MPMusicPlayerController.shuffleMode cannot be set - ios

Question

Hello I have a question about the MPMusicPlayerController in Swift. I am currently working on a Music App were I want to shuffle music by songs. So when the App Starts it basically sets the Playback Queue and then the Shuffle Mode. I can successfully set the queue (and play the songs) but I get an error when I set the Shuffle Mode:
musicPlayer.musicPlayer.shuffleMode = .songs
ERROR:
2018-07-03 15:01:36.450977+0200 Hitbeat[29053:8378883] [SDKPlayback] -[MPMusicPlayerController setShuffleMode:2] completed error: Error Domain=MPCPlayerRequestErrorDomain Code=1 "No commands provided." UserInfo={NSDebugDescription=No commands provided.}
What does that mean?
I have the idea that it may be because the queue is not set completely when setting the shuffleMode but I am not sure and it would not make any sense that one would have to set a song queue first in order to set the mode in which order songs to play. Maybe something else is the problem?
Also everything takes place on the Main Thread. (MPMusicPlayerController always has to be called in the Main Thread)
Thanks a lot I hope you guys can help me.
here are some code snippets:
MusicPlayerManager.swift
import os.log
import MediaPlayer
import NotificationCenter
class MusicPlayerManager {
let musicPlayer: MPMusicPlayerController
lazy var musicPickerAndAdder = MusicPickerAndAdder()
init() {
// Instantiate a new music player
musicPlayer = MPMusicPlayerApplicationController.applicationQueuePlayer
// Add a playback queue containing all songs on the device
switch MPMediaLibrary.authorizationStatus() {
case .authorized:
let catalogSongStoreID: String = ""
let catalogQueueDescriptor = MPMusicPlayerStoreQueueDescriptor(storeIDs: [catalogSongStoreID])
musicPlayer.setQueue(with: catalogQueueDescriptor)
default:
break
}
Timer.scheduledTimer(withTimeInterval: 15, repeats: false) {_ in
print("shuffle mode setter")
self.musicPlayer.shuffleMode = MPMusicShuffleMode.songs
}
}
func updateOnlineMusicQueue() {
var musicPickerIds = [String]()
DispatchQueue.global(qos: .userInitiated).sync {
musicPickerIds = musicPickerAndAdder.ids
}
if !musicPickerIds.isEmpty{
musicPlayer.setQueue(with: musicPickerIds)
}else {
updateOfflineMusicQueue()
}
musicPlayer.pause()
}
func play() {
if musicPlayer.playbackState == .playing {
musicPlayer.pause()
musicPlayer.skipToBeginning()
}
if !musicPlayer.isPreparedToPlay {
musicPlayer.prepareToPlay { (error) in
if error == nil {
self.musicPlayer.play()
self.startSongMasterTimer()
}
}
}else {
musicPlayer.play()
startSongMasterTimer()
}
}
func pauseAndSkip() {
// if self.musicPlayer.shuffleMode.rawValue != 2 { // does not work here would work on pause and skip
// self.musicPlayer.shuffleMode = MPMusicShuffleMode.songs
// }
//print("shuffler \(self.musicPlayer.shuffleMode.rawValue)")
//print("At \(musicPlayer.currentPlaybackTime) of \((musicPlayer.nowPlayingItem?.playbackDuration!)")
musicPlayer.pause()
//if musicPlayer.nowPlayingItem != nil {
musicPlayer.skipToNextItem()
//}
musicPlayer.prepareToPlay { (error) in
if error == nil {
self.musicPlayer.pause()
}
}
}
func currentSongInfo() -> SongInfo {
let songTitle = musicPlayer.nowPlayingItem?.title?.replacingOccurrences(of: "-", with: " ") ?? "" // To guarantee there is only one - between Song and Artist
let artistName = musicPlayer.nowPlayingItem?.artist?.replacingOccurrences(of: "-", with: " ") ?? ""
let songInfo = SongInfo(title: songTitle, artist: artistName)
return songInfo
}
func addSongToLibrary() {
//print("Id of Item to Add: \(musicPlayer.nowPlayingItem?.playbackStoreID)")
if musicPlayer.nowPlayingItem != nil {
musicPickerAndAdder.addResourceToUserMusicLibrary(resourceId: (musicPlayer.nowPlayingItem?.playbackStoreID)!)
}
//ToDo add to myHitbeat Playlist
}
}
class SongInfo {
let title: String
let artist: String
init(title:String,artist:String) {
self.title = title
self.artist = artist
}
}
MusicPickerAndAdder.swift
import Foundation
class MusicPickerAndAdder {
lazy var authorizationManager: AuthorizationManager = {
return AuthorizationManager(appleMusicManager: self.appleMusicManager)
}()
var appleMusicManager = AppleMusicManager()
private var idsArraySize = 100
static var idCategoriesStakes = ["Chart_Ids" : 0.10,
"Recently_Played_Ids" : 0.10,
"Experiment_Ids" : 0.30,
"Recommendations_Ids" : 0.50,] // Addition of all Values must be 1 (100%)
private var chartIds: [String] {
var chartsIds = [String]()
let chartsIdsGroup = DispatchGroup()
chartsIdsGroup.enter()
let limit = Int(Double(idsArraySize) * MusicPickerAndAdder.idCategoriesStakes["Recently_Played_Ids"]!)
appleMusicManager.performAppleMusicGetChartSongs(regionCode: Locale.current.regionCode?.lowercased() ?? "us", limit: limit) { (storeIds, error) in
if error != nil {
print("There was an Error getting Charts")
chartsIdsGroup.leave()
return
}
chartsIds = storeIds
chartsIdsGroup.leave()
}
chartsIdsGroup.wait()
print("Charts sucessfully fetched")
return chartsIds
}
private var recentlyPlayedIds: [String] {
var recentIds = [String]()
let recentIdsGroup = DispatchGroup()
recentIdsGroup.enter()
let limit = Int(Double(idsArraySize) * MusicPickerAndAdder.idCategoriesStakes["Recently_Played_Ids"]!)
appleMusicManager.performAppleMusicGetRecentlyPlayed(userToken: authorizationManager.userToken, limit: limit) {
(storeIds, error) in
if error != nil {
print("There was an Error getting Recently Played")
recentIdsGroup.leave()
return
}
recentIds = storeIds
recentIdsGroup.leave()
}
recentIdsGroup.wait()
print("Recently Played sucessfully fetched: \(recentIds)")
return recentIds
}
private var experimentIds: [String] {
return ["pl.u-XkD04oZIY0Kxrl"]
}
private var recommendationsIds: [String] {
return [String]()
}
// Never request Ids in Main (UI) Thread
var ids: [String] {
var ids = [String]()
ids += recentlyPlayedIds
ids += chartIds
ids += experimentIds
ids += recommendationsIds
print("Store Ids for Songs \(ids)")
return ids.shuffled() // shuffles list of items
}
init() {
requestAppleMusicAuthorization()
}
//MARK: Private Methods
private func requestAppleMusicAuthorization() {
UserDefaults.standard.register(defaults: ["tutorial": true])
if !UserDefaults.standard.bool(forKey: "tutorial") {
authorizationManager.requestCloudServiceAuthorization()
authorizationManager.requestMediaLibraryAuthorization()
}
}
}
extension MusicPickerAndAdder { // to Add Songs
func addResourceToUserMusicLibrary(resourceId: String) {
appleMusicManager.performAddResourceToLibrary(resourceId: resourceId, userToken: authorizationManager.userToken)
}
}
extension MutableCollection {
/// Shuffles the contents of this collection.
mutating func shuffle() {
let c = count
guard c > 1 else { return }
for (firstUnshuffled, unshuffledCount) in zip(indices, stride(from: c, to: 1, by: -1)) {
// Change `Int` in the next line to `IndexDistance` in < Swift 4.1
let d: Int = numericCast(arc4random_uniform(numericCast(unshuffledCount)))
let i = index(firstUnshuffled, offsetBy: d)
swapAt(firstUnshuffled, i)
}
}
}
extension Sequence {
/// Returns an array with the contents of this sequence, shuffled.
func shuffled() -> [Element] {
var result = Array(self)
result.shuffle()
return result
}
}
PS: MusicPickerAndAdder may look a little messy though I don't think the problem lies there! What it basically does is fetching some data from the Apple Music API which works fine, and adding Songs to the User Library which works too.

