Incremental work to support playlist editing.

CHANGELOG.txt

@@ -7,7 +7,8 @@ musikcube:
 
 musikdroid:
 
-* gapless playback!
+* gapless playback (for supported media)! enable in settings > playback 
+  engine > "ExoPlayer Gapless (experimental)"
 * album art is now displayed in album rows when browsing
 * context menus on most screens with the ability to switch between related 
   content (e.g. albums by this artist, artists in this genre, etc)
@@ -22,7 +23,6 @@ musikdroid:
 * updated Glide from v3 -> v4
 * updated to Android Studio 3.0.1 and related tooling
 
-
 sdk:
 
 * removed all Destroy() methods, standardized on Release() across the board

src/musikdroid/README.md

@@ -11,7 +11,7 @@ because `musikdroid` is not available in the Google Play store, it uses [fabric.
 
 this should allow you to build and test locally without special keys. TODO: simplify
 
-the project is currently built using `Android Studio 3.0 Canary 6`
+the project is currently built using `Android Studio 3.0.1`
 
 # attribution
 

src/musikdroid/app/src/main/AndroidManifest.xml

@@ -51,6 +51,11 @@
 
         </activity>
 
+        <activity android:name=".ui.tracks.activity.EditPlaylistActivity"
+            android:screenOrientation="portrait"
+            android:windowSoftInputMode="adjustResize">
+        </activity>
+
         <activity
             android:name="io.casey.musikcube.remote.ui.category.activity.CategoryBrowseActivity"
             android:screenOrientation="portrait"

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/framework/ViewModel.kt

@@ -6,40 +6,58 @@ import android.os.Looper
 import com.uacf.taskrunner.Runner
 import com.uacf.taskrunner.Task
 import io.casey.musikcube.remote.Application
+import io.reactivex.Observable
+import io.reactivex.android.schedulers.AndroidSchedulers
+import io.reactivex.subjects.PublishSubject
+import io.reactivex.subjects.Subject
 import java.util.concurrent.atomic.AtomicLong
 
-abstract class ViewModel<ListenerT>(protected val runner: Runner? = null): Runner.TaskCallbacks {
+abstract class ViewModel<T>(protected val runner: Runner? = null): Runner.TaskCallbacks {
     val id: Long = nextId.incrementAndGet()
+    private val publisher by lazy { createSubject() }
 
     interface Provider {
         fun <T: ViewModel<*>> createViewModel(): T?
     }
 
-    protected var listener: ListenerT? = null
+    protected var listener: T? = null
         private set
 
-    fun onPause() {
+    open fun onPause() {
     }
 
-    fun onResume() {
+    open fun onResume() {
     }
 
-    fun onDestroy() {
+    open fun onDestroy() {
         listener = null
         handler.postDelayed(cleanup, cleanupDelayMs)
     }
 
-    fun observe(listener: ListenerT) {
-        this.listener = listener
+    open fun onCleanup() {
+
+    }
+
+    fun observe(): Observable<T> {
+        return publisher
+            .observeOn(AndroidSchedulers.mainThread())
+            .subscribeOn(AndroidSchedulers.mainThread())
     }
 
     val context: Context = Application.instance!!
 
-    internal val cleanup = object: Runnable {
-        override fun run() {
-            listener = null
-            idToInstance.remove(id)
-        }
+    internal val cleanup = Runnable {
+        listener = null
+        idToInstance.remove(id)
+        onCleanup()
+    }
+
+    protected fun publish(value: T) {
+        publisher.onNext(value)
+    }
+
+    open fun createSubject(): Subject<T> {
+        return PublishSubject.create<T>()
     }
 
     override fun onTaskError(name: String?, id: Long, task: Task<*, *>?, error: Throwable?) {

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/playback/impl/remote/RemotePlaybackService.kt

@@ -373,7 +373,6 @@ class RemotePlaybackService : IPlaybackService {
 
     override val playlistQueryFactory: TrackListSlidingWindow.QueryFactory = object : TrackListSlidingWindow.QueryFactory() {
         override fun count(): Observable<Int> = dataProvider.getPlayQueueTracksCount()
-        override fun all(): Observable<List<ITrack>>? = dataProvider.getPlayQueueTracks()
         override fun page(offset: Int, limit: Int): Observable<List<ITrack>> = dataProvider.getPlayQueueTracks(limit, offset)
         override fun offline(): Boolean  = false
     }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/playback/impl/streaming/StreamingPlaybackService.kt

