gistfile1.txt

 int size = pics_array.length;
 
 /* this method called when the forward button clicked (for testing) */
    public void go (View view) {
        if (index < size - 1) {
            index++;
            default_Pic.setImageResource(pics_array[index]);
        }else {
            index = 0;
            default_Pic.setImageResource(pics_array[index]);
        }



    }
  /* this method called when the back button clicked (for testing) +++need fixing+++ */

    public void back (View view) {

        if (index <= 0) {
            index = size - 1 ;
            default_Pic.setImageResource(pics_array[index]);
        }else {
            index--;
            default_Pic.setImageResource(pics_array[index]);
        }

    }