Firebase Android-基于uniqueID从同一对象的两个节点检索数据

Question

这是我的假火基地结构。

 { "Restaurant":{
    pushId: {
            "Node A":{
                    0:{ id = 1234
                        // data of some object type
                      }
                    1:{ id = 2345
                      // data of some object type
                      }
                    2:{ id = 3456
                      // data of some object type
                      }
                 }
            "Node B":{
                    0:{ id = 6789
                        // data of some object type
                      }
                    1:{ id = 9876
                      // data of some object type
                      }
                    2:{ id = 0000
                      // data of some object type
                      }
                 }
        }

    }
}

ref.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot dataSnapshotChildren : dataSnapshot.getChildren()) {
                final DatabaseReference reference = dataSnapshotChildren.child(pref.getString("user_uid", null)).getRef();
                for (int j = 0; j < stringArray.length; j++) {
                    Log.d("res_details activity", "stringArray: " + stringArray[j]);
                    reference.orderByChild("id").equalTo(stringArray[j]).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            Log.d("res_details activity", "dataSnapshot: " + dataSnapshot.getValue());
                            for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()) {
                                Restaurant restaurant = singleSnapshot.getValue(Restaurant.class);
                                Log.d("res_details activity", "restaurant: " + restaurant);
                                restaurantArrayList.add(restaurant);
                            }
                            Log.d("res_details activity", "restaurantArrayList: " + restaurantArrayList.size());
                            setValue(restaurantArrayList);
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {

                            Log.d("res_details activity", "databaseError: " + databaseError);

                        }
                    });

                }
            }

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

更新新代码段：

  ref.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            Log.d("res_details activity", "s: " + s);
            for (DataSnapshot dataSnapshotChildren : dataSnapshot.getChildren()) {

                for (int j = 0; j < stringArray.length; j++) {
                    Log.d("res_details activity", "reference: " + dataSnapshotChildren.getRef().toString());
                    Log.d("res_details activity", "stringArray: " + stringArray[j]);
                    databaseReference.orderByChild("id").equalTo(stringArray[j]).addChildEventListener(new ChildEventListener() {
                        @Override
                        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                            Log.d("res_details activity", "dataSnapshot: " + dataSnapshot.getValue());
                            for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()) {
                                Restaurant restaurant = singleSnapshot.getValue(Restaurant.class);
                                Log.d("res_details activity", "restaurant: " + restaurant);
                                restaurantArrayList.add(restaurant);
                            }
                            Log.d("res_details activity", "restaurantArrayList: " + restaurantArrayList.size());
                            setValue(restaurantArrayList);
                        }


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

                        }
....

我也尝试过ChildEventListener。现在它甚至不会触发嵌套的ChildEventListener。我现在没有任何结果。所有的引用都是正确的。查询正确。我不明白为什么snippet不检索数据。现在完全混乱了。

Answer 1

快照包含hashmap对象。节点A和节点B将被表示为具有相应值（Object）的键。看一看具有类似您的数据结构的示例。

ref.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                    HashMap<String, Long> m = (HashMap<String, Long>) snapshot.getValue();
                    Log.d("test", String.valueOf(m.get("id")));
                }
            }

请配置您的筛选条件，您就可以开始了！