如何从android中的滑块菜单中替换视图分页器上方的片段

Question

我有活动和滑块菜单。单击滑块菜单我正在替换活动上的许多其他片段。但在第一个位置我有查看寻呼机。所以一旦我要点击第二个位置，其他片段正在替换，但是一旦我点击第一个位置，viewpager就没有创建。

public class MainActivity extends SlidingActivity implements   FragmentDrawer.FragmentDrawerListener,  CaseStudiesFragment.OnCaseStudiesAttachedFragmentListener {

   private String toolbarTitle;
   private ViewPager pager;
   SwipeMainFragmentPagerAdapter swipeMainFragmentPagerAdapter;
    private Toolbar toolbar;
    private List<Integer> _pageHistory;
   Fragment fragment;

@Override
   public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setBehindContentView(R.layout.menu_frame);
    _pageHistory = new ArrayList<>();
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeAsUpIndicator(R.mipmap.ic_menu);
    FragmentDrawer drawerMenuFragment = new FragmentDrawer();
    FragmentTransaction t = getSupportFragmentManager().beginTransaction();
    t.replace(R.id.menu_frame, drawerMenuFragment);
    t.commit();
    SlidingMenu sm = getSlidingMenu();
    sm.setOnClosedListener(new SlidingMenu.OnClosedListener() {

        @Override
        public void onClosed() {

        }
    });
    sm.setShadowWidthRes(R.dimen.shadow_width);
    sm.setFadeDegree(0.35f);
    sm.setMode(SlidingMenu.LEFT);
    sm.setBehindWidthRes(R.dimen.slidingmenu_width);
    sm.setBehindOffsetRes(R.dimen.slidingmenu_offset);
    sm.setTouchModeAbove(SlidingMenu.TOUCHMODE_FULLSCREEN);
    sm.setShadowDrawable(R.drawable.shadow);
    setUpViewPager();
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    getSupportFragmentManager().putFragment(outState, "mContent", fragment);
}

private void setUpViewPager() {
    pager = (ViewPager) findViewById(R.id.viewpager);
    swipeMainFragmentPagerAdapter = new SwipeMainFragmentPagerAdapter(getSupportFragmentManager());
    pager.setAdapter(swipeMainFragmentPagerAdapter);
    pager.getAdapter().notifyDataSetChanged();
  //  pager.invalidate();
    pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrollStateChanged(int arg0) {
        }

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

        @Override
        public void onPageSelected(int position) {
            switch (position) {
                case 0:
                    getSlidingMenu().setTouchModeAbove(SlidingMenu.TOUCHMODE_FULLSCREEN);
                    break;
                default:
                    getSlidingMenu().setTouchModeAbove(SlidingMenu.TOUCHMODE_MARGIN);
                    break;
            }
        }
    });
    pager.setCurrentItem(0);
}

@Override
public void onCaseStudy(View view, int position) {

}

private class SwipeMainFragmentPagerAdapter extends FragmentStatePagerAdapter {


    public SwipeMainFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        final Fragment result;

        switch (position) {
            case 0:
                result = new SwipeCardViewFragment();
                break;
            case 1:
                result = new WebViewsFragment();
                break;
            default:
                result = null;
                break;
        }

        return result;
    }

    @Override
    public int getCount() {
        return 2;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Fragment fragment = (Fragment) super.instantiateItem(container, position);
        return fragment;
    }

    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }
}

@Override
public void onDrawerItemSelected(View view, int position) {
    displayView(position);
    getSlidingMenu().showContent();
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home) {
        toggle();
    }
    return super.onOptionsItemSelected(item);
}

private void displayView(int position) {

    toolbarTitle = getString(R.string.all_updates_item);
    switch (position) {
        case 0:
            //
            if (pager.getCurrentItem()!=position){
                pager.setCurrentItem(0);
            }
            toolbarTitle = getString(R.string.all_updates_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 1:
            pager.setCurrentItem(0);
            toolbarTitle = getString(R.string.trending_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 2:
            pager.setCurrentItem(0);
            toolbarTitle = getString(R.string.notification_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 3:
            pager.setCurrentItem(0);
            toolbarTitle = getString(R.string.bookmarks_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 4:
            pager.setCurrentItem(0);
            toolbarTitle = getString(R.string.medical_updates_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 5:
            fragment = new CaseStudiesFragment();
            toolbarTitle = getString(R.string.case_studies_item);
            break;
        case 6:
            fragment = new ProductCatelogFragment();
            toolbarTitle = getString(R.string.product_catelog);
            break;
        case 7:
            pager.setCurrentItem(0);
            toolbarTitle = getString(R.string.webinars_item);
            getSupportActionBar().setTitle(toolbarTitle);
            break;
        case 8:
            fragment = new PollFragment();
            toolbarTitle = getString(R.string.poll_item);
            break;
        case 9:
            fragment = new ConnectionsFragment();
            toolbarTitle = getString(R.string.connection_item);
            break;
        case 10:
            fragment = new ReportAnAeFragment();
            toolbarTitle = getString(R.string.report_item);
            break;
        case 12:
            fragment = new MedicalInfoFragment();
            toolbarTitle = getString(R.string.medical_info_item);
            break;
        case 13:
            finish();
            break;
        default:
            break;
    }
    if (fragment != null) {

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.content_frame, fragment, null);
        fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        fragmentTransaction.addToBackStack(toolbarTitle);
        fragmentTransaction.commit();
       // getSupportActionBar().setTitle(null);
    }
}

}