java - Firebase 读取每个条目中的子目录

Question

如何获取数据库中所有“Floor”元素的列表。如果我使用以下数据库，我的列表应该有 3 个元素。列表应包含 id 为 1234、4321、2341 的元素。

 mydatabase
    -buildings
     --LNBxRoNBhVZyXniqe9t
      ---checked
      ---anzI
      ---anzA
      ---floors
       ----f1
        -----1234
         ------description
         ------id
       ----f2
        -----4321
         ------description
         ------id

     --LXdsafRfasdf12asdfJ
      ---checked
      ---anzI
      ---anzA
      ---floors
       ----f1
        -----2341
         ------description
         ------id

This is my DAO:

     private FirebaseDatabase database = FirebaseDatabase.getInstance();
    DatabaseReference myRef = database.getReference("buildings");
    @Override
    public void initialize() {
        myRef.addListenerForSingleValueEvent(new ValueEventListener() {
        List<Floors> list = new LinkedList<>();

        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
                        ????
                       }

          @Override
          public void onCancelled(DatabaseError error) {
          Log.w(TAG, "Failed to read value.", error.toException());
           }});

Answer 1

您需要遍历从 Firebase 获取的 DataSnapshot。像这样的事情

myRef.addListenerForSingleValueEvent(new ValueEventListener() {
  @Override
  public void onDataChange(DataSnapshot dataSnapshot) {
    for (DataSnapshot buildingSnapshot: dataSnapshot.getChildren()) {
      for (DataSnapshot floorSnapshot: buildingSnapshot.child("floors").getChildren()) {
        for (DataSnapshot numberSnapshot: floorSnapshot.getChildren()) {
          Log.i(TAG, numberSnapshot.getKey()); // "1234", "4321", "2341"
          Log.i(TAG, ""+numberSnapshot.child("id").getValue());
        }          
      }
    }
  }

  @Override
  public void onCancelled(DatabaseError error) {
    Log.w(TAG, "Failed to read value.", error.toException());
  }
});