android FragmentPagerAdapter的“标准”配置

private class ImagePagerAdapter extends FragmentPagerAdapter {         public List<ImageItem> fileList;         public ImagePagerAdapter(FragmentManager fm, List<ImageItem> fileList) {            super(fm);            this.fileList = fileList;        }         @Override        public int getCount() {            return fileList == null ? 0 : fileList.size();        }        @Override        public int getItemPosition(Object object) {            return POSITION_NONE;        }        @Override        public boolean isViewFromObject(View view, Object obj) {            return view == ((Fragment) obj).getView();        }        @Override        public void destroyItem(ViewGroup container, int position, Object object) {            Fragment fragment = ((Fragment) object);            container.removeView(fragment.getView());            FragmentUtils.removeFragmentRecently(getSupportFragmentManager(), fragment);        }        @Override        public Fragment getItem(int position) {            String url = fileList.get(position).getActualUrl();            return ImageDetailFragment.newInstance(url);        }     }