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Issue with Fragment Navigation. Click on my second Fragment, It still shows me my first fragment tabs

I'm trying a fragment navigation drawer, Everything works out fine, but the issue is that I don't want to have a fragment fab on my second fragment.
I really appreciate the help given. Thank you!
I will leave an image of the outcome, So it might be easier to see what I mean
https://imgur.com/a/9U4aGDF
Homepage.java
public class Homepage extends AppCompatActivity implements
NavigationView.OnNavigationItemSelectedListener {
private static final String TAG = "Homepage";
private SectionsPageAdapter mSectionsPageAdapter;
private ViewPager mViewPager;
private DrawerLayout drawer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_homepage);
mSectionsPageAdapter = new
SectionsPageAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.viewpagers);
setupViewPager(mViewPager);
Log.i("viewpager",mViewPager.toString());
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
Toolbar toolbar = findViewById(R.id.toolbar);
drawer = findViewById(R.id.drawer_layout);
NavigationView navigationview = findViewById(R.id.nav_view);
navigationview.setNavigationItemSelectedListener(this);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer,
toolbar,
R.string.navigation_drawer_open,
R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new HomeFragment()).commit();
navigationview.setCheckedItem(R.id.nav_home);
}
}
private void setupViewPager(ViewPager viewPager) {
SectionsPageAdapter adapter = new SectionsPageAdapter(getSupportFragmentManager());
adapter.addFragment(new FragmentPopular(), "Popular");
adapter.addFragment(new FragmentUpcoming(), "Upcoming");
Log.i("adaptaerrrrr",adapter.toString());
viewPager.setAdapter(adapter);
}
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem menuItem) {
Fragment fragment = null;
switch (menuItem.getItemId()) {
case R.id.nav_home:
fragment = new HomeFragment();
break;
case R.id.nav_profile:
fragment = new ProfileFragment();
break;
case R.id.nav_discussion:
fragment = new DiscussionFragment();
break;
}
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragment).commit();
drawer.closeDrawer(GravityCompat.START);
return true;
}
#Override
public void onBackPressed() {
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
}
super.onBackPressed();
}
}
SectionsPageAdapter.java
public class SectionsPageAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public void addFragment(Fragment fm, String title) {
mFragmentList.add(fm);
mFragmentTitleList.add(title);
}
public SectionsPageAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Popular Games";
case 1 :
return "Upcoming Games";
}
return null;
}
#Override
public int getCount() {
return mFragmentList.size();
}
}
activity_homepage.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/drawer_layout"
android:fitsSystemWindows="true"
tools:context=".Activities.Homepage"
android:background="#000000"
tools:openDrawer="start">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/common_google_signin_btn_text_dark_focused"
android:id="#+id/toolbar"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Dark"
android:elevation="4dp"/>
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary" />
<android.support.v4.view.ViewPager
android:id="#+id/viewpagers"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
<FrameLayout
android:id="#+id/fragment_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</FrameLayout>
</LinearLayout>
<android.support.design.widget.NavigationView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:id="#+id/nav_view"
app:headerLayout="#layout/nav_header"
app:menu="#menu/drawer_menu"/>
</android.support.v4.widget.DrawerLayout>
profileFragment.java
public class ProfileFragment extends Fragment {
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable
ViewGroup container, #Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_profile, container, false);
}
}
fragment_profile.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#FFF"
android:clickable="true">
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text ="Profile Fragment"
android:textSize="30sp"
android:layout_centerInParent="true"/>
</RelativeLayout>

getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,fragment).commit();
paste this code before break statement in onNavigationItemSelectedMethod.
you have to attach the fragment to activity.

Why is my tab layout for android not working?