@@ -774,20 +774,6 @@ class StreamingPlaybackService(context: Context) : IPlaybackService {
             return null
         }
 
-        override fun all(): Observable<List<ITrack>>? {
-            val params = params
-            if (params != null) {
-                if (Strings.notEmpty(params.category) && (params.categoryId >= 0)) {
-                    return dataProvider.getTracksByCategory(
-                        params.category ?: "", params.categoryId, params.filter)
-                }
-                else {
-                    return dataProvider.getTracks(params.filter)
-                }
-            }
-            return null
-        }
-
         override fun page(offset: Int, limit: Int): Observable<List<ITrack>>? {
             val params = params
             if (params != null) {

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/websocket/Messages.kt

@@ -77,6 +77,7 @@ class Messages {
             val ID = "id"
             val COUNT = "count"
             val COUNT_ONLY = "count_only"
+            val IDS_ONLY = "ids_only"
             val OFFSET = "offset"
             val LIMIT = "limit"
             val INDEX = "index"

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/websocket/WebSocketService.kt

@@ -330,6 +330,8 @@ class WebSocketService constructor(private val context: Context) {
             subject.onError(ex)
         }
 
+        subject.doOnDispose { cancelMessage(mrd.id) }
+
         if (!intercepted) {
             socket?.sendText(message.toString())
         }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/websocket/model/IDataProvider.kt

@@ -22,6 +22,7 @@ interface IDataProvider {
     fun getTracks(externalIds: Set<String>): Observable<Map<String, ITrack>>
 
     fun getTrackCountByCategory(category: String, id: Long, filter: String = ""): Observable<Int>
+    fun getTrackIdsByCategory(category: String, id: Long, filter: String = ""): Observable<List<String>>
     fun getTracksByCategory(category: String, id: Long, filter: String = ""): Observable<List<ITrack>>
     fun getTracksByCategory(category: String, id: Long, limit: Int, offset: Int, filter: String = ""): Observable<List<ITrack>>
 
@@ -36,6 +37,7 @@ interface IDataProvider {
     fun createPlaylist(playlistName: String, categoryType: String = "", categoryId: Long = -1, filter: String = ""): Observable<Long>
     fun createPlaylist(playlistName: String, tracks: List<ITrack> = ArrayList()): Observable<Long>
     fun createPlaylistWithExternalIds(playlistName: String, externalIds: List<String> = ArrayList()): Observable<Long>
+    fun overwritePlaylistWithExternalIds(playlistId: Long, externalIds: List<String> = ArrayList()): Observable<Long>
     fun appendToPlaylist(playlistId: Long, categoryType: String = "", categoryId: Long = -1, filter: String = "", offset: Long = -1): Observable<Boolean>
     fun appendToPlaylist(playlistId: Long, tracks: List<ITrack> = ArrayList(), offset: Long = -1): Observable<Boolean>
     fun appendToPlaylist(playlistId: Long, categoryValue: ICategoryValue): Observable<Boolean>

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/service/websocket/model/impl/remote/RemoteDataProvider.kt

@@ -116,6 +116,21 @@ class RemoteDataProvider(private val service: WebSocketService) : IDataProvider
             .observeOn(AndroidSchedulers.mainThread())
     }
 
+    override fun getTrackIdsByCategory(category: String, id: Long, filter: String): Observable<List<String>> {
+        val message = SocketMessage.Builder
+            .request(Messages.Request.QueryTracksByCategory)
+            .addOption(Messages.Key.FILTER, filter)
+            .addOption(Messages.Key.CATEGORY, category)
+            .addOption(Messages.Key.ID, id)
+            .addOption(Messages.Key.COUNT_ONLY, false)
+            .addOption(Messages.Key.IDS_ONLY, true)
+            .build()
+
+        return service.observe(message, client)
+            .flatMap<List<String>> { socketMessage -> toStringList(socketMessage) }
+            .observeOn(AndroidSchedulers.mainThread())
+    }
+
     override fun getTracksByCategory(category: String, id: Long, filter: String): Observable<List<ITrack>> =
         getTracksByCategory(category, id, -1, -1, filter)
 
