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
沒修改前代碼：

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 "新訂單":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "跟蹤中":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "轉出":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "成交":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "流失":
                    return NewOrderFragment.newInstance(badgeRefreshListener);
                case "無效":
                    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;
        }
    }

出問題主要出現在標紅的地方，代碼修改過為

return new NewOrderFragment();
問題解決

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