I am trying to make a tab sliding activity for my app but I am not able to find what is going wrong.
Here is the code for the tab activity:
public class TabActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tab);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
ViewPager viewPager = findViewById(R.id.container);
viewPager.setAdapter(new SectionsPagerAdapter(getSupportFragmentManager()));
TabLayout tabLayout = findViewById(R.id.tabs);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_tab, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public static abstract class LayoutFragment extends Fragment {
private final int layout;
public LayoutFragment(#LayoutRes int layout) {
this.layout = layout;
}
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(layout, container, false);
}
#RequiresApi(api = Build.VERSION_CODES.KITKAT)
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
}
public static class Fragment1 extends LayoutFragment {
public Fragment1() {
super(R.layout.fragment_one);
}
}
public static class Fragment2 extends Fragment {
public Fragment2() {
super(R.layout.fragment_two);
}
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
switch (position) {
case 0:
return new Fragment1();
default:
return new Fragment2();
}
}
#Override
public int getCount() {
return 2;
}
}
}
The code is compiling perfectly but the tabs for fragment1 and fragment2 are not appearing at all.
I am not able to figure out what's going wrong and where, I would appreciate any help.
Edit:
Here is my XML code:
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/wallpaper"
android:fitsSystemWindows="true"
tools:context=".TabActivity">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="#dimen/appbar_padding_top"
android:theme="#style/AppTheme.AppBarOverlay">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_weight="1"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:title="#string/app_name">
</androidx.appcompat.widget.Toolbar>
<com.google.android.material.tabs.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.tabs.TabItem
android:id="#+id/tabItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/tab1" />
<com.google.android.material.tabs.TabItem
android:id="#+id/tabItem2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/tab2" />
</com.google.android.material.tabs.TabLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.viewpager.widget.ViewPager
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />

I think you forget to set up your view pager with tabs try this one.
ViewPager viewPager = findViewById(R.id.container);
viewPager.setAdapter(new SectionsPagerAdapter(getSupportFragmentManager()));
TabLayout tabLayout = findViewById(R.id.tabs);
tablayout.setUpWithViewPager(viewPager);

try this
tabLayout.setupWithViewPager(viewPager);
and remove this lines
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(viewPager));
EDIT
try to using LinearLayout instead of android.support.design.widget.CoordinatorLayout
EDIT
try this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/tab_bg"
app:tabGravity="fill"
app:tabIndicatorHeight="2dp"
app:tabMode="fixed" />
</android.support.design.widget.AppBarLayout>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#color/colorAccent" />
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</LinearLayout>
and in activity do this
private void init(){
ViewPager viewPager = v.findViewById(R.id.viewpager);
setupViewPager(viewPager);
TabLayout tabLayout = v.findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
tabLayout.setTabMode(TabLayout.MODE_FIXED);
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
TextView tab1 = (TextView) ((LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.custom_tab, null, false);
TextView tab2 = (TextView) ((LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.custom_tab, null, false);
tabLayout.getTabAt(0).setCustomView(tab1);
tabLayout.getTabAt(1).setCustomView(tab2);
}
private void setupViewPager(final ViewPager viewPager) {
ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getChildFragmentManager());
viewPager.setOffscreenPageLimit(3);
viewPager.setAdapter(viewPagerAdapter);
}
public class ViewPagerAdapter extends FragmentPagerAdapter {
public ViewPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
#Override
public Fragment getItem(int position) {
if(position == 0) return new Fragment1();
if(position == 1) return new Fragment2();
throw new IllegalStateException("Unexpected position " + position);
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
if(position == 0) return "Fragment 1";
if(position == 1) return "Fragment 2";
throw new IllegalStateException("Unexpected position " + position);
}
}
here is custom_tab.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView
android:id="#+id/text1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

i am using tab layout , in one of them i have a button , i want to change the fragment when that button is clicked

I have a layout with three TabItem and a ViewPager, the tabs are working and showing , but when i want to load a new fragment , for example with a click of a button on one of those tab layouts , whatever I do, I can't change the fragment. I want to load a fragment when a button on one of my tabs is clicked, but the bellow code doesn't work
getSupportFragmentManager().beginTransaction().
add(R.id.frame_layout_container,userDetailFragment).commit();
replace also dosn't work , i am a beginner in android development , can someone please help me ?
extra explanation: in one of them i have a listview , what i want is when i click on that item , i shall go to the detail about that item. here is the code in the main xml file :
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:fitsSystemWindows="true"
android:id="#+id/drawer_layout"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent" android:orientation="vertical" android:id="#+id/LinearLayout">
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:id="#+id/toolbar"
android:background="#37548D"
android:elevation="4dp" />
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/tab_layout"
android:background="#115A91"
app:tabSelectedTextColor="#FFF"
app:tabTextColor="#0A1102"
>
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/enter_tab"
android:text="#string/inter_fragment"
/>
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/contact_tab"
android:text="#string/fragment_contacts"
/>
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/register_tab"
android:text="#string/register_fragment"
/>
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/frame_layout_container"
/>
</LinearLayout>
<android.support.design.widget.NavigationView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:id="#+id/navigation_view"
app:headerLayout="#layout/drawer_layout"
app:menu="#menu/main_menu"
/>
</android.support.v4.widget.DrawerLayout>
update : this is the code of my UserDetailFragment with is a ListFragment
public class ContactsFragment extends ListFragment {
CallBacks callBacks;
public ContactsFragment() { }
ArrayList<UserObject> userObjects;
BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
userObjects = intent.getParcelableArrayListExtra(Intent_Service.SERVICE_PAYLOAD);
ArrayAdapter<UserObject> userObjectArrayAdapter = new UserArrayAdapter(context,0,userObjects);
setListAdapter(userObjectArrayAdapter);
}
};
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = new Intent(getActivity(), Intent_Service.class);
getActivity().startService(intent);
LocalBroadcastManager.getInstance(getActivity().getApplicationContext()).
registerReceiver(broadcastReceiver,new IntentFilter(Intent_Service.SERVICE_MESSAGE));
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_contacts,null);
}
public void onListItemClick(ListView l, View v, int position, long id) {
UserObject userObject = userObjects.get(position);
this.callBacks.send_user_object(userObject);
}
public interface CallBacks {
public void send_user_object(UserObject userObject);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
this.callBacks = (CallBacks)context;
}
}
and this is the code of my MainActivity :
public class MainActivity extends AppCompatActivity implements ContactsFragment.CallBacks {
android.support.v7.widget.Toolbar toolbar;
PageAdapter pageAdapter;
ViewPager viewPager;
TabLayout tabLayout;
TabItem contacts;
TabItem register;
TabItem signIn;
// ArashBroadCast broadcastReceiver = new ArashBroadCast(this);
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_page_drawer);
tab_variable_initialiser();
setSupportActionBar(toolbar);
NavigationView navigationView = findViewById(R.id.navigation_view);
navigationView.setItemIconTintList(null);
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener(){
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
if(tab.getPosition() == 1) {
toolbar.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.tab_contacts));
tabLayout.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.main_contacts));
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().setStatusBarColor(ContextCompat.getColor(MainActivity.this,R.color.status_contacts));
}
} else if(tab.getPosition() == 2) {
toolbar.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.tab_register));
tabLayout.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.main_register));
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().setStatusBarColor(ContextCompat.getColor(MainActivity.this,R.color.status_register));
}
} else {
toolbar.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.tab_signin));
tabLayout.setBackgroundColor(ContextCompat.getColor(MainActivity.this,R.color.main_signin));
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().setStatusBarColor(ContextCompat.getColor(MainActivity.this,R.color.status_signin));
}
}
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
// tabLayout.setupWithViewPager(viewPager);
}
protected void onDestroy() {
super.onDestroy();
}
public void tab_variable_initialiser() {
this.tabLayout = findViewById(R.id.tab_layout);
this.contacts = findViewById(R.id.contact_tab);
this.register = findViewById(R.id.register_tab);
this.signIn = findViewById(R.id.enter_tab);
this.viewPager = findViewById(R.id.view_pager);
this.pageAdapter = new PageAdapter(getSupportFragmentManager(),tabLayout.getTabCount());
this.viewPager.setAdapter(pageAdapter);
this.toolbar = findViewById(R.id.toolbar);
}
#Override
public void send_user_object(UserObject userObject) {
UserDetailFragment userDetailFragment = new UserDetailFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.contact_fragment_layout,userDetailFragment).commit();
}
}
if i use R.id.contact_tab , it works , but it dosn't replace the whole fragment , instead the userDetailFragment is shown bellow the list .
and i get the error : No view found for id 0x7f080031 (arash.samandar.recyclerview_final:id/contact_tab) for fragment UserDetailFragment{e489f08 #3 id=0x7f080031}

You should link your viewpager with your tablayout
tabLayout.setupWithViewPager(viewPager)
edit
how to style your TabLayout
first add your style :
<style name="AppTabLayoutDetail" parent="Widget.Design.TabLayout">
<item name="tabIndicatorColor">#color/colorPrimary</item>
<item name="tabIndicatorHeight">2dp</item>
<item name="tabPaddingStart">6dp</item>
<item name="tabPaddingEnd">6dp</item>
<item name="tabBackground">?attr/selectableItemBackground</item>
<item name="tabTextAppearance">#style/AppTabTextAppearance</item>
<item name="tabSelectedTextColor">#color/colorPrimary</item>
</style>
<style name="AppTabTextAppearance" parent="TextAppearance.Design.Tab">
<item name="android:textSize">12sp</item>
<item name="android:textColor">#b3ffffff</item>
<item name="textAllCaps">false</item>
</style>
then add it to your TabLayout
<android.support.design.widget.TabLayout
......
style="#style/AppTabLayoutDetail"
......
/>
Don't forget to remove listener from your tablayout and just link it with your pager

