Drop Down List or Spinner

public class MainActivity extends AppCompatActivity {

    Button button;
    Spinner spinner;
    EditText et;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = findViewById(R.id.btn_submit);
        et = findViewById(R.id.et_name1);
        spinner = findViewById(R.id.spinner1);

        // Spinner click listener
        //spinner.setOnItemSelectedListener(this);

        // Spinner Drop down elements
        List<String> categories = new ArrayList<String>();
        categories.add("Item 1");
        categories.add("Item 2");
        categories.add("Item 3");
        categories.add("Item 4");
        categories.add("Item 5");
        categories.add("Item 6");

        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, categories);

        // Drop down layout style - list view with radio button
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // attaching data adapter to spinner
        spinner.setAdapter(dataAdapter);

        //Drop Down Selected Event
        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                String sel_name = adapterView.getSelectedItem().toString();
                Toast.makeText(MainActivity.this, "Selected item : "+sel_name, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });

        //Button Submit Event
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String ddl_str =    String.valueOf(spinner.getSelectedItem());
                Toast.makeText(MainActivity.this, "Submitted : "+ddl_str, Toast.LENGTH_SHORT).show();
            }
        });

    }
}