Getting a null reference on RecyclerView

Question

I am trying to use RecyclerView and its adapter in a fragment. Whenever I try to open that fragment app crashes and throws an exception:

Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget RecyclerView$Adapter)' on a null object reference

MyActivity.java:

public class upperClass extends ... { ... public static innerClass extends CorrectedPreferenceFragment ... { private RecyclerView groupsInCommonRecyclerView; private View v; ... @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { v = inflater.inflate(R.layout.recipient_common_groups, container, false); groupsInCommonRecyclerView = (RecyclerView) v.findViewById(R.id.recycler_view); groupsInCommonRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); ArrayList<GroupsInCommonItem> commonGroups = initializeGroupsInCommon(); GroupsInCommonRecycleViewAdapter groupsInCommonRecycleViewAdapter = new GroupsInCommonRecycleViewAdapter(getContext(), commonGroups); groupsInCommonRecyclerView.setAdapter(groupsInCommonRecycleViewAdapter); return v; } }

recipient_common_groups.xml:

<?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.support.v7.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/recycler_view"> </android.support.v7.widget.RecyclerView> </LinearLayout>

what do you do in initializeGroupsInCommon() method ?

Vivek Mishra
– Vivek Mishra

2019-07-01 06:06:23 +00:00
Commented Jul 1, 2019 at 6:06 — Vivek Mishra
– Vivek Mishra, Commented Jul 1, 2019 at 6:06
why are you declaring inner class as static ?

Umar Hussain
– Umar Hussain

2019-07-01 06:11:17 +00:00
Commented Jul 1, 2019 at 6:11 — Umar Hussain
– Umar Hussain, Commented Jul 1, 2019 at 6:11
Populating List with dummy data. @VivekMishra

Murat
– Murat

2019-07-01 06:13:45 +00:00
Commented Jul 1, 2019 at 6:13 — Murat
– Murat, Commented Jul 1, 2019 at 6:13
The static keyword is the culprit

Sahil Manchanda
– Sahil Manchanda

2019-07-01 06:27:55 +00:00
Commented Jul 1, 2019 at 6:27 — Sahil Manchanda
– Sahil Manchanda, Commented Jul 1, 2019 at 6:27

Ridcully · Accepted Answer · 2019-07-01 06:12:45Z

Seems that groupsInCommonRecyclerView becomes null somewhere after setting layout manager and before setting adapter. Not obvious from posted code, so try going through your code with debugger step by step.

Gowtham K K · Accepted Answer · 2019-07-01 06:14:08Z

getActivity() sometimes return null. So I suggest you to override onAttach() in fragment to get the context. This means your layout manager is null because of null context and is not provided to the recyclerview .So while setting the adapter it throws the exception. Try this and post the update of working status.

public class upperClass extends ... { ... public static innerClass extends CorrectedPreferenceFragment ... { private RecyclerView groupsInCommonRecyclerView; private View v; private Context c; @Override public void onAttach(Context c) { super.onAttach(c); this.c = c; //this is one of the best way to get context of the activity to which the particular activity is associated with } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { v = inflater.inflate(R.layout.recipient_common_groups, container, false); groupsInCommonRecyclerView = (RecyclerView) v.findViewById(R.id.recycler_view); LinearLayoutManager lm = new LinearLayoutManager(c); lm.setOrientation(LinearLayoutManager.VERTICAL); groupsInCommonRecyclerView.setLayoutManager(lm); ArrayList<GroupsInCommonItem> commonGroups = initializeGroupsInCommon(); GroupsInCommonRecycleViewAdapter groupsInCommonRecycleViewAdapter = new GroupsInCommonRecycleViewAdapter(c, commonGroups); groupsInCommonRecyclerView.setAdapter(groupsInCommonRecycleViewAdapter); return v; } }

sandeep kolhal · Accepted Answer · 2019-07-01 06:33:06Z

0

I think you have not bind your recyclerview in activity by using findViewById... Please check.

answered Jul 1, 2019 at 6:33

sandeep kolhal

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