Accessing array in firestore and print found if it is present

I want to access fname which is an array in firestore and if it is present print found or else not found but i am not able to access an array.

where as if fname is create as string int firestore than i am able to print "Found"

return StreamBuilder(
      stream: Firestore.instance.collection('users').snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) return Text('Loading Data');
        return ListView.builder(
            itemCount: snapshot.data.documents.length,
            itemBuilder: (context, index) {
              return Card(
                  child: ListTile(
                leading: snapshot.data.documents[index].data['user'] == ["John"]
                    ? Text("Found")
                    : Text('No position found'),

Solution 1: hasan karaman-goodsoft

   await _refdata.child("users").once().then((DataSnapshot snap2) {
bool result;
result= snap2.value.where((element)=> elemet.devices.fname=="jhon);
});
  leading:
            result ==true
                ? Text(&quot;Found&quot;)
                : Text('No position found'),

------or-------

       leading:

     Text(snapshot.data.documents[index].data[""devices].data['fname'])=="John"
                    ? Text("Found")
                    : Text('No position found'),