Develop Reference

Can't Import any GameObject in a List

I'm trying to make a list where I can add objects in my scene, later on I'm going to loop through them to determine the closest object to my character and make the character perform certain actions. As soon as I created a list, it won't allow me to add any object to my list or reference it and I don't understand why that's happening. Here's a video to further clarify my issue
List Not working for me
my code for further inquiries
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class RobberMechanic : MonoBehaviour
{
public List<GameObject> testing = new List<GameObject>();
// void Start()
// {
// }
// // Update is called once per frame
// void Update()
// {
// }
}
Note: wanted to clarify that my unity version was on 2020.3.1f and now I've tried upgrading to 2020.3.10f and this issue occurs in both versions

what you are trying to do is not possible as you are dragging a gameobject inside your list from the hierarchy onto a prefab in the assets folder. Dragging and dropping works on gameObjects that are already inside the a scene/hierarchy.
To achieve your goal you must either:
Add your Terrorist prefab in the scene. Drag your Sphinx object inside it. The Terrorist prefab will then have the appropriate reference of the gameObject and can be used properly.
Turn your Terrorist object into a scriptable gameObject you can then add all sorts of different properties and will be easier to manage. There are tons of videos and documentation on it as well.

You're trying to add a GameObject from your scene to a list in a Prefab which is not possible, you'll have to drop your prefab into the scene before adding game objects to it or make a Prefab of the object you're trying to add to the list.

How to end a game in C# from a Collision

This is the current script that I have. I have a ball that is player, and I want a collision with my game object tagged as "pit" to end the game. When the game ends I want my game over canvas to pop up. The current script detects the hit when the player rolls over the pit, however, currently, nothing else happens. Both my player and pit have rigidbodies and colliders attached to them. I would really appreciate any help with how to get my code to work properly.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Trigger : MonoBehaviour
{
public GameObject GameManager;
private void OnTriggerEnter(Collider other)
{
Debug.Log("hit detected")
if(other.gameObject.tag == "pit")
{
GameManager.GetComponent<Game_Manager>().EndGame();
}
}
}
My EndGame code is in my GameManager script. The is the part of that script that deals with ending the game.
public void EndGame ()
{
player.GetComponent<Rigidbody>().constraints = RigidbodyConstraints.FreezePosition;
hasGameStarted = true;
inMenuUI.gameObject.SetActive(false);
inGameUI.gameObject.SetActive(false);
gameOverUI.gameObject.SetActive(true);
}

If I'm correct in interpreting your question, your script successfully detects player death already. If you want a game over screen you have a couple of options:
You can create a UI canvas with a panel on it that obscures the whole screen and put the words Game Over.
Or, probably the better option is to create an entirely new Unity scene and make the Game Over canvas there. When you want to trigger the game over screen you simply use:
Scene manager.LoadScene("Scene name");
You have to add "using UnityEngine.SceneManagement;" at the top of your script. Also note you have to add your Game Over scene to the list of scenes in you game. I believe this can be done by navigating to File>Build settings>scenes and then pressing add open scenes assuming the game over scene is open.

Create objects with ground plane detection only once with Vuforia & Unity

I am trying to create an AR app using Unity & Vuforia. I have a 3D model that needs to be spawned when ground plane is detected.But this needs to happen only once.
The way Vuforia work is, it keeps on spawning objects when new plane is detected. So what i need to do is either detect plane only once or spawn the object only once. As i am new to Unity, i need help doing this. Great if someone could tell me what i need to do to achieve this.

Vuforia has updated.Now There is no DeploymentStageOnce script.Inorder to stop duplicating while we touch, we have to turn off Duplicate Stage in Content Positioning Behaviour (Script)Check the Inspector when we click Plane Finder.

In your app you should have a Plane Finder object somewhere with the following properties set by default
The Plane Finder object has a Behaviour component attached that calls a Position Content method if a plane was found. That method belongs to the Content Positioning Behaviour and it makes an instance (Clone) of your Ground Plane Stage. In order to avoid more than one instance you should import the vuforia Deploy Stage Once script located here: https://library.vuforia.com/articles/Solution/ground-plane-guide.html and you should change the Plane Finder Behaviour as the following:

I struggled a long with it, in short we must disable AnchorInputListenerBehaviour after hit.
I attached a new script on PlaneFinder with this code below:
<!-- language-all: c# -->
public void OnInteractiveHitTest(HitTestResult result)
{
var listenerBehaviour = GetComponent<AnchorInputListenerBehaviour>();
if (listenerBehaviour != null)
{
listenerBehaviour.enabled = false;
}
}
I added event on Plane Finder Behavior
That's all, I hope it will be useful.

For Updated Versions:
go to "Advanced" setting and "On Interactive Hit Test" script -> Select "Off" option for the script.

