Android RecyclerView NullPointerException

Question

Currently i'm working a project, where i need to implement a RecyclerView/CardView. From MainActivity i call fragments in a switch case, where all fragments work. Whenever i press on the Fragment CardViewTabelFragment (in the emulator), then i crash and get a NullPointerException. Everything in MainActivity is working. I hope my description of my problem lives up to your expectations, if not then i can elaborate and/or attach more code. Feedback is also appreciated, so that i be more throughout next time I post a question here.

This is the fragment i call, when i'm in MainActivity:

public class CardViewTabelFragment extends Fragment {


private RecyclerView recyclerView;
private RecyclerAdapter adapter;

public CardViewTabelFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate( R.layout.fragment_card_view_tabel, container, false );

    recyclerView = (RecyclerView) view.findViewById( R.id.recycler_view );

    adapter = new RecyclerAdapter();

    recyclerView.setAdapter( adapter );

    final RecyclerView.LayoutManager layoutManager = new LinearLayoutManager( getActivity() );

    ((LinearLayoutManager) layoutManager).setOrientation( LinearLayoutManager.VERTICAL );

    recyclerView.setLayoutManager( layoutManager ) ;

    return view;

  }

}

new RecyclerAdapter(); extends to another java class where code is as follows:

public class RecyclerAdapter extends RecyclerView.Adapter {

public static String[] title = new String[] {"Sensor 1", "Sensor 2"};

public static String[] beskrivelse = new String[] {"Temperatur & Humdity Sensorer", "Light Sensorer"};


@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from( parent.getContext() ).inflate( R.layout.fragment_card_view_tabel, parent, false );
    return new RecyclerViewHolder( view );
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

    ((RecyclerViewHolder) holder).bindView( position );

}

@Override
public int getItemCount() {
    return title.length;
}

private class RecyclerViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    private TextView mBeskrivelse;
    private TextView mTitle;

    public RecyclerViewHolder(View itemView) {
        super( itemView );

        mBeskrivelse = (TextView) itemView.findViewById( R.id.item_beskrivelse );
        mTitle = (TextView) itemView.findViewById( R.id.item_title );
        itemView.setOnClickListener( this );


    }

    @Override
    public void onClick(View v) {

    }

    public void bindView(int position) {

        mBeskrivelse.setText( beskrivelse[position] );
        mTitle.setText( title[position] );

    }

  }

}

` My LogCat is as follows, where u can clearly see, that the Exception occurs at

recyclerView.setAdapter( adapter );

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.yusuf.cxweb, PID: 31207
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference
    at com.example.yusuf.cxweb.CardViewTabelFragment.onCreateView(CardViewTabelFragment.java:39)
    at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)
    at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
    at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
    at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
    at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
    at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)
    at android.os.Handler.handleCallback(Handler.java:790)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

* UPDATE *

XML FILE FOR fragment_card_view_tabel

   <?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="match_parent"
    android:orientation="vertical">

    <android.support.v7.widget.CardView
        android:id="@+id/card_container1"
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:layout_margin="16dp"
        app:cardBackgroundColor="@color/colorGrass"
        app:cardCornerRadius="4dp"
        app:cardElevation="8dp">

        <TextView
            android:id="@+id/item_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textStyle="bold"
            android:layout_gravity="center"
            android:textColor="@color/colorWhite"
            android:text="Sensor 1"
            android:textAppearance="@style/TextAppearance.AppCompat.Large" />

        <TextView
            android:id="@+id/item_beskrivelse"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="30dp"
            android:text="Sensor 1"
            android:textAppearance="@style/TextAppearance.AppCompat.Large"
            android:textColor="@color/colorWhite"
            android:textSize="14sp" />
    </android.support.v7.widget.CardView>


</LinearLayout>

* LAST UPDATE *

To make this work, i had to change the layout in the inflater -> from "fragment_card_view_table" to "card_list", which is another xml file i have, where the recyclerview is in. Thanks a lot to "TheWanderer" who pointed me in the right direction!

Just been updated and attached to the question. Thanks for the answer. — Buster3650, Sep 26 '18 at 17:08
There is no recyclerview tag and no id in xml which you specified in Fragment class. Where you have used RecyclerView in xml ?? — Abhishek Sharma, Sep 26 '18 at 17:19
I am an idiot, and you pointed me in the right direction. I have another XML File, where the recyclerview is, and i didn't call that in my CardViewTableFragment. I'll update the answer to my question, and credit you. Thanks a lot ! — Buster3650, Sep 26 '18 at 17:34

score 0 · Answer 1 · answered Sep 26 '18 at 17:07

In onCreateView() only view inflation should take place.

Initialize your RecyclerView in onViewCreatedMethod().

EDIT :

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate( R.layout.fragment_card_view_tabel, container, false );
return view;
}




@Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(v, savedInstanceState);
recyclerView = (RecyclerView) view.findViewById( R.id.recycler_view );

    adapter = new RecyclerAdapter();

    recyclerView.setAdapter( adapter );

    final RecyclerView.LayoutManager layoutManager = new LinearLayoutManager( getActivity() );

    ((LinearLayoutManager) layoutManager).setOrientation( LinearLayoutManager.VERTICAL );

    recyclerView.setLayoutManager( layoutManager ) ;
}

This won't fix the issue. You can do View logic in `onCreateView()`. — TheWanderer, Sep 26 '18 at 17:11
Just tried, but unfortunately it didn't work. Thanks though, I appreciate the effort! — Buster3650, Sep 26 '18 at 17:14

score 0 · Answer 2 · answered Sep 26 '18 at 17:40

0

You're using the wrong layout XML. The one you're inflating has no RecyclerView in it. Make sure you're inflating the layout that actually contains the RecyclerView you want.

answered Sep 26 '18 at 17:40

TheWanderer

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score 0 · Answer 3 · answered Sep 26 '18 at 17:42

In these two lines

// Inflate the layout for this fragment
    View view = inflater.inflate( R.layout.fragment_card_view_tabel, container, false );

    recyclerView = (RecyclerView) view.findViewById( R.id.recycler_view );

First you are inflating the xml, then in the second line you are saying find the recyclerview in that xml.

Of course it is going to throw a NPE.

You will need to add RecyclerView there in the xml and give it the id recycler_view

score 0 · Answer 4 · answered Sep 26 '18 at 18:05

As the exception states that the setAdapter() gets null pointer exception. I think you are doing the mistake in initialization of List or ArrayList. In general you need to pass the List or ArrayList in the RecyclerAdapter Constructor. But you have done it in the static manner. Also I'm not sure whether you are overriding this method

   // total number of rows
    @Override
    public int getItemCount() {
        return yourDataArrayOrList.size();
    }

Refer this link. Try to change your code according to this structure if possible.

Android RecyclerView NullPointerException

4 Answers4