Answer 1

Okay after trying everything out possible I came up with two solutions that work for me. Weirdly I found out that a freeze of the interface only occurs when no song has played so far. If a song is currently playing or even if a song has played and was paused afterwards there is no ui freeze. So I came up with this function:
private func setShuffleMode() { // does work though startup and restarting takes longer
musicPlayer.play()
Timer.scheduledTimer(withTimeInterval: 1.5, repeats: false) {_ in
print("shuffle mode setter")
self.musicPlayer.pause()
//self.musicPlayer.pause()// may stop interface freezing if occuring
self.musicPlayer.shuffleMode = MPMusicShuffleMode.songs // freeze of ui only occurs when no song played before
}
}
I tried out several time intervals it still failed sometimes if it was a second it never failed on 1.5 seconds so I left it there
The problem though was that starting the App as well as restarting it was taking a little bit longer. So I came up with a second solution
private func setShuffleMode2 () { // still in test if shuffle mode gets set fast or even ever set
Timer.scheduledTimer(withTimeInterval: 5, repeats: true) {timer in
if self.musicPlayer.playbackState == .playing && self.musicPlayer.currentPlaybackTime > 3{
self.musicPlayer.shuffleMode = .songs
print("shuffle mode setter")
timer.invalidate()
}
}
}
Here I have a repeating timer which is always checking if an item is playing and if it is playing for a certain time already, if it is it sets the shuffle mode and stops repeating. I have tested the second function and it worked great though there is the trade of that there is always the possibility that it is not getting called for some time. How long that will be depends on the time interval and currentPlaybackTime > someTime value.