after a lot of practice I found the solution :
what I learned :
You have to use a FragmentPagerAdapter to handle your fragment changes. There are 3 important things:
1) remove the previous fragment .
2) call notifyDataSetChanged() to refresh the list of pages.
3) return POSITION_NONE in getItemPosition if it's asking for an old fragment.
Here is the practice code I used with a Left and a Right tab. and I change dynamically the fragments depending on what the user does
here is my code :
public class MyPager extends ViewPager {
private MyPagerAdapter mMyPagerAdapter;
public MyPager(Context context, FragmentActivity activity) {
super(context);
mMyPagerAdapter = new MyPagerAdapter(activity.getSupportFragmentManager());
setAdapter(mMyPagerAdapter);
}
public void replaceLeftFragment(Fragment fragment) {
mMyPagerAdapter.replaceLeftFragment(fragment);
}
public void replaceRightFragment(Fragment fragment) {
mMyPagerAdapter.replaceRightFragment(fragment);
}
}
public class MyPagerAdapter extends FragmentPagerAdapter {
private FragmentManager mFragmentManager;
private Fragment mLeftFragment;
private Fragment mRightFragment;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
mFragmentManager = fm;
}
#Override
public Fragment getItem(int position) {
if (position == 0) {
return mLeftFragment;
} else {
return mRightFragment;
}
}
#Override
public int getCount() {
final int nbLeft = (mLeftFragment == null) ? 0 : 1;
final int nbRight = (mRightFragment == null) ? 0 : 1;
return (nbLeft + nbRight);
}
public void replaceLeftFragment(Fragment fragment) {
if (mLeftFragment != null) {
mFragmentManager.beginTransaction().remove(mLeftFragment).commit();
}
mLeftFragment = fragment;
notifyDataSetChanged();
}
public void replaceRightFragment(Fragment fragment) {
if (mRightFragment != null) {
mFragmentManager.beginTransaction().remove(mRightFragment).commit();
}
mRightFragment = fragment;
notifyDataSetChanged();
}
#Override
public int getItemPosition(Object object) {
if ((object!=mLeftFragment) && (object!=mRightFragment)) {
return POSITION_NONE;
}
return super.getItemPosition(object);
}
}
Please give a thumbs up if it helped you, which I now it will.
thanks .

