带有Firebase的Android Spinner

Question

如何从Firebase检索微调器中的值。

d2.child("Course").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                final List<String> Course = new ArrayList<String>();
            for (DataSnapshot areaSnapshot: dataSnapshot.getChildren()) {
                String CName = areaSnapshot.child("name").getValue(String.class);
                Course.add(CName);
            }
            spinner = (MaterialSpinner) findViewById(R.id.reg_Course);
            ArrayAdapter<String> areasAdapter = new ArrayAdapter<String>(RegisterActivity.this, android.R.layout.simple_spinner_item,  Course);
            areasAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(areasAdapter);

        }

这是代码的样子，但微调框中没有任何显示