private class MealsInCategoryPagerAdapter extends FragmentStatePagerAdapter {
        private SparseArray<WeakReference<MealsListFragment>> fragments=new SparseArray<>();
        MealsInCategoryPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i)
        {
            if(i==0)
                return MealsListFragment.newInstance(category, -1);
            else return MealsListFragment.newInstance(category, category.children[i-1].id);
        }

        @Override
        public int getCount() {
            int count=1;
            if(category.children!=null)
                count+=category.children.length;
            return count;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            if(position==0)
                return MyApplication.getInstance().getString(R.string.all);
            else return category.children[position-1].title;
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            Object newObject = super.instantiateItem(container, position);
            fragments.append(position, new WeakReference<>((MealsListFragment)newObject));
            return newObject;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            fragments.delete(position);
            super.destroyItem(container, position, object);
        }

        public SparseArray<WeakReference<MealsListFragment>> getAllFragments()
        {
            return fragments;
        }
    }