
}
}

Your code is inside the void MoveEnemy() function.
I'm assuming your script is attached to in-game enemies. Your code doesn't run because the MoveEnemy function no longer runs if there are no enemies.
So, you need to handle enemy movement and scene handling in different scripts.
The code that checks the enemy holder's number of children should be placed inside a void Update() function. This Update() function should be placed on an object that never gets deleted. Its advantage is that it runs every frame.
As a convention, devs generally use separate empty objects or even the camera to attach scripts which contain Update functions that handle the scene. Good luck!
Read more on Update

UNITY PREFABS DOESN'T SHOW UP IN GAME TAB

As you can see in the screenshoot I can't see prefabs in the game tab but only in the editor. I have made a simple function for shooting(not finished yet), it works fine, it spawns the prefabs but i can't see them in the game tab, I have already tried changing the Sorting Layer, move the camera, change Z position but nothing appen.
This is my code:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class PlayerAttack : MonoBehaviour
{
[SerializeField]
float delayBetweenShots = 0.4f;
float timePassedSinceLast = 0f;
// Start is called before the first frame update
void Start()
{
timePassedSinceLast = delayBetweenShots;
}
// Update is called once per frame
void Update()
{
Aiming();
Shooting();
}
void Aiming()
{
var objectPos = Camera.main.WorldToScreenPoint(transform.position);
var dir = Input.mousePosition - objectPos;
transform.rotation = Quaternion.Euler(new Vector3(0,0,Mathf.Atan2(-dir.x, dir.y) * Mathf.Rad2Deg));
}
void Shooting()
{
if(Input.GetMouseButton(0) && timePassedSinceLast >= delayBetweenShots)
{
GameObject bullet = (GameObject)Instantiate(Resources.Load("bullet"), transform.position, transform.rotation);
timePassedSinceLast = 0f;
}
else
{
timePassedSinceLast += Time.deltaTime;
}
}
}

The prefabs get instantiated correctly. As others suggested as well, the best way to find "lost" objects in your game is to shoot some stuff, pause the game, go into scene view, turn on 3D mode and double click one of the prefabs in the hierarchy. The camera will take you straight to your object.

I want my object to fall when the player is near it

I want my objects to fall when the player got to that scene . My game have a long map and I want them not to fall when I start the game .There is any code for player detection in the view? for the objects to fall?
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class FallDown : MonoBehaviour
{
public float fallSpeed = 8.0f;
//Variables for starting position and length until reset
private Vector3 _startingPos;
public float FallDistance = 5f;
void Start()
{
transform.Translate(Vector3.down * fallSpeed * Time.deltaTime, Space.World);
// Save starting position
_startingPos = transform.position;
}
void Update()
{
transform.Translate(Vector3.down * fallSpeed * Time.deltaTime, Space.World);
// If the object has fallen longer than
// Starting height + FallDistance from its start position
if (transform.position.y > _startingPos.y + FallDistance)
{
transform.position = _startingPos;
}
}
}

While the answer above is correct, Colliders might not be what you want to implement in this case. Colliders are used to, well, detect collisions, while you want the objects to fall when the player is at a specific distance from them. For this, I'd suggest adding a reference to the player GameObject first:
private GameObject playerRef;
And in the Start function find the player:
playerRef = GameObject.Find("yourPlayerGameObjectNameHere");
Get the GameObjects that you want to fall either by finding them, like above, or by passing a public reference to them through the inspector. Afterwards, you can use Vector3.distance between each GameObject and the player, like so:
if( Vector3.Distance(player.transform.position, fallingObject.transform.position) < yourDistanceHere ){
// Make the object fall
}

Have you tried implementing this behavior using Colliders?
To do it so, all you've got to do is add both a Collider Component and a RigidBody to your player and to the falling objects.
Once you've added them and configured their parameters, you can check the collision by using the method OnColissionEnter. This method will be triggered every time that a collision is detected by the GameObject that is holding the script. In your case, the falling objects should hold it.
private void OnCollisionEnter(Collision other)
{
//MAKE THE OBJECTS FALL
}