@@ -241,7 +256,7 @@ class RemoteDataProvider(private val service: WebSocketService) : IDataProvider
 
     override fun createPlaylistWithExternalIds(playlistName: String, externalIds: List<String>): Observable<Long> {
         if (playlistName.isBlank()) {
-            return Observable.just(0)
+            return Observable.just(-1L)
         }
 
         val jsonArray = JSONArray()
@@ -258,6 +273,25 @@ class RemoteDataProvider(private val service: WebSocketService) : IDataProvider
             .observeOn(AndroidSchedulers.mainThread())
     }
 
+    override fun overwritePlaylistWithExternalIds(playlistId: Long, externalIds: List<String>): Observable<Long> {
+        if (playlistId < 0L) {
+            return Observable.just(-1L)
+        }
+
+        val jsonArray = JSONArray()
+        externalIds.forEach { jsonArray.put(it) }
+
+        val message = SocketMessage.Builder
+            .request(Messages.Request.SavePlaylist)
+            .addOption(Messages.Key.PLAYLIST_ID, playlistId)
+            .addOption(Messages.Key.EXTERNAL_IDS, jsonArray)
+            .build()
+
+        return service.observe(message, client)
+            .flatMap<Long> { socketMessage -> extractId(socketMessage, Messages.Key.PLAYLIST_ID) }
+            .observeOn(AndroidSchedulers.mainThread())
+    }
+
     override fun appendToPlaylist(playlistId: Long, categoryType: String, categoryId: Long, filter: String, offset: Long): Observable<Boolean> {
         val message = SocketMessage.Builder
             .request(Messages.Request.AppendToPlaylist)
@@ -461,6 +495,15 @@ class RemoteDataProvider(private val service: WebSocketService) : IDataProvider
             return Observable.just(albums)
         }
 
+        private fun toStringList(socketMessage: SocketMessage): Observable<List<String>> {
+            val strings = ArrayList<String>()
+            val json = socketMessage.getJsonArrayOption(Messages.Key.DATA, JSONArray())!!
+            for (i in 0 until json.length()) {
+                strings.add(json.getString(i))
+            }
+            return Observable.just(strings)
+        }
+
         private fun toCount(message: SocketMessage): Observable<Int> {
             return Observable.just(message.getIntOption(Messages.Key.COUNT, 0))
         }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/home/activity/MainActivity.kt

@@ -410,30 +410,29 @@ class MainActivity : BaseActivity() {
     private fun scheduleUpdateTime(immediate: Boolean) {
         handler.removeCallbacks(updateTimeRunnable)
         handler.postDelayed(updateTimeRunnable, (if (immediate) 0 else 1000).toLong())
+        handler.removeCallbacks(updateTimeRunnable)
     }
 
-    private val updateTimeRunnable = object: Runnable {
-        override fun run() {
-            val duration = playback.service.duration
-            val current: Double = if (seekbarValue == -1) playback.service.currentTime else seekbarValue.toDouble()
+    private val updateTimeRunnable = Runnable {
+        val duration = playback.service.duration
+        val current: Double = if (seekbarValue == -1) playback.service.currentTime else seekbarValue.toDouble()
 
-            currentTime.text = Duration.format(current)
-            totalTime.text = Duration.format(duration)
-            seekbar.max = duration.toInt()
-            seekbar.progress = current.toInt()
-            seekbar.secondaryProgress = playback.service.bufferedTime.toInt()
+        currentTime.text = Duration.format(current)
+        totalTime.text = Duration.format(duration)
+        seekbar.max = duration.toInt()
+        seekbar.progress = current.toInt()
+        seekbar.secondaryProgress = playback.service.bufferedTime.toInt()
 
-            var currentTimeColor = R.color.theme_foreground
-            if (playback.service.state === PlaybackState.Paused) {
-                currentTimeColor =
-                    if (++blink % 2 == 0) R.color.theme_foreground
-                    else R.color.theme_blink_foreground
-            }
-
-            currentTime.setTextColor(getColorCompat(currentTimeColor))
-
-            scheduleUpdateTime(false)
+        var currentTimeColor = R.color.theme_foreground
+        if (playback.service.state === PlaybackState.Paused) {
+            currentTimeColor =
+                if (++blink % 2 == 0) R.color.theme_foreground
+                else R.color.theme_blink_foreground
         }
+
+        currentTime.setTextColor(getColorCompat(currentTimeColor))
+
+        scheduleUpdateTime(false)
     }
 
     private val muteListener = { _: CompoundButton, b: Boolean ->

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/playqueue/adapter/PlayQueueAdapter.kt

