聊天片段不更新 recyclerview

Question

我有 Fragment，我有 recyclerview，它在第一次启动时工作正常（当片段第一次启动时）。我可以发送和接收消息。但是当我从通知转到聊天片段时，它会停止更新 recyclerview。我必须从最近的应用程序中清除应用程序，然后当我从通知中转到聊天片段时它工作正常。

当我在点击通知后收到消息作为通知时，它会打开相同的聊天屏幕（首先加载所有以前的消息），当我单击发送按钮发送消息时，它会发送给其他用户，但不会更新我的回收站视图。

正常加载聊天片段

getFragmentManager().beginTransaction().add(R.id.Navigation_Drawer, chatFragment).commit();

通过异步任务从通知中加载片段

((Navigation_Drawer)context).getFragmentManager().beginTransaction().replace(R.id.Navigation_Drawer, chatFragment).commit();

ChatScreenFragment

    public class Chat_Screen_Fragment extends Fragment implements View.OnClickListener, ChildEventListener{

    public static final String TAG = "###CHAT SCREEN###";

    List<Chat_Wrapper> message = new ArrayList<>();


    Chat_Adapter adapter;
    RecyclerView recyclerView;
    LinearLayoutManager layoutManager;


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View v=inflater.inflate(R.layout.chat_screen_main_fragment,container,false);
        setRetainInstance(true);
        // GET INTENT VALUES FROM USER PROFILE CLASS

        UserName_Intent = getArguments().getString("Get_Name");
        UserImage_Intent = getArguments().getString("Get_Image");
        UserPhone_Intent = getArguments().getString("Get_Phone");
        UserID_Intent = getArguments().getString("Get_ID");
        FirebaseToken_Intent = getArguments().getString("Get_Token"); //Firebase Token of other person
        Room_Name_Intent = getArguments().getString("Get_Other"); // Room Name of chat
        UserLastSeen_Intent=getArguments().getString("LastSeen");
        //Sender_FCMToken = Session.getFirebaseID();
        // RECYCLER VIEW
        recyclerView = v.findViewById(R.id.Chat_Screen_Message_List);
        layoutManager = new LinearLayoutManager(getActivity());
        layoutManager.setStackFromEnd(true);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(layoutManager);
databaseReference = FirebaseDatabase.getInstance().getReference().child(Room_Name_Intent);
        databaseReference.addChildEventListener(this);

        adapter = new Chat_Adapter(getActivity(), message);
        recyclerView.setAdapter(adapter);
        // FETCH OLD MESSAGE FROM DATABASE
        chatDatabase();
        return v;
    }
    // FIREBASE REAL TIME DATABASE WHICH FETCH ALL MESSAGES (SYNC) FROM ONLINE DATABASE
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        append_chat_conversation(dataSnapshot);
    }

    @Override
    public void onChildChanged(DataSnapshot dataSnapshot, String s) {
        append_chat_conversation(dataSnapshot);
    }

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

    @Override
    public void onChildMoved(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
    private synchronized void append_chat_conversation(DataSnapshot dataSnapshot) {
        iterator = dataSnapshot.getChildren().iterator();
        while (iterator.hasNext()) {
            // NOW GET ALL DATA FROM FIREBASE DATABASE AND SAVE IT INTO STRINGS THEN CHECK EACH BY ITS MESSAGE TYPE
            Chat_Msg = (String) ((DataSnapshot) iterator.next()).getValue();
            Chat_FROM = (String) ((DataSnapshot) iterator.next()).getValue();
            Chat_FCM_TO= (String) ((DataSnapshot) iterator.next()).getValue();

            Chat_Database tempChatDatabase = new Chat_Database(getActivity());
            boolean hasValue=tempChatDatabase.CheckValueExist(_ID);
            if (!hasValue) {
                Log.d(TAG,"Chat Message "+Chat_Msg);
                    long id=chat_database.Insert_Chat(Session.getUserID(),Room_Name_Intent, UserID_Intent, "Text", Chat_Msg, Chat_FROM, Chat_TO, Chat_TimeStamp, Chat_FCM_FROM, Chat_FCM_TO, Session.getPhoneNO(), UserPhone_Intent,Random_ID,UserImage_Intent,UserLastSeen_Intent,Chat_FROM_ID);

                    //Adding Chat Data Into Database
                    Log.d(TAG,"Database Entry ID "+id);
                    if (id==0){
                        Log.d(TAG,"Database Already Has Value Of This Random Id ");
                        return;
                    }
                    Chat_Wrapper chat_wrapper = new Chat_Wrapper(Chat_Msg, null, null, null, null, null, null, Chat_TimeStamp, User_Intent, UserImage_Intent, Chat_FROM, null,null,id);
                    message.add(chat_wrapper);
                  adapter.notifyDataSetChanged();
                Log.d(TAG, "FIREBASE STORAGE PHOTO-3-MESSAGE ARRAY SIZE " + message.size());
                recyclerView.post(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "Moving to Bottom");
                        recyclerView.smoothScrollToPosition(adapter.getItemCount());