Android - TabLayout - Fragments are empty sometimes

I have created an app with a Tabbed Activity. I have 3 Tabs and in the first tab I have added a RecyclerView. At first everything works fine. But when I start the app now, the fragments are empty. Even the fragments of the 2nd and 3rd Tabs are empty, where I only placed a TextView. Here is the code from the MainActivity, it is mainly generated from Android Studio, I only added some code to change the Toolbar title and changed some small things:
public class MainActivity extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
private Toolbar toolbar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setTitle("Pflege");
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.tab_icon_pflege);
tabLayout.getTabAt(1).setIcon(R.drawable.tab_icon_dokumentation);
tabLayout.getTabAt(2).setIcon(R.drawable.tab_icon_probleme);
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
switch(tab.getPosition()) {
case 0:
mViewPager.setCurrentItem(0);
toolbar.setTitle("Pflege");
break;
case 1:
mViewPager.setCurrentItem(1);
toolbar.setTitle("Daten");
break;
case 2:
mViewPager.setCurrentItem(2);
toolbar.setTitle("Probleme");
break;
default:
mViewPager.setCurrentItem(tab.getPosition());
toolbar.setTitle("Pflege");
break;
}
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch(position){
case 0:
Tab1Pflege tab1 = new Tab1Pflege();
return tab1;
case 1:
Tab2Dokumentation tab2 = new Tab2Dokumentation();
return tab2;
case 2:
Tab3Probleme tab3 = new Tab3Probleme();
return tab3;
default:
return null;
}
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Pflege";
case 1:
return "Daten";
case 2:
return "Probleme";
}
return null;
}
}
}
Here is the XML File for the MainActivity. I changed a bit, that the tabs will be placed at the bottom of the screen:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="eis1617.muellerkimmeyer.app.MainActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="#dimen/appbar_padding_top"
android:theme="#style/AppTheme.AppBarOverlay"
android:background="#3f84dd">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:layout_above="#+id/tabs" />
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:elevation="80dp"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="56dp"
android:clickable="true"
app:tabGravity="fill"
app:tabIndicatorHeight="0dp"
app:tabMode="fixed"
app:tabBackground="#drawable/tab_color_selector"
android:background="#3f84dd"/>
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>
Now here is the fragment for the first tab. It contains the RecyclerView:
public class Tab1Pflege extends Fragment {
private RecyclerView recyclerView;
private RecyclerView.Adapter rvAdapter;
private RecyclerView.LayoutManager rvLayoutManager;
private ArrayList<String> listItems;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.tab1_pflege, container, false);
listItems = new ArrayList<>();
listItems.add("Test1");
listItems.add("Test2");
listItems.add("Test3");
recyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);
rvLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(rvLayoutManager);
rvAdapter = new RvAdapter(listItems);
recyclerView.setAdapter(rvAdapter);
return rootView;
}
}
And here is the XML File for that tab:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="eis1617.muellerkimmeyer.app.MainActivity">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/recyclerView"
/>
</RelativeLayout>
And here the XML file for the list items. There is a TextView on the left and an ImageView on the right:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="50dp"
android:background="?attr/selectableItemBackground">
<TextView
android:text="TextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/itemTitle"
android:layout_marginLeft="21dp"
android:layout_marginStart="21dp"
android:layout_centerVertical="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:textSize="20sp" />
<ImageView
android:layout_width="50dp"
android:layout_height="50dp"
android:id="#+id/itemImage"
android:layout_marginRight="11dp"
android:layout_marginEnd="11dp"
android:layout_centerVertical="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</RelativeLayout>
And finally here is my Adapter class for the RecyclerView:
public class RvAdapter extends RecyclerView.Adapter<RvAdapter.MyViewHolder> {
ArrayList<String> listItems;
public RvAdapter (ArrayList<String> listItems){
this.listItems = listItems;
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.rv_item_layout, null);
return new MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(MyViewHolder holder, final int position) {
holder.itemTitle.setText(listItems.get(position));
holder.itemImage.setImageResource(R.drawable.ic_keyboard_arrow_right);
}
#Override
public int getItemCount() {
return listItems.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder{
TextView itemTitle;
ImageView itemImage;
public MyViewHolder(View itemView){
super(itemView);
itemTitle = (TextView) itemView.findViewById(R.id.itemTitle);
itemImage = (ImageView) itemView.findViewById(R.id.itemImage);
}
}
}
I have already tried to replace "extends FragmentPagerAdapter" in MainActivity with "extends FragmentStatePagerAdapter". But the fragments are still empty. Someone know what could be the problem? Sometimes when I change something for example in the XML file for the list items, it works again. But when I restart the app it didnt work anymore. Looks like it is random if it works or not.

ViewPager not showing fragments

I can't get this to work. The basic app functions as it's supposed to but the ViewPager on one of the layout files doesn't show any fragment at all. I checked the code multiple times but I can't find a bug. When I tried debugging it I noticed that it doesn't even initialize the fragments classes which it's supposed to when you select a tab.
My MainActivity:
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
new GetData(this).execute();
TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
tab_layout.addTab(tab_layout.newTab().setText("CASUAL"));
tab_layout.addTab(tab_layout.newTab().setText("RANKED"));
tab_layout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tab_layout.getTabCount());
viewPager.setAdapter(adapter);
tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_stats) {
// Handle the camera action
} else if (id == R.id.nav_about) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
My PagerAdapter:
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
CasualStats tab1 = new CasualStats();
return tab1;
case 1:
RankedStats tab2 = new RankedStats();
return tab2;
default:
return null;
}
}
#Override
public int getCount() {
return mNumOfTabs;
}
}
Layout with the ViewPager:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"><![CDATA[
        android:id="#+id/pager"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:layout_below="#id/tab_layout"/>
]]>
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:id="#+id/tab_layout">
</android.support.design.widget.TabLayout>
<view
android:layout_width="wrap_content"
android:layout_height="wrap_content"
class="android.support.v4.view.ViewPager"
android:layout_alignParentStart="true"
android:id="#+id/view_pager"
android:layout_below="#+id/tab_layout" />
</RelativeLayout>
The classes for the tab fragments which are supposed to be displayed in the ViewPager are just normal auto generated Android Studio fragment classes.
One of the fragments:
public class CasualStats extends Fragment{
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public CasualStats() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment CasualStats.
*/
// TODO: Rename and change types and number of parameters
public static CasualStats newInstance(String param1, String param2) {
CasualStats fragment = new CasualStats();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_casual_stats, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
The xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.app.anzel.r6s.CasualStats">
<!-- TODO: Update blank fragment layout -->
<TextView
android:text="1st fragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:layout_marginStart="28dp"
android:layout_marginTop="22dp"
android:id="#+id/textView"
android:visibility="visible" />
</RelativeLayout>

