Update UserTileChats to auto-refresh UI on Firebase changes.

lib/components/user_tile_chats.dart

@@ -1,3 +1,4 @@
+import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:flutter/material.dart';
 
 import '../models/message.dart';
@@ -45,7 +46,6 @@ class UserTileChats extends StatelessWidget {
   Widget buildProfileIcon() {
     return Row(
       children: [
-        // Profile image
         if (profileImageUrl != null && profileImageUrl!.isNotEmpty)
           CircleAvatar(
             backgroundImage: NetworkImage(profileImageUrl!),
@@ -53,7 +53,7 @@ class UserTileChats extends StatelessWidget {
           ),
         // Icon if profile image is not set
         if (profileImageUrl == null || profileImageUrl!.isEmpty)
-          const Icon(Icons.person),
+          const Icon(Icons.person, size: 36),
 
         const SizedBox(width: 12),
       ],
@@ -61,13 +61,10 @@ class UserTileChats extends StatelessWidget {
   }
 
   Widget buildMsgContent() {
-    String msgDateString = '';
-    String msgContent = '';
-    bool? outgoing;
     String chatRoomID = getCompoundId([currentUserId ?? '', otherUserId ?? '']);
 
-    return FutureBuilder<Message?>(
+    return StreamBuilder<Message?>(
-      future: ChatService().getLastMessage(chatRoomID),
+      stream: ChatService().getLastMessageStream(chatRoomID),
       builder: (context, snapshot) {
         if (snapshot.connectionState == ConnectionState.waiting) {
           return const CircularProgressIndicator();
@@ -82,7 +79,13 @@ class UserTileChats extends StatelessWidget {
           return buildMsgDetails('No messages yet', '', null);
         } else {
           Message lastMessage = snapshot.data!;
+          String msgDateString = '';
+          String msgContent = '';
+          bool? outgoing;
+          if (lastMessage.timestamp !=
+              Timestamp.fromMillisecondsSinceEpoch(0)) {
             msgDateString = formatTimestamp(lastMessage.timestamp);
+          }
 
           if (lastMessage.senderID == currentUserId) {
             msgContent = 'Me: ${lastMessage.message}';

lib/services/chat/chat_service.dart

@@ -58,6 +58,24 @@ class ChatService {
     await batch.commit();
   }
 
+  /// Retrieves a stream of the last message of a chatroom.
+  Stream<Message?> getLastMessageStream(String chatRoomID) {
+    return _firestore
+        .collection(Constants.dbCollectionChatRooms)
+        .doc(chatRoomID)
+        .collection(Constants.dbCollectionMessages)
+        .orderBy(Constants.dbFieldMessageTimestamp, descending: true)
+        .limit(1)
+        .snapshots()
+        .map((snapshot) {
+      if (snapshot.docs.isEmpty) {
+        return null;
+      }
+      var lastMessageDoc = snapshot.docs.first;
+      return Message.fromMap(lastMessageDoc.data());
+    });
+  }
+
   /// Retrieves the last message of a chatroom.
   ///
   /// Returns [null] in case of an error.
@@ -77,6 +95,7 @@ class ChatService {
           .limit(1)
           .get();
 
+      if(messageSnapshot.docs.isNotEmpty) {
         DocumentSnapshot lastMessageDoc = messageSnapshot.docs.first;
         if (lastMessageDoc.exists) {
           senderID = lastMessageDoc[Constants.dbFieldMessageSenderId];
@@ -85,8 +104,11 @@ class ChatService {
           message = lastMessageDoc[Constants.dbFieldMessageText];
           timestamp = lastMessageDoc[Constants.dbFieldMessageTimestamp];
         }
+      } else {
+        debugPrint('Info: getLastMessage -> messageSnapshot is EMPTY');
+      }
     } catch (e) {
-      debugPrint('DebugPrint: getLastMessage -> ${e.toString()}');
+      debugPrint('Error on getLastMessage: ${e.toString()}');
       return null;
     }