SwiftUI 预览 MPMediaItemArtwork

Question

我有一个基于结构的数组，其中包括歌曲标题和艺术家作为字符串，其艺术作品作为类型MPMediaItemArtwork。为了让预览在Swift UI 中工作，我参考了

struct TrackRow_Previews: PreviewProvider {
    static var previews: some View {
        TrackRow(track: Track(name: "Track 1", artist: "Artist 1", artwork: [MPMediaItemArtwork]))
    }
}

当我注释掉预览时，视图工作正常，因此我能够将选定的MPMediaItemArtwork 打印到控制台，即MPConcreteMediaItemArtwork: 0x281efb890。但它也不接受。我可以为预览图稿添加什么价值以使预览提供程序正常工作？

额外细节：

struct Track: Hashable {
    var name: String
    var artist: String
    var artwork: MPMediaItemArtwork
}

func getTracks(chosenPlaylist: String) {
        trackArray = []
        for playlist in playlists! {
            if (playlist.value(forProperty: MPMediaPlaylistPropertyName)as! String) == chosenPlaylist {
                let songs = playlist.items
                            for song in songs {
                                if song.artwork != nil {
                                trackArray.append(Track(name: (song.value(forProperty: MPMediaItemPropertyTitle) as! String), artist:(song.value(forProperty: MPMediaItemPropertyArtist) as! String), artwork: song.artwork!))
                                }
                            }
                sortArray()
            }
        }
    }

Answer 1

我的问题是我没有导入 MediaPlayer，因为视图不需要它，但显然预览视图需要它。有效的代码如下：

struct TrackRow_Previews: PreviewProvider {
    static var previews: some View {
        TrackRow(track: Track(name: "Track 1", artist: "Artist 1", artwork:MPMediaItemArtwork(image: UIImage(imageLiteralResourceName: "Artwork"))))
    }
}

Answer 2

我将假设 artwork 是 MPMediaItemArtwork 的数组，因此对于预览，我只需抓取数组中的第一项，如下所示：

struct MPMediaItemArtwork {
   var name: String
}

struct Track {
    var name: String
    var artist: String
    var artwork: [MPMediaItemArtwork]
}

struct ContentView_Previews: PreviewProvider {
    static var artwork = MPMediaItemArtwork(name: "0x281efb890")
    static var mediaArray: [MPMediaItemArtwork] = [artwork]

    static var previews: some View {
        TrackRow(track: Track(name: "Track 1", artist: "Artist 1", artwork: [mediaArray[0]]))
    }
}