@@ -23,7 +23,7 @@ class PlayQueueAdapter(val tracks: TrackListSlidingWindow,
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
         val inflater = LayoutInflater.from(parent.context)
-        val view = inflater.inflate(R.layout.play_queue_row, parent, false)
+        val view = inflater.inflate(R.layout.playlist_track_row, parent, false)
         val action = view.findViewById<View>(R.id.action)
         view.setOnClickListener{ v -> listener.onItemClicked(v.tag as Int) }
         action.setOnClickListener{ v -> listener.onActionClicked(v, v.tag as ITrack) }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/shared/extension/Extensions.kt

@@ -28,15 +28,12 @@ import io.casey.musikcube.remote.util.Strings
 val EXTRA_ACTIVITY_TITLE = "extra_title"
 
 fun AppCompatActivity.setupDefaultRecyclerView(
-                             recyclerView: RecyclerView,
-                             adapter: RecyclerView.Adapter<*>) {
+    recyclerView: RecyclerView, adapter: RecyclerView.Adapter<*>)
+{
     val layoutManager = LinearLayoutManager(this)
-
+    val dividerItemDecoration = DividerItemDecoration(this, layoutManager.orientation)
     recyclerView.layoutManager = LinearLayoutManager(this)
     recyclerView.adapter = adapter
-
-    val dividerItemDecoration = DividerItemDecoration(this, layoutManager.orientation)
-
     recyclerView.addItemDecoration(dividerItemDecoration)
 }
 

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/shared/mixin/ItemContextMenuMixin.kt

@@ -28,6 +28,7 @@ import io.casey.musikcube.remote.ui.shared.extension.showErrorSnackbar
 import io.casey.musikcube.remote.ui.shared.extension.showKeyboard
 import io.casey.musikcube.remote.ui.shared.extension.showSnackbar
 import io.casey.musikcube.remote.ui.shared.fragment.BaseDialogFragment
+import io.casey.musikcube.remote.ui.tracks.activity.EditPlaylistActivity
 import io.casey.musikcube.remote.ui.tracks.activity.TrackListActivity
 import io.reactivex.Observable
 import io.reactivex.rxkotlin.subscribeBy
@@ -233,6 +234,9 @@ class ItemContextMenuMixin(private val activity: AppCompatActivity,
                 R.id.menu_playlist_delete -> {
                     ConfirmDeletePlaylistDialog.show(activity, this, playlistName, playlistId)
                 }
+                R.id.menu_playlist_edit -> {
+                    activity.startActivity(EditPlaylistActivity.getStartIntent(activity, playlistId))
+                }
                 R.id.menu_playlist_rename -> {
                     EnterPlaylistNameDialog.showForRename(activity, this, playlistName, playlistId)
                 }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/shared/mixin/ViewModelMixin.kt

@@ -7,7 +7,12 @@ import io.casey.musikcube.remote.framework.ViewModel
 class ViewModelMixin(private val provider: ViewModel.Provider): MixinBase() {
     private var viewModel: ViewModel<*>? = null
 
-    fun <T: ViewModel<*>> get(): T? = this.viewModel as T?
+    fun <T: ViewModel<*>> get(): T? {
+        if (viewModel == null) {
+            viewModel = provider.createViewModel()
+        }
+        return viewModel as T?
+    }
 
     override fun onCreate(bundle: Bundle) {
         super.onCreate(bundle)

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/shared/model/TrackListSlidingWindow.kt

@@ -40,7 +40,6 @@ class TrackListSlidingWindow(private val recyclerView: FastScrollRecyclerView,
 
     abstract class QueryFactory {
         abstract fun count(): Observable<Int>?
-        abstract fun all(): Observable<List<ITrack>>?
         abstract fun page(offset: Int, limit: Int): Observable<List<ITrack>>?
         abstract fun offline(): Boolean
     }

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/tracks/activity/EditPlaylistActivity.kt

