Null Reference Exception & Queues

Hello,

I am having a few issues with my code. The game I have been writing for months does not seem to run well when implementing a game level manager to control 'game over' and 'start' game states. The essence of the game is to make a cube jump from platform to platform; nothing really new here. I used Queues to generate the prefab and one of the main issues I'm having is that when I'm able to run level 1, and the cube falls and triggers a game over; I've chosen that for this game the 'game over' call segues into the 'level select screen' composed of a grid like selection of locked and unlocked levels (I used MadLevelManager for this).

The GameManager prompts the user to initiate the game by pressing the screen.

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.UI;
3. using System.Collections;
4. using MadLevelManager;
5.  
6. public class GameManager : MonoBehaviour {
7.  
8.  
9.  
10.  
11.     private static GameManager instance;
12.  
13.  
14.     public Text scoreText;
15.  
16.  
17.  
18.  
19.  
20.     public GUIText     oneUpText,
21.                     distanceText,
22.                     gameOverText,
23.                     instructionsText,
24.                     TokenText,
25.                     FuelText;
26.  
27.    
28.  
29.     void Start () {
30.  
31.  
32.         GameEventManager.GameStart += GameStart;
33.         GameEventManager.GameOver += GameOver;
34.         gameOverText.enabled = false;
35.      
36.  
37.  
38.     }
39.  
40.     void Update () {
41.  
42.  
43.         //First thing called.
44.         if (Input.GetButtonDown("Fire1")) {
45.  
46.             GameEventManager.TriggerGameStart();
47.         }
48.  
49.     }
50.  
51.  
52.  
53.     private void GameStart () {
54.  
55.  
56.         instance = this;
57.  
58.  
59.         gameOverText.enabled = false;
60.  
61.  
62.         instructionsText.enabled = false;
63.  
64.      
65.         enabled = false;
66.     }
67.  
68.     private void GameOver () {
69.  
70.         gameOverText.enabled = true;
71.  
72.  
73.         instructionsText.enabled = true;
74.         enabled = true;
75.     }
76.    

There is a Platform generator, again nothing new to see here, just your run of the mill prefab generator/spawner.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections.Generic;
3.  
4. public class SkylineManager : MonoBehaviour {
5.  
6.  
7.  
8.  
9.  
10.     public PlatformGenerator platformManager= null;
11.  
12.  
13.     public Vector3 nextPosition;
14.  
15.  
16.     //the transform.
17.     public Transform prefab;
18.  
19.     public int numberOfObjects;
20.     public float recycleOffset;
21.     public Vector3 startPosition;
22.     public Vector3 minSize, maxSize;
23.  
24.  
25.     private Queue<Transform> objectQueue;
26.  
27.  
28.     //Awake is always called before any start function.
29.     void Awake() {
30.  
31.         //Check if instance already exists
32.         if(platformManager== null)
33.  
34.             //if not, set instance to this
35.             platformManager = this;
36.  
37.         //If instance already exists and it's not this:
38.         else if (platformManager != this)
39.  
40.             //Then destroy this. This enforces our singleton.
41.             Destroy (gameObject);
42.  
43.         DontDestroyOnLoad(gameObject);
44.  
45.  
46.  
47.  
48.  
49.     }
50.  
51.  
52.  
53.     void Start () {
54.  
55.  
56.  
57.         GameEventManager.GameStart += GameStart;
58.         GameEventManager.GameOver += GameOver;
59.  
60.  
61.         objectQueue = new Queue<Transform>(numberOfObjects);
62.  
63.  
64.  
65.             for  (int i = 0; i < numberOfObjects; i++)
66.  
67.         {      
68.                   objectQueue.Enqueue ((Transform)Instantiate (prefab, new Vector3(0f,0f,-100f), Quaternion.identity));
69.         }
70.  
71.  
72.     enabled = false;
73.     }
74.  
75.     private void GameStart () {
76.         nextPosition = startPosition;
77.         for(int i = 0; i < numberOfObjects; i++){
78.             Recycle();
79.         }
80.  
81.  
82.         enabled = true;
83.     }
84.  
85.     private void GameOver () {
86.  
87.      
88.         enabled = false;
89.     }
90.  
91.     void Update () {
92.  
93.         if (objectQueue.Peek().localPosition.x + recycleOffset < Cube.distanceTraveled) {
94.             Recycle();
95.         }
96.     }
97.  
98.  
99.     private void Recycle () {
100.  
101.  
102.  
103.  
104.  
105.  
106.         //scaling factor
107.         Vector3 scale = new Vector3(
108.             Random.Range(minSize.x, maxSize.x),
109.             Random.Range(minSize.y, maxSize.y),
110.             Random.Range(minSize.z, maxSize.z));
111.  
112.  
113.  
114.         Vector3 position = nextPosition;
115.         position.x += scale.x * 0.5f;
116.         position.y += scale.y * 0.5f;
117.        
118.  
119.  
120.  
121.         Transform o = objectQueue.Dequeue();
122.         o.localScale = scale;
123.         o.localPosition = position;
124.         nextPosition.x +=  scale.x;
125.  
126.         objectQueue.Enqueue(o);
127.        
128.  
129.  
130.     }
131.  
132.  
133. }

The script above is shared by two prefab objects that automatically generate themselves with different z values although as you can see, the script above has these variables hard coded.

The platform generator is slightly different than the code above, except it adds a gap between the objects and is rigid so as to allow the cube to hover. I am getting null reference exceptions from the console specifically dealing with my enable = true and enable = false flags.

The player reaches game over when colliding with a cube lying underneath the main scene at value y= -40

the code looks something like this:

Code (CSharp):

1. using MadLevelManager;
2.  
3. void OnTriggerEnter(Collider collider) {
4.  
5.         //If the object colliding with this trigger is     //cube itself. Query for values.
6.  
7.         if (collider.gameObject.tag == ("Cube")) {
8.  
9.      
10.             GameEventManager.TriggerGameOver();
11.             MadLevelProfile.SetCompleted (MadLevel.currentLevelName, false);
12.          
13.             MadLevel.LoadLevelByName("Level Select");
14.      
15.  
16.             }
17.  
18.  
19.  
20.  
21.     }

Now the GameEventManager looks like this:

Code (CSharp):

1. public static class GameEventManager {
2.  
3.     public delegate void GameEvent();
4.  
5.  
6.     //GameEvent Delegates
7.     public static event GameEvent GameStart, GameOver;
8.  
9.     public static void TriggerGameStart(){
10.         if(GameStart != null){
11.             GameStart();
12.         }
13.     }
14.  
15.     public static void TriggerGameOver(){
16.  
17.         if(GameOver != null){
18.             GameOver();
19.         }
20.     }
21. }

The issue is mainly at 'Game Over', the cube exits the scene and then we're prompted to the 'level select scene' -- Very simple mechanism of going from one level to the next. Because we failed to reach an end-of-scene cube that I left-out for brevity (located at the end of the scene with a similar OnTriggerEnter mechanism querying for the 'tag' of the cube) the player is forwarded to the grid-layout level-select screen which is implemented by MadLevelManager by MadPixelMachine(I believe?)

 

I was considering maybe adding a different state/event called 'Level Select Mode' which means, the player is no longer on this scene; keep certain things here and destroy those i don't need; or something or other....