ViewPager中的碎片不刷新内容或其视图

MainActivity.java

public class MainActivity extends ActionBarActivity {

    Toolbar toolbar;
    ViewPager pager;
    ViewPagerAdapter adapter;
    SlidingTabLayout tabs;
    private ArrayList<String> mLanguagesArray = null;
    int Numboftabs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        Bundle extras = getIntent().getExtras();
        if (extras != null) {
            mLanguagesArray = new ArrayList<String>();
            mLanguagesArray.addAll(extras.getStringArrayList("languages"));
            Numboftabs = mLanguagesArray.size();
        } 
    }

        toolbar = (Toolbar) findViewById(R.id.tool_bar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setIcon(R.drawable.ic_launcher);

        adapter = new ViewPagerAdapter(getSupportFragmentManager(),
                mLanguagesArray, Numboftabs, MainActivity.this);

        pager = (ViewPager) findViewById(R.id.pager);
        pager.setAdapter(adapter);

        // Assiging the Sliding Tab Layout View
        tabs = (SlidingTabLayout) findViewById(R.id.tabs);

        tabs.setViewPager(pager);
        tabs.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrollStateChanged(int arg0) {
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {
            }

            @Override
            public void onPageSelected(int arg0) {
                refreshListInFragment(arg0);
            }
        });
    }
    protected void refreshListInFragment(int position) {
        String currentLanguage = mLanguagesArray.get(position);
        FragmentManager fm = getSupportFragmentManager();
        ListviewFragment fragment = (ListviewFragment) fm
                .findFragmentById(R.id.pager);
        fragment.loadListview(currentLanguage);
    }
}
public class MainActivity e