@@ -0,0 +1,106 @@
+package io.casey.musikcube.remote.ui.tracks.activity
+
+import android.content.Context
+import android.content.Intent
+import android.os.Bundle
+import android.support.v7.widget.RecyclerView
+import android.support.v7.widget.helper.ItemTouchHelper
+import android.view.Menu
+import android.view.MenuItem
+import io.casey.musikcube.remote.R
+import io.casey.musikcube.remote.framework.ViewModel
+import io.casey.musikcube.remote.ui.shared.activity.BaseActivity
+import io.casey.musikcube.remote.ui.shared.extension.setupDefaultRecyclerView
+import io.casey.musikcube.remote.ui.shared.mixin.DataProviderMixin
+import io.casey.musikcube.remote.ui.shared.mixin.ViewModelMixin
+import io.casey.musikcube.remote.ui.tracks.adapter.EditPlaylistAdapter
+import io.casey.musikcube.remote.ui.tracks.model.EditPlaylistViewModel
+import io.casey.musikcube.remote.ui.tracks.model.EditPlaylistViewModel.Status
+import io.reactivex.rxkotlin.subscribeBy
+
+class EditPlaylistActivity: BaseActivity() {
+    private lateinit var viewModel: EditPlaylistViewModel
+    private lateinit var data: DataProviderMixin
+    private lateinit var adapter: EditPlaylistAdapter
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        mixin(ViewModelMixin(this))
+        data = mixin(DataProviderMixin())
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.recycler_view_activity)
+        viewModel = getViewModel()!!
+        viewModel.attach(data.provider)
+        val recycler = findViewById<RecyclerView>(R.id.recycler_view)
+        val touchHelper = ItemTouchHelper(touchHelperCallback)
+        touchHelper.attachToRecyclerView(recycler)
+        adapter = EditPlaylistAdapter(viewModel, touchHelper)
+        setupDefaultRecyclerView(recycler, adapter)
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu): Boolean {
+        menuInflater.inflate(R.menu.edit_playlist_menu, menu)
+        return true
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        if (item.itemId == R.id.action_save) {
+            viewModel.save().subscribeBy(
+                onNext = { playlistId ->
+                    if (playlistId != -1L) {
+                        finish()
+                    }
+                    else {
+                        /* TODO ERROR SNACKBAR */
+                    }
+                },
+                onError = {
+                    /* TODO ERROR SNACKBAR */
+                })
+        }
+        return super.onOptionsItemSelected(item)
+    }
+
+    override fun onResume() {
+        super.onResume()
+
+        disposables.add(viewModel.observe().subscribeBy(
+            onNext = { status ->
+                if (status == Status.Updated) {
+                    adapter.notifyDataSetChanged()
+                }
+            },
+            onError = { }
+        ))
+    }
+
+    override fun <T: ViewModel<*>> createViewModel(): T? {
+        return EditPlaylistViewModel(intent.extras.getLong(EXTRA_PLAYLIST_ID, -1L)) as T
+    }
+
+    private val touchHelperCallback = object:ItemTouchHelper.SimpleCallback(
+            ItemTouchHelper.UP or ItemTouchHelper.DOWN,
+            ItemTouchHelper.LEFT)
+    {
+        override fun onMove(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
+            val from = viewHolder.adapterPosition
+            val to = target.adapterPosition
+            viewModel.move(from, to)
+            adapter.notifyItemMoved(from, to)
+            return true
+        }
+
+        override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
+            viewModel.remove(viewHolder.adapterPosition)
+            adapter.notifyItemRemoved(viewHolder.adapterPosition)
+        }
+    }
+
+    companion object {
+        private val EXTRA_PLAYLIST_ID = "extra_playlist_id"
+
+        fun getStartIntent(context: Context, playlistId: Long): Intent {
+            return Intent(context, EditPlaylistActivity::class.java)
+                .putExtra(EXTRA_PLAYLIST_ID, playlistId)
+        }
+    }
+}

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/tracks/activity/TrackListActivity.kt

@@ -185,9 +185,6 @@ class TrackListActivity : BaseActivity(), Filterable {
                override fun count(): Observable<Int> =
                    data.provider.getTrackCountByCategory(categoryType ?: "", categoryId, lastFilter)
 
-                override fun all(): Observable<List<ITrack>>? =
-                    data.provider.getTracksByCategory(categoryType ?: "", categoryId, lastFilter)
-
                 override fun page(offset: Int, limit: Int): Observable<List<ITrack>> =
                     data.provider.getTracksByCategory(categoryType ?: "", categoryId, limit, offset, lastFilter)
 
