Having trouble fading out an image and fading in another one using ITrackableEventHandler

This is (below the image) the DefaultTrackableEventHandler.cs that I have modified (it is attached to my image target).
As you can see, I have 2 elements (element 0 and element 1) that I am trying to fade out (element 1) and fade in (element 0).
The fade in and out work well, but always happen twice before completing and I do not understand why. Everything happens in the code below.

If you think of a more elegant method, please let me know as I have 23 elements in fact coming to that Materials array in the Mesh Renderer.

A big big thank you for any hint!





/*==============================================================================
Copyright (c) 2017 PTC Inc. All Rights Reserved.
Copyright (c) 2010-2014 Qualcomm Connected Experiences, Inc.
All Rights Reserved.
Confidential and Proprietary - Protected under copyright and other laws.
==============================================================================*/
using UnityEngine;
using UnityEngine.Video;
using Vuforia;
using System.Collections;

/// <summary>
/// A custom handler that implements the ITrackableEventHandler interface.
/// </summary>
public class DefaultTrackableEventHandler : MonoBehaviour, ITrackableEventHandler
{
#region PRIVATE_MEMBER_VARIABLES
protected TrackableBehaviour mTrackableBehaviour;

//My Variables
public AudioSource asource;
public AudioClip aClip;
public VideoPlayer vPlayer;
private Material[] mats;

public static bool targetDetected = false;
#endregion // PRIVATE_MEMBER_VARIABLES
#region UNTIY_MONOBEHAVIOUR_METHODS

protected virtual void Start()
{
mTrackableBehaviour = GetComponent<TrackableBehaviour>();
if (mTrackableBehaviour)
mTrackableBehaviour.RegisterTrackableEventHandler(this);
}
#endregion // UNTIY_MONOBEHAVIOUR_METHODS

#region PUBLIC_METHODS
//Make only the voix-off text NOT transparent initially. Remember
// that the last element in materials array is displayed on the screen cube.
void InitializeMaterials(Material[] mats)
{
for (int i=0; i < mats.Length; i++)
{
//Check if i->first image
if (mats .name != "0-TexteMuseeORF")
{
Color tempCol = mats.color;
tempCol.a = 1;
mats .color = tempCol;
}
else
{
Color tempCol = mats.color;
tempCol.a = 0;
mats .color = tempCol;
}
}
}

IEnumerator FadeOutThenIn(Material mat1, Material mat2)
{
//Fade out
for (float f = 1f; f >= 0f; f -= 0.005f)
{
Color c = mat1.color;
c.a = f;
mat1.color = c;
yield return null;
}
//Fade in
for (float f = 0f; f <= 1f; f += 0.005f)
{
Color c = mat2.color;
c.a = f;
mat2.color = c;
yield return null;
}
}

//***************We will fix this bad code later!!!***************
// void FadeWhenSoundCompleted2_1()
// {
// {
// StartCoroutine (FadeOutThenIn (mats[2], mats[1]));
// }
// }
void FadeWhenSoundCompleted1_0()
{
{
StartCoroutine (FadeOutThenIn (mats[1], mats[0]));
}
}

void DisplayVideoWhenFadingCompleted()
{
this.vPlayer.gameObject.SetActive(true);
vPlayer.Play ();
}

/// <summary>
/// Implementation of the ITrackableEventHandler function called when the
/// tracking state changes.
/// </summary>
public void OnTrackableStateChanged(
TrackableBehaviour.Status previousStatus,
TrackableBehaviour.Status newStatus)
{
if (newStatus == TrackableBehaviour.Status.DETECTED ||
newStatus == TrackableBehaviour.Status.TRACKED ||
newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)
{
////Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");
OnTrackingFound();
if ((mTrackableBehaviour.TrackableName == "CortegeMacabre"))
{
//Get materials from the mesh renderer
mats = GetComponentInChildren<MeshRenderer> ().materials;

//Make only voix-off text NOT transparent initially.
// Only element 1 here is visible as it is the last element entered (the text).
InitializeMaterials (mats);

//Cancel all calls to Invoke to avoid a mess when target is lost and found
// again many times before the audio or the fadeInOut complete.
CancelInvoke ("FadeWhenSoundCompleted1_0");
//CancelInvoke ("DisplayVideoWhenFadingCompleted");

//Disable the Game Object (screen) "VideoRoueAGodets", make it invisible at the beginning
this.vPlayer.gameObject.SetActive(false);

//Play the voix off
asource.Play();

//When the voix off has completed, do the fading
Invoke ("FadeWhenSoundCompleted1_0", aClip.length + 2f);

//When fading has completed, display the video
//Invoke("DisplayVideoWhenFadingCompleted", aClip.length + 6f);
}
}
else if (previousStatus == TrackableBehaviour.Status.TRACKED &&
newStatus == TrackableBehaviour.Status.NOT_FOUND)
{
Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");
OnTrackingLost();
if ((mTrackableBehaviour.TrackableName == "CortegeMacabre"))
{
asource.loop = false;
asource.Stop ();
vPlayer.Stop ();
}
}
else
{
// For combo of previousStatus=UNKNOWN + newStatus=UNKNOWN|NOT_FOUND
// Vuforia is starting, but tracking has not been lost or found yet
// Call OnTrackingLost() to hide the augmentations
OnTrackingLost();
}
}
#endregion // PUBLIC_METHODS
#region PRIVATE_METHODS
//Called when any of the image target is tracked
protected virtual void OnTrackingFound()
{
//Target detected
targetDetected = true;
var rendererComponents = GetComponentsInChildren<Renderer>(true);
var colliderComponents = GetComponentsInChildren<Collider>(true);
var canvasComponents = GetComponentsInChildren<Canvas>(true);
// Enable rendering:
foreach (var component in rendererComponents)
component.enabled = true;
// Enable colliders:
foreach (var component in colliderComponents)
component.enabled = true;
// Enable canvas':
foreach (var component in canvasComponents)
component.enabled = true;
}
protected virtual void OnTrackingLost()
{
//Target detected
targetDetected = false;
var rendererComponents = GetComponentsInChildren<Renderer>(true);
var colliderComponents = GetComponentsInChildren<Collider>(true);
var canvasComponents = GetComponentsInChildren<Canvas>(true);
// Disable rendering:
foreach (var component in rendererComponents)
component.enabled = false;
// Disable colliders:
foreach (var component in colliderComponents)
component.enabled = false;
// Disable canvas':
foreach (var component in canvasComponents)
component.enabled = false;
}
#endregion // PRIVATE_METHODS
}