Develop Reference

Error: E/RecyclerView: No adapter attached; skipping layout on Fragments

I am trying to display a RecyclerView on a fragment using FireBase Database, but for some unknown reason its giving me this error: E/RecyclerView: No adapter attached; Im pretty sure im actually attaching the adapter, here's the code:
Main Activity
public class MainActivity extends AppCompatActivity {
Fragment currentFragment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(savedInstanceState == null){
currentFragment = new MapsFragment();
changeFragment(currentFragment);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu,menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()){
case R.id.menu_bookmarkList:
currentFragment = new ListaFragment();
break;
case R.id.menu_mapa:
currentFragment = new MapsFragment();
break;
}
changeFragment(currentFragment);
return super.onOptionsItemSelected(item);
}
private void changeFragment(Fragment currentFragment) {
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,currentFragment).commit();
}
}
ListaFragment (the one that should display the Recycler):
public class ListaFragment extends Fragment implements MyAdapter.RecyclerItemClick{
private MyAdapter myAdapter;
private RecyclerView recycler;
FirebaseDatabase database;
DatabaseReference myRef;
public ListaFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); }
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_lista, container, false);
database = FirebaseDatabase.getInstance();
myRef = database.getReference("Marcador");
recycler = (RecyclerView) v.findViewById(R.id.recyler);
recycler.setLayoutManager(new LinearLayoutManager(getContext()));
FirebaseRecyclerOptions<Marcador> options = new FirebaseRecyclerOptions.Builder<Marcador>()
.setQuery(myRef, Marcador.class).build();
myAdapter = new MyAdapter(options,this);
recycler.setAdapter(myAdapter);
return v;
}
#Override
public void onStart(){
super.onStart();
myAdapter.startListening();
}
#Override
public void onStop() {
super.onStop();
myAdapter.stopListening();
}
#Override
public void itemClick(Marcador marcador) {
}
}
And the adapter i've done (im skipping the xml's since they are quite simple):
public class MyAdapter extends FirebaseRecyclerAdapter<Marcador,MyAdapter.MarcadorHolder> {
private Context context;
private RecyclerItemClick itemClick;
public MyAdapter(#NonNull FirebaseRecyclerOptions<Marcador> options, RecyclerItemClick itemClick) {
super(options);
this.itemClick = itemClick;
}
#Override
protected void onBindViewHolder(#NonNull final MarcadorHolder holder, int position, #NonNull Marcador model) {
final Marcador marcador = getItem(position);
holder.textViewNom.setText(model.getNom());
holder.textViewLatitude.setText(String.valueOf(model.getLatitude()));
holder.textViewLongitude.setText(model.getLongitude());
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
itemClick.itemClick(marcador);
}
});
}
#NonNull
#Override
public MarcadorHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.recylcer_view_item,parent,false);
context = parent.getContext();
return new MarcadorHolder(v);
}
public class MarcadorHolder extends RecyclerView.ViewHolder{
TextView textViewNom;
TextView textViewLatitude;
TextView textViewLongitude;
public MarcadorHolder(#NonNull View itemView) {
super(itemView);
textViewNom = itemView.findViewById(R.id.textViewNom);
textViewLatitude = itemView.findViewById(R.id.textViewLatitud);
textViewLongitude = itemView.findViewById(R.id.textViewLongitut);
}
}
public interface RecyclerItemClick {
void itemClick(Marcador marcador);
}
}
I hope someone can give me an answer of why this is happening, since i've checked other options and i can't really get through it.
XML's attached of fragment:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".fragments.ListaFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyler"
android:layout_width="match_parent"
android:layout_height="545dp" />
</LinearLayout>
XML attached of item of recycler view:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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="60dp" android:background="#CDCDCD" android:layout_marginBottom="5dp"
>
<TextView
android:id="#+id/textViewNom"
android:layout_width="410dp"
android:layout_height="55dp"
android:layout_marginLeft="15dp"
android:layout_marginTop="5dp"
android:text="Title"
android:textSize="20sp"
android:textStyle="bold" />
<TextView
android:id="#+id/textViewLatitud"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginTop="35dp"
android:text="latitud" />
<TextView
android:id="#+id/textViewLongitut"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="125dp"
android:layout_marginTop="35dp"
android:text="longitut" />
<ImageView
android:id="#+id/imageView"
android:layout_width="45dp"
android:layout_height="45dp"
android:layout_marginLeft="265dp"
android:layout_marginTop="10dp"
/>
</RelativeLayout>

