AndroidでSpinner(listbox)を出す（動的に値を生成）

activity_main.xml

    <Spinner
        android:id="@+id/spn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

        createSpinner();
    }

    private void createSpinner(){
        ArrayList<String> list = new ArrayList<>();
        SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd", Locale.JAPAN);
        Calendar cal = Calendar.getInstance();

        for (int i = 0; i < 11; i++){
            cal.set(Calendar.DAY_OF_MONTH, cal.get(Calendar.DAY_OF_MONTH) + 1);
            list.add(format.format(cal.getTime()));
        }

        ArrayAdapter<String> adapter = new ArrayAdapter<>(
                this, android.R.layout.simple_spinner_dropdown_item, list
        );

        Spinner spn = (Spinner) findViewById(R.id.spn);
        spn.setAdapter(adapter);
    }
}