java - Android Firebase 查询多个值

Question

我想获取类别为“abc”的医生的所有 uid(示例)，然后将这些检索到的 uid 存储到数组列表中。我想要与以下 sql 查询显示的结果相同的结果:
从医生中选择uid，其中类别=“abc”；

下一个 Activity 的代码写在下面

private void loadDoctors() {

    ArrayList<String> uid = getIntent().getStringArrayListExtra("doctor_list");

    for (int i =0;i<uid.size();i++){
        DatabaseReference doctors = FirebaseDatabase.getInstance().getReference("Doctors").child(uid.get(i));
        Adapter = new FirebaseRecyclerAdapter<DoctorModel, DoctorViewHolder>(
                DoctorModel.class,
                R.layout.doctors_home,
                DoctorViewHolder.class,
                doctors
        ) {
            @Override
            protected void populateViewHolder(final DoctorViewHolder viewHolder, final DoctorModel model, int position) {
                viewHolder.doctor_name.setText(model.getName());

                Glide.with(Doctors.this).load(model.getProfileimage()).into(viewHolder.doctor_image);

                viewHolder.qualification.setText(model.getQualification());

                viewHolder.rating.setText(model.getRating());

            }

        };
        Adapter.notifyDataSetChanged();
        doctors_list.setAdapter(Adapter);
    }

Answer 1

要解决此问题，请使用以下代码行:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference doctorsRef = rootRef.child("Doctors");
Query categoryQuery = doctorsRef.orderByChild("category").equalTo("Cardiology");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        List<String> uidList = new ArrayList<>();
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String uid = ds.getKey();
            uidList.add(uid);
        }

        //Do what you need to do with your list
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
categoryQuery.addListenerForSingleValueEvent(valueEventListener);

最后，您将得到一个包含 uid 的列表。还有一件事需要注意，因为 Firebease API 是异步的，所以您只能在 onDataChange() 方法中使用该列表。