如何在 DropdownButton flutter 中的数组中放置 String 的 snapShot 列表

Question

I have a DropdownButton here and a snapshot of string But I want to put a list inside a DropdownMenuItem so I can select it later How can I do that?. code:

String? selectedUserName;

                       StreamBuilder(
                          stream: FirebaseFirestore.instance
                              .collection("groups")
                              .doc(groupId)
                              .snapshots(),
                          builder: (context,
                              AsyncSnapshot<DocumentSnapshot> snapshot) {
                           //I want to put this snapshot inside the DropdownMenuItem
                            var userDocumentUid = snapshot.data?["members"]as List?;
                            if (!snapshot.hasData) {
                              return Container();
                            }
                             return DropdownButton(
                                        hint: const Text("to"),
                                        value: selectedUserName,
                                        onChanged: (newValue) {
                                          setState(() {
                                            selectedUserName =
                                                newValue as String?;
                                          });
                                        },
                                        items: userDocumentUid!.map(
                                          (userDocumentUid) {
                                            return DropdownMenuItem<String?>(
                                              value: userDocumentUid,
                                              child: Text(userDocumentUid),
                                            );
                                          },
                                        ).toList(),
                                      )

Image:

Answer 1

While you are receiving a list of string, try to add data type and map the list to return widget.

builder: (context, AsyncSnapshot<DocumentSnapshot> snapshot) {
  //I want to put this snapshot inside the DropdownMenuItem
  var userDocumentUid = snapshot.data?["members"] as List?;
  if (!snapshot.hasData || userDocumentUid == null) {
    return Container();
  }
  return DropdownButton<String?>(
    hint: const Text("to"),
    value: selectedUserName,
    onChanged: (newValue) {
      setState(() {
        selectedUserName = newValue;
      });
    },
    items: userDocumentUid.map(
      (userDocumentUid) {
        return DropdownMenuItem(
          value: userDocumentUid,
          child: Text(userDocumentUid),
        );
      },
    ).toList(),
  );
},