NullPointerException is thrown when tabLayout is created

Question

Hello I want to create tabLayout with the help of ViewPager class so that I can swipe among the tabs.

I am creating tabs I setup fragments, viewPagerAdapter and viewPager. Here I initialized tabLayout too but I don't understand this error. Please help me to solve.

Here is my main xml which contains tabular layout :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.davda.musicmain.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <include
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            layout="@layout/toolbar_layout"
            >

            <android.support.design.widget.TabLayout
                android:layout_height="wrap_content"
                android:layout_width="match_parent"
                android:id="@+id/tabLayout"
                app:tabMode="scrollable"
                app:tabGravity="center">

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

Here is my code :

    tb = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(tb);


    tabLayout = (TabLayout) findViewById(R.id.tabLayout);
    viewPager = (ViewPager) findViewById(R.id.viewPager);

    viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());

    viewPagerAdapter.addFrags(new Albums(), "Albums"); // `new Albums()` should be inside `FragmentPagerAdapter.getItem()`
    viewPagerAdapter.addFrags(new Tracks(), "Tracks"); // `new Tracks()` should be inside `FragmentPagerAdapter.getItem()`
    viewPagerAdapter.addFrags(new Artists(), "Artists"); // `new Artists()` should be inside `FragmentPagerAdapter.getItem()`

    viewPager.setAdapter(viewPagerAdapter);
    tabLayout.setupWithViewPager(viewPager);

Here is stacktrace :

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.davda.musicmain, PID: 32662
              java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.davda.musicmain/com.example.davda.musicmain.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.TabLayout.setupWithViewPager(android.support.v4.view.ViewPager)' on a null object reference
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2702)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2788)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1503)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6209)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.TabLayout.setupWithViewPager(android.support.v4.view.ViewPager)' on a null object reference
                  at com.example.davda.musicmain.MainActivity.onCreate(MainActivity.java:35)
                  at android.app.Activity.performCreate(Activity.java:6745)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2655)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2788) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1503) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6209) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
D/AppTracker: App Event: crash
Application terminated.

post the xml layout and onCreate method – Prabha Karan Feb 21 '17 at 07:19 — Prabha Karan, Feb 21 '17 at 07:19
clean build your apk... – rafsanahmad007 Feb 21 '17 at 07:31 — rafsanahmad007, Feb 21 '17 at 07:31
Not sloved by clean building apk @rafsanahmad007 – Pedo Feb 21 '17 at 07:42 — Pedo, Feb 21 '17 at 07:42

score 2 · Answer 1 · answered Feb 21 '17 at 07:44

2

Just put the TabLayout outside the <include> tag.

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <include
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        layout="@layout/toolbar_layout"
        />

    <android.support.design.widget.TabLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:id="@+id/tabLayout"
        app:tabMode="scrollable"
        app:tabGravity="center"/>

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

answered Feb 21 '17 at 07:44

Akash Patel

2,757
1
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No @Akash It gives me runtime exception that you must implement OnFragmentInteractionListener – Pedo Feb 21 '17 at 08:34
@Pedo add your error and mention that in which line you get error. – Akash Patel Feb 21 '17 at 08:54
Okay I m editing in the question – Pedo Feb 21 '17 at 09:10

score 1 · Answer 2 · edited Jan 21 '21 at 19:53

Please refer this code 1. Check the setContentView() your xml layout is correctly in which xml you have the viewpager,tablayout that must be placed. 2. check the id for tab layout,viewpager.

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

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    tabLayout = (TabLayout) findViewById(R.id.tabLayout);
    viewPager = (ViewPager) findViewById(R.id.viewPager);
    viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());

    viewPager.setAdapter(viewPagerAdapter);
    tabLayout.setupWithViewPager(viewPager);

}

And

  public class ViewPagerAdapter extends FragmentPagerAdapter {
      public ViewPagerAdapter(FragmentManager fragmentManager) {
          super(fragmentManager);
      }
  
      @Override
      public Fragment getItem(int position) {
          if(position == 0) return new CallLogFragment();
          if(position == 1) return new MissedCallFragment();
          if(position == 2) return new ReceivedCallFragment();
          if(position == 3) return new OutgoingCallFragment();

          throw new IllegalStateException("Unexpected position " + position);
      }
  
      @Override
      public int getCount() {
          return 4;
      }
  
      @Override
      public CharSequence getPageTitle(int position) {
          if(position == 0) return "Call Log";
          if(position == 1) return "Missed Call";
          if(position == 2) return "Received Call";
          if(position == 3) return "Outgoing Call";
        
          throw new IllegalStateException("Unexpected position " + position);
      }
  }

No this is not a problem these all are correct. – Pedo Feb 21 '17 at 07:36 — Pedo, Feb 21 '17 at 07:36

NullPointerException is thrown when tabLayout is created

2 Answers2