use the TracksActivity for displaying folder tracks too

app/src/main/kotlin/com/simplemobiletools/musicplayer/activities/TracksActivity.kt

@@ -25,29 +25,43 @@ import org.greenrobot.eventbus.EventBus
 import org.greenrobot.eventbus.Subscribe
 import org.greenrobot.eventbus.ThreadMode
 
+const val TYPE_PLAYLIST = 1
+const val TYPE_FOLDER = 2
+const val TYPE_ALBUM = 3
+
+// this activity is used for displaying Playlist and Folder tracks, also Album tracks with a possible album header at the top
 // Artists -> Albums -> Tracks
 class TracksActivity : SimpleActivity() {
     private var bus: EventBus? = null
     private var playlist: Playlist? = null
+    private var tracksType = 0
     private var lastFilePickerPath = ""
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_tracks)
-
         bus = EventBus.getDefault()
         bus!!.register(this)
 
         val playlistType = object : TypeToken<Playlist>() {}.type
         playlist = Gson().fromJson<Playlist>(intent.getStringExtra(PLAYLIST), playlistType)
         if (playlist != null) {
+            tracksType = TYPE_PLAYLIST
             invalidateOptionsMenu()
         }
 
         val albumType = object : TypeToken<Album>() {}.type
         val album = Gson().fromJson<Album>(intent.getStringExtra(ALBUM), albumType)
+        if (album != null) {
+            tracksType = TYPE_ALBUM
+        }
 
-        title = playlist?.title ?: album.title
+        val folder = intent.getStringExtra(FOLDER)
+        if (folder != null) {
+            tracksType = TYPE_FOLDER
+        }
+
+        title = playlist?.title ?: album?.title ?: folder
 
         val adjustedPrimaryColor = getAdjustedPrimaryColor()
         tracks_fastscroller.updateColors(adjustedPrimaryColor)
@@ -61,24 +75,30 @@ class TracksActivity : SimpleActivity() {
         ensureBackgroundThread {
             val tracks = ArrayList<Track>()
             val listItems = ArrayList<ListItem>()
-            if (playlist != null) {
-                val playlistTracks = tracksDAO.getTracksFromPlaylist(playlist!!.id)
-                runOnUiThread {
-                    tracks_placeholder.beVisibleIf(playlistTracks.isEmpty())
-                    tracks_placeholder_2.beVisibleIf(playlistTracks.isEmpty())
+            when (tracksType) {
+                TYPE_PLAYLIST -> {
+                    val playlistTracks = tracksDAO.getTracksFromPlaylist(playlist!!.id)
+                    runOnUiThread {
+                        tracks_placeholder.beVisibleIf(playlistTracks.isEmpty())
+                        tracks_placeholder_2.beVisibleIf(playlistTracks.isEmpty())
+                    }
+
+                    tracks.addAll(playlistTracks)
+                    listItems.addAll(tracks)
                 }
+                TYPE_ALBUM -> {
+                    val albumTracks = getAlbumTracksSync(album.id)
+                    albumTracks.sortWith(compareBy({ it.trackId }, { it.title.toLowerCase() }))
+                    tracks.addAll(albumTracks)
 
-                tracks.addAll(playlistTracks)
-                listItems.addAll(tracks)
-            } else {
-                val albumTracks = getAlbumTracksSync(album.id)
-                albumTracks.sortWith(compareBy({ it.trackId }, { it.title.toLowerCase() }))
-                tracks.addAll(albumTracks)
+                    val coverArt = ContentUris.withAppendedId(artworkUri, album.id).toString()
+                    val header = AlbumHeader(album.title, coverArt, album.year, tracks.size, tracks.sumBy { it.duration }, album.artist)
+                    listItems.add(header)
+                    listItems.addAll(tracks)
+                }
+                else -> {
 