@@ -201,9 +198,6 @@ class TrackListActivity : BaseActivity(), Filterable {
                 override fun count(): Observable<Int> =
                     data.provider.getTrackCount(lastFilter)
 
-                override fun all(): Observable<List<ITrack>>? =
-                    data.provider.getTracks(lastFilter)
-
                 override fun page(offset: Int, limit: Int): Observable<List<ITrack>> =
                     data.provider.getTracks(limit, offset, lastFilter)
 

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/tracks/adapter/EditPlaylistAdapter.kt

@@ -0,0 +1,70 @@
+package io.casey.musikcube.remote.ui.tracks.adapter
+
+import android.support.v7.widget.RecyclerView
+import android.support.v7.widget.helper.ItemTouchHelper
+import android.view.LayoutInflater
+import android.view.MotionEvent
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import io.casey.musikcube.remote.R
+import io.casey.musikcube.remote.service.websocket.model.ITrack
+import io.casey.musikcube.remote.ui.shared.extension.fallback
+import io.casey.musikcube.remote.ui.tracks.model.EditPlaylistViewModel
+
+class EditPlaylistAdapter(private val viewModel: EditPlaylistViewModel,
+                          private val touchHelper: ItemTouchHelper): RecyclerView.Adapter<EditPlaylistAdapter.ViewHolder>() {
+    override fun getItemCount(): Int {
+        return viewModel.count
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        val inflater = LayoutInflater.from(parent.context)
+        val view = inflater.inflate(R.layout.edit_playlist_track_row, parent, false)
+        val holder = ViewHolder(view)
+        val drag = view.findViewById<View>(R.id.dragHandle)
+        val swipe = view.findViewById<View>(R.id.swipeHandle)
+        view.setOnClickListener(emptyClickListener)
+        drag.setOnTouchListener(dragTouchHandler)
+        swipe.setOnTouchListener(dragTouchHandler)
+        drag.tag = holder
+        swipe.tag = holder
+        return holder
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+        holder.bind(viewModel[position])
+    }
+
+    private val emptyClickListener = object: View.OnClickListener {
+        override fun onClick(view: View?) {
+            /* we do this so we get a ripple effect when the user touches the view,
+            so there's an indication something is happening before the drag starts */
+        }
+    }
+
+    private val dragTouchHandler = object: View.OnTouchListener {
+        override fun onTouch(view: View, event: MotionEvent?): Boolean {
+            if (event?.actionMasked == MotionEvent.ACTION_DOWN) {
+                if (view.id == R.id.dragHandle) {
+                    touchHelper.startDrag(view.tag as RecyclerView.ViewHolder)
+                }
+                else if (view.id == R.id.swipeHandle) {
+                    touchHelper.startSwipe(view.tag as RecyclerView.ViewHolder)
+                    return true
+                }
+            }
+            return false
+        }
+    }
+
+    class ViewHolder internal constructor(internal val view: View) : RecyclerView.ViewHolder(view) {
+        private val title = itemView.findViewById<TextView>(R.id.title)
+        private val subtitle = itemView.findViewById<TextView>(R.id.subtitle)
+
+        fun bind(track: ITrack) {
+            title.text = fallback(track.title, "-")
+            subtitle.text = fallback(track.albumArtist, "-")
+        }
+    }
+}

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/ui/tracks/model/EditPlaylistViewModel.kt

