Can't change sprite image of a button

I want to change button Source Image via OnClick event but it doesn’t work. The public function is attached to the button which image i want to change. Here’s code:

Sprite sOff, sOn;

void Start () {
        sOn = Resources.Load<Sprite>("soundon1");
        sOff = Resources.Load<Sprite>("soundoff");
if (reference.AudioOn == true)
                button.image.sprite = sOn;
            else
                button.image.sprite = sOff;
}

public void ChangeSprite() {
        if (button.image.sprite == sOn)
            button.image.sprite = sOff;
        if (button.image.sprite == sOff)
            button.image.sprite = sOn;
    }

Sprites are loading fine. Changing sprite works in Start function but I can’t do it by clicking on the button. Any ideas why?

You’re checking to see if the current sprite is set to the ‘on’ sprite, and if it is then setting it to ‘off’. This is fine, however you’re then checking to see if it’s ‘off’ and setting it to ‘on’. Since you just got done setting it to off this will always trigger. You need to use an ‘else’ in there, like this:

public void ChangeSprite() {
         if (button.image.sprite == sOn)
             button.image.sprite = sOff;
         else if (button.image.sprite == sOff)
             button.image.sprite = sOn;
     }

or, since it’s just two possible states, can simplify a bit like this:

public void ChangeSprite() {
         if (button.image.sprite == sOn)
             button.image.sprite = sOff;
         else
             button.image.sprite = sOn;
     }