diff --git a/app/src/main/java/com/example/tampopo_client/models/Activity.java b/app/src/main/java/com/example/tampopo_client/models/Activity.java
index 7c3d626..6dcf984 100644
--- a/app/src/main/java/com/example/tampopo_client/models/Activity.java
+++ b/app/src/main/java/com/example/tampopo_client/models/Activity.java
@@ -13,6 +13,9 @@
         this.updateTime = updateTime;
     }
 
+    public Activity() {
+    }
+
     public String getUserId() {
         return userId;
     }
diff --git a/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
index 3df02a7..810bc38 100644
--- a/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
+++ b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
@@ -40,6 +40,8 @@
     private final Map<String, MutableLiveData<List<Activity>>> friendToActivitiesLiveData; // <フレンドのユーザーID, フレンドのアクティビティのリスト>
     private final MutableLiveData<List<String>> friendUserIdsLiveData; // フレンドのユーザーIDのリスト
 
+    private List<String> prevFriendUserIds = null;
+
     private final String myUserId;
     private final String myToken;
 
@@ -62,7 +64,7 @@
         activitiesResource = retrofit.create(ActivitiesResource.class);
         userResource = retrofit.create(UserResource.class);
 
-        friendToActivitiesLiveData = Map.of();
+        friendToActivitiesLiveData = new HashMap<>();
         friendUserIdsLiveData = new MutableLiveData<>(List.of());
         myLatestActivityLiveData = new MutableLiveData<>(null);
 
@@ -263,27 +265,30 @@
             @Override
             public void onResponse(@NonNull Call<List<String>> call, @NonNull Response<List<String>> response) {
                 if (response.isSuccessful()) {
-                    friendUserIdsLiveData.postValue(response.body());
 
                     // MEMO: 入れ込んだだけ
                     // フレンドのIDをアクティビティ更新順に並べ替える
                     List<String> friendUserIds = friendUserIdsLiveData.getValue();
-                    SortedSet<Friend> friends = new TreeSet<>(new Friend.UpdateTimeComparator());
+                    if (prevFriendUserIds == null || !prevFriendUserIds.equals(friendUserIds)) {
+                        prevFriendUserIds = friendUserIds;
+                        friendUserIdsLiveData.postValue(response.body());
+                        SortedSet<Friend> friends = new TreeSet<>(new Friend.UpdateTimeComparator());
 
-                    assert friendUserIds != null;
-                    friendUserIds.forEach(userId -> {
-                        List<Activity> activities = getActivitiesLiveDataFromUserId(userId).getValue();
-                        if (activities == null || activities.isEmpty()) {
-                            return;
-                        }
+                        assert friendUserIds != null;
+                        friendUserIds.forEach(userId -> {
+                            List<Activity> activities = getActivitiesLiveDataFromUserId(userId).getValue();
+                            if (activities == null || activities.isEmpty()) {
+                                return;
+                            }
 
-                        Activity latestActivity = activities.get(0);
-                        friends.add(new Friend(userId, latestActivity.getUpdateTime()));
-                    });
+                            Activity latestActivity = activities.get(0);
+                            friends.add(new Friend(userId, latestActivity.getUpdateTime()));
+                        });
 
-                    // 並び替えたフレンドのユーザーIDを順番に格納して更新する
-                    sortedFriendUserIds.clear();
-                    friends.forEach(friend -> sortedFriendUserIds.add(friend.getUserId()));
+                        // 並び替えたフレンドのユーザーIDを順番に格納して更新する
+                        sortedFriendUserIds.clear();
+                        friends.forEach(friend -> sortedFriendUserIds.add(friend.getUserId()));
+                    }
                 }
             }
 
@@ -305,6 +310,9 @@
      * @return 取得対象のユーザーのアクティビティのリストのライブデータ
      */
     public MutableLiveData<List<Activity>> getActivitiesLiveDataFromUserId(String userId) {
+        if(!friendToActivitiesLiveData.containsKey(userId)){
+            friendToActivitiesLiveData.put(userId, new MutableLiveData<>());
+        }
         return friendToActivitiesLiveData.get(userId);
     }
 
diff --git a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
index 19dca60..d75baff 100644
--- a/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
+++ b/app/src/main/java/com/example/tampopo_client/views/MainActivity.java
@@ -317,6 +317,8 @@
 //            Activity activity = entry;
 
             FriendIconView userView = userViews.get(friendId);
+            MutableLiveData<List<Activity>> activitiesLiveData = activityViewModel.getActivitiesLiveDataFromUserId(friendId);
+
 
             if (userView == null) {
                 // 新しいユーザなので、アイコン＋コメントを作成
@@ -351,6 +353,7 @@
                 // Mapに登録、画面に追加
                 userViews.put(friendId, container);
                 messageList.addView(container);
+                activitiesLiveData.observeForever(container);
 
 //            } else {
 //                // 既に表示されている → コメントだけ更新