How to put a recyclerview inside a recyclerView in android

Question

so I have a RecyclerView inside a RecyclerView . And I'm getting this error regarding my LayoutManager for the RecyclerView .. The data im working with is a OpenHours object, where Open Hours is a class I made to encapsulate a store's opening and closing hours through the week. The error is pointing to this line in my parent recycler view (which is the first recycler view written on top):

recyclerView.setLayoutManager(new LinearLayoutManager(getBaseContext()));

Here is my class.

public class HoursActivity extends AppCompatActivity
{
    private RecyclerView rV;
    private TextView addHoursTV;
    private HoursRecyclerViewAdapter hoursRecyclerViewAdapter;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hours);
        bindActivity();
    }
    private void bindActivity()
    {
        if(!Global_Class.getInstance().getValue().openHoursArrayList.isEmpty())
        {
            rV = (RecyclerView) findViewById(R.id.activity_hours_RV);
            rV.setLayoutManager(new LinearLayoutManager(getBaseContext()));
            hoursRecyclerViewAdapter = new HoursRecyclerViewAdapter(getBaseContext(),Global_Class.getInstance().getValue().openHoursArrayList);
            rV.setAdapter(hoursRecyclerViewAdapter);
            rV.setItemAnimator(new DefaultItemAnimator());
        }
        addHoursTV = (TextView) findViewById(R.id.activity_hours_addHoursTV);
        addHoursTV.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(HoursActivity.this,SetHours.class);
                startActivity(i);
            }
        });
    }
    //An recycler view adapter that can take in multiple views
    public class HoursRecyclerViewAdapter extends RecyclerView.Adapter<HoursRecyclerViewAdapter.MyViewHolder>
    {
        private LayoutInflater inflater;
        private ArrayList<OpenHours> infoList = new ArrayList<>();
        private Context context;

        public HoursRecyclerViewAdapter(Context context, ArrayList<OpenHours> data)
        {
            inflater = LayoutInflater.from(context);
            this.infoList = data;
            this.context = context;
        }
        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
        {
            View view = inflater.inflate(R.layout.view_hours,parent,false);
            MyViewHolder holder = new MyViewHolder(view);//special way to avoid "findViewById everytime you make a view
            Log.d("Qamar", "onCreateviewHolder called");
            return holder;
        }
        @Override
        public void onBindViewHolder(MyViewHolder holder, final int position)//onBindViewHolder does all the work.
        {
            HoursTwoRecyclerViewAdapter hoursTwoRecyclerViewAdapter;
            hoursTwoRecyclerViewAdapter = new HoursTwoRecyclerViewAdapter(getBaseContext(),infoList);
            holder.recyclerView.setAdapter(hoursTwoRecyclerViewAdapter);
            holder.recyclerView.setItemAnimator(new DefaultItemAnimator());
        }
        @Override
        public int getItemCount()
        {
            return infoList.size();
        }
        class MyViewHolder extends RecyclerView.ViewHolder
        {
            RecyclerView recyclerView;
            public MyViewHolder(View itemView)
            {
                super(itemView);
                recyclerView = (RecyclerView) findViewById(R.id.view_hours_RV);
                recyclerView.setLayoutManager(new LinearLayoutManager(getBaseContext()));
            }
        }
    }
    //An recycler view adapter that can take in multiple views
    public class HoursTwoRecyclerViewAdapter extends RecyclerView.Adapter<HoursTwoRecyclerViewAdapter.MyViewHolder>
    {
        private LayoutInflater inflater;
        private ArrayList<OpenHours> infoList = new ArrayList<>();
        private Context context;

        public HoursTwoRecyclerViewAdapter(Context context, ArrayList<OpenHours> data)
        {
            inflater = LayoutInflater.from(context);
            this.infoList = data;
            this.context = context;
        }
        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
        {
            View view = inflater.inflate(R.layout.view_hours_two,parent,false);
            MyViewHolder holder = new MyViewHolder(view);//special way to avoid "findViewById everytime you make a view
            Log.d("Qamar", "onCreateviewHolder called");
            return holder;
        }
        @Override
        public void onBindViewHolder(MyViewHolder holder, final int position)//onBindViewHolder does all the work.
        {
            OpenHours openHours = infoList.get(position);
            holder.dayTV.setText(openHours.getDaysOpen().get(position));
            holder.openingTimeHrTV.setText(openHours.getOpeningHour().substring(0,1));
            holder.openingTimeMinuteTV.setText(openHours.getOpeningHour().substring(2,3));
            holder.closingTimeHrTV.setText(openHours.getClosingHour().substring(0,1));
            holder.closingTimeMinuteTV.setText(openHours.getClosingHour().substring(2,3));

        }
        @Override
        public int getItemCount()
        {
            return infoList.size();
        }
        class MyViewHolder extends RecyclerView.ViewHolder
        {
            TextView dayTV,openingTimeHrTV,openingTimeMinuteTV,closingTimeHrTV,closingTimeMinuteTV;
            public MyViewHolder(View itemView)
            {
                super(itemView);
                dayTV = (TextView) findViewById(R.id.view_hours_2_day);
                openingTimeHrTV = (TextView) findViewById(R.id.view_hours_2_openingTimeHour);
                openingTimeMinuteTV = (TextView) findViewById(R.id.view_hours_2_openingTimeMinute);
                closingTimeHrTV = (TextView) findViewById(R.id.view_hours_2_closingTimeHour);
                closingTimeMinuteTV = (TextView) findViewById(R.id.view_hours_2_closingTimeMinute);


            }
        }
    }
}

And here is my first parent recycler view xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <include
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        layout="@layout/toolbar_layout">
    </include>
    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/activity_hours_RV"/>
    <android.support.v4.widget.Space
        android:layout_width="match_parent"
        android:layout_height="20dp" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:text="Add extra hours"
        android:textColor="@color/green_test"
        android:id="@+id/activity_hours_addHoursTV"/>
</LinearLayout>

And my child xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="100dp">
    <android.support.v7.widget.RecyclerView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/view_hours_RV"/>

</LinearLayout>

Finally here is my log error:

10-14 21:42:26.804 18552-18552/com.daprlabs.aaron.swipedeck2 E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.daprlabs.aaron.swipedeck2.CardInfo.HoursActivity$HoursRecyclerViewAdapter$MyViewHolder.<init>(HoursActivity.java:97)
at com.daprlabs.aaron.swipedeck2.CardInfo.HoursActivity$HoursRecyclerViewAdapter.onCreateViewHolder(HoursActivity.java:73)
at com.daprlabs.aaron.swipedeck2.CardInfo.HoursActivity$HoursRecyclerViewAdapter.onCreateViewHolder(HoursActivity.java:57)
at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:5836)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5060)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4970)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2029)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1414)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1377)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:578)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3315)
at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:2843)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5953)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2685)
at android.view.View.measure(View.java:18834)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2131)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1237)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1474)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1125)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6100)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5525)
at java.lang.re

Answer 1

Remove

recyclerView.setLayoutManager(new LinearLayoutManager(getBaseContext()));

from your MyViewHolder class and add that line in your onBindViewHolder

LinearLayoutManager linearLayoutManager = new LinearLayoutManager(context,    LinearLayoutManager.HORIZONTAL, false);
holder.recyclerView.setLayoutManager(linearLayoutManager);