Do use below lines
LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recycler.setLayoutManager(layoutManager);
recycler.setAdapter(adapter);

According to Fragment API Reference:
It is recommended to only inflate the layout in this method and move logic that operates on the returned View to onViewCreated(View, Bundle).
So in onCreateView you should only inflate your layout hence the View v = inflater.inflate(R.layout.fragment_lista, container, false); you used and move logic of your code to onViewCreated and the reason you facing E/RecyclerView: No adapter attached; is because you're trying to setting adapter for your recyclerview before even creation/inflation of the view which is failing to complete therefore after the creation/inflation is done there's no adapter attached to recyclerview.

It is generally recommended to not initialize the component using findViewById in onViewCreated() as per the The Google Developer Documents.
You should inflate your layout in onCreateView but shouldn't
initialize other views using findViewById in onCreateView.
Because in this method not every View is not Properly initialized. So, prefer to use onViewCreated() to get your view's Id and do setUp the UI.

Shared element back transition not working with recyclerview and cardviews in fragments

I'm trying to create a transition between a recycler view with cardviews fragment to a fragment that only contains 1 card. The problem is that the back transition is not working, while the enter transition is. If I remove setReorderingAllowed(true); then the back transition is working, but the enter transition stops working.
This is what I have.
Fragment with recyclerview with cardviews
public class OrdersFragment extends Fragment implements OrderAdapter.OnOrderListener {
private OrderAdapter mAdapter;
private TextView bonnenTextView;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
postponeEnterTransition();
}
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_bonnen, container, false);
bonnenTextView = view.findViewById(R.id.bonnen_text_view);
RecyclerView orderRecyclerView = view.findViewById(R.id.order_recycler_view);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getContext());
orderRecyclerView.setLayoutManager(layoutManager);
if (mAdapter == null) {
mAdapter = new OrderAdapter(this);
fetchOrders();
}
orderRecyclerView.setAdapter(mAdapter);
return view;
}
private void fetchOrders() {
new OrderFetcher().fetch(new Callback() {
#Override
public void onComplete(Result result) {
if (result instanceof Result.Success) {
mAdapter.setOrders((Order[]) ((Result.Success<?>)result).data);
mAdapter.notifyDataSetChanged();
} else {
Toast.makeText(getContext(), "Could not load orders", Toast.LENGTH_SHORT).show();
}
startPostponedEnterTransition();
}
});
}
#Override
public void onOrderClick(int position, View view, Order order) {
Log.i("OrderClick", "Transition name " + view.getTransitionName());
View carrierTextView = view.findViewById(R.id.carrier_text_view);
View numberTextView = view.findViewById(R.id.id_text_view);
View pickerTextView = view.findViewById(R.id.picker_text_view);
View locationTextView = view.findViewById(R.id.location_text_view);
FragmentTransaction transaction = getParentFragmentManager().beginTransaction();
transaction.addSharedElement(view, view.getTransitionName());
transaction.addSharedElement(carrierTextView, carrierTextView.getTransitionName());
transaction.addSharedElement(numberTextView, numberTextView.getTransitionName());
transaction.addSharedElement(pickerTextView, pickerTextView.getTransitionName());
transaction.addSharedElement(locationTextView, locationTextView.getTransitionName());
transaction.addSharedElement(bonnenTextView, bonnenTextView.getTransitionName());
transaction.replace(R.id.nav_host_fragment, BonFragment.newInstance(view.getTransitionName(), order));
transaction.addToBackStack(null);
transaction.setReorderingAllowed(true);
transaction.commit();
}
}
xml that goes with fragment above
<?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"
tools:context=".ui.orders.OrdersFragment">
<TextView
android:id="#+id/bonnen_text_view"
android:transitionName="bonnen_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:text="#string/orders"
android:textColor="#color/secondary"
android:textSize="40sp"
android:textStyle="bold"
android:typeface="normal" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/order_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="20dp"/>
</LinearLayout>
Fragment with single cardview
public static BonFragment newInstance(String cardTransitionName, Order order) {
BonFragment bonFragment = new BonFragment();
Bundle args = new Bundle();
args.putParcelable("orderParcel", order);
args.putString("cardTransitionName", cardTransitionName);
bonFragment.setArguments(args);
return bonFragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View root = inflater.inflate(R.layout.fragment_bon, container, false);
CardView orderCard = root.findViewById(R.id.order_card);
TextView carrierTextView = root.findViewById(R.id.carrier_text_view);
TextView numberTextView = root.findViewById(R.id.id_text_view);
TextView pickerTextView = root.findViewById(R.id.picker_text_view);
TextView locationTextView = root.findViewById(R.id.location_text_view);
if (getArguments() != null && getArguments().getParcelable("orderParcel") != null) {
Order order = getArguments().getParcelable("orderParcel");
orderCard.setTransitionName(getArguments().getString("cardTransitionName"));
if (order != null) {
carrierTextView.setTransitionName("carrier" + order.getIndex());
carrierTextView.setText(order.getCarrier());
numberTextView.setTransitionName("number" + order.getIndex());
numberTextView.setText(String.valueOf(order.getNumber()));
pickerTextView.setTransitionName("picker" + order.getIndex());
pickerTextView.setText(order.getPicker());
locationTextView.setTransitionName("location" + order.getIndex());
locationTextView.setText(order.getPosition());
carrierTextView.setText("Lorem Ipsum");
numberTextView.setText("Dolor sit amet");
pickerTextView.setText("consectetur adipiscing elit");
locationTextView.setText("Mauris semper");
}
}
orderCard.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
getParentFragmentManager().popBackStack();
}
});
Transition transition = TransitionInflater.from(getContext()).inflateTransition(R.transition.card_transition);
setSharedElementEnterTransition(transition);
setSharedElementReturnTransition(transition);
return root;
}
xml that goes with fragment above
<?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"
tools:context=".ui.orders.OrdersFragment">
<TextView
android:transitionName="bonnen_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginTop="10dp"
android:text="#string/orders"
android:textColor="#color/secondary"
android:textSize="40sp"
android:textStyle="bold"
android:typeface="normal" />
<androidx.cardview.widget.CardView
android:id="#+id/order_card"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:cardBackgroundColor="#color/primaryLight"
android:foreground="?android:attr/selectableItemBackground"
android:clickable="true"
android:layout_margin="25dp">
<LinearLayout
android:transitionName="order_card_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_margin="10dp">
<TextView
android:id="#+id/carrier_text_view"
android:transitionName="carrier_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#color/secondary"
android:textSize="20sp"
android:textStyle="bold"/>
<TextView
android:id="#+id/id_text_view"
android:transitionName="id_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#color/secondary" />
<TextView
android:id="#+id/picker_text_view"
android:transitionName="picker_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#color/secondary" />
<TextView
android:id="#+id/location_text_view"
android:transitionName="location_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#color/secondary" />
</LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
This is what it looks like with setReorderingAllowed(true);
This is what it looks like without setReorderingAllowed(true);
EDIT
After applying the answer given by ianhanniballake I got it working.
Here is what I did for future reference.
The only changes I made is in the OrdersFragment class.
I removed the override of the onCreate() method.
I removed the startPostponedEnterTransition(); from my fetchOrders() method and I added
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
postponeEnterTransition();
final ViewGroup parentView = (ViewGroup) view.getParent();
parentView.getViewTreeObserver()
.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
parentView.getViewTreeObserver().removeOnPreDrawListener(this);
startPostponedEnterTransition();
return true;
}
});
super.onViewCreated(view, savedInstanceState);
}
That's it