@@ -0,0 +1,142 @@
+package io.casey.musikcube.remote.ui.tracks.model
+
+import io.casey.musikcube.remote.framework.ViewModel
+import io.casey.musikcube.remote.service.websocket.Messages.Category.Companion.PLAYLISTS
+import io.casey.musikcube.remote.service.websocket.model.IDataProvider
+import io.casey.musikcube.remote.service.websocket.model.ITrack
+import io.casey.musikcube.remote.service.websocket.model.impl.remote.RemoteTrack
+import io.reactivex.Observable
+import io.reactivex.disposables.Disposable
+import io.reactivex.rxkotlin.subscribeBy
+import org.json.JSONObject
+
+class EditPlaylistViewModel(private val playlistId: Long): ViewModel<EditPlaylistViewModel.Status>() {
+    enum class Status { NotLoaded, Error, Loading, Saving, Updated }
+
+    private data class CacheEntry(var track: ITrack, var dirty: Boolean = false)
+
+    private var metadataDisposable: Disposable? = null
+    private var requestOffset = -1
+    private var dataProvider: IDataProvider? = null
+    private var externalIds: MutableList<String> = mutableListOf()
+
+    private val cache = object : LinkedHashMap<String, CacheEntry>() {
+        override fun removeEldestEntry(eldest: MutableMap.MutableEntry<String, CacheEntry>): Boolean = size >= MAX_SIZE
+    }
+
+    var modified: Boolean = false
+        private set(value) {
+            field = value
+        }
+
+    fun attach(dataProvider: IDataProvider) {
+        this.dataProvider = dataProvider
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        this.dataProvider = null
+    }
+
+    var status: Status = Status.NotLoaded
+        private set(value) {
+            field = value
+            publish(value)
+        }
+
+    val count: Int
+        get() {
+            if (externalIds.isEmpty() && status != Status.Loading) {
+                refreshTrackIds()
+            }
+            return externalIds.size
+        }
+
+    operator fun get(index: Int): ITrack {
+        val entry = cache[externalIds[index]]
+        if (entry == null) {
+            refreshPageAround(index)
+        }
+        return entry?.track ?: DEFAULT_TRACK
+    }
+
+    fun save(): Observable<Long> {
+        if (!modified) {
+            return Observable.just(playlistId)
+        }
+
+        return dataProvider?.overwritePlaylistWithExternalIds(playlistId, externalIds.toList()) ?: Observable.just(-1L)
+    }
+
+    fun remove(index: Int) {
+        externalIds.removeAt(index)
+    }
+
+    fun move(from: Int, to: Int) {
+        val id = externalIds.removeAt(from)
+        externalIds.add(if (to > from) (to - 1) else to, id)
+    }
+
+    private fun refreshTrackIds() {
+        status = Status.Loading
+        dataProvider?.let {
+            status = Status.Loading
+
+            it.getTrackIdsByCategory(PLAYLISTS, playlistId).subscribeBy(
+                onNext = { result ->
+                    externalIds = result.toMutableList()
+                    status = Status.Updated
+                },
+                onError = {
+                    status = Status.Error
+                })
+        }
+    }
+
+    private fun refreshPageAround(offset: Int) {
+        if (requestOffset != -1 && offset >= requestOffset && offset < requestOffset + PAGE_SIZE) {
+            return /* in flight */
+        }
+
+        dataProvider?.let {
+            metadataDisposable?.dispose()
+            metadataDisposable = null
+
+            requestOffset = Math.max(0, offset - PAGE_SIZE / 4)
+            val end = Math.min(externalIds.size, requestOffset + PAGE_SIZE)
+            val ids = mutableSetOf<String>()
+            for (i in requestOffset until end) {
+                val id = externalIds[i]
+                val entry = cache[id]
+                if (entry == null || entry.dirty) {
+                    ids.add(id)
+                }
+            }
+
+            if (ids.isNotEmpty()) {
+                status = Status.Loading
+
+                metadataDisposable = it.getTracks(ids)
+                    .flatMapIterable { list: Map<String, ITrack> -> list.asIterable() }
+                    .subscribeBy(
+                        onNext = { entry: Map.Entry<String, ITrack> ->
+                            cache.put(entry.key, CacheEntry(entry.value))
+                        },
+                        onError = {
+                            status = Status.Error
+                            requestOffset = -1
+                        },
+                        onComplete = {
+                            status = Status.Updated
+                            requestOffset = -1
+                        })
+            }
+        }
+    }
+
+    companion object {
+        private val DEFAULT_TRACK = RemoteTrack(JSONObject())
+        private val PAGE_SIZE = 40
+        private val MAX_SIZE = 150
+    }
+}

src/musikdroid/app/src/main/res/drawable-v21/ic_leftarrow.xml

@@ -0,0 +1,4 @@
+<vector android:height="16dp" android:viewportHeight="24.0"
+    android:viewportWidth="24.0" android:width="16dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="?attr/colorControlNormal" android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>
+</vector>

src/musikdroid/app/src/main/res/drawable-v21/ic_reorder.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="?attr/colorControlNormal"
+        android:pathData="M3,15h18v-2L3,13v2zM3,19h18v-2L3,17v2zM3,11h18L21,9L3,9v2zM3,5v2h18L21,5L3,5z"/>
+</vector>

