Android: AsyncTask and reading internet data

Question

I have written a code to download some data from internet. Than i wanted to put it into asyncTask. And after that downloading stopped working. It looks like it cant finish try{} part so skips to exeption.

From main activity "Nekaj" i call loadData() class, which extends AsyncData. From there i call "oto" class inside try command. "oto" class is used to read stuff from internet and returns array of strings. This worked when i called oto class directly from "Nekaj"class. What did I do wrong with using AsyncTask? Here is the code:

    public class Nekaj extends Activity {

TextView Tkolo, Tbroj1;
String[] brojevi_varijabla;
String privremena_varijabla = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.bez_provjere_739);
    Tkolo = (TextView) findViewById(R.id.Xkolo);
    Tbroj1 = (TextView) findViewById(R.id.Xbroj1);

    /*
     * try { privremena_varijabla = test.kolo_739();
     * Tkolo.setText(privremena_varijabla); } catch (Exception e) { // TODO
     * Auto-generated catch block e.printStackTrace(); }
     */

    new loadData().execute();
}

public class loadData extends AsyncTask<String, Integer, String> {

    @Override
    protected String doