Attempt to write to field 'android.support.v4.app.FragmentManagerImpl android.support.v4.app.Fragment.mFragmentManager' on a null object reference

E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: org.example.magnusluca.drawertestapp, PID: 3624
java.lang.NullPointerException: Attempt to write to field 'android.support.v4.app.FragmentManagerImpl android.support.v4.app.Fragment.mFragmentManager' on a null object reference
没修改前代码：

public class OrderManagerFragmentPagerAdapter extends FragmentPagerAdapter {
        private FollowingResult.DataEntity.CountEntity countEntity;

        public OrderManagerFragmentPagerAdapter(FragmentManager fm, FollowingResult.DataEntity.CountEntity countEntity) {
            super(fm);
            this.countEntity = countEntity;
        }

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

        @Override public Fragment getItem(int position) {
            OrderManagerFragment badgeRefreshListener = OrderManagerFragment
                .this;
            String strTabTitle = TITLES[position];
            switch (strTabTitle) {
                case "新订单":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "跟踪中":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "转出":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "成交":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "流失":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "无效":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                default:
                    return null;
            }
        }

        @Override public CharSequence getPageTitle(int position) {
            return TITLES[position % TITLES.length];
        }

        @Override public int getCount() {
            return TITLES.length;
        }
    }

出问题主要出现在标红的地方，代码修改过为

return new NewOrderFragment();
问题解决

stackoverflow上面解决方案：http://stackoverflow.com/questions/26822516/how-to-display-3-fragments-inside-pageviewer