diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumBottomSheetViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumBottomSheetViewModel.java
index fad33471..435e11f7 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumBottomSheetViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumBottomSheetViewModel.java
@@ -16,8 +16,8 @@ import com.cappielloantonio.play.repository.ArtistRepository;
 import java.util.List;
 
 public class AlbumBottomSheetViewModel extends AndroidViewModel {
-    private AlbumRepository albumRepository;
-    private ArtistRepository artistRepository;
+    private final AlbumRepository albumRepository;
+    private final ArtistRepository artistRepository;
 
     private Album album;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumCatalogueViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumCatalogueViewModel.java
index a7c84e16..7e9415bb 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumCatalogueViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumCatalogueViewModel.java
@@ -11,9 +11,7 @@ import androidx.lifecycle.MutableLiveData;
 import com.cappielloantonio.play.App;
 import com.cappielloantonio.play.interfaces.MediaCallback;
 import com.cappielloantonio.play.model.Album;
-import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.subsonic.models.AlbumID3;
-import com.cappielloantonio.play.subsonic.models.ResponseStatus;
 import com.cappielloantonio.play.subsonic.models.SubsonicResponse;
 import com.cappielloantonio.play.util.MappingUtil;
 
@@ -24,7 +22,7 @@ import retrofit2.Call;
 import retrofit2.Callback;
 
 public class AlbumCatalogueViewModel extends AndroidViewModel {
-    private MutableLiveData<List<Album>> albumList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<Album>> albumList = new MutableLiveData<>(new ArrayList<>());
 
     private int page = 0;
 
@@ -45,7 +43,7 @@ public class AlbumCatalogueViewModel extends AndroidViewModel {
             @Override
             public void onLoadMedia(List<?> media) {
                 List<Album> liveAlbum = albumList.getValue();
-                if(liveAlbum == null) liveAlbum = new ArrayList<>();
+                if (liveAlbum == null) liveAlbum = new ArrayList<>();
                 liveAlbum.addAll(MappingUtil.mapAlbum((List<AlbumID3>) media));
                 albumList.setValue(liveAlbum);
 
@@ -63,8 +61,8 @@ public class AlbumCatalogueViewModel extends AndroidViewModel {
                 .getAlbumList2("alphabeticalByName", size, offset, null, null)
                 .enqueue(new Callback<SubsonicResponse>() {
                     @Override
-                    public void onResponse(Call<SubsonicResponse> call, retrofit2.Response<SubsonicResponse> response) {
-                        if (response.body().getStatus().getValue().equals(ResponseStatus.OK)) {
+                    public void onResponse(@NonNull Call<SubsonicResponse> call, @NonNull retrofit2.Response<SubsonicResponse> response) {
+                        if (response.isSuccessful() && response.body() != null && response.body().getAlbumList2() != null) {
                             List<AlbumID3> albumList = new ArrayList<>();
                             albumList.addAll(response.body().getAlbumList2().getAlbums());
                             callback.onLoadMedia(albumList);
@@ -72,7 +70,7 @@ public class AlbumCatalogueViewModel extends AndroidViewModel {
                     }
 
                     @Override
-                    public void onFailure(Call<SubsonicResponse> call, Throwable t) {
+                    public void onFailure(@NonNull Call<SubsonicResponse> call, @NonNull Throwable t) {
                         callback.onError(new Exception(t.getMessage()));
                     }
                 });
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumListPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumListPageViewModel.java
index 33c72882..618971e0 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumListPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumListPageViewModel.java
@@ -10,7 +10,6 @@ import androidx.lifecycle.MutableLiveData;
 
 import com.cappielloantonio.play.model.Album;
 import com.cappielloantonio.play.model.Artist;
-import com.cappielloantonio.play.model.Song;
 import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.repository.DownloadRepository;
 import com.cappielloantonio.play.util.MappingUtil;
@@ -19,8 +18,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class AlbumListPageViewModel extends AndroidViewModel {
-    private AlbumRepository albumRepository;
-    private DownloadRepository downloadRepository;
+    private final AlbumRepository albumRepository;
+    private final DownloadRepository downloadRepository;
 
