您需要将从firestore检索到的数据转换为它们各自的数据结构类型。
例如："Address"将是<String,dynamic>类型的Map。
"Products"将是Map<String,dynamic>的List，但转换为dynamic类型的List将正常工作。

Future<void> getOrderDetails(String id) async {
final orderSnapshot = await FirebaseFirestore.instance
    .collection('orders')
    .where('Order id', isEqualTo: id)
    .get();
if (orderSnapshot.docs.isEmpty) {
  return;
}
final orderData = orderSnapshot.docs.first.data();
status = orderData['Status'];
print(status);
this.id = id;
print(this.id);
Timestamp t;
t = orderData['Date & Time'];
startDate = t.toDate();
print(startDate);

//new code below
var addressMap = orderData['address'] as Map<String,dynamic>;
var buildingNum = addressMap['Building Number'];
print('building number: $buildingNum');

var productList = orderData['Products'] as List<dynamic>;
for(var productItemMap in productList){
  print('product name: ${productItemMap['name']}');
}
}