从未调用过 FIrebase 数据库 addListenerForSingleValueEvent 侦听器

Question

我有一个聊天屏幕，它有 Firebase 数据库支持聊天消息。我可以 post 向屏幕和数据库发送消息，但是当我离开聊天并返回聊天屏幕时就会出现问题。

聊天屏幕变空，我想从 Firebase 数据库加载所有以前的聊天。所以我又创建了一个带有聊天节点的 Firebase 引用，但无法让用户聊天，因为永远不会调用 onCreate 中的 onDataChange。

这是我的聊天画面class

public class Chat_Screen extends AppCompatActivity implements View.OnClickListener,ChildEventListener{

    public static final String TAG = "###CHAT SCREEN###";
    private EditText TypedMsg;
    private ImageButton SendButton,Emo_Button;
    String UserName_Intent,UserImage_Intent,UserID_Intent,Room_Name_Intent;
    String Chat_Msg,Chat_UserName;

    RecyclerView.Adapter adapter;
    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;

    Iterator iterator;
    Toolbar toolbar;
    private ProgressDialog progressDialog;

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

    DatabaseReference databaseReference;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.chat_screen_main);
        TypedMsg= (EditText) findViewById(R.id.Chat_Screen_Text_Message);
        SendButton= (ImageButton) findViewById(R.id.Chat_Screen_Send);
        Emo_Button= (ImageButton) findViewById(R.id.Chat_Screen_Smiley);
        toolbar= (Toolbar) findViewById(R.id.Chat_Screen_Toolbar);
        progressDialog=new ProgressDialog(this);
        progressDialog.setMessage("This Is Chat Room");
        progressDialog.show();

        // GET INTENT VALUES FROM USER PROFILE CLASS

        UserName_Intent=getIntent().getExtras().getString("Get_Name");
        UserImage_Intent=getIntent().getExtras().getString("Get_Image");
        UserID_Intent=getIntent().getExtras().getString("Get_Phone");
        Room_Name_Intent=getIntent().getExtras().getString("room_user");

        // RECYCLER VIEW
        recyclerView= (RecyclerView) findViewById(R.id.Chat_Screen_Message_List);
        recyclerView.setHasFixedSize(true);
        layoutManager=new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);


        //FIREBASE FETCH ALL PREVIOUS CHAT OF USERS/CHATROOM ------THIS NEVER CALLS
        DatabaseReference db=FirebaseDatabase.getInstance().getReference(Room_Name_Intent);
        Log.d(TAG,"Database Reference of child "+db);
        db.addListenerForSingleValueEvent(new ValueEventListener() {

            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                    Log.d(TAG,"Value of SnapShop is calling");
                    Log.d(TAG,"Value of SnapShop is calling "+snapshot.getValue());
                    Log.d(TAG,"Value of SnapShop is calling 2nd "+snapshot.getValue());

                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });



        Log.d(TAG,"Value of List "+message+" Value of Adapter "+adapter);
        adapter=new Chat_Adapter(this,message);
        recyclerView.setAdapter(adapter);



        //INITIALIZING MESSAGE ARRAYLIST


        SendButton.setOnClickListener(this);

        databaseReference= FirebaseDatabase.getInstance().getReference().getRoot().child(Room_Name_Intent);
        databaseReference.addChildEventListener(this);


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.chat_screen_menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        //HANDLE ITEM SELECTION
        switch (item.getItemId()) {
            case R.id.sendFile:
                Log.d(TAG, "Send File Menu Clicked");
                return true;
            case R.id.geo:
                Log.d(TAG, "Geo Fencing Button Clicked");
                return true;
            case R.id.Call:
                Log.d(TAG, "Call Button Clicked");
                Toast.makeText(this, "Call Button Clicked", Toast.LENGTH_LONG).show();
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }

    }

    @Override
    public void onClick(View v) {
        int itemClick=v.getId();

        switch (itemClick){
            case R.id.Chat_Screen_Send:
                Log.d(TAG,"Send Button Pressed");

                Log.d(TAG,"FireBase Chat Room Level "+databaseReference);
                //GET MESSAGE FROM EDIT TEXT INTO HASHMAP TO UPDATE DATABASE
                Map<String,Object> map=new HashMap<>();
                map.put("Name",UserName_Intent);
                map.put("Message",TypedMsg.getText().toString());

                String Temp_Key=databaseReference.push().getKey();
                Map<String,Object> RoomKey=new HashMap<>();
                databaseReference.updateChildren(RoomKey);
                DatabaseReference message_Root=databaseReference.child(Temp_Key);
                message_Root.updateChildren(map);
                Log.d(TAG,"Msg Root "+message_Root);

                TypedMsg.setText("");
                break;

        }

    }


    @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 void append_chat_conversation(DataSnapshot dataSnapshot){
        iterator=dataSnapshot.getChildren().iterator();
        while (iterator.hasNext()){

            Chat_Msg=(String) ((DataSnapshot)iterator.next()).getValue();
            Chat_UserName= (String) ((DataSnapshot)iterator.next()).getValue();

            Calendar calendar=Calendar.getInstance(Locale.getDefault());
            int hour=calendar.get(Calendar.HOUR_OF_DAY);
            int min=calendar.get(Calendar.MINUTE);
            int second=calendar.get(Calendar.SECOND);
            Log.d(TAG,"Time of the Day "+hour+" -- "+min+" -- "+second);
            String time=(hour+" -- "+min+" -- "+second);





            Log.d(TAG,Chat_Msg+" TIME "+time+" PHONE "+UserID_Intent+" User Image "+UserImage_Intent+" User Name "+UserName_Intent);

            Chat_Wrapper chat_wrapper=new Chat_Wrapper(Chat_Msg,time,UserID_Intent,UserImage_Intent);
            message.add(chat_wrapper);

            adapter.notifyItemInserted(adapter.getItemCount()+1);


            Log.d(TAG,"Chat Msg & User Name "+Chat_Msg+" "+Chat_UserName+" Message List "+message.size());

        }
    }
}

Answer 1

使用

获取整个结构

DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();

然后用mDatabase.child("yourChildId")得到你想要的child。这个returns给你一个参考。将 .addListenerForSingleValueEvent 设置为该引用。你尝试过这样的事情吗？

Answer 2

这可能是因为每次您在调用 firebase.updateChildren 时输入子节点，它都会删除所有以前的数据并创建新节点，您的代码没问题，它会获取所有数据。只要确保您每次进入房间时都不会创建新房间

从未调用过 FIrebase 数据库 addListenerForSingleValueEvent 侦听器

FIrebase Database addListenerForSingleValueEvent listner never called

android

chat

firebase

firebase-realtime-database