Only TabItem instances can be added to TabLayout

Question

hello guys i was trying to add tab layout in navigation drawer activity which i created from welcome screen in android studio. but when i try to implement the code and run the application the app is crashing and is showing the rendering issue with XML file here is the code of .xml file

<?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"  
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.madhu.management.QuestionPaperActivity"
    tools:showIn="@layout/app_bar_question_paper">

    <android.support.design.widget.TabLayout
        android:id="@+id/tablayout_id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        app:tabGravity="fill"
        app:tabIndicatorColor="@color/colorAccent"
        app:tabMode="fixed">

        <android.support.v4.view.ViewPager
            android:id="@+id/viewpager_id"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

        </android.support.v4.view.ViewPager>

    </android.support.design.widget.TabLayout>

</LinearLayout>`

and here is the .class file

` public class QuestionPaperActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    //declaring access specifiers for tablayout
private TabLayout tabLayout;
private ViewPager viewPager;
private ViewPagerAdapter adapter;


//declaring variables for navigation layout
    DrawerLayout drawer;
    NavigationView navigationView;
    Toolbar toolbar = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_question_paper);
        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();
            }
        });

         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.addDrawerListener(toggle);
    toggle.syncState();

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

    tabLayout = (TabLayout) findViewById(R.id.tablayout_id);
    viewPager = (ViewPager) findViewById(R.id.viewpager_id);
    adapter = new ViewPagerAdapter(getSupportFragmentManager());

    //adding fragments here
    adapter.AddFragment(new InternalQuestionFragment(),"Internal Papers");
    adapter.AddFragment(new ExternalQuestionFragment(),"External Papers");
    viewPager.setAdapter(adapter);
    tabLayout.setupWithViewPager(viewPager);
}

@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.dash_board, 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();
    switch (id) {

        case R.id.nav_notice:
            Intent h = new Intent(QuestionPaperActivity.this, NoticeActivity.class);
            startActivity(h);
            break;
        case R.id.nav_notes:
            Intent i = new Intent(QuestionPaperActivity.this, NotesActivity.class);
            startActivity(i);
            break;
        case R.id.nav_question_papers:
            Intent g = new Intent(QuestionPaperActivity.this, QuestionPaperActivity.class);
            startActivity(g);
            break;
        case R.id.nav_update:
            Intent s = new Intent(QuestionPaperActivity.this, UpdatesActivity.class);
            startActivity(s);
            break;
    }
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

}`

Answer 1

From your xml file, take android.support.v4.view.ViewPager out from the TabLayout. This is because TabLayout can only contain tabitem instances. Make it like 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"  
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.madhu.management.QuestionPaperActivity"
    tools:showIn="@layout/app_bar_question_paper">

    <android.support.design.widget.TabLayout
        android:id="@+id/tablayout_id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        app:tabGravity="fill"
        app:tabIndicatorColor="@color/colorAccent"
        app:tabMode="fixed">

    </android.support.design.widget.TabLayout>
    <android.support.v4.view.ViewPager
            android:id="@+id/viewpager_id"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

        </android.support.v4.view.ViewPager>


</LinearLayout>`