UIActivityViewController始终在文本之前共享图像

Question

在我的应用中，我想分享当前的歌曲和艺术家，然后是专辑封面。这是我的代码：

    var sharingItems = [AnyObject]()

    let currentSong = musicPlayer.nowPlayingItem?.title
    let currentArtist = musicPlayer.nowPlayingItem?.artist
    let artwork = musicPlayer.nowPlayingItem?.artwork
    let artworkImage = artwork?.imageWithSize(CGSizeMake(100, 100))

    let shareText = "Now playing \(currentSong!) by \(currentArtist!) via Ryan's awesome app"

    sharingItems.append(shareText) //text first, then image
    sharingItems.append(artworkImage!)

    let activityViewController = UIActivityViewController(activityItems: sharingItems, applicationActivities: nil)
    activityViewController.excludedActivityTypes = [UIActivityTypeAddToReadingList, UIActivityTypeAssignToContact, UIActivityTypeOpenInIBooks, UIActivityTypePrint, UIActivityTypeSaveToCameraRoll]
    self.presentViewController(activityViewController, animated: true, completion: nil)

当我选择共享选项（如Messges）时，图像位于TextField中的文本之前。如果图像在数组中是最后一个，为什么它首先出现？