我想将集合内容打印到listbuilder

我的围巾式正文代码直接在将来的生成器上插入了Firestore读取查询

                body: new Container(
                decoration: BoxDecoration(

                    color: Colors.white10
                ),child:  playlistsref.document().collection('usersPlaylists').getDocuments() == null
                    ? Center(
                  child: new CircularProgressIndicator(
                    valueColor: new AlwaysStoppedAnimation<Color>(Colors.white
                    ),strokeWidth: 3.0,),)
                    : FutureBuilder(
                  future: playlistsref.document().collection('usersPlaylists').getDocuments(),builder: (context,snapshot) {
                    return ListView.builder(
                      itemCount: snapshot.data.documents.length,itemBuilder: (BuildContext context,int index) {
                        Playlist playlist = Playlist.fromDoc(snapshot.data.documents[index]);
                        return _buildPlaylistTile(playlist);
                      },);
                  },

和最终播放列表Ref = _firestore.collection（'playlists'）;在常量dart文件中

因为它不具有initState

并且代码不起作用并返回错误：在null上调用了getter'documents'

如何解决此错误并正确打印文档