I want to retrieve data from Firestore and show them in my flutter app , but the document has a map called 'users' , my question is how I can access to This map field ?

StreamBuilder(
    stream: FirebaseFirestore.instance
        .collection('Channels')
        .where('participants', arrayContains: UserInfoData.userID)
        .snapshots(),
    builder: (context, AsyncSnapshot<QuerySnapshot> streamSnapshot) {
      switch (streamSnapshot.connectionState) {
        case ConnectionState.waiting:
          return Center(
            child: CircularProgressIndicator(),
          );

        default:
          if (streamSnapshot.hasError) {
            print(streamSnapshot.hasError.toString());
          } else {
            final channels = streamSnapshot.data!.docs;
            if (channels.isEmpty) {
              return Text('ff');
            } else
              return ListView.builder(
                itemCount: channels.length,
                itemBuilder: (context, i) => ListTile(
                  leading: CircleAvatar(
                    backgroundImage:
                        NetworkImage(channels[i]['announceImage']),
                  ),
                  title: Text(channels[i]['reciverID']),
                ),
              );
          }
      }
      return Text('ok');
    },
  ),
);

CodePudding user response：

You can get the values over here just like any other map containing keys. In your case, users is a map containing keys lastname, name, userid. channels[i]['users'] would get you the users map. To get the value for a particular key ,you can think of channels[i]['users'] as a whole, like an array.

So you could get the values by doing the following :

String lastname = channels[i]['users']['lastname']
String name = channels[i]['users']['name']