MainActivity.java

public class MainActivity extends AppCompatActivity {

    private ApiService apiService = HttpClient.getApiService();
    private TextView tvStatus, tvInfo;
    private Button btnHttpRequest, btnReset;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tvStatus = findViewById(R.id.tvStatus);
        tvInfo = findViewById(R.id.tvInfo);
        btnHttpRequest = findViewById(R.id.btnHttpRequest);
        btnReset = findViewById(R.id.btnReset);

        btnHttpRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getFirstTodo();
            }
        });

        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                tvStatus.setText("Press below button to fire HTTP request");
                tvInfo.setText("No data");
            }
        });
    }

    private void getFirstTodo() {
        tvStatus.setText("HTTP Request in progress.");
        apiService.getFirstTodo()
                .observeOn(SchedulerProvider.ui())
                .subscribeOn(SchedulerProvider.io())
                .subscribe(new Consumer<Todo>() {
                    @Override
                    public void accept(Todo todo) throws Exception {
                        // Update the UI
                        tvStatus.setText("Request Completed! \nhttps://jsonplaceholder.typicode.com");
                        tvInfo.setText(todo.getFormattedInfo());
                    }
                }, new Consumer<Throwable>() {
                    @Override
                    public void accept(Throwable throwable) throws Exception {
                        // Throw error
                        throwable.printStackTrace();
                    }
                });
    }
}