-                val coverArt = ContentUris.withAppendedId(artworkUri, album.id).toString()
-                val header = AlbumHeader(album.title, coverArt, album.year, tracks.size, tracks.sumBy { it.duration }, album.artist)
-                listItems.add(header)
-                listItems.addAll(tracks)
+                }
             }
 
             runOnUiThread {
@@ -121,9 +141,9 @@ class TracksActivity : SimpleActivity() {
         menuInflater.inflate(R.menu.menu_playlist, menu)
 
         menu.apply {
-            findItem(R.id.sort).isVisible = playlist != null
-            findItem(R.id.add_file_to_playlist).isVisible = playlist != null
-            findItem(R.id.add_folder_to_playlist).isVisible = playlist != null
+            findItem(R.id.sort).isVisible = tracksType != TYPE_ALBUM
+            findItem(R.id.add_file_to_playlist).isVisible = tracksType == TYPE_PLAYLIST
+            findItem(R.id.add_folder_to_playlist).isVisible = tracksType == TYPE_PLAYLIST
         }
 
         updateMenuItemColors(menu)
@@ -141,7 +161,7 @@ class TracksActivity : SimpleActivity() {
     }
 
     private fun showSortingDialog() {
-        ChangeSortingDialog(this, ACTIVITY_PLAYLIST) {
+        ChangeSortingDialog(this, ACTIVITY_PLAYLIST_FOLDER) {
             val adapter = tracks_list.adapter as? TracksAdapter ?: return@ChangeSortingDialog
             val tracks = adapter.tracks
             Track.sorting = config.playlistTracksSorting
@@ -209,7 +229,6 @@ class TracksActivity : SimpleActivity() {
         val newTracks = tracksDAO.getTracksFromPlaylist(playlist!!.id).toMutableList() as ArrayList<Track>
         runOnUiThread {
             (tracks_list.adapter as? TracksAdapter)?.updateItems(newTracks)
-
             tracks_placeholder.beVisibleIf(newTracks.isEmpty())
             tracks_placeholder_2.beVisibleIf(newTracks.isEmpty())
         }
@@ -222,11 +241,10 @@ class TracksActivity : SimpleActivity() {
     }
 
     private fun itemClicked(track: Track) {
-        val tracks = if (playlist != null) {
-            (tracks_list.adapter as? TracksAdapter)?.tracks?.toMutableList() as? ArrayList<Track> ?: ArrayList()
-        } else {
-            (tracks_list.adapter as? TracksHeaderAdapter)?.items?.filterIsInstance<Track>()?.toMutableList() as? ArrayList<Track>
-                ?: ArrayList()
+        val tracks = when (tracksType) {
+            TYPE_PLAYLIST -> (tracks_list.adapter as? TracksAdapter)?.tracks?.toMutableList() as? ArrayList<Track> ?: ArrayList()
+            TYPE_ALBUM -> (tracks_list.adapter as? TracksHeaderAdapter)?.items?.filterIsInstance<Track>()?.toMutableList() as? ArrayList<Track> ?: ArrayList()
+            else -> ArrayList()
         }
 
         resetQueueItems(tracks) {

app/src/main/kotlin/com/simplemobiletools/musicplayer/dialogs/ChangeSortingDialog.kt

@@ -25,7 +25,7 @@ class ChangeSortingDialog(val activity: Activity, val location: Int, val callbac
             TAB_FOLDERS -> config.folderSorting
             TAB_ARTISTS -> config.artistSorting
             TAB_ALBUMS -> config.albumSorting
-            ACTIVITY_PLAYLIST -> config.playlistTracksSorting
+            ACTIVITY_PLAYLIST_FOLDER -> config.playlistTracksSorting
             else -> config.trackSorting
         }
 
