艺术家专辑数量

Question

这是我的问题 =)

MPMediaQuery *artistQuery = [MPMediaQuery artistsQuery];
NSArray *songsByArtist = [artistQuery collections];

songsByArtist 中 MPMediaItemCollections 的每个艺术家的专辑数量如何获取？

示例：

披头士乐队 3 专辑

交流/直流 6 专辑

谢谢！！

Answer 1

我使用谓词获得艺术家的专辑和歌曲数量：

MPMediaPropertyPredicate *artistNamePredicate = [MPMediaPropertyPredicate predicateWithValue:@"ArtistName" forProperty:MPMediaItemPropertyArtist];
MPMediaQuery *myComplexQuery = [[MPMediaQuery alloc] init];
[myComplexQuery addFilterPredicate: artistNamePredicate];
NSInteger songCount = [[myComplexQuery collections] count]; //number of songs
myComplexQuery.groupingType = MPMediaGroupingAlbum;
NSInteger albumCount = [[myComplexQuery collections] count]; //number of albums

Answer 2

artistsQuery 便利构造函数不按专辑排序和分组。 artistsQuery 返回所有艺术家的媒体项目集合数组，按艺术家姓名的字母顺序排序。嵌套在每个艺术家集合中的是与该艺术家的所有歌曲相关联的媒体项数组。嵌套数组按歌曲名称的字母顺序排序。

按艺术家计算专辑数量的一种方法是枚举每个艺术家收藏的所有歌曲项目，并使用NSMutableSet 来跟踪与每首歌曲相关的不同专辑标题。然后将集合的计数添加为NSMutableDictionary 中每个艺术家键的值。不会添加任何重复的专辑标题，因为 NSMutableSet 只会采用不同的对象：

MPMediaQuery *artistQuery = [MPMediaQuery artistsQuery];
NSArray *songsByArtist = [artistQuery collections];
NSMutableDictionary *artistDictionary = [NSMutableDictionary dictionary];
NSMutableSet *tempSet = [NSMutableSet set];

[songsByArtist enumerateObjectsUsingBlock:^(MPMediaItemCollection *artistCollection, NSUInteger idx, BOOL *stop) {
    NSString *artistName = [[artistCollection representativeItem] valueForProperty:MPMediaItemPropertyArtist];

    [[artistCollection items] enumerateObjectsUsingBlock:^(MPMediaItem *songItem, NSUInteger idx, BOOL *stop) {
        NSString *albumName = [songItem valueForProperty:MPMediaItemPropertyAlbumTitle];
        [tempSet addObject:albumName];
    }];
    [artistDictionary setValue:[NSNumber numberWithUnsignedInteger:[tempSet count]] 
                        forKey:artistName];
    [tempSet removeAllObjects];
}];
NSLog(@"Artist Album Count Dictionary: %@", artistDictionary);

如果将查询更改为albumsQuery 会更简洁。此查询按专辑名称对集合进行分组和排序。然后只需枚举专辑收藏的数组并在NSCountedSet 中记录每张专辑的代表艺术家姓名。计数集将跟踪对象被插入的次数：

MPMediaQuery *albumQuery = [MPMediaQuery albumsQuery];
NSArray *albumCollection = [albumQuery collections];
NSCountedSet *artistAlbumCounter = [NSCountedSet set];

[albumCollection enumerateObjectsUsingBlock:^(MPMediaItemCollection *album, NSUInteger idx, BOOL *stop) {
    NSString *artistName = [[album representativeItem] valueForProperty:MPMediaItemPropertyArtist];
    [artistAlbumCounter addObject:artistName];
}];
NSLog(@"Artist Album Counted Set: %@", artistAlbumCounter);

您还可以使用countForObject: 方法在NSCountedSet 中检索给定对象的计数。

Answer 3

Bryan 答案的 Swift 2 翻译：

var artistQuery = MPMediaQuery.artistsQuery()
var artistQuery.groupingType = MPMediaGrouping.AlbumArtist
var songsByArtist = artistQuery.collections
var artistDictionary = NSMutableDictionary()
var tempSet = NSMutableSet()

songsByArtist.enumerateObjectsUsingBlock { (artistCollection, idx, stop) -> Void in
     let collection = artistCollection as! MPMediaItemCollection
     let rowItem = collection.representativeItem

     let artistName = rowItem?.valueForProperty(MPMediaItemPropertyAlbumArtist)

     let collectionContent:NSArray = collection.items

     collectionContent.enumerateObjectsUsingBlock { (songItem, idx, stop) -> Void in
          let item = songItem as! MPMediaItem

          let albumName = item.valueForProperty(MPMediaItemPropertyAlbumTitle)
          self.tempSet.addObject(albumName!)
     }

     self.artistDictionary.setValue(NSNumber(unsignedInteger: self.tempSet.count), forKey: artistName! as! String)
     self.tempSet.removeAllObjects()
}
print("Album Count Dictionary: \(artistDictionary)")

Answer 4

专辑如果对您有帮助，请向我们查询或在下面的此链接中查看更多信息

http://developer.apple.com/library/ios/#documentation/mediaplayer/reference/MPMediaQuery_ClassReference/Reference/Reference.html

