使用Flutter显示/隐藏小部件时出现问题

Question

它的工作原理如下（或者应该这样）： 我使用始终以FALSE（_isMsgVisible = FALSE）开头的Visibility（）小部件。在initState（）中，我读取了文件，如果没有记录，则显示帮助（_isMsgVisible = TRUE）。如果有记录，则显示带有数据的ListView。 问题在于，当有数据时，帮助会快速出现，并且仅在执行initState（）之后消失。 仅在执行initState（）之后如何控制显示？ 对不起，我的英语不好?

class _PlaylistState extends State<PlaylistScreen>
  bool _isMsgVisible = false;

  @override
  void initState() {
    super.initState();
    _selectedPage = 1;
    _playlistDetails.clear();
    _getDetails();
  }

  Future<Null> _getDetails() async {
    _playlistDetails.clear();

    final String url = '$URL_PLAYLISTS/read.php?user=${widget.userId}';

    final mapResponse = await http.get(url);
    final responseJson = json.decode(mapResponse.body);

    if (responseJson["result"] == "ok") {
      if (mounted) {
        setState(() {
          for (Map playlist in responseJson["data"]) {
            _playlistDetails.add(Playlist.fromJson(playlist));
          }
        });
      }
    }
    setState(() {
      _playlistDetails.length == 0 ? _isMsgVisible = true : _isMsgVisible = false;
    });
  }

  _myPlaylists() {
    Expanded e = new Expanded(
      child: _playlistDetails.length == 0
              ? new Visibility(
                  visible: _isMsgVisible,
                  child: MyInfoMessageBox(
                    text:
                        "Lista somente as playlists criadas por você, podendo ser públicas ou privadas.", 
                    title: "Minhas Playlists",
                  ),
                )
              : new ListView.builder(
                  itemCount: _playlistDetails.length,
                  itemBuilder: (context, index) {
                    return _buildDismiss(_playlistDetails, index);
                  },
                ),
    );
    setState(() {
      if (_playlistDetails.length == 0) {
        _isMsgVisible = true;
      } else {
        _isMsgVisible = false;
      }
    });
    return e;
  }