從Firebase獲取列表

Question

我正在嘗試創建一個Android應用，我正在使用Firebase存儲信息列表。我能夠在沒有問題的情況下將實時數據庫中的信息存儲起來，但是我目前遇到的問題是試圖找出在添加新內容時如何檢索列表。

當我在列表中添加，更改或刪除值時，不會調用任何childEventListener。

FirebaseDatabase database; 
DatabaseReference toDatabase; 

... 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_world_play_hide); 

     hideAvatar = (Button) findViewById(R.id.hideAvatar); 

     database = FirebaseDatabase.getInstance(); 
     toDatabase = database.getReference("jsierra"); 

     ... 

     hideAvatar.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 

       ... 

       getCurrentLocation(); 
       currentCoordinates = new LatLng(latitude, longitude); 
       data store = new data(currentCoordinates); 

       toDatabase.push().setValue(store); 

       map.addMarker(new MarkerOptions().position(currentCoordinates)); 
      } 
     }); 
    } 

protected void onStart() { 
     apiClient.connect(); 
     super.onStart(); 

     DatabaseReference test = toDatabase.child("jsierra"); 

     test.addChildEventListener(new ChildEventListener() { 

      @Override 
      public void onChildAdded(DataSnapshot dataSnapshot, String s) { 
       Toast.makeText(getBaseContext(), "Child Added", Toast.LENGTH_LONG).show(); 
       givenData = dataSnapshot.getValue(data.class); 
      } 

      @Override 
      public void onChildChanged(DataSnapshot dataSnapshot, String s) { 
       givenData = dataSnapshot.getValue(data.class); 
       Toast.makeText(getBaseContext(), "Child Changed", Toast.LENGTH_LONG).show(); 
      } 

      @Override 
      public void onChildRemoved(DataSnapshot dataSnapshot) { 
       givenData = dataSnapshot.getValue(data.class); 
       Toast.makeText(getBaseContext(), "Child Removed", Toast.LENGTH_LONG).show(); 
      } 

      @Override 
      public void onChildMoved(DataSnapshot dataSnapshot, String s) { 
       givenData = dataSnapshot.getValue(data.class); 
       Toast.makeText(getBaseContext(), "Child Moved", Toast.LENGTH_LONG).show(); 
      } 

      @Override 
      public void onCancelled(DatabaseError databaseError) { 
       Toast.makeText(getBaseContext(), "Failed", Toast.LENGTH_LONG).show(); 
      } 
     }); 
    } 

Answer 1

您的test參考是錯誤的。變化：

DatabaseReference test = toDatabase.child("jsierra"); 

到：

DatabaseReference test = database.getReference("jsierra");