CODEWITHSUNDEEP
androidunity-game-engineaugmented-reality
NoobAndroidDev
NoobAndroidDev

Reputation: 1

C# call other class variable but return null (Unity3D)

I'm using Unity Augmented Reality. Why does my application return a null value if I call a public value of an other class?

These are my classes:

using UnityEngine;
using System.Collections;

public class GUIControlScript : MonoBehaviour {

public GUISkin MenuSkin;
public Texture BoxBackground;
public DefaultTrackableEventHandler DTEH;
public string ttx;

void OnGUI(){
    Screen.orientation = ScreenOrientation.Landscape;
    GUI.skin = MenuSkin;
    GUI.Box(new Rect(0, 0, Screen.width, 600), BoxBackground);
    GUI.BeginGroup(new Rect(Screen.width / 2 - 150, Screen.height / 2 - 150, 300, 300));
    try
    {
        GUI.Button(new Rect(0, 0, 500, 500), ttx);
    }
    catch(System.Exception e)
    {

    }
    GUI.EndGroup();
}

void Update()
{
    ttx = DTEH.TrackableText; //This is the problem!
}

This is the class where I'm calling the variable

using UnityEngine;

public class DefaultTrackableEventHandler : MonoBehaviour,
                                        ITrackableEventHandler
{
#region PRIVATE_MEMBER_VARIABLES

private TrackableBehaviour mTrackableBehaviour;
public string TrackableText = "";

#endregion // PRIVATE_MEMBER_VARIABLES

#region UNTIY_MONOBEHAVIOUR_METHODS

void Start()
{
    mTrackableBehaviour = GetComponent<TrackableBehaviour>();
    if (mTrackableBehaviour)
    {
        mTrackableBehaviour.RegisterTrackableEventHandler(this);
    }

    OnTrackingLost();
}

#endregion // UNTIY_MONOBEHAVIOUR_METHODS

#region PUBLIC_METHODS

// Implementation of the ITrackableEventHandler function called when the
// tracking state changes.
public void OnTrackableStateChanged(
                                TrackableBehaviour.Status previousStatus,
                                TrackableBehaviour.Status newStatus)
{
    if (newStatus == TrackableBehaviour.Status.DETECTED ||
        newStatus == TrackableBehaviour.Status.TRACKED)
    {
        OnTrackingFound();

    }
    else
    {
        OnTrackingLost();
    }
}

#endregion // PUBLIC_METHODS

#region PRIVATE_METHODS

private void OnTrackingFound()
{
    Renderer[] rendererComponents = GetComponentsInChildren<Renderer>();

    // Enable rendering:
    foreach (Renderer component in rendererComponents) {
        component.enabled = true;
    }
    if (mTrackableBehaviour.TrackableName.Equals("farmasi"))
    {
        TrackableText = "farmasi";
    }
    Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");
}

private void OnTrackingLost()
{
    Renderer[] rendererComponents = GetComponentsInChildren<Renderer>();

    // Disable rendering:
    foreach (Renderer component in rendererComponents) {
        component.enabled = false;
    }

    Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");
}

#endregion // PRIVATE_METHODS

Upvotes: 0

Views: 1561

Answers (2)

cmhley
cmhley

Reputation: 66

Since you have DefaultTrackableEventHandler extending MonoBehaviour, it needs to be attached to a GameObject in order for it to initialize. You can do this in one of two ways:

  1. In the inspector viewing the GameObject that GUIControlScript is attached to: add the Script manually to the GameObject by clicking Add Component, choosing Scripts (or wherever your scripts are located), and clicking on DefaultTrackableEventHandler. In the code, you can then access the DefaultTrackableEventHandler script by calling GetComponent:

    public class GUIControlScript : MonoBehaviour {
    private DefaultTrackableEventHandler dteh;

    void Start() {
        dteh = GetComponent<DefaultTrackableEventHandler>();
    }
}

  2. In the GUIControlScript script, call AddComponent to programmatically add the DefaultTrackableEventHandler script to the GameObject:

    public class GUIControlScript : MonoBehaviour {
    private DefaultTrackableEventHandler dteh;

    void Start() {
        dteh = gameObject.AddComponent<DefaultTrackableEventHandler>();
    }
}

You do not always have to manually add the Component to the GameObject itself. Typically if you don't have any public variables that you want to change directly in the Inspector, then you can just programmatically add the Component.

Upvotes: 1

Joetjah
Joetjah

Reputation: 6132

Using the discussion in the comments, we managed to narrow it down to see what is null exactly. You call public DefaultTrackableEventHandler DTEH;, but you never initiate it. Try adding another function in your GUIControlScript-class like this:

void Start()
{
    DTEH = new DefaultTrackableEventHandler();
}

That way, you didn't only give DTEH a type, but you initialized it as well.

Upvotes: 1

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