@@ -57,7 +57,7 @@ class ChangeSortingDialog(val activity: Activity, val location: Int, val callbac
                 radioItems.add(RadioItem(1, activity.getString(R.string.artist_name), PLAYER_SORT_BY_ARTIST_TITLE))
                 radioItems.add(RadioItem(2, activity.getString(R.string.year), PLAYER_SORT_BY_YEAR))
             }
-            TAB_TRACKS, ACTIVITY_PLAYLIST -> {
+            TAB_TRACKS, ACTIVITY_PLAYLIST_FOLDER -> {
                 radioItems.add(RadioItem(0, activity.getString(R.string.title), PLAYER_SORT_BY_TITLE))
                 radioItems.add(RadioItem(1, activity.getString(R.string.artist), PLAYER_SORT_BY_ARTIST_TITLE))
                 radioItems.add(RadioItem(2, activity.getString(R.string.duration), PLAYER_SORT_BY_DURATION))
@@ -103,7 +103,7 @@ class ChangeSortingDialog(val activity: Activity, val location: Int, val callbac
                 TAB_ARTISTS -> config.artistSorting = sorting
                 TAB_ALBUMS -> config.albumSorting = sorting
                 TAB_TRACKS -> config.trackSorting = sorting
-                ACTIVITY_PLAYLIST -> config.playlistTracksSorting = sorting
+                ACTIVITY_PLAYLIST_FOLDER -> config.playlistTracksSorting = sorting
             }
 
             callback()

app/src/main/kotlin/com/simplemobiletools/musicplayer/fragments/FoldersFragment.kt

@@ -1,6 +1,7 @@
 package com.simplemobiletools.musicplayer.fragments
 
 import android.content.Context
+import android.content.Intent
 import android.util.AttributeSet
 import com.simplemobiletools.commons.adapters.MyRecyclerViewAdapter
 import com.simplemobiletools.commons.extensions.areSystemAnimationsEnabled
@@ -8,12 +9,14 @@ import com.simplemobiletools.commons.extensions.beGoneIf
 import com.simplemobiletools.commons.extensions.beVisibleIf
 import com.simplemobiletools.musicplayer.R
 import com.simplemobiletools.musicplayer.activities.SimpleActivity
+import com.simplemobiletools.musicplayer.activities.TracksActivity
 import com.simplemobiletools.musicplayer.adapters.FoldersAdapter
 import com.simplemobiletools.musicplayer.dialogs.ChangeSortingDialog
 import com.simplemobiletools.musicplayer.extensions.config
 import com.simplemobiletools.musicplayer.extensions.getAlbumTracksSync
 import com.simplemobiletools.musicplayer.extensions.getAlbumsSync
 import com.simplemobiletools.musicplayer.extensions.getArtistsSync
+import com.simplemobiletools.musicplayer.helpers.FOLDER
 import com.simplemobiletools.musicplayer.helpers.TAB_FOLDERS
 import com.simplemobiletools.musicplayer.models.Album
 import com.simplemobiletools.musicplayer.models.Folder
@@ -54,7 +57,10 @@ class FoldersFragment(context: Context, attributeSet: AttributeSet) : MyViewPage
             val adapter = folders_list.adapter
             if (adapter == null) {
                 FoldersAdapter(activity, folders, folders_list) {
-
+                    Intent(activity, TracksActivity::class.java).apply {
+                        putExtra(FOLDER, (it as Folder).title)
+                        activity.startActivity(this)
+                    }
                 }.apply {
                     folders_list.adapter = this
                 }

app/src/main/kotlin/com/simplemobiletools/musicplayer/helpers/Constants.kt

@@ -15,6 +15,7 @@ const val ARTIST = "artist"
 const val ALBUM = "album"
 const val TRACK = "track"
 const val PLAYLIST = "playlist"
+const val FOLDER = "folder"
 
 private const val PATH = "com.simplemobiletools.musicplayer.action."
 val artworkUri = Uri.parse("content://media/external/audio/albumart")
@@ -67,7 +68,7 @@ const val TAB_FOLDERS = 1
 const val TAB_ARTISTS = 2
 const val TAB_ALBUMS = 3
 const val TAB_TRACKS = 4
-const val ACTIVITY_PLAYLIST = 5
+const val ACTIVITY_PLAYLIST_FOLDER = 5
 
 // use custom sorting constants, there are too many app specific ones
 const val PLAYER_SORT_BY_TITLE = 1