                    }
                });

                }               

                }

            }

            Log.d(TAG, "MESSAGE ARRAY SIZE " + message.size());

            tempChatDatabase.isDatabaseClose();
        }

        adapter.notifyDataSetChanged();
        recyclerView.post(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "Moving to Bottom");
                recyclerView.smoothScrollToPosition(message.size()-1);
                //recyclerView.smoothScrollToPosition(adapter.getItemCount());

            }
        });
    }
    private void chatDatabase(){
        //Database Init and Filling Adapter
        Log.d(TAG,"Chat Database Function");
        chat_database=new Chat_Database(getActivity());
        chatCursor=chat_database.getUserChat(UserID_Intent);
        boolean checkDB_Exist=functions.DatabaseExist(getActivity(),"CHAT_DATABASE.DB");
        boolean chatItemsCounts=chatCursor.getCount()>0;
        chatCursor.moveToFirst();
        Log.d(TAG,"Value At Chat Database "+ checkDB_Exist+" "+chatItemsCounts);
        if (checkDB_Exist && chatCursor.getCount()>0 && chatCursor.getString(chatCursor.getColumnIndex("RECEIVER_USER_ID")).equals(UserID_Intent)){

            Log.d(TAG,"Database Exist Chat Database");
            message.clear();
            chatCursor.moveToFirst();
            do {
                database_rowID=chatCursor.getInt(chatCursor.getColumnIndex("ID"));
                database_userID=chatCursor.getString(chatCursor.getColumnIndex("USER_ID"));
                database_RoomName =chatCursor.getString(chatCursor.getColumnIndex("ROOM_NAME"));
                database_ReceiverID=chatCursor.getString(chatCursor.getColumnIndex("RECEIVER_USER_ID"));
                database_MessageType=chatCursor.getString(chatCursor.getColumnIndex("MESSAGE_TYPE"));
                database_Message=chatCursor.getString(chatCursor.getColumnIndex("USER_MESSAGE"));
                database_MsgFrom=chatCursor.getString(chatCursor.getColumnIndex("SENDER_NAME"));
                database_MsgTo=chatCursor.getString(chatCursor.getColumnIndex("RECEIVER_NAME"));
                database_TimeStamp=chatCursor.getString(chatCursor.getColumnIndex("TIME_STAMP"));
                database_FCMfrom=chatCursor.getString(chatCursor.getColumnIndex("SENDER_TOKEN"));
                database_FCMto=chatCursor.getString(chatCursor.getColumnIndex("RECEIVER_TOKEN"));
                database_LocalPath=chatCursor.getString(chatCursor.getColumnIndex("DOWNLOADED_AT"));
                database_PhoneFrom=chatCursor.getString(chatCursor.getColumnIndex("MY_PHONE"));
                database_PhoneTo=chatCursor.getString(chatCursor.getColumnIndex("OTHER_PHONE"));

                Log.d(TAG,"Value Of Database Message String = "+database_Message);
                Log.d(TAG,"Row ID of Database "+database_rowID);
                // Check Message Type


                    Log.d(TAG,"Message Type Is Text");
                    Chat_Wrapper text = new Chat_Wrapper(database_Message, null, null, null, null, null, null, database_TimeStamp, database_PhoneTo, UserImage_Intent, database_MsgFrom,null,null,database_rowID);
                    message.add(text);



            }
            while(chatCursor.moveToNext());

            Room_Name_Intent = database_RoomName;
            layoutManager = new LinearLayoutManager(getActivity());
            recyclerView.setLayoutManager(layoutManager);
            adapter.notifyDataSetChanged();
            chatCursor.close();
            boolean value = chat_database.isDatabaseClose();
            recyclerView.post(new Runnable() {
                @Override
                public void run() {
                    Log.d(TAG, "Moving to Bottom");
                    recyclerView.smoothScrollToPosition(message.size()-1);

                }
            });
            Log.d(TAG,"Value Of Database Close or Not "+value);

        }
    }
}

我还注意到，当我评论 chatDatabase() 函数时，从本地数据库获取早期消息的方法工作正常。但仍然无法解决问题。

以防万一。

1. 当我从最近的应用中清除应用时
2. 评论chatDatabase()函数
3. 当我第一次启动片段时。

Answer 1

虽然 Fragment 实例本身被保留，但它会在其分离/替换时销毁并重新创建其视图。

将您的 firebase 和适配器初始化逻辑移至 onCreate，仅将 RecyclerView 初始化留在 onCreateView 中。

您还应该覆盖 onDestroyView 并在此处明确引用 layoutManager 和 recyclerView。

请注意，在这种情况下，您必须分离您的 firebase 回调或处理 getView()（或 recyclerView，如果在 onDestroyView 中清除引用）为空的情况，然后跳过更新 UI。