无法在 Android Studio 中从 Firebase 实时数据库检索数据

Question

我想访问 img 但当我尝试时什么都不起作用

FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("med");

System.out.println(myRef);
System.out.println(database.getReference().child("med"));

database.getReference().child("med").addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        System.out.println("11111111");
    }

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

当我输入 onDataChange function 时，甚至没有打印 11111111

有什么问题，我如何获得我需要的数据？

Answer 1

试试这个

//Getter and Setter Class
   public class GetSet {
        public String img;
    
        public String getImg() {
            return img;
        }
    
        public void setImg(String img) {
            this.img = img;
        }
    }

创建时

final FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference ref = database.getReference().child("med").child("1");
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                GetSet adapter = dataSnapshot.getValue(GetSet.class);
                String image=adapter.getImg();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });