How can I see all data with RecyclerView? - android-studio

Question

I cannot show all datas to RecyclerView.I keep getting this error:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)' on a null object reference
at com.cdirect.weatherapp.MyLocations.onCreate(MyLocations.java:50)
MyLocations.java: 50:
rcView.setAdapter(adapter);
MyLocations.java code:
public class MyLocations extends AppCompatActivity {
BottomNavigationView altNav;
RecyclerView rcView;
ArrayList<Locations> locationsList;
DatabaseReference dbRef;
Adapter adapter;
#Override
public void onBackPressed() {
super.onBackPressed();
startActivity(new Intent(MyLocations.this,MainActivity.class));
finish();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
dbRef = FirebaseDatabase.getInstance().getReference("Locations");
altNav = (BottomNavigationView) findViewById(R.id.altNav);
rcView = findViewById(R.id.rvLocations);
locationsList = new ArrayList<>();
adapter = new Adapter(MyLocations.this, locationsList);
rcView.setAdapter(adapter); //ERROR LINE
rcView.setLayoutManager(new LinearLayoutManager(this));
Adapter.java codes:
public class Adapter extends RecyclerView.Adapter<Adapter.MyViewHolder> {
ArrayList<Locations> locationsArrayList;
Context context;
public Adapter (Context context, ArrayList<Locations> locationsArrayList){
this.locationsArrayList=locationsArrayList;
this.context = context;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(context).inflate(R.layout.recycler_view_row,parent,false);
return new MyViewHolder(v);
}
#Override
public void onBindViewHolder(#NonNull MyViewHolder holder, int position) {
Locations loc = locationsArrayList.get(position);
holder.location.setText(loc.getLocation());
holder.temperature.setText(loc.getTemp());
}
#Override
public int getItemCount() {
return locationsArrayList.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder{
TextView location, temperature;
public MyViewHolder(#NonNull View itemView) {
super(itemView);
location = itemView.findViewById(R.id.tvLocation);
temperature= itemView.findViewById(R.id.tvTemp);
}
}
}
Locations.java code:
public class Locations {
String location;
String temp;
String id;
public Locations(String location, String temp, String id) {
this.location = location;
this.temp = temp;
this.id = id;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public String getTemp() {
return temp;
}
public void setTemp(String temp) {
this.temp = temp;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}
I cannot solve where is the problem. Can you help me?