Answer 5

感谢 Tim E，我第一次无法让您的代码运行，但我将其修改为现在可以运行。

    let artistQuery = MPMediaQuery.artistsQuery()
    artistQuery.groupingType = MPMediaGrouping.AlbumArtist

    let songsByArtist = artistQuery.collections! as NSArray
    let artistDictionary = NSMutableDictionary()
    let tempSet = NSMutableSet()

    songsByArtist.enumerateObjectsUsingBlock( { (artistCollection, idx, stop) -> Void in
        let collection = artistCollection as! MPMediaItemCollection
        let rowItem = collection.representativeItem

        let artistName = rowItem?.valueForProperty(MPMediaItemPropertyAlbumArtist)

        let collectionContent:NSArray = collection.items

        collectionContent.enumerateObjectsUsingBlock({ (songItem, idx, stop) -> Void in
            let item = songItem as! MPMediaItem

            let albumName = item.valueForProperty(MPMediaItemPropertyAlbumTitle)
            tempSet.addObject(albumName!)
        })

        artistDictionary.setValue(NSNumber(unsignedInteger: UInt(tempSet.count)), forKey: artistName! as! String)
        tempSet.removeAllObjects()
    })

    print("Album Count Dictionary: \(artistDictionary)") 

Answer 6

抱歉回复晚了。

发布我的答案以防对某人有帮助。

以下代码按专辑艺术家获取所有艺术家分组，并获取专辑中的所有专辑和歌曲。

    /// Get all artists and their songs
///
func getAllArtists() {
    let query: MPMediaQuery = MPMediaQuery.artists()
    query.groupingType = .albumArtist

    let artistsColelctions = query.collections

    artists.removeAll()


    var tempSet = NSMutableSet()



    guard artistsColelctions != nil else {
        return
    }

    // 1. Create Artist Objects from collection

    for collection in artistsColelctions! {
        let item: MPMediaItem? = collection.representativeItem

        var artistName = item?.value(forKey: MPMediaItemPropertyArtist) as? String ?? "<Unknown>"
        artistName = artistName.trimmingCharacters(in: NSCharacterSet.whitespacesAndNewlines)
        let artistId = item!.value(forProperty: MPMediaItemPropertyArtistPersistentID) as! NSNumber


        // temp
        let albumName = item?.albumTitle
        let albumID  = item?.albumPersistentID

        print(albumName)
        print(albumID)



        // Create artist item

        let artist = Artist()
        artist.name = artistName
        artist.artworkTitle = String(artistName.characters.prefix(1)).uppercased()
        artist.artistId = String(describing: artistId)


        // 2. Get Albums for respective Artist object
        //--------------------------------------------

        let mediaQuery2 = MPMediaQuery.albums()
        let predicate2 = MPMediaPropertyPredicate.init(value: artistId, forProperty: MPMediaItemPropertyArtistPersistentID)
        mediaQuery2.addFilterPredicate(predicate2)

        let albums = mediaQuery2.collections

        for collection in albums! {
            let item: MPMediaItem? = collection.representativeItem

            let albumName = item?.value(forKey: MPMediaItemPropertyAlbumTitle) as? String ?? "<Unknown>"
            let albumId = item!.value(forProperty: MPMediaItemPropertyAlbumPersistentID) as! NSNumber
            let artistName = item?.value(forKey: MPMediaItemPropertyAlbumArtist) as? String ?? "unknown"

            let genreName = item?.genre ?? ""

            let year = item?.releaseDate ?? item?.dateAdded

            let dateAdded = item?.dateAdded

            // Create album object

            let album = Album()
            album.name = albumName
            album.artistName = artistName
            album.genre = genreName
            album.releaseDate = year
            album.dateAdded = dateAdded
            album.albumId = String(describing: albumId)

            // Add artwork to album object
            let artwork = Artwork.init(forAlbum: item)
            album.artwork = artwork


            // 3. Get Songs inside the resepctive Album object
            //---------------------------------------------------

            let mediaQuery = MPMediaQuery.songs()
            let predicate = MPMediaPropertyPredicate.init(value: albumId, forProperty: MPMediaItemPropertyAlbumPersistentID)
            mediaQuery.addFilterPredicate(predicate)
            let song = mediaQuery.items

            if let allSongs = song {
                var index = 0

                for item in allSongs {
                    let pathURL: URL? = item.value(forProperty: MPMediaItemPropertyAssetURL) as? URL
                    let isCloud = item.value(forProperty: MPMediaItemPropertyIsCloudItem) as! Bool

                    let trackInfo = TrackInfo()
                    trackInfo.index = index
                    trackInfo.mediaItem = item
                    trackInfo.isCloudItem = isCloud

                    trackInfo.isExplicitItem = item.isExplicitItem

                    trackInfo.isSelected = false
                    trackInfo.songURL = pathURL
                    album.songs?.append(trackInfo)
                    index += 1
                }
            }


            artist.albums?.append(album)

        }

        // Finally add the artist object to Artists Array
        artists.append(artist)

        }


    }