Android下如何从Firebase中获取基于不同子对象的数据总量

DatabaseReference ref = FirebaseDatabase.getInstance().getReference("your_node");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        long total = dataSnapshot.getChildrenCount();
        // 使用total变量
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // 处理错误
    }
});

FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("your_collection")
  .get()
  .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
      @Override
      public void onComplete(@NonNull Task<QuerySnapshot> task) {
          if (task.isSuccessful()) {
              long total = task.getResult().size();
              // 使用total变量
          } else {
              // 处理错误
          }
      }
  });