     public String title;
     public Artist artist;
@@ -39,32 +38,22 @@ public class AlbumListPageViewModel extends AndroidViewModel {
 
         switch (title) {
             case Album.RECENTLY_PLAYED:
-                albumRepository.getAlbums("recent", 500, null, null).observe(activity, albums -> {
-                    albumList.setValue(albums);
-                });
+                albumRepository.getAlbums("recent", 500, null, null).observe(activity, albums -> albumList.setValue(albums));
                 break;
             case Album.MOST_PLAYED:
-                albumRepository.getAlbums("frequent", 500, null, null).observe(activity, albums -> {
-                    albumList.setValue(albums);
-                });
+                albumRepository.getAlbums("frequent", 500, null, null).observe(activity, albums -> albumList.setValue(albums));
                 break;
             case Album.RECENTLY_ADDED:
-                albumRepository.getAlbums("newest", 500, null, null).observe(activity, albums -> {
-                    albumList.setValue(albums);
-                });
+                albumRepository.getAlbums("newest", 500, null, null).observe(activity, albums -> albumList.setValue(albums));
                 break;
             case Album.STARRED:
                 albumList = albumRepository.getStarredAlbums();
                 break;
             case Album.DOWNLOADED:
-                downloadRepository.getLiveDownload().observe(activity, downloads -> {
-                    albumList.setValue(MappingUtil.mapDownloadToAlbum(downloads));
-                });
+                downloadRepository.getLiveDownload().observe(activity, downloads -> albumList.setValue(MappingUtil.mapDownloadToAlbum(downloads)));
                 break;
             case Album.FROM_ARTIST:
-                downloadRepository.getLiveDownloadFromArtist(artist.getId()).observe(activity, downloads -> {
-                    albumList.setValue(MappingUtil.mapDownloadToAlbum(downloads));
-                });
+                downloadRepository.getLiveDownloadFromArtist(artist.getId()).observe(activity, downloads -> albumList.setValue(MappingUtil.mapDownloadToAlbum(downloads)));
                 break;
         }
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumPageViewModel.java
index e02a7782..34698862 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/AlbumPageViewModel.java
@@ -14,16 +14,14 @@ import com.cappielloantonio.play.model.Song;
 import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.repository.ArtistRepository;
 import com.cappielloantonio.play.repository.DownloadRepository;
-import com.cappielloantonio.play.repository.SongRepository;
 import com.cappielloantonio.play.util.MappingUtil;
-import com.cappielloantonio.play.util.MusicUtil;
 
 import java.util.List;
 
 public class AlbumPageViewModel extends AndroidViewModel {
-    private AlbumRepository albumRepository;
-    private ArtistRepository artistRepository;
-    private DownloadRepository downloadRepository;
+    private final AlbumRepository albumRepository;
+    private final ArtistRepository artistRepository;
+    private final DownloadRepository downloadRepository;
 
     private MutableLiveData<List<Song>> songLiveList = new MutableLiveData<>();
 
@@ -39,7 +37,7 @@ public class AlbumPageViewModel extends AndroidViewModel {
     }
 
     public LiveData<List<Song>> getAlbumSongLiveList(FragmentActivity activity) {
-        if(isOffline) {
+        if (isOffline) {
             downloadRepository.getLiveDownloadFromAlbum(album.getId()).observe(activity, downloads -> songLiveList.postValue(MappingUtil.mapDownloadToSong(downloads)));
         } else {
             songLiveList = albumRepository.getAlbumTracks(album.getId());
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistBottomSheetViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistBottomSheetViewModel.java
index 3fa7cf12..6f330fa2 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistBottomSheetViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistBottomSheetViewModel.java
@@ -7,10 +7,9 @@ import androidx.lifecycle.AndroidViewModel;
 
 import com.cappielloantonio.play.model.Artist;
 import com.cappielloantonio.play.repository.AlbumRepository;
-import com.cappielloantonio.play.repository.ArtistRepository;
 
