I want to retrieve data from my Realtime Database server so that I can update values based on the reg-id (stored this as a child string, not as Auth) I have saved for the user.

I have done this till now

    private void updateDatatoFirebase(String regid, String doctor_name, String city,String speciality) {
    Map<String, Object> update=new HashMap<>();
    update.put("doctor",doctor_name);
    update.put("city",city);
    update.put("speciality",speciality);

    DatabaseReference dbref=FirebaseDatabase.getInstance().getReference();
    dbref.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            
            for (DataSnapshot ds : snapshot.getChildren()){
                key = snapshot.getKey();


                if(checkid.equalsIgnoreCase(regid))
                {
                    dbref.updateChildren(update);
                    Toast.makeText(need_help.this, "Data in Database updated", Toast.LENGTH_SHORT).show();
                }

                else
                    Toast.makeText(need_help.this, "No such id found", Toast.LENGTH_SHORT).show();
               
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {
           
            Toast.makeText(need_help.this, "Fail to add data "   error, Toast.LENGTH_SHORT).show();
        }
    });
}

to update but it won't update and I have saved data like this

private void addDatatoFirebase(String regid, String doctor_name, String city,String speciality) {
    
    root=firebaseDatabase.getReference().child("RegId").child(regid);
    HashMap<String, String> usermap=new HashMap<>();
    usermap.put("doctor",doctor_name);
    usermap.put("city",city);
    usermap.put("speciality",speciality);
    root.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
           
            root.push().setValue(usermap);

            
            Toast.makeText(need_help.this, "Data in Database updated", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {
          
            Toast.makeText(need_help.this, "Fail to add data "   error, Toast.LENGTH_SHORT).show();
        }
    });

CodePudding user response：

To be able to update all children under a particular node, for instance, 1234, you have to pass to the following method, 1234 as the first argument:

private void updateDatatoFirebase(String regid, String doctor_name, String city,String speciality) {
    Map<String, Object> update=new HashMap<>();
    update.put("doctor",doctor_name);
    update.put("city",city);
    update.put("speciality",speciality);

    DatabaseReference dbref=FirebaseDatabase.getInstance().getReference();
    dbref.child("RegId").child(regid).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            for (DataSnapshot ds : snapshot.getChildren()){
                ds.getRef().updateChildren(update).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if (task.isSuccessful()) {
                            Toast.makeText(need_help.this, "Data in Database updated", Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(need_help.this, "Failed with an error: "   task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                });
                
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {
            Toast.makeText(need_help.this, "Fail to add data "   error, Toast.LENGTH_SHORT).show();
        }
    });
}

Things to notice:

• I have added two extra calls .child("RegId") and .child(regid) call right after the root reference.
• I have used the ds to call getRef() and then .updateChildren(update).
• I have attached a listener to see if something goes wrong when updating the children under 1234.