Retriving data from firebase to populate a RecyclerView

I want to retrieve some data from FireBase in order to populate a RecyclerView.My app idea is : a user picks some locations from a map fragment and then stores them in Firebase Database.Those saved locations are displayed in a Places fragment where I want to use a RecylcerView.When I run the app i get the following errors

08-29 23:01:35.257 25039-25039/com.aplicatiechat.mcristi.firebaseandmapsdemoforlearning E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.aplicatiechat.mcristi.firebaseandmapsdemoforlearning, PID: 25039
com.google.firebase.database.DatabaseException: Class com.aplicatiechat.mcristi.firebaseandmapsdemoforlearning.Places is missing a constructor with no arguments
at com.google.android.gms.internal.zzekq.zze(Unknown Source)
at com.google.android.gms.internal.zzekp.zzb(Unknown Source)
at com.google.android.gms.internal.zzekp.zza(Unknown Source)
at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:22)
at com.firebase.ui.database.ObservableSnapshotArray.getObject(ObservableSnapshotArray.java:141)
at com.firebase.ui.database.CachingObservableSnapshotArray.getObject(CachingObservableSnapshotArray.java:40)
at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:127)
at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:164)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6673)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6714)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5647)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5913)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5752)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5748)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2232)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1559)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1519)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:614)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3812)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3529)
at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1767)
at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:356)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:777)
at android.view.Choreographer.doCallbacks(Choreographer.java:590)
at android.view.Choreographer.doFrame(Choreographer.java:559)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:763)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)


This is my Places Fragment:

public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
mView = inflater.inflate(R.layout.places_fragment, container, false);
mRecylcerView = mView.findViewById(R.id.places);
mRecylcerView.setHasFixedSize(true);
mRecylcerView.setLayoutManager(new LinearLayoutManager(getContext()));

return mView;



@Override
public void onStart()
super.onStart();
mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
mDataBase = FirebaseDatabase.getInstance().getReference().child("users").child(mFirebaseUser.getUid());
DatabaseReference places = FirebaseDatabase.getInstance().getReference().child("users").child(mFirebaseUser.getUid()).child("place");
DatabaseReference keys = FirebaseDatabase.getInstance().getReference().child("users").child(mFirebaseUser.getUid()).child("key");
FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder> firebaseRecyclerAdapter = new FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder>(Places.class,R.layout.place_layout,PlacesViewHolder.class,places,keys)
@Override
protected void populateViewHolder(PlacesViewHolder viewHolder, Places model, int position)
viewHolder.setLat(model.getLat());
viewHolder.setLon(model.getLon());

;
mRecylcerView.setAdapter(firebaseRecyclerAdapter);


}
class PlacesViewHolder extends RecyclerView.ViewHolder
View mView;
private TextView lat;
private TextView lon;


public PlacesViewHolder(View itemView)
super(itemView);
mView = itemView;
lat = mView.findViewById(R.id.lat_view);
lon = mView.findViewById(R.id.lon_view);


public void setLat(String n)
lat.setText(n);


public void setLon(String e)
lon.setText(e);




and here it is my Model Places class:

public class Places extends RecyclerView.ViewHolder
private String lat;
private String lon;

public Places(View itemView)
super(itemView);



public String getLat()
return lat;


public void setLat(String lat)
this.lat = lat;


public String getLon()
return lon;


public void setLon(String lon)
this.lon = lon;





Here is a screenshow with my databse :
Firebase database

1 Answer
1

Add an empty constructor in your Places class as

Places

public Places()


because firebase recycler adapter did not find this empty constructor in your Places class. And replace this

FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder> firebaseRecyclerAdapter = new FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder>(Places.class,R.layout.place_layout,PlacesViewHolder.class,places,keys)


with

FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder> firebaseRecyclerAdapter = new FirebaseIndexRecyclerAdapter<Places,PlacesViewHolder>(Places.class,R.layout.place_layout,PlacesViewHolder.class,keys,places) {


And you need to remove the extend from Places class.

Required, but never shown

Required, but never shown

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