 public class ArtistBottomSheetViewModel extends AndroidViewModel {
-    private AlbumRepository albumRepository;
+    private final AlbumRepository albumRepository;
 
     private Artist artist;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistCatalogueViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistCatalogueViewModel.java
index 87fee3f7..1781f59f 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistCatalogueViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistCatalogueViewModel.java
@@ -10,10 +10,8 @@ import androidx.lifecycle.MutableLiveData;
 
 import com.cappielloantonio.play.App;
 import com.cappielloantonio.play.model.Artist;
-import com.cappielloantonio.play.repository.ArtistRepository;
 import com.cappielloantonio.play.subsonic.models.ArtistID3;
 import com.cappielloantonio.play.subsonic.models.IndexID3;
-import com.cappielloantonio.play.subsonic.models.ResponseStatus;
 import com.cappielloantonio.play.subsonic.models.SubsonicResponse;
 import com.cappielloantonio.play.util.MappingUtil;
 
@@ -24,7 +22,7 @@ import retrofit2.Call;
 import retrofit2.Callback;
 
 public class ArtistCatalogueViewModel extends AndroidViewModel {
-    private MutableLiveData<List<Artist>> artistList = new MutableLiveData<>(new ArrayList<>());
+    private final MutableLiveData<List<Artist>> artistList = new MutableLiveData<>(new ArrayList<>());
 
     public ArtistCatalogueViewModel(@NonNull Application application) {
         super(application);
@@ -40,8 +38,8 @@ public class ArtistCatalogueViewModel extends AndroidViewModel {
                 .getArtists()
                 .enqueue(new Callback<SubsonicResponse>() {
                     @Override
-                    public void onResponse(Call<SubsonicResponse> call, retrofit2.Response<SubsonicResponse> response) {
-                        if (response.body().getStatus().getValue().equals(ResponseStatus.OK)) {
+                    public void onResponse(@NonNull Call<SubsonicResponse> call, @NonNull retrofit2.Response<SubsonicResponse> response) {
+                        if (response.isSuccessful() && response.body() != null && response.body().getArtists() != null) {
                             List<ArtistID3> artists = new ArrayList<>();
 
                             for (IndexID3 index : response.body().getArtists().getIndices()) {
@@ -53,7 +51,7 @@ public class ArtistCatalogueViewModel extends AndroidViewModel {
                     }
 
                     @Override
-                    public void onFailure(Call<SubsonicResponse> call, Throwable t) {
+                    public void onFailure(@NonNull Call<SubsonicResponse> call, @NonNull Throwable t) {
 
                     }
                 });
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistListPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistListPageViewModel.java
index a208a7fb..07e0d313 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistListPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistListPageViewModel.java
@@ -21,8 +21,8 @@ import java.util.TreeSet;
 import java.util.stream.Collectors;
 
 public class ArtistListPageViewModel extends AndroidViewModel {
-    private ArtistRepository artistRepository;
-    private DownloadRepository downloadRepository;
+    private final ArtistRepository artistRepository;
+    private final DownloadRepository downloadRepository;
 
     public String title;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistPageViewModel.java
index 27410231..ed94823e 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/ArtistPageViewModel.java
@@ -5,25 +5,18 @@ import android.app.Application;
 import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
 
 import com.cappielloantonio.play.model.Album;
 import com.cappielloantonio.play.model.Artist;
 import com.cappielloantonio.play.model.Song;
 import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.repository.ArtistRepository;
-import com.cappielloantonio.play.repository.SongRepository;
 
-import java.util.ArrayList;
 import java.util.List;
 
 public class ArtistPageViewModel extends AndroidViewModel {
-    private AlbumRepository albumRepository;
-    private ArtistRepository artistRepository;
-
-    private LiveData<List<Song>> songList = new MutableLiveData<>();
-    private LiveData<List<Album>> albumList = new MutableLiveData<>();
-    private LiveData<Artist> artistInfo = new MutableLiveData<>();
+    private final AlbumRepository albumRepository;
+    private final ArtistRepository artistRepository;
 
     private Artist artist;
 