Shooting laser continuously in Unity

I'm trying to create a falling word game like z-type. Once the game starts a few words are displayed on the screen. When the user types a letter and if that matches with the first letter of any of the words displayed, an activeWord tag is added to the word. I have also created a laser script that checks if the tag is active and when that happens, it shoots the laser.
What's happening right now is that the laser is shot only once i.e when the first letter matches but doesn't shoot a laser when the remaining words are typed.
This is the laser script:
using UnityEngine;
using UnityEngine.UI;
public class Laser : MonoBehaviour {
public float speed = 10.0f;
private Vector3 laserTarget;
private void Update () {
GameObject activeWord = GameObject.FindGameObjectWithTag("activeWord");
if (activeWord && activeWord.GetComponent<Text>().text.Length > 0) {
laserTarget = activeWord.transform.position; // find position of word
transform.Translate(laserTarget * speed * Time.deltaTime); // shoot the laser
}
}
}
I'm also adding the code that I use in the display/UI field.
public void RemoveLetter() {
/* remove the first letter if its correct and so
on for the remaining letters. change the color of the word to red and add
the "activeddWord" tag.*/
text.text = text.text.Remove(0, 1);
text.color = Color.red;
text.gameObject.tag = "activeWord";
}
public void RemoveWord() { // destroy the word once all the letters match
Destroy(gameObject);
}
Can someone please have a look at the code and tell me where I'm making a mistake.

I think you have to reset the position of your laser if it reaches the target:
public float speed = 10.0f;
private Vector3 laserTarget;
private Vector3 laserOrigin;
private void Start () {
// save laser's origin position
laserOrigin = transform.position;
}
private void Update () {
GameObject activeWord = GameObject.FindGameObjectWithTag("activeWord");
if (activeWord && activeWord.GetComponent<Text>().text.Length > 0)
{
laserTarget = activeWord.transform.position; // find position of word
transform.Translate(laserTarget * speed * Time.deltaTime); // shoot the laser
float distance = Vector3.Distance(laserTarget , transform.position);
if(distance < 0.05f){ // I don't know your scaling, perhaps change the limit here!
transform.position = laserOrigin;
}
}
}

Here is one way you can do this using Instantiate() and prefabs. The benefit of this method is that it is scalable. You can create multiple lasers with minimal tweaking. Please note that to use multiple lasers you will have to remove WaitForThisLaserDestroyed;.
To get this to work you will have to start by changing your laser gameObject into a prefab and adding this script onto it:
https://docs.unity3d.com/Manual/Prefabs.html
public class Laser : MonoBehaviour
{
public float speed = 10.0f;
public Vector3 laserTarget;
public float destroyLaserAfterTime = 3f;
private void Update ()
{
transform.Translate(laserTarget * speed * Time.deltaTime);
}
}
And then on some arbitrary other object. For example an empty game object in the same scene:
public class LaserInitializer : MonoBehaviour
{
public GameObject laserPrefab;
public GameObject laserOrigin;
private GameObject WaitForThisLaserDestroyed;
private void Update ()
{
GameObject activeWord = GameObject.FindGameObjectWithTag("activeWord");
if (WaitForThisLaserDestroyed == null && activeWord && activeWord.GetComponent<Text>().text.Length > 0)
{
CreateLaser(activeWord);
}
}
private void CreateLaser(GameObject activeWord)
{
GameObject activeLaser = Instantiate(laserPrefab, laserOrigin.Transform.Position, Quaternion.identity) as GameObject;
Laser laserScript = activeLaser.GetComponent<Laser>();
laserScript.laserTarget = activeWord.transform.position;
WaitForLaserDestroyed = activeLaser;
Destroy(activeLaser, destroyLaserAfterTime);
}
}
To explain the code:
The Laser prefab has its own script for moving towards the word, and as soon as it exists and has the target passed to it, it will move towards the active word.
Somewhere else in the scene you have a game object that exists to hold the second script. Lets call it the "controller game object". It checks to see if the words are "active", as per the earlier design. When a word is active this script creates exactly one laser, and tells it to target the active word.
You have another gameobject (this can be the same one as the controller game object), that marks the origin of the laser. You can do this in other ways, but I thought that using a game object to mark the start point would be an easy way for beginners.