Most of the answers are correct but kind of obsolete, the correct way to do that is by code.
Create for example a gameObject called GameManager and pass the GroundPlaneStage and a prefab of the object you want to spawn to a script attached to that GameManager for example call it GameManagerScript.cs, and create a small function called spawnObjects which does the following:
public class SceneManagerScript : MonoBehaviour {
public GameObject objPrefab;
public GameObject ground;
private int count = 0;
public void spawnObject() {
Instantiate(objPrefab, new Vector3(count, 0, 0), Quaternion.identity, ground.transform);
count += 2;
}
}
then after that go to the PlaneFinder specifically to the PlaneFinderBehaviour.cs component you will have callbacks for OnInteractiveHitTest and OnAutomaticHitTest, in your case you need the OnAutomativeHitTest, click + and add a new callback (the function spawnObject in code above like in the image below)
also when you instantiate the object of your preference via the prefab don't forget to write the proper position updates to prevent the objects from getting added in the same position
also don't forget to make the GroundPlaneStage the parent of the object and realize that the position you are adding in the Instantiate() function is relative to that parent (GroundPlaneStage which is represented in the code above with the variable ground)
Finally don't forget to uncheck Duplicate Stage from the "Content Positioning Behaviour" component in the Plane Finder as shown in the picture below:
I hope that helps

please try the vuforia website for this problem
Introduction to Ground Plane in Unity

Unity instantiates multiple objects instead of one - on click

Here's the code I'm having problems with:
public class PlaneBehaviour : MonoBehaviour {
public GameObject ClickSymbol;
public void Update() {
if (Input.GetMouseButtonDown(0)) {
Instantiate(ClickSymbol, Input.mousePosition, Quaternion.identity);
}
}
}
When user clicks the left mouse button, then multiple ClickSymbol's will be instantiated. How to prevent that behavior (create the object only once) ?

As for the PlaneBehaviour script, it's attached to multiple (not
intersecting, not overlapping) objects on a plane
That's what I thought you are doing and wanted to verify this before adding an answer. Joe's answer should work but this is a bad design.
You get the multiple Objects instead of one because the script is attached to multiple Objects.
The proper solution here is to have one script that reads from the Input then call a function or trigger an event in another script if required. Create a new script called InputReader or with similar name then move your if (Input.GetMouseButtonDown(0))... Make that that this new script is only attached to one GameObject. Just attach it to an empty GameObject. That's it.
It will prevent problems such as executing code twice when there is an input event.
Now, let;s say that you want to notify another script attached to another GameObject when key is pressed, you can find that GameObject, get that script that is attached to it then call its function.
GameObject obj = GameObject.Find("YourOtherObjectName");
Script script = obj.GetComponent<Script >();
script.notifyKeyPress();
I attached it to multiple game objects to be able to detect which game
object was clicked
That's not how to detect which GameObject is clicked. Since this is a plane, I assume it is a 3D Object with a 3D collider. See 6.For 3D Object (Mesh Renderer/any 3D Collider) from my other post on how to do this.

Instantiate gameobject from a script that is on that gameobject

I have a script called DialogueController, which is attached to a canvas. I would like to instantiate that canvas from the DialogueController script. Whenever I attempt to do this, all of the public objects that were assigned to the canvas through the Unity editor are set to null (including the canvas itself, which is what I am trying to instantiate).
Is there a simple way to do this? I have an alternative solution, but being able to do this would keep my code slightly more compartmentalized.

You could initialize these variables from the script itself, using the resources folders (and the Resources.Load() method). Something like that:
//The canvas is at the path "Assets/Resources/canvas".
function Start () {
your_canvas = Instantiate(Resources.Load("canvas"));
}

From the comments, it seems like you need an initial "seed" instance of that Canvas which contains your script to instantiate more copies if you need. Part 2 is most common for your needs
The easiest way is to have one instance of said canvas already in the scene. You could have the drawable/visible canvas part "disabled" by unticking the little checkbox in the inspector, and then have it enable itself in a function of a script on the GameObject...
void Start ()
{
thisCanvas = GetComponent<Canvas>();
thisCanvas.enabled = true;
}
of course, another way would just be to instantiate one copy from another script which you already have in the scene - classic case:
Create a BLANK GameObject in your scene (CTRL+Shift+N), [F2] rename it "GameManager" (SOME unity functions still bug out when there are spaces in GameObject names BTW) and then attach a new script called GameManager.
This script is basically just here to make sure the right scenes load, and instantiate certain prefabs, make network connections, set player variables that you haven't done from the editor etc etc
so:
using UnityEngine;
using System.Collections;
public class GameManager : MonoBehaviour
{
public GameObject myObject;
void Start ()
{
Instantiate(myObject, transform.position, transform.rotation);
}
}
now drag+drop your "prefab" which you want to instantiate into the slot on your "GameManager" in the inspector.
Note that it doesn't have to be when the game starts, another example is the GameManager script having a function listening for whenever a login is needed, and at that time - it instantiates your login dialog.