As per the Use shared element transitions with a RecyclerView guide, you're calling startPostponedEnterTransition() too early - after setting your data (and calling notifyDataSetChanged() to inform the adapter), you need to wait until the RecyclerView is actually measured and laid out. This requires that you add an OnPreDrawListener and only call startPostponedEnterTransition() once that fires.

In Kotlin you need to start the transition in doOnPreDraw callback of the recyclerView like below:
recyclerView.doOnPreDraw {
startPostponedEnterTransition()
}

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 4 years ago.
I'm trying to put a GridView in my custom popup modal to display some information in a grid but I keep on getting a NullPointerException yet all the steps look right to me. When I run the debug mode It says the my LayoutInflater. I am not sure if maybe that's the issue or not.
My Error:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.davidlutta.purenote/com.davidlutta.purenote.UI.Activities.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.davidlutta.purenote.UI.Fragments.Home_Fragment.onCreateView(Home_Fragment.java:82)
My Fragment Class
public class Home_Fragment extends Fragment {
#BindView(R.id.floatingActionButton) FloatingActionButton floatingActionButton;
private String TAG = ">>>>>>>>";
Dialog customDialog;
public Home_Fragment() {
// Required empty public constructor
}
public static Home_Fragment newInstance() {
Home_Fragment fragment = new Home_Fragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_home_, container, false);
ButterKnife.bind(this,root);
customDialog = new Dialog(getContext());
floatingActionButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.setContentView(R.layout.upload_popup);
ImageView closeDialogButton = (ImageView) customDialog.findViewById(R.id.closeButton);
closeDialogButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
customDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
customDialog.show();
}
});
GridView gridView = (GridView) getActivity().findViewById(R.id.gridView);
GridViewAdapter gridViewAdapter = new GridViewAdapter(getContext());
gridView.setAdapter(gridViewAdapter);
gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toasty.info(getContext(),"I Work",Toast.LENGTH_SHORT).show();
}
});
return root;
}}
My GridView Adapter
public class GridViewAdapter extends BaseAdapter {
LayoutInflater layoutInflater;
Context context;
public GridViewAdapter(Context context) {
this.context = context;
}
int[] images = {
R.drawable.text,
R.drawable.pdf,
R.drawable.popupscanner,
R.drawable.text
};
String[] titles = {
"Write Note",
"Upload Note",
"Scan Document",
"Text Recogniton"
};
#Override
public int getCount() {
return titles.length;
}
#Override
public Object getItem(int position) {
return null;
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
layoutInflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
View view = layoutInflater.inflate(R.layout.row_info,null);
TextView title = (TextView) convertView.findViewById(R.id.titleTextView);
ImageView icon = (ImageView) convertView.findViewById(R.id.iconImageView);
title.setText(titles[position]);
icon.setImageResource(images[position]);
return view;
}}
My XML file
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_marginLeft="5dp"
android:gravity="center">
<ImageView
android:id="#+id/closeButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/ic_close_black_24dp"
android:layout_marginTop="7dp"
android:layout_marginRight="7dp"
android:elevation="#dimen/card_elevation"
android:layout_alignParentRight="true"/>
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:cardCornerRadius="#dimen/card_radius"
app:cardBackgroundColor="#color/colorCream"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_marginTop="25dp"
android:layout_marginBottom="25dp">
<GridView
android:id="#+id/gridView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="2"
android:verticalSpacing="1dp"
android:horizontalSpacing="1dp"></GridView>
</LinearLayout>
</LinearLayout>
</androidx.cardview.widget.CardView>
Which mistake have I made ?

