populateViewHolder non in esecuzione con FirebaseRecyclerAdapter (Android)

Question

Sto cercando di utilizzare un FirebaseRecyclerAdapter per popolare un RecyclerView in un frammento, con i dati dal mio database Firebase.

Il mio problema principale è che il metodo populateViewHolder non viene mai chiamato, quindi non ho visualizzato nulla nel RecyclerView.

Ho seguito i punti dalla documentazione Firebase UI:

https://github.com/firebase/FirebaseUI-Android/blob/master/database/README.md

Le norme sul mio database Firebase:

{ 
    "rules": { 
    ".read": "true", 
    ".write": "true" 
    } 
} 

Nel mio Gradle, ho aggiunto questa dipendenza :

compile 'com.firebaseui:firebase-ui-database:0.4.1' 

Ecco il metodo onCreateView nel mio frammento:

public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.fragment_dev_list, container, false); 

    Log.d("ROOT_VIEW", rootView.toString()); 

    mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view); 
    Log.d("RECYCLER_VIEW", mRecyclerView.toString()); 

    mRecyclerView.setHasFixedSize(true); 
    mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); 
    Log.d("ITEM_RECYCLER", Integer.toString(mRecyclerView.getLayoutManager().getItemCount())); 

    DatabaseReference devs = FirebaseDatabase.getInstance().getReference().child("users").child("devs"); 

    FirebaseRecyclerAdapter<Developer, DeveloperViewHolder> adapter = 
      new FirebaseRecyclerAdapter<Developer, DeveloperViewHolder>(
        Developer.class, 
        R.layout.dev_list_row, 
        DeveloperViewHolder.class, 
        devs 
      ) { 
       @Override 
       protected void populateViewHolder(DeveloperViewHolder viewHolder, Developer developer, int position) { 
        Log.d("ON CREATE VIEW", "before"); 
        viewHolder.setFirstName(developer.getFirstN()); 
        viewHolder.setLastName(developer.getLastN()); 
        viewHolder.setAddress(developer.getAddress()); 
        Log.d("ON CREATE VIEW", "populate"); 
       } 
      }; 


    Log.d("COUNT_ADAPTER", Integer.toString(adapter.getItemCount())); 
    Log.d("ADAPTER", adapter.toString()); 
    Log.d("RECYCLER VIEW", mRecyclerView.toString()); 
    mRecyclerView.setAdapter(adapter); 
    Log.d("ON CREATE VIEW", "end"); 

    return rootView; 
} 

Ed ecco la mia DeveloperViewHolder classe:

public static class DeveloperViewHolder extends RecyclerView.ViewHolder { 
    TextView firstName; 
    TextView lastName; 
    TextView address; 
    View mView; 


    public DeveloperViewHolder(View v) { 
     super(v); 
     this.mView = v; 
    } 

    public void setFirstName(String firstN) { 
     this.firstName = (TextView) mView.findViewById(R.id.firstname_row); 
     this.firstName.setText(firstN); 
    } 

    public void setLastName(String lastN) { 
     this.lastName = (TextView) mView.findViewById(R.id.lastname_row); 
     this.lastName.setText(lastN); 
    } 

    public void setAddress(String addr) { 
     this.address = (TextView) mView.findViewById(R.id.address_row); 
     this.address.setText(addr); 
    } 
} 

Il Developer classe (classe del modello):

public class Developer { 

    private String firstN; 
    private String lastN; 
    private String email; 
    private String address; 

     public Developer() { 

     } 

    public Developer(String firstN, String lastN, String email, String address)  { 
     this.firstN = firstN; 
     this.lastN = lastN; 
     this.email = email; 
     this.address = address; 
    } 

    public String getFirstN() { 
     return firstN; 
    } 

    public void setFirstN(String firstN) { 
     this.firstN = firstN; 
    } 

    public String getLastN() { 
     return lastN; 
    } 

    public void setLastN(String lastN) { 
     this.lastN = lastN; 
    } 

    public String getEmail() { 
     return email; 
    } 

    public void setEmail(String email) { 
     this.email = email; 
    } 

    public String getAddress() { 
     return address; 
    } 

    public void setAddress(String address) { 
     this.address = address; 
    } 
} 

E, infine, alcuni tronchi:

[ 07-08 09:42:42.773 18621:18668 D/   ] 
                      HostConnection::get() New Host Connection established 0x7f938cdb65c0, tid 18668 
I/OpenGLRenderer: Initialized EGL, version 1.4 
D/OpenGLRenderer: Enabling debug mode 0 
I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead. 
I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead. 
I/AppCompatViewInflater: app:theme is now deprecated. Please move to using android:theme instead. 
D/ACTION BAR?: android.support.v7.app.ToolbarActionBar@23efcd8a 
D/ROOT_VIEW: android.widget.LinearLayout{27403c65 V.E..... ......I. 0,0-0,0} 
D/RECYCLER_VIEW: android.support.v7.widget.RecyclerView{23dead3a VFED.V.. ......I. 0,0-0,0 #7f0e00e5 app:id/recycler_view} 
D/ITEM_RECYCLER: 0 
I/DynamiteModule: Considering local module com.google.android.gms.firebase_database:2 and remote module com.google.android.gms.firebase_database:2 
I/DynamiteModule: Selected remote version of com.google.android.gms.firebase_database, version >= 2 
D/COUNT_ADAPTER: 0 
D/ADAPTER: raphaelgrau.example.com.tabsapp.fragment.tabs.DevListFragment$1@29ec2dc7 
D/RECYCLER VIEW: android.support.v7.widget.RecyclerView{23dead3a VFED.V.. ......I. 0,0-0,0 #7f0e00e5 app:id/recycler_view} 
D/ON CREATE VIEW: end 
E/DynamiteModule: Failed to load module descriptor class: Didn't find class "com.google.android.gms.dynamite.descriptors.com.google.firebase.auth.ModuleDescriptor" on path: DexPathList[[zip file "/data/app/raphaelgrau.example.com.tabsapp-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]] 
background_crash  E/DynamiteModule: Failed to load module descriptor class: Didn't find class "com.google.android.gms.dynamite.descriptors.com.google.android.gms.crash.ModuleDescriptor" on path: DexPathList[[zip file "/data/app/raphaelgrau.example.com.tabsapp-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]] 
background_crash W/ResourcesManager: Asset path '/system/framework/com.android.media.remotedisplay.jar' does not exist or contains no resources. 
background_crash W/ResourcesManager: Asset path '/system/framework/com.android.location.provider.jar' does not exist or contains no resources. 
background_crash W/ResourcesManager: Asset path '/system/framework/com.android.media.remotedisplay.jar' does not exist or contains no resources. 
background_crash W/ResourcesManager: Asset path '/system/framework/com.android.location.provider.jar' does not exist or contains no resources. 
background_crash D/ChimeraCfgMgr: Reading stored module config 
background_crash I/DynamiteModule: Considering local module com.google.android.gms.crash:0 and remote module com.google.android.gms.crash:2 
background_crash I/DynamiteModule: Selected remote version of com.google.android.gms.crash, version >= 2 
background_crash D/ChimeraFileApk: Primary ABI of requesting process is x86_64 
background_crash I/art: DexFile_isDexOptNeeded failed to open oat file '/data/dalvik-cache/x86_64/data@data@com.google.android.gms@app_chimera@m@00000002@DynamiteModulesC_GmsCore_prodlmp_alldpi_release.apk@classes.dex' for file location '/data/data/com.google.android.gms/app_chimera/m/00000002/DynamiteModulesC_GmsCore_prodlmp_alldpi_release.apk': Failed to open oat filename for reading: No such file or directory 
background_crash D/ChimeraFileApk: Classloading successful. Optimized code found. 
background_crash I/FirebaseCrashReceiverServiceImpl: FirebaseCrashReceiverServiceImpl created by ClassLoader com.google.android.chimera.container.internal.DelegateLastPathClassLoader[DexPathList[[zip file "/data/data/com.google.android.gms/app_chimera/m/00000002/DynamiteModulesC_GmsCore_prodlmp_alldpi_release.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]] 
background_crash D/FirebaseCrashReceiverServiceImpl: onCreate 
background_crash I/DynamiteModule: Considering local module com.google.android.gms.flags:0 and remote module com.google.android.gms.flags:1 
background_crash I/DynamiteModule: Selected remote version of com.google.android.gms.flags, version >= 1 
background_crash I/FirebaseCrashSenderServiceImpl: FirebaseCrashSenderServiceImpl created by ClassLoader com.google.android.chimera.container.internal.DelegateLastPathClassLoader[DexPathList[[zip file "/data/data/com.google.android.gms/app_chimera/m/00000002/DynamiteModulesC_GmsCore_prodlmp_alldpi_release.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]] 
background_crash D/FirebaseCrashSenderServiceImpl: onCreate 

Answer 1

ho fissato il mio problema grazie a questo documento:

https://codelabs.developers.google.com/codelabs/firebase-android/#6

avevo bisogno di aggiungere un RecyclerView.AdapterDataObserver(): Problema

mFirebaseAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() { 
    @Override 
    public void onItemRangeInserted(int positionStart, int itemCount) { 
     super.onItemRangeInserted(positionStart, itemCount); 
     int friendlyMessageCount = mFirebaseAdapter.getItemCount(); 
     int lastVisiblePosition = 
       mLinearLayoutManager.findLastCompletelyVisibleItemPosition(); 
     // If the recycler view is initially being loaded or the 
     // user is at the bottom of the list, scroll to the bottom 
     // of the list to show the newly added message. 
     if (lastVisiblePosition == -1 || 
       (positionStart >= (friendlyMessageCount - 1) && 
         lastVisiblePosition == (positionStart - 1))) { 
      mMessageRecyclerView.scrollToPosition(positionStart); 
     } 
    } 
}); 

risolto!