MainActivity.java

public class MainActivity extends AppCompatActivity {

    private WikipediaService wikipediaService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        wikipediaService = BaseService.getInstance().getWikiService();
        doSearch("Retrofit2");
    }

    private void doSearch(String query) {
        HashMap<String, String> options = new HashMap<>();
        options.put("srsearch", query);
        options.put("sroffset", "0");
        wikipediaService.search(options).enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                ResponseBody responseBody = response.body();
                if (responseBody != null) {
                  // Faça o restante das coisas aqui
                }
            }

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {

            }
        });
    }
}