Replace: "GridView gridView = (GridView) getActivity().findViewById(R.id.gridView)"
by: "GridView gridView = (GridView) root.findViewById(R.id.gridView)"
I think because of your GridView is placed inside fragment_home.xml, not inside your activity layout xml file. So when you call getActivity().findViewById(..), it can't find the gridview and return null.
Hope this help you!

Migrating RecyclerView from Activity to Fragment - can't use findViewById

I copied the following code from the MainActivity to a separate fragment, but I can't get findViewById to work:
I get "cannot resolve method findViewById(int)"
these are the related files:
**Also as a beginner, could you let me know if there's a general problem with my code that needs to fixed?
MyFragment.java:
public class MyFragment extends Fragment {
public myFragment() {
// Required empty public constructor
}
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_my, container, false);
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
mRecyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mLayoutManager);
//placeholder data
String[] myDataset = new String[16];
myDataset[0] = "Data0";
myDataset[1] = "Data1";
myDataset[2] = "Data2";
myDataset[3] = "Data3";
myDataset[4] = "Data4";
myDataset[5] = "Data5";
myDataset[6] = "Data6";
myDataset[7] = "Data7";
myDataset[8] = "Data8";
myDataset[9] = "Data9";
myDataset[10] = "Data10";
myDataset[11] = "Data11";
myDataset[12] = "Data12";
myDataset[13] = "Data13";
myDataset[14] = "Data14";
myDataset[15] = "Data15";
// specify an adapter (see also next example)
mAdapter = new MyAdapter(myDataset);
mRecyclerView.setAdapter(mAdapter);
}
}
MyAdapter.java:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private String[] mDataset;
// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public static class MyViewHolder extends RecyclerView.ViewHolder {
// each data item is just a string in this case
public TextView upTv;
public TextView downTv;
public View layout;
public MyViewHolder(View v) {
super(v);
layout = v;
upTv = (TextView)v.findViewById(R.id.upTv);
downTv = (TextView)v.findViewById(R.id.downTv);
}
}
// Provide a suitable constructor (depends on the kind of dataset)
public MyAdapter(String[] myDataset) {
mDataset = myDataset;
}
// Create new views (invoked by the layout manager)
#Override
public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.my_text_view, parent, false);
MyViewHolder vh = new MyViewHolder(v);
return vh;
}
// Replace the contents of a view (invoked by the layout manager)
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
// - get element from your dataset at this position
// - replace the contents of the view with that element
holder.upTv.setText(mDataset[position]);
holder.downTv.setText(mDataset[position]);
}
// Return the size of your dataset (invoked by the layout manager)
#Override
public int getItemCount() {
return mDataset.length;
}
}
fragment_my.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<android.support.v7.widget.RecyclerView
android:id="#+id/my_recycler_view"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="4dp"
android:scrollbars="vertical"/>
</android.support.constraint.ConstraintLayout>
my_text_view.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="?android:attr/listPreferredItemHeight"
android:padding="6dip" >
<ImageView
android:id="#+id/icon"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_alignParentBottom="true"
android:layout_alignParentTop="true"
android:layout_marginRight="6dip"
android:contentDescription="TODO"
android:src="#drawable/ic_launcher_background" />
<TextView
android:id="#+id/downTv"
android:layout_width="fill_parent"
android:layout_height="26dip"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_toRightOf="#id/icon"
android:text="downTv"
android:textSize="12sp" />
<TextView
android:id="#+id/upTv"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:layout_alignWithParentIfMissing="true"
android:layout_toRightOf="#id/icon"
android:gravity="center_vertical"
android:text="upTv"
android:textSize="16sp" />
</RelativeLayout>

Here's your problem:
return inflater.inflate(R.layout.fragment_my, container, false);
You cannot add more code after the return statement. You will need to take the reference of the inflated view and use it to find the reference of child views.
View rootView = inflater.inflate(R.layout.fragment_my, container, false);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.my_recycler_view);
// other code
return rootView;

