Replaced back arrow with x in some places and cleaned some code up

app/src/main/java/com/kabouzeid/gramophone/model/smartplaylist/AbsSmartPlaylist.java

@@ -33,7 +33,7 @@ public abstract class AbsSmartPlaylist extends Playlist {
         this.iconRes = R.drawable.ic_queue_music_white_24dp;
     }
 
-    @Nullable
+    @NonNull
     public SmartPlaylistSongAdapter createAdapter(AppCompatActivity activity, @Nullable CabHolder cabHolder) {
         return new SmartPlaylistSongAdapter(activity, this, cabHolder);
     }
@@ -51,7 +51,7 @@ public abstract class AbsSmartPlaylist extends Playlist {
     }
 
     @Override
-    public boolean equals(@NonNull final Object obj) {
+    public boolean equals(@Nullable final Object obj) {
         if (super.equals(obj)) {
             if (getClass() != obj.getClass()) {
                 return false;

app/src/main/java/com/kabouzeid/gramophone/ui/activities/AlbumDetailActivity.java

@@ -424,6 +424,7 @@ public class AlbumDetailActivity extends AbsFabActivity implements PaletteColorH
         if (cab != null && cab.isActive()) cab.finish();
         cab = new MaterialCab(this, R.id.cab_stub)
                 .setMenu(menuRes)
+                .setCloseDrawableRes(R.drawable.ic_close_white_24dp)
                 .setBackgroundColor(getPaletteColor())
                 .start(new MaterialCab.Callback() {
                     @Override

app/src/main/java/com/kabouzeid/gramophone/ui/activities/ArtistDetailActivity.java

@@ -570,6 +570,7 @@ public class ArtistDetailActivity extends AbsFabActivity implements PaletteColor
         if (cab != null && cab.isActive()) cab.finish();
         cab = new MaterialCab(this, R.id.cab_stub)
                 .setMenu(menuRes)
+                .setCloseDrawableRes(R.drawable.ic_close_white_24dp)
                 .setBackgroundColor(getPaletteColor())
                 .start(new MaterialCab.Callback() {
                     @Override

app/src/main/java/com/kabouzeid/gramophone/ui/activities/MainActivity.java

@@ -67,7 +67,7 @@ import butterknife.ButterKnife;
 import butterknife.InjectView;
 
 public class MainActivity extends AbsFabActivity
-        implements KabViewsDisableAble, CabHolder, View.OnClickListener {
+        implements KabViewsDisableAble, CabHolder {
 
     public static final String TAG = MainActivity.class.getSimpleName();
 
@@ -256,7 +256,18 @@ public class MainActivity extends AbsFabActivity
         if (song.id != -1) {
             if (navigationDrawerHeader == null) {
                 navigationDrawerHeader = navigationView.inflateHeaderView(R.layout.navigation_drawer_header);
-                navigationDrawerHeader.setOnClickListener(this);
+                //noinspection ConstantConditions
+                navigationDrawerHeader.setOnClickListener(new View.OnClickListener() {
+                    @Override
+                    public void onClick(View v) {
+                        //noinspection ConstantConditions
+                        NavigationUtil.openCurrentPlayingIfPossible(MainActivity.this, getSharedViewsWithFab(new Pair[]{
+                                Pair.create(navigationDrawerHeader.findViewById(R.id.album_art),
+                                        getResources().getString(R.string.transition_album_cover)
+                                )
+                        }));
+                    }
+                });
             }
             ((TextView) navigationDrawerHeader.findViewById(R.id.song_title)).setText(song.title);
             ((TextView) navigationDrawerHeader.findViewById(R.id.song_artist)).setText(song.artistName);
@@ -270,8 +281,10 @@ public class MainActivity extends AbsFabActivity
                             .build()
             );
         } else {
-            navigationView.removeHeaderView(navigationDrawerHeader);
+            if (navigationDrawerHeader != null) {
-            navigationDrawerHeader = null;
+                navigationView.removeHeaderView(navigationDrawerHeader);
+                navigationDrawerHeader = null;
+            }
         }
     }
 
