private void setItemAsSelected(int position){
        if(mPreviousSelectedIndicator != null){
            mPreviousSelectedIndicator.setImageDrawable(mUnselectedDrawable);
            mPreviousSelectedIndicator.setPadding(
                    (int)mUnSelectedPadding_Left,
                    (int)mUnSelectedPadding_Top,
                    (int)mUnSelectedPadding_Right,
                    (int)mUnSelectedPadding_Bottom
            );
        }
        ImageView currentSelected = (ImageView)getChildAt(position + 1);
        if(currentSelected != null){
            currentSelected.setImageDrawable(mSelectedDrawable);
            currentSelected.setPadding(
                    (int)mSelectedPadding_Left,
                    (int)mSelectedPadding_Top,
                    (int)mSelectedPadding_Right,
                    (int)mSelectedPadding_Bottom
            );
            mPreviousSelectedIndicator = currentSelected;
        }
        mPreviousSelectedPosition = position;
    }
since we used a adapter wrapper, so we can't getCount directly from wrapper.
@return
library/src/main/java/com/daimajia/slider/library/Indicators/PagerIndicator.java