A really good way to use fragments is to initialize certain variables(e.g- activity,context,root view etc) associated with the parent activity when you switch to a fragment.
for example you can do sth like,
private Context context;
private MainActivity activity; //Let MainActivity is your parent activity
private View view; //fields kept inside the fragment class,now we need to keep them initialized
//initialize activity/context from onAttach
#Override
public void onAttach(Context c) {
super.onAttach(c);
Activity a;
context=c;
if (c instanceof Activity){
a=(Activity) c;
if(a instanceof MainActivity)
activity=(MainActivity) a;
}
}
//initialize view from onViewCreated
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
this.view=view;
}
now you can use them wherever u want inside the fragment class without triggering any nullptrs and other stuff
e.g- you can go
this.view.findViewById(your_resId);
this.activity.getSupportFragmentManager();
etc and a lot of other stuffs when you need ,using these fields you initialized
also specifically in this case of using recyclerView dont forget to call,
adapter.notifyDataSetChanged() whenever you think the list you are showing in the recyclerView went through some change.

I do not have enough reputation to comment so i am writing this as answer to your comment.
You need to notify adapter using below code.
mAdapter.notifyDataSetChanged();

Recycler view not rendering view

I am not getting any view from the recycler, I did some debug and the constructor of the adapter is called with items on its list, also the method
getItemCount()
but none of the rest seem to be executed.
I´ve been wandering around stack looking for this problem and i found different approaches to a solution, problem is none worked out for me, maybe I am just missing something i can´t see.
I read somewhere that it could be because the recycler view is inside an scroll view, but the solution given did not worked for me
my custom adapter:
public class CircumstancesAdapter extends RecyclerView.Adapter<CircumstancesAdapter.CircumstancesViewHolder> {
List<CatalogRespModel> circumList;
Context mContext;
public CircumstancesAdapter(List<CatalogRespModel> list, Context context) {
this.circumList = list;
this.mContext = context;
}
#Override
public CircumstancesViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.row_item_circumstances, parent, false);
return new CircumstancesViewHolder(view);
}
#Override
public void onBindViewHolder(CircumstancesViewHolder holder, int position) {
holder.tvCircum.setText(circumList.get(position).get_Descripcion());
}
#Override
public int getItemCount() {
if(circumList != null) return circumList.size();
else return 0;
}
public class CircumstancesViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
RadioButton rbCircum;
TextView tvCircum;
private Context context;
public CircumstancesViewHolder(View itemView) {
super(itemView);
rbCircum = (RadioButton) itemView.findViewById(R.id.rb_circ);
rbCircum.setOnClickListener(this);
tvCircum = (TextView) itemView.findViewById(R.id.tv_circ);
this.context = itemView.getContext();
}
#Override
public void onClick(View v) {
}
}
}
my container layout:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- TODO: Update blank fragment layout -->
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="15dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="20dp"
android:paddingLeft="20dp"
android:paddingRight="20dp"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="8dp"
android:id="#+id/text2"
android:text="#string/text_circ"
android:textSize="20sp"
android:textColor="#color/colorPrimaryshadow"/>
<RelativeLayout
android:id="#+id/placa"
android:layout_width="180dp"
android:layout_height="120dp"
android:layout_gravity="center"
android:background="#drawable/placa">
<TextView
android:id="#+id/tv_plate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"
android:layout_centerInParent="true"
android:text="#string/dummy"
android:textSize="40sp"
android:textColor="#android:color/black"/>
</RelativeLayout>
<ImageView
android:id="#+id/iv_indicator"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:clickable="true"
android:src="#drawable/conductora" />
<android.support.v7.widget.RecyclerView
android:id="#+id/rview_circumstances"
android:layout_width="match_parent"
android:background="#fff"
android:orientation="vertical"