@@ -596,27 +609,17 @@ public class MainActivity extends AbsFabActivity
         if (cab != null && cab.isActive()) cab.finish();
         cab = new MaterialCab(this, R.id.cab_stub)
                 .setMenu(menu)
+                .setCloseDrawableRes(R.drawable.ic_close_white_24dp)
                 .setBackgroundColor(PreferenceUtils.getInstance(this).getThemeColorPrimary())
                 .start(callback);
         return cab;
     }
 
-    @Override
-    public void onClick(View v) {
-        if (v == navigationDrawerHeader) {
-            NavigationUtil.openCurrentPlayingIfPossible(this, getSharedViewsWithFab(new Pair[]{
-                    Pair.create(((ImageView) navigationDrawerHeader.findViewById(R.id.album_art)),
-                            getResources().getString(R.string.transition_album_cover)
-                    )
-            }));
-        }
-    }
-
     public void addOnAppBarOffsetChangedListener(OnOffsetChangedListener onOffsetChangedListener) {
         appbar.addOnOffsetChangedListener(onOffsetChangedListener);
     }
 
-    public void removeOnAppBArOffsetChangedListener(OnOffsetChangedListener onOffsetChangedListener) {
+    public void removeOnAppBarOffsetChangedListener(OnOffsetChangedListener onOffsetChangedListener) {
         appbar.removeOnOffsetChangedListener(onOffsetChangedListener);
     }
 

app/src/main/java/com/kabouzeid/gramophone/ui/activities/MusicControllerActivity.java

@@ -180,6 +180,7 @@ public class MusicControllerActivity extends AbsFabActivity {
         //noinspection ConstantConditions
         getSupportActionBar().setTitle(null);
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
+        getSupportActionBar().setHomeAsUpIndicator(R.drawable.ic_close_white_24dp);
     }
 
     private void animateFabCircularRevealOnEnterTransitionEnd() {

app/src/main/java/com/kabouzeid/gramophone/ui/activities/PlaylistDetailActivity.java

@@ -2,7 +2,6 @@ package com.kabouzeid.gramophone.ui.activities;
 
 import android.os.Bundle;
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 import android.support.v7.widget.GridLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.Toolbar;
@@ -45,10 +44,8 @@ public class PlaylistDetailActivity extends AbsFabActivity implements CabHolder
     @InjectView(android.R.id.empty)
     TextView empty;
 
-    @Nullable
     private Playlist playlist;
     private MaterialCab cab;
-    @Nullable
     private AbsPlaylistSongAdapter adapter;
 
     @Override
@@ -111,6 +108,7 @@ public class PlaylistDetailActivity extends AbsFabActivity implements CabHolder
         } catch (ClassCastException ignored) {
         }
         if (playlist == null) {
+            playlist = new Playlist();
             finish();
         }
     }
@@ -159,6 +157,7 @@ public class PlaylistDetailActivity extends AbsFabActivity implements CabHolder
         if (cab != null && cab.isActive()) cab.finish();
         cab = new MaterialCab(this, R.id.cab_stub)
                 .setMenu(menu)
+                .setCloseDrawableRes(R.drawable.ic_close_white_24dp)
                 .setBackgroundColor(PreferenceUtils.getInstance(this).getThemeColorPrimary())
                 .start(callback);
         return cab;

app/src/main/java/com/kabouzeid/gramophone/ui/fragments/mainactivityfragments/AbsMainActivityRecyclerViewFragment.java

@@ -137,6 +137,7 @@ public abstract class AbsMainActivityRecyclerViewFragment extends AbsMainActivit
     @Override
     public void onDestroyView() {
         super.onDestroyView();
+        getMainActivity().removeOnAppBarOffsetChangedListener(this);
         ButterKnife.reset(this);
     }
 }