src/musikdroid/app/src/main/res/drawable-v21/ic_trashcan.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="?attr/colorControlNormal"
+        android:pathData="M6,19c0,1.1 0.9,2 2,2h8c1.1,0 2,-0.9 2,-2L18,7L6,7v12zM8.46,11.88l1.41,-1.41L12,12.59l2.12,-2.12 1.41,1.41L13.41,14l2.12,2.12 -1.41,1.41L12,15.41l-2.12,2.12 -1.41,-1.41L10.59,14l-2.13,-2.12zM15.5,4l-1,-1h-5l-1,1L5,4v2h14L19,4z"/>
+</vector>

src/musikdroid/app/src/main/res/drawable-v21/opaque_row_background.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ripple
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:color="?attr/colorControlHighlight">
+    <item android:drawable="@color/theme_background"/>
+</ripple>

src/musikdroid/app/src/main/res/layout/edit_playlist_track_row.xml

@@ -0,0 +1,85 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/rowView"
+    android:orientation="vertical"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="@drawable/opaque_row_background"
+    android:minHeight="52dp">
+
+    <ImageView
+        android:id="@+id/dragHandle"
+        android:src="@drawable/ic_reorder"
+        android:scaleType="center"
+        android:padding="4dp"
+        android:layout_marginStart="8dp"
+        android:layout_centerVertical="true"
+        android:layout_alignParentStart="true"
+        android:layout_width="36dp"
+        android:layout_height="36dp"
+        android:gravity="center"/>
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_centerVertical="true"
+        android:layout_toEndOf="@+id/dragHandle"
+        android:layout_toStartOf="@+id/swipeHandle"
+        android:orientation="vertical">
+
+        <TextView
+            android:id="@+id/title"
+            android:layout_marginLeft="8dp"
+            android:layout_marginRight="8dp"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:maxLines="1"
+            android:ellipsize="end"
+            android:textColor="@color/theme_foreground"
+            tools:text="title"/>
+
+        <TextView
+            android:textSize="12dp"
+            android:id="@+id/subtitle"
+            android:layout_marginLeft="8dp"
+            android:layout_marginRight="8dp"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:maxLines="1"
+            android:ellipsize="end"
+            android:textColor="@color/theme_disabled_foreground"
+            tools:text="subtitle"/>
+
+    </LinearLayout>
+
+    <LinearLayout
+        android:id="@+id/swipeHandle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:paddingEnd="8dp"
+        android:paddingTop="4dp"
+        android:paddingBottom="4dp"
+        android:paddingStart="4dp"
+        android:minHeight="52dp"
+        android:layout_centerVertical="true"
+        android:layout_alignParentEnd="true">
+
+        <ImageView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center"
+            android:layout_marginEnd="-4dp"
+            android:scaleType="center"
+            android:src="@drawable/ic_leftarrow" />
+
+        <ImageView
+            android:background="@drawable/ic_trashcan"
+            android:layout_width="24dp"
+            android:layout_height="24dp"
+            android:layout_gravity="center"/>
+
+    </LinearLayout>
+
+</RelativeLayout>

src/musikdroid/app/src/main/res/menu/edit_playlist_menu.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_save"
+        app:showAsAction="always"
+        android:title="@string/button_save"/>
+
+</menu>

src/musikdroid/app/src/main/res/menu/playlist_item_context_menu.xml

@@ -4,6 +4,10 @@
         android:id="@+id/menu_playlist_play"
         android:title="@string/menu_play_playlist"/>
 
+    <item
+        android:id="@+id/menu_playlist_edit"
+        android:title="@string/menu_edit_playlist"/>
+
     <item
         android:id="@+id/menu_playlist_rename"
         android:title="@string/menu_rename_playlist"/>

src/musikdroid/app/src/main/res/values/strings.xml

@@ -78,6 +78,7 @@
     <string name="menu_show_genres">genres</string>
     <string name="menu_delete_playlist">delete</string>
     <string name="menu_rename_playlist">rename</string>
+    <string name="menu_edit_playlist">edit</string>
     <string name="menu_play_playlist">play now</string>
     <string name="unknown_value">&lt;unknown&gt;</string>
     <string name="snackbar_streaming_enabled">switched to streaming mode</string>