@@ -35,18 +28,15 @@ public class ArtistPageViewModel extends AndroidViewModel {
     }
 
     public LiveData<List<Album>> getAlbumList() {
-        albumList = albumRepository.getArtistAlbums(artist.getId());
-        return albumList;
+        return albumRepository.getArtistAlbums(artist.getId());
     }
 
     public LiveData<Artist> getArtistInfo(String id) {
-        artistInfo = artistRepository.getArtistFullInfo(id);
-        return artistInfo;
+        return artistRepository.getArtistFullInfo(id);
     }
 
     public LiveData<List<Song>> getArtistTopSongList(int count) {
-        songList = artistRepository.getTopSongs(artist.getName(), count);
-        return songList;
+        return artistRepository.getTopSongs(artist.getName(), count);
     }
 
     public Artist getArtist() {
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/DownloadViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/DownloadViewModel.java
index 53900f86..de4ea641 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/DownloadViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/DownloadViewModel.java
@@ -32,9 +32,7 @@ public class DownloadViewModel extends AndroidViewModel {
     }
 
     public LiveData<List<Artist>> getDownloadedArtists(LifecycleOwner owner, int size) {
-        downloadRepository.getLiveDownloadSample(size, true, false, false).observe(owner, downloads -> {
-            downloadedArtistSample.postValue(MappingUtil.mapDownloadToArtist(downloads));
-        });
+        downloadRepository.getLiveDownloadSample(size, true, false, false).observe(owner, downloads -> downloadedArtistSample.postValue(MappingUtil.mapDownloadToArtist(downloads)));
         return downloadedArtistSample;
     }
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/FilterViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/FilterViewModel.java
index 79c50abd..70b740fe 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/FilterViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/FilterViewModel.java
@@ -13,10 +13,10 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class FilterViewModel extends AndroidViewModel {
-    private GenreRepository genreRepository;
+    private final GenreRepository genreRepository;
 
-    private ArrayList<String> selectedFiltersID = new ArrayList<>();
-    private ArrayList<String> selectedFilters = new ArrayList<>();
+    private final ArrayList<String> selectedFiltersID = new ArrayList<>();
+    private final ArrayList<String> selectedFilters = new ArrayList<>();
 
     public FilterViewModel(@NonNull Application application) {
         super(application);
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/GenreCatalogueViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/GenreCatalogueViewModel.java
index bf17b31b..cc449d37 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/GenreCatalogueViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/GenreCatalogueViewModel.java
@@ -12,9 +12,7 @@ import com.cappielloantonio.play.repository.GenreRepository;
 import java.util.List;
 
 public class GenreCatalogueViewModel extends AndroidViewModel {
-    private GenreRepository genreRepository;
-
-    private LiveData<List<Genre>> genreList;
+    private final GenreRepository genreRepository;
 
     public GenreCatalogueViewModel(@NonNull Application application) {
         super(application);
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/HomeViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/HomeViewModel.java
index c2b99573..63f3148c 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/HomeViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/HomeViewModel.java
@@ -10,11 +10,9 @@ import androidx.lifecycle.MutableLiveData;
 
 import com.cappielloantonio.play.model.Album;
 import com.cappielloantonio.play.model.Artist;
-import com.cappielloantonio.play.model.Download;
 import com.cappielloantonio.play.model.Song;
 import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.repository.ArtistRepository;
-import com.cappielloantonio.play.repository.DownloadRepository;
 import com.cappielloantonio.play.repository.SongRepository;
 
 import java.util.List;
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/LibraryViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/LibraryViewModel.java
index 9c3460b3..7e2fd26c 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/LibraryViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/LibraryViewModel.java
@@ -18,7 +18,6 @@ import com.cappielloantonio.play.repository.GenreRepository;
 import com.cappielloantonio.play.repository.PlaylistRepository;
 
 import java.util.Calendar;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/LoginViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/LoginViewModel.java
index 2cdef0c3..6fdd7973 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/LoginViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/LoginViewModel.java
@@ -1,33 +1,19 @@
 package com.cappielloantonio.play.viewmodel;
 
