从firebase中获取文档

Question

我尝试从initstate获取文档并调用函数，但是第一次获取null却不知道如何解决。

void initState() {
    super.initState();
    print("this  dummy @@@@@@@@@@22222");
    getData();
  }

  var list;

  getData() async {
    QuerySnapshot querySnapshot =
        await Firestore.instance.collection('clients').getDocuments();
      list = querySnapshot.documents;
      print("querySnapshot !!!!!!!!${querySnapshot.documents}");
    print("!!!!!!!!!!@@@@@@@@@@@22l${list[0]['idOrder']}");
      print("the list ${list}");
  }

Performing hot restart...
Syncing files to device Redmi Note 4...
Restarted application in 3,458ms.
I/flutter (24825): this  dummy @@@@@@@@@@22222
I/flutter (24825): function@@@@@@@@222
I/flutter (24825): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (24825): The following NoSuchMethodError was thrown building Clients1(dirty, state: _Clients#f2298):
I/flutter (24825): The method '[]' was called on null.
I/flutter (24825): Receiver: null
I/flutter (24825): Tried calling: [](0)