NullReference when prefabbutton becomes visible

Hello Guys,

I get a NullReference in my programm due to a prefabbutton. If I make the prefabbutton visible/active when I start the program it throws this error, and if I make it invisible and create another instance and make that visible while the program is running, it throws the same error.

Code (CSharp):

1.  
2. public void Awake()
3.     {
4.         token = (Token) storageHandler.LoadData("token");
5.         semesterNumber.text = "semester1"; // line 39
6.     }

Code (CSharp):

1. public void AddMoreButton()
2.     {
3.         if (lectureInput.text.Length < 1)
4.         {
5.             return;
6.         }
7.         lectureTitle.text = lectureInput.text;
8.         creditsTitle.text = creditsInput.text;
9.         swsTitle.text = swsInput.text;
10.         GameObject button = (GameObject) Instantiate (prefabButton);
11.         Button buttonInstance = button.GetComponentInChildren<Button>();
12.         buttonInstance.onClick.AddListener(() => {  });
13.         button.transform.SetParent(panel.transform, false);
14.         button.layer = 5;
15.         button.SetActive(true);  //line 99
16.  
17.         GameObject childButton = (GameObject)Instantiate(deleteButton);
18.         Button childButtonInstance = childButton.GetComponentInChildren<Button>();
19.         childButtonInstance.onClick.AddListener(() => { Destroy(button); });
20.         childButton.transform.SetParent(button.transform, false);
21.         childButton.layer = 5;
22.         childButton.SetActive(true);
23.  
24.         ClearInputs();
25.     }

NullReferenceException: Object reference not set to an instance of an object
SemesterScript.Awake () (at Assets/Scripts/SemesterPage/SemesterScript.cs:39)
UnityEngine.GameObject:SetActive()
SemesterScript:AddMoreButton() (at Assets/Scripts/SemesterPage/SemesterScript.cs:99)
UnityEngine.EventSystems.EventSystem:Update()

 

Use code tags, and let us know what line the error points to when you doubleclick it.

 

As a general rule of thumb, Awake should be used for initializations that can be done entirely within the current script (without accessing any external objects), or using resources that are guaranteed to be available at the time the GameObject and Component are created and Awake is called. If you're needing to access other GameObjects for some part of the initialization process, or other Components on the same GameObject, and the call order is not guaranteed by the Script Execution Order, then you should place those parts in Start instead.

I would also check to make sure that the semesterNumber reference is actually set in the inspector, assuming that it's an inspector-assigned member (which isn't completely clear from the portion of code you've provided).

 

It directs me to line 39

 

The semesterNumber is a Text UI Element where the reference is set in the inspector.

 

Which line is line 39? You've pasted only a fragment of your script file, so the line number in your script file doesn't help us locate the error.

 

Its commented in the code. Line 5 of the first code section.