שינוי רקע של כפתור

public void changeBack(View view) {

   
count
++;
   
count = count % 3
;
   
if (count == 1
)
       
b1.setBackground(getDrawable(R.drawable.xpic
));
   
if (count == 2
)
       
b1.setBackground(getDrawable(R.drawable.circlepic
));
   
if (count == 0
)
       
b1.setBackground(getDrawable(R.drawable.blank
));
}