火力地堡onDataChange方法不叫即使數據發生變化

Question

我的代碼如下所示：如下圖所示

private DatabaseReference mFirebaseDatabase; 
    private FirebaseDatabase mFirebaseInstance; 
    private static final String TAG = "OrderManagementFragment"; 


    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.fragment_order_managment, container, false); 

     //get reference to the orders node 
     mFirebaseDatabase = mFirebaseInstance.getReference("orders"); 

     // app_title change listener 
     mFirebaseInstance.getReference("58ca237b2e2c211dc0c7ed9b").addValueEventListener(new ValueEventListener() { 
      @Override 
      public void onDataChange(DataSnapshot dataSnapshot) { 
       Toast.makeText(getActivity(), dataSnapshot.getValue(String.class), Toast.LENGTH_LONG).show(); 
       Log.d(TAG, "onDataChange: " + dataSnapshot.getValue(String.class)); 


      } 

      @Override 
      public void onCancelled(DatabaseError error) { 
       // Failed to read value 
       Toast.makeText(getActivity(), error.getMessage(), Toast.LENGTH_LONG).show(); 
       Log.d(TAG, "onCancelled: " + error.getMessage()); 
      } 
     }); 

     return view; 
    } 

我對火力的憑據：

現在，這裏發生的是，無論何時數據從後端改變，onDatachange方法永遠不會被調用。所以在這個方法中有什麼缺失？

我正在測試通過android模擬器，這是它的問題？

Answer 1

我改變了你的代碼，你不需要引用inconstructor因爲應用方法會知道你需要什麼。

數據沒有改變，因爲你的佈局沒有靜態的textView。當你有一個麪包，其啓動一旦你還是你不能看到它的改變

//get reference to the orders node 
      mFirebaseDatabase = mFirebaseInstance.getReference(); 

      // app_title change listener 
      mFirebaseInstance.addValueEventListener(new ValueEventListener() { 
       @Override 
       public void onDataChange(DataSnapshot dataSnapshot) { 
        Toast.makeText(getActivity(), dataSnapshot.child("YOUR REFERENCE HERE")getValue(String.class), Toast.LENGTH_LONG).show(); 

       } 

我給你從我的應用實例：

mDatabase = FirebaseDatabase.getInstance().getReference(); 
     settingsText2.setText("Loading..."); 
     mDatabase.addValueEventListener(new ValueEventListener() { 
      @Override 
      public void onDataChange(final DataSnapshot dataSnapshot) { 
       settingsTextWithScrollView.setText(dataSnapshot.child("Youtube1").child("Text").getValue(String.class)); 
       settingsText2.setText(dataSnapshot.child("Youtube1").child("Information").getValue(String.class)); 
       settingsTextWithScrollView.setOnClickListener(new View.OnClickListener() { 
        @Override 
        public void onClick(View v) { 
         openYoutubeIntent(dataSnapshot.child("Youtube1").child("Link").getValue(String.class)); 
        } 
       }); 
       settingsText3.setText(dataSnapshot.child("Youtube2").child("Text").getValue(String.class)); 
       settingsText4.setText(dataSnapshot.child("Youtube2").child("Information").getValue(String.class)); 
       settingsText3.setOnClickListener(new View.OnClickListener() { 
        @Override 
        public void onClick(View v) { 
         openYoutubeIntent(dataSnapshot.child("Youtube2").child("Link").getValue(String.class)); 
        } 
       }); 
       settingsText5.setText(dataSnapshot.child("Youtube3").child("Text").getValue(String.class)); 
       settingsText6.setText(dataSnapshot.child("Youtube3").child("Information").getValue(String.class)); 
       settingsText5.setOnClickListener(new View.OnClickListener() { 
        @Override 
        public void onClick(View v) { 
         openYoutubeIntent(dataSnapshot.child("Youtube3").child("Link").getValue(String.class)); 
        } 
       }); 
      } 
      @Override 
      public void onCancelled(DatabaseError databaseError) { 

      } 
     }); 
    } 

Answer 2

它是一個靜態調用像這樣

FirebaseDatabase database=FirebaseDatabase.getInstance(); 
DataBaseRefrence dbRef=database.getRefrence("nodeOfData"); 
DataSnapshot ds=dbRef.getChildren("gettingWhatIsInNodeOfData"); or 
better yet chain them DataSnapshot 
ds=FirebaseDatabase.getInstance().getRefrence("orders").getChildren();