Instantiate is null

[ilovebird]

I have a Singleton Class called "BLSingleton", which has a public GameObject prefabPop, I drag a prefab to it, and a function:
public void showPopview() {
    GameObject popView = (GameObject) Instantiate(prefabPop);
}

but in other class when I call BLSingleton.GetInstance().showPopview(), there is an error:
ArgumentException: The thing you want to instantiate is null.

Anybody knows why? Thanks very much.

[ilovebird]

I modified the singleton class to common class called "BLUtility" like this:

public GameObject prefabPop;
public void showPopview ()
{
    GameObject popView = (GameObject) Instantiate(prefabPop);
}

and in another class, I called showPopview()
BLUtility utility = new BLUtility();
utility.showPopview();

but the problem is still the same.

[ArenMook]

Your question doesn't seem to have anything to do with NGUI. Your "prefabPop" was likely never set to anything.

[ilovebird]

I have dragged a gameobject to prefabPop,
and in the same class ("BLUtility.cs"), I can Instantiate(prefabPop) correctly
but in another class("test.cs"), I try:

BLUtility utility = new BLUtility();
utility.showPopview();

it was not right.

[ArenMook]

If BLUtility derives from MonoBehaviour, you can't just "new" it. You have to AddComponent.

Again, I don't see how this is related to NGUI.

[ilovebird]

Thanks for you answer, I'm using NGUI recently, so I post here unthinkingly.