android:layout_height="wrap_content"/>
<Button
android:id="#+id/boton_continuar_circustanciasa"
android:layout_marginTop="15dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/continuar"
android:layout_marginBottom="10dp"
android:elevation="30dp"
android:layout_gravity="center"/>
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</FrameLayout>
my row layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:background="#fff"
android:paddingTop="2dp"
android:paddingBottom="2dp"
android:layout_height="wrap_content">
<RadioButton
android:id="#+id/rb_circ"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:buttonTint="#color/colorAccentDark"
android:gravity="center_vertical"
android:textSize="14sp" />
<TextView
android:layout_gravity="center_vertical"
android:gravity="center_vertical"
android:id="#+id/tv_circ"
android:textSize="14sp"
android:text="texto de prueba"
android:textColor="#color/colorAccentDark"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
and in my onCreateView inside the fragment:
recyclerView = (RecyclerView) rootView.findViewById(R.id.rview_circumstances);
recyclerView.setNestedScrollingEnabled(false);
recyclerView.setHasFixedSize(true);
if(Catalogs.circumstancesArray.size() > 0){
adapter = new CircumstancesAdapter(Catalogs.circumstancesArray, getContext());
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(adapter);
}
Note: I checked the List size and is greater than 0
Fragment code as requested:
public class CircumstancesFragment extends Fragment {
Button btnContinue;
TextView tvPlate;
private ImageView ivIndicator;
private static int iNumDevices;
IFragmentListener iFragmentListener;
private RecyclerView recyclerView;
RecyclerView.Adapter adapter;
private final static String TAGMap = CircumstancesFragment.class.getSimpleName();
public static final String TAG = "CircumstancesFragment.java";
public static CircumstancesFragment getInstance(Bundle bundle){
if(bundle != null){
iNumDevices = bundle.getInt("numDevices");
}
return new CircumstancesFragment();
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if(context != null){
if(context instanceof IFragmentListener){
iFragmentListener = (IFragmentListener) context;
} else
throw new RuntimeException("el contexto no esta implementando la interfaz");
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
final View rootView = inflater.inflate(R.layout.fragment_circustancias_, container, false);
btnContinue = (Button) rootView.findViewById(R.id.boton_continuar_circustanciasa);
tvPlate = (TextView) rootView.findViewById(R.id.tv_plate);
recyclerView = (RecyclerView) rootView.findViewById(R.id.rview_circumstances);
ivIndicator = (ImageView) rootView.findViewById(R.id.iv_indicator);
recyclerView.setNestedScrollingEnabled(false);
recyclerView.setHasFixedSize(true);
if(Catalogs.circumstancesArray.size() > 0){
adapter = new CircumstancesAdapter(Catalogs.circumstancesArray, getContext());
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
btnContinue.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view)
{
try
{
iFragmentListener.notify(null, TAG);
} catch (Exception ex)
{
Log.d("error", ex.getMessage());
}
}
});
setLayout(iNumDevices);
return rootView;
}
private void setLayout(int i){
tvPlate.setText(FdccoreConstants.insuredArray.get(0).get_Placa_Vehiculo());
if(i== FdccoreConstants.ONE_DEVICE){
ivIndicator.setImageResource(R.drawable.conductora);
}else if(i== FdccoreConstants.TWO_DEVICE){
ivIndicator.setImageResource(R.drawable.only_conductor);
}
}
private void resetView(){
}
}

Please provide more code because Your layout and adapter is working fine.
I only changed Your model list to String.
Maybe in place when You checked list size and list.size() > 0 add
adapter.notifyDataSetChanged();
=====
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rview_circumstances);
recyclerView.setNestedScrollingEnabled(false);
recyclerView.setHasFixedSize(true);
list = new ArrayList<>();
list.add("asd");
list.add("sasf");
list.add("asasfasf");
list.add("asgagsad");
list.add("asgas");
list.add("asagasgd");
list.add("asreyeryd");
list.add("asgsheyd");
CircumstancesAdapter adapter = new CircumstancesAdapter(list, this);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);

solution: somehow in order to work with the scroll view i must add this line
compile 'com.android.support:recyclerview-v7:25.3.1'
compiling only appcompat-v7 wont work