The problem is that you have nested fragments and use getFragmentManager(); You should use getChildFragmentManager() instead.
java:
viewPagerAdapter = new PagerAdapter(getChildFragmentManager())
kotlin:
viewPagerAdapter = PagerAdapter(childFragmentManager)

I feel kind of stupid. The problem was with the ViewPager as I suspected. After 3h of code debugging I just moved the ViewPager from the layout with the tabs to another layout which basically connects all of the layouts.

The below sample code is working fine with viewpager and tabs. Try it out.
Main activity layout
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<android.support.design.widget.TabLayout
android:id="#+id/tab_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="?attr/actionBarSize" />
<include layout="#layout/content_main" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/fab_margin"
app:srcCompat="#android:drawable/ic_dialog_email" />
Then viewpager container layout
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="?attr/actionBarSize"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.test.myapplication.MainActivity"
tools:showIn="#layout/app_bar_main">
<android.support.v4.view.ViewPager
android:id="#+id/page_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FF0000" />
</RelativeLayout>
And here is the main activity part:
package com.test.myapplication;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.support.v4.app.*;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
ViewPager pager = (ViewPager)findViewById(R.id.page_container);
pager.setAdapter(new Adapter(getSupportFragmentManager()));
TabLayout tabs = (TabLayout)findViewById(R.id.tab_container);
tabs.setupWithViewPager(pager, true);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
public static class Adapter extends FragmentStatePagerAdapter {
private String[] titles = new String[] {"ONE", "TWO"};
public Adapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position){
case 0:
return new com.test.myapplication.Fragment();
case 1:
return new Fragment1();
}
return null;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
return titles[position];
}
}
}

If you are using any tablayout with viewpager inside NestedScrollView, make sure to put android:fillViewport="true"
Reference in the nested scrollview. Note that, if you are working with navigation drawer, your fragment may not have a nested scrollview, but your activity fragment container maybe inside a nested scroll view. Because even an empty layout with a background color (for debugging the issue) does not show up, so it was not the problem of view pager in my case, it was the problem with nested scroll view.
Debugging tip: Instead of viewpager, put some layout and set a
background color to see if the layout is visible. If the layout itself
is not visible, then you have issue with the parent layout, most
probably NestedScrollView.

You are missing setupWithViewPager, and you don't need setOnTabSelectedListener:
tab_layout.setupWithViewPager(viewPager)
Let's look here:
http://www.androidhive.info/2015/09/android-material-design-working-with-tabs/
You have to override also getPageTitle in adapter and there return tab title.
Last, don't use <view ..class> in xml, create normal xml view:
<android.support.v4.view.ViewPager
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:id="#+id/view_pager"
android:layout_below="#+id/tab_layout"/>

try this:
in your layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:id="#+id/tab_layout">
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:id="#+id/view_pager"
android:layout_below="#+id/tab_layout" />
</RelativeLayout>
in activity:
TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
tab_layout.addTab(tab_layout.newTab().setText("CASUAL"));
tab_layout.addTab(tab_layout.newTab().setText("RANKED"));
tab_layout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tab_layout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(2);
tab_layout.post(new Runnable() {
#Override
public void run() {
tab_layout.setupWithViewPager(viewPager);
}
});
tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
PagerAdapter :
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
// an array of tab titles
private String tabTitles[] = new String[]{"CASUAL", "RANKED"};
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
CasualStats tab1 = new CasualStats();
return tab1;
case 1:
RankedStats tab2 = new RankedStats();
return tab2;
default:
return null;
}
}
#Override
public int getCount() {
return mNumOfTabs;
}
#Override
public CharSequence getPageTitle(int position) {
return tabTitles[position];
}
}