Get active scene when next scene loads - unity3d

Question

So I've been trying to make a game but when I press the button the scene reloads itself. What I want to do is make it so that whenever a scene is loaded it gets the build index of the active scene.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
public class LevelSwitch : MonoBehaviour
{
int CurrentSceneBuildIndex;
bool sceneLoaded;
void Update()
{
if (sceneLoaded == true )
{
CurrentSceneBuildIndex = SceneManager.GetActiveScene().buildIndex;
}
}
public void NextLevel()
{
SceneManager.LoadScene(CurrentSceneBuildIndex + 3 );
sceneLoaded = true;
}
public void LevelSelect()
{
SceneManager.LoadScene("LevelSelect");
}
}

Answer 1

The issue:
Ok, so the issue with your solution is that when a new scene is loaded in Unity, GameObjects and their attached scripts are not kept between scenes. In your scripts function NextLevel() you are loading the scene and then setting the sceneLoaded boolean to true however this is after the new scene is loaded and we know that GameObjects and their attached scripts do not transfer between scenes which means this boolean value does not transfer to the next scene either. This is unless a GameObject is marked with dontdestroyonload.
So what can we do to fix this?
To get the current build index of the scene when it is loaded you can attach a script to a GameObject in the scene you want to get the index of which uses SceneManager.sceneLoaded to detect when the scene is finished loading and then get the index.
For example:
using UnityEngine;
using UnityEngine.SceneManagement;
public class ExampleCode : MonoBehaviour
{
void OnEnable()
{
Debug.Log("OnEnable called");
SceneManager.sceneLoaded += OnSceneLoaded; // This tells the script to call the function "OnSceneLoaded" when the scene manager detects the scene has finished loading with the parameters of the scene object and the mode of how the scene was loaded
}
void OnSceneLoaded(Scene scene, LoadSceneMode mode)
{
Debug.Log("OnSceneLoaded: " + scene.name + ", Build Index : " + scene.buildIndex.ToString());
Debug.Log("Load Mode : " + mode);
}
// called third
void Start()
{
Debug.Log("Start");
}
// called when the game or scene closes
void OnDisable()
{
Debug.Log("OnDisable");
SceneManager.sceneLoaded -= OnSceneLoaded; // This tells the script to stop calling OnSceneLoaded when the scene manager detects a new scene has been loaded
}
}