 import android.app.Application;
-import android.content.Context;
 
 import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
 
-import com.cappielloantonio.play.App;
-import com.cappielloantonio.play.interfaces.MediaCallback;
-import com.cappielloantonio.play.model.Album;
 import com.cappielloantonio.play.model.Server;
-import com.cappielloantonio.play.model.Song;
-import com.cappielloantonio.play.repository.AlbumRepository;
 import com.cappielloantonio.play.repository.ServerRepository;
-import com.cappielloantonio.play.subsonic.models.AlbumID3;
-import com.cappielloantonio.play.subsonic.models.ResponseStatus;
-import com.cappielloantonio.play.subsonic.models.SubsonicResponse;
-import com.cappielloantonio.play.util.MappingUtil;
 
-import java.util.ArrayList;
 import java.util.List;
 
-import retrofit2.Call;
-import retrofit2.Callback;
-
 public class LoginViewModel extends AndroidViewModel {
-    private ServerRepository serverRepository;
+    private final ServerRepository serverRepository;
+
     private Server toEdit = null;
 
     public LoginViewModel(@NonNull Application application) {
@@ -45,10 +31,9 @@ public class LoginViewModel extends AndroidViewModel {
     }
 
     public void deleteServer(Server server) {
-        if(server != null) {
+        if (server != null) {
             serverRepository.delete(server);
-        }
-        else if(toEdit != null) {
+        } else if (toEdit != null) {
             serverRepository.delete(toEdit);
         }
     }
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/MainViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/MainViewModel.java
index 0e3a2a7f..93d4fc3e 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/MainViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/MainViewModel.java
@@ -10,7 +10,7 @@ import com.cappielloantonio.play.repository.QueueRepository;
 public class MainViewModel extends AndroidViewModel {
     private static final String TAG = "SearchViewModel";
 
-    private Application application;
+    private final Application application;
 
     public MainViewModel(@NonNull Application application) {
         super(application);
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlayerBottomSheetViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlayerBottomSheetViewModel.java
index ad48295c..a4fb344c 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlayerBottomSheetViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlayerBottomSheetViewModel.java
@@ -17,10 +17,10 @@ import java.util.List;
 public class PlayerBottomSheetViewModel extends AndroidViewModel {
     private static final String TAG = "PlayerBottomSheetViewModel";
 
-    private SongRepository songRepository;
-    private QueueRepository queueRepository;
+    private final SongRepository songRepository;
+    private final QueueRepository queueRepository;
 
-    private LiveData<List<Queue>> queueSong;
+    private final LiveData<List<Queue>> queueSong;
 
     public PlayerBottomSheetViewModel(@NonNull Application application) {
         super(application);
@@ -43,12 +43,14 @@ public class PlayerBottomSheetViewModel extends AndroidViewModel {
     public void setFavorite() {
         Song song = MusicPlayerRemote.getCurrentSong();
 
-        if (song.isFavorite()) {
-            songRepository.unstar(song.getId());
-            song.setFavorite(false);
-        } else {
-            songRepository.star(song.getId());
-            song.setFavorite(true);
+        if (song != null) {
+            if (song.isFavorite()) {
+                songRepository.unstar(song.getId());
+                song.setFavorite(false);
+            } else {
+                songRepository.star(song.getId());
+                song.setFavorite(true);
+            }
         }
     }
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistCatalogueViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistCatalogueViewModel.java
index 2d39d5ba..eac3554e 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistCatalogueViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistCatalogueViewModel.java
@@ -1,31 +1,18 @@
 package com.cappielloantonio.play.viewmodel;
 
 import android.app.Application;
-import android.content.Context;
 
 import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
 
-import com.cappielloantonio.play.App;
 import com.cappielloantonio.play.model.Playlist;
 import com.cappielloantonio.play.repository.PlaylistRepository;
-import com.cappielloantonio.play.subsonic.models.ResponseStatus;
-import com.cappielloantonio.play.subsonic.models.SubsonicResponse;
-import com.cappielloantonio.play.util.MappingUtil;
 
