RaycastHit2D.collider always null?

I have custom buttons created by sprites, which has component of BoxCollider2D. I want to Raycast for the detection of touch. following is what I set it up:

There are 3 buttons in a Control_3, BtnLeft, BtnCenter and BtnRight, those setting:

And following is the code what I did fot the detection of touch:

1. void update(){
2. int i =0;
3. while(i <Input.touchCount){
4. Touch t =Input.GetTouch(i);
5. if(t.phase ==TouchPhase.Began){
6. RaycastHit2D hit;
7. hit =Physics2D.Raycast(Camera.main.ScreenToWorldPoint(t.position),Vector2.zero);
8. Debug.Log(hit.collider);
9. if(hit.collider !=null){
10. Debug.Log(hit.collider.name);
11. }
12. }
13. i++;
14. }
15. }

However, the hit.collider always return a null value. I have no idea why would it happen. Could anyone help me, please?

 

collider is the property for the 3d version so it will be null if you have a 2d collider on it. I think there is a collider2d property.

 

This answer is completely incorrect. hit.collider returns a Collider2D in this case.