Second response of the Web Service still has the value of the first

Question

The first thing I do in my application is send a message to the server, only to test if the connection is active and working. When receiving "ok" from the server I continue the application.

On the next screen I have to show a list of names, so I request the list. But it shows nothing the first time I start the screen, for something to appear I need to reload the screen, as when I turn the cell phone from portrait to landscape. It also appears if I put a button that forces the screen to be recreated.

After some tests I identified that the list was not appearing at first because the content she was receiving was "ok", which I get when making the connection check. I also identified that the Log responsible for showing what is coming from the requests made (in the function below attached) was correct, showing having received the list of names, but I also noticed that it is being shown after the Log that I put in the function that takes the information of the function below. How is that possible? I called a function and put an object to pick up the return, but the object has a value set before the return of my function. And this set value is the value of my last request.

I am using this library: Compile org.jbundle.util.osgi.wrapped:org.jbundle.util.osgi.wrapped.org.apache.http.client:4.1.2

Example: the initial request takes the right answer, hers. Also because it is the >first, already the request of the list that is the 2nd picks the answer of the 1st >request. If I reload the page this means that a new >request is made, right? That would be the list request. Now the list appears, >but it appears because she got the answer to the second request, which is also >a list. The answer to the 3rd request was not used, and if I make a >4th request this will take the information from the 3rd and so on.

Below is the code used to make the requests.

public class HttpConnection {
    public static String getSetDataWeb(String url, String method, String data) throws URISyntaxException {
        HttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);
        String answer = "";

        try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpGet request = new HttpGet();
            // Setamos nossa URI
            request.setURI(new URI(url));
            // Executamos nossa transação HTTP
            HttpResponse response = httpclient.execute(request);
            // Pegamos o conteúdo advindo como resposta e inserimos em um InputStream
            answer = EntityUtils.toString(response.getEntity());
            Log.d("RESPOSTAhttp", answer);    
        }
        catch(NullPointerException e){ e.printStackTrace(); }
        catch(ClientProtocolException e){ e.printStackTrace(); }
        catch(IOException e){ e.printStackTrace(); }
        return(answer);
    }
}

Function sending the requested URL to httpConnection

public static String comandaDetalhes(final String numCartao) throws SQLException {
        new Thread(){
            public void run(){
                try{
                    n = HttpConnection.getSetDataWeb("http://192.168.1.20:7070/comanda/detalhes/"+numCartao, "", "");
                } catch(Exception e) {

                }
            }
        }.start();

        return n;
    }

Function that asks for the list of names for the function that uses httpConnection

public List<Conteudo> getComandaDetalhes(){
        conteudosL = new ArrayList<>();
        //--------INICIO PEGAR ComandaS---------
        if(chamadas == 0){
            try {
                String teste = ComandaDAO.comandaDetalhes(getIntent().getStringExtra("NumeroCartao"));
                Log.d("DETALHESCOMANDA", teste);
                if(teste != "Comanda inexistente!"){
                    JSONObject jo = new JSONObject(teste);
                    chamadas =0;
                    JSONArray jaBebidas = new JSONArray(jo.getString("bebidas"));
                    Log.d("RESPOSTADetalhesBebidas", String.valueOf(jaBebidas));
                    JSONArray jaPratos = new JSONArray(jo.getString("pratos"));
                    Log.d("RESPOSTADetalhesPratos", String.valueOf(jaPratos));
                    JSONArray jaComanda = new JSONArray(jo.getString("comanda"));
                    Log.d("RESPOSTADetalhesComanda", String.valueOf(jaComanda));

                    for(int i = 0; i<jaBebidas.length(); i++){
                        jo = jaBebidas.getJSONObject(i);
                        Conteudo conteudos = new Conteudo();
                        conteudos.setNome("x" + jo.getInt("quantidade_bebidas_comanda")
                                + "  " + jo.getString("nome_bebida") + "  R$ "
                                + jo.getDouble("preco_bebida"));
                        conteudosL.add(conteudos);
                    }
                    for(int i = 0; i<jaPratos.length(); i++){
                        jo = jaPratos.getJSONObject(i);
                        Conteudo conteudos = new Conteudo();
                        conteudos.setNome("x" + jo.getInt("quantidade_pratos_comanda")
                                + "  " + jo.getString("nome_prato") + "  R$ "
                                + jo.getDouble("preco_prato"));
                        Log.d("PratoAdicionado", conteudos.getNome());
                        conteudosL.add(conteudos);
                    }
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        return conteudosL;
    }

Answer 1

From what I’m seeing, in your capacity comandaDetalhes, you start a Thread but immediately returns this variable n, which is the variable that will receive the value of the answer when it ends, hoping that n already has the expected value (or that it will only return when it has). That’s not gonna happen.

On the second call to comandaDetalhes, the value of n returned the value that was assigned in the first answer, ie the "OK". What you need to understand here is that return n (probably) wheel before of

n = HttpConnection.getSetDataWeb("http://192.168.1.20:7070/comanda/detalhes/"+numCartao, "", "");

Asynchronous programming is different. It’s no use trying to turn a code that uses Threads into sequential code that won’t work. The best is to learn the paradigm of truth otherwise you will always fall into these traps.

In addition, there are other problems, the most alarming being the fact that you are swallowing exceptions. This is a huge shot in the foot, because when the bug appear (and he going appear), you will need all the information and error message you can get.