-import java.util.ArrayList;
 import java.util.List;
 
-import retrofit2.Call;
-import retrofit2.Callback;
-
 public class PlaylistCatalogueViewModel extends AndroidViewModel {
-    private MutableLiveData<List<Playlist>> playlists;
-
-    private PlaylistRepository playlistRepository;
-    private String query = "";
+    private final PlaylistRepository playlistRepository;
 
     public PlaylistCatalogueViewModel(@NonNull Application application) {
         super(application);
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistChooserViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistChooserViewModel.java
index eaeb3574..302c7bb5 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistChooserViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistChooserViewModel.java
@@ -16,9 +16,9 @@ import java.util.Collections;
 import java.util.List;
 
 public class PlaylistChooserViewModel extends AndroidViewModel {
-    private PlaylistRepository playlistRepository;
+    private final PlaylistRepository playlistRepository;
 
-    private MutableLiveData<List<Playlist>> playlists;
+    private final MutableLiveData<List<Playlist>> playlists = new MutableLiveData<>(null);
     private Song toAdd;
 
     public PlaylistChooserViewModel(@NonNull Application application) {
@@ -26,7 +26,8 @@ public class PlaylistChooserViewModel extends AndroidViewModel {
 
         playlistRepository = new PlaylistRepository(application);
 
-        playlists = playlistRepository.getPlaylists(false, -1);
+        playlistRepository.getPlaylists(false, -1).observeForever(playlists::postValue);
+
     }
 
     public LiveData<List<Playlist>> getPlaylistList() {
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistEditorViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistEditorViewModel.java
index b2a5efda..f70d1a79 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistEditorViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistEditorViewModel.java
@@ -20,7 +20,7 @@ import java.util.Objects;
 public class PlaylistEditorViewModel extends AndroidViewModel {
     private static final String TAG = "PlaylistEditorViewModel";
 
-    private PlaylistRepository playlistRepository;
+    private final PlaylistRepository playlistRepository;
 
     private Song toAdd;
     private Playlist toEdit;
@@ -88,8 +88,10 @@ public class PlaylistEditorViewModel extends AndroidViewModel {
         List<Song> songs = songLiveList.getValue();
         ArrayList<String> ids = new ArrayList<>();
 
-        for (Song song : songs) {
-            ids.add(song.getId());
+        if (songs != null && !songs.isEmpty()) {
+            for (Song song : songs) {
+                ids.add(song.getId());
+            }
         }
 
         return ids;
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistPageViewModel.java
index f8259069..0193cdef 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/PlaylistPageViewModel.java
@@ -13,7 +13,7 @@ import com.cappielloantonio.play.repository.PlaylistRepository;
 import java.util.List;
 
 public class PlaylistPageViewModel extends AndroidViewModel {
-    private PlaylistRepository playlistRepository;
+    private final PlaylistRepository playlistRepository;
 
     private Playlist playlist;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/RatingViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/RatingViewModel.java
index f2330a98..80635b83 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/RatingViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/RatingViewModel.java
@@ -14,9 +14,9 @@ import com.cappielloantonio.play.repository.ArtistRepository;
 import com.cappielloantonio.play.repository.SongRepository;
 
 public class RatingViewModel extends AndroidViewModel {
-    private SongRepository songRepository;
-    private AlbumRepository albumRepository;
-    private ArtistRepository artistRepository;
+    private final SongRepository songRepository;
+    private final AlbumRepository albumRepository;
+    private final ArtistRepository artistRepository;
 
     private Song song;
     private Album album;
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/SearchViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/SearchViewModel.java
index a0ba311b..d1ca9d77 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/SearchViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/SearchViewModel.java
@@ -5,18 +5,12 @@ import android.app.Application;
 import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
 
 import com.cappielloantonio.play.model.Album;
 import com.cappielloantonio.play.model.Artist;
-import com.cappielloantonio.play.model.Genre;
 import com.cappielloantonio.play.model.RecentSearch;
 import com.cappielloantonio.play.model.Song;
-import com.cappielloantonio.play.repository.AlbumRepository;
-import com.cappielloantonio.play.repository.ArtistRepository;
-import com.cappielloantonio.play.repository.GenreRepository;
 import com.cappielloantonio.play.repository.SearchingRepository;
-import com.cappielloantonio.play.repository.SongRepository;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -26,11 +20,7 @@ public class SearchViewModel extends AndroidViewModel {
 
     private String query = "";
 
-    private SearchingRepository searchingRepository;
-
-    private LiveData<List<Song>> searchSong = new MutableLiveData<>(new ArrayList<>());
-    private LiveData<List<Album>> searchAlbum = new MutableLiveData<>(new ArrayList<>());
-    private LiveData<List<Artist>> searchArtist = new MutableLiveData<>(new ArrayList<>());
+    private final SearchingRepository searchingRepository;
 
     public SearchViewModel(@NonNull Application application) {
         super(application);
@@ -51,18 +41,15 @@ public class SearchViewModel extends AndroidViewModel {
     }
 
     public LiveData<List<Song>> searchSong(String title) {
-        searchSong = searchingRepository.getSearchedSongs(title);
-        return searchSong;
+        return searchingRepository.getSearchedSongs(title);
     }
 
     public LiveData<List<Album>> searchAlbum(String name) {
-        searchAlbum = searchingRepository.getSearchedAlbums(name);
-        return searchAlbum;
+        return searchingRepository.getSearchedAlbums(name);
     }
 
     public LiveData<List<Artist>> searchArtist(String name) {
-        searchArtist = searchingRepository.getSearchedArtists(name);
-        return searchArtist;
+        return searchingRepository.getSearchedArtists(name);
     }
 
     public void insertNewSearch(String search) {
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/SettingViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/SettingViewModel.java
index e28be490..23e1c4f0 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/SettingViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/SettingViewModel.java
@@ -6,14 +6,12 @@ import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 
 import com.cappielloantonio.play.interfaces.ScanCallback;
-import com.cappielloantonio.play.repository.QueueRepository;
 import com.cappielloantonio.play.repository.ScanRepository;
-import com.cappielloantonio.play.repository.SongRepository;
 
 public class SettingViewModel extends AndroidViewModel {
     private static final String TAG = "SettingViewModel";
 
-    private ScanRepository scanRepository;
+    private final ScanRepository scanRepository;
 
     public SettingViewModel(@NonNull Application application) {
         super(application);
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/SongBottomSheetViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/SongBottomSheetViewModel.java
index 977aa708..9e7ee2b3 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/SongBottomSheetViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/SongBottomSheetViewModel.java
@@ -14,9 +14,9 @@ import com.cappielloantonio.play.repository.ArtistRepository;
 import com.cappielloantonio.play.repository.SongRepository;
 
 public class SongBottomSheetViewModel extends AndroidViewModel {
-    private SongRepository songRepository;
-    private AlbumRepository albumRepository;
-    private ArtistRepository artistRepository;
+    private final SongRepository songRepository;
+    private final AlbumRepository albumRepository;
+    private final ArtistRepository artistRepository;
 
     private Song song;
 
diff --git a/app/src/main/java/com/cappielloantonio/play/viewmodel/SongListPageViewModel.java b/app/src/main/java/com/cappielloantonio/play/viewmodel/SongListPageViewModel.java
index eb08d417..74d75bd4 100644
--- a/app/src/main/java/com/cappielloantonio/play/viewmodel/SongListPageViewModel.java
+++ b/app/src/main/java/com/cappielloantonio/play/viewmodel/SongListPageViewModel.java
@@ -22,9 +22,9 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class SongListPageViewModel extends AndroidViewModel {
-    private SongRepository songRepository;
-    private ArtistRepository artistRepository;
-    private DownloadRepository downloadRepository;
+    private final SongRepository songRepository;
+    private final ArtistRepository artistRepository;
+    private final DownloadRepository downloadRepository;
 
     public String title;
     public Genre genre;