TabLayout with ViewPager on a fragment - Lollipop devices

Question

I am developing an app where in my MainActivity I am using a Navigation Drawer to switch the fragments on the Frame layout.

One of those fragments is a 'help' Fragment in which I am using a Tab layout and a viewpager to swipe among three pages, 'about us', 'help'& 'contact us'

Everything works fine on below lollipop devices.The actionbar seems to stick to the tab layout (used toolbar as an actionbar).

But on Lollipop devices it is shown like the actionbar and the tablayout are separated.

How can I achieve the same on lollipop devices also?

MainActivity :

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

NavigationView navigationView;
ActionBarDrawerToggle toggle;
DrawerLayout drawer;
FragmentManager fm = getSupportFragmentManager();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setTitle("Title");

    drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

@Override
public boolean onNavigationItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.nav_help) {
         getSupportActionBar().setTitle("Help");
        fm.beginTransaction().replace(R.id.l_frame_layout, new Help(),"help").commit();
    } 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;}

Help.java

public class Help extends Fragment {
ViewPager pager;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.layout_help, container, false);
    return(rootView);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    final TabLayout tabLayout = (TabLayout)getActivity(). findViewById(R.id.tllayout_helpTABLAYOUTtl);
    tabLayout.addTab(tabLayout.newTab().setText("ABOUT"));
    tabLayout.addTab(tabLayout.newTab().setText("HELP"));
    tabLayout.addTab(tabLayout.newTab().setText("CONTACT"));

    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    actionBar = getActivity().getActionBar();

    pager = (ViewPager)getActivity().findViewById(R.id.vplayout_helpVIEVPAGERvp);
    pager.setAdapter(new MyPagerAdapter(getFragmentManager()));

    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            pager.setCurrentItem(tab.getPosition());
        }
        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }
        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });

    pager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }
        @Override
        public void onPageSelected(int position) {


        }
        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });
}

class MyPagerAdapter extends FragmentStatePagerAdapter {
    public MyPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int pos) {
        switch(pos) {

            case 0: AboutUs tab1 = new AboutUs();
                return  tab1;

            case 1: HelpRecharge tab2 = new HelpRecharge();
                return  tab2;

            case 2: ContactUs tab3 = new ContactUs();
                return  tab3;

            default: return  null;
        }
    }

   @Override
    public int getCount() {
        return 3;
    }
}}

Answer 1

Seems like you have elevation set for the action bar in your style xml.

For Android 5.0+, if you want to set your actionbar style as below:

<item name="android:elevation">0dp</item>

and for Support library compatibility use:

<item name="elevation">0dp</item>

Example of style for a AppCompat light theme:

<style name="Theme.MyApp.ActionBar" parent="style/Widget.AppCompat.Light.ActionBar.Solid.Inverse">
   <!-- remove shadow below action bar -->
   <!-- <item name="android:elevation">0dp</item> -->
   <!-- Support library compatibility -->
   <item name="elevation">0dp</item>
</style>

Then apply this custom ActionBar style to you app theme:

<style name="Theme.MyApp" parent="Theme.AppCompat.Light">
    <item name="actionBarStyle">@style/Theme.MyApp.ActionBar</item>
</style>

Also for pre 5.0 Android, add this too to your app theme:

<!-- Remove shadow below action bar Android < 5.0 -->
<item name="android:windowContentOverlay">@null</item>

Answer 2

尝试通过添加以下代码动态设置工具栏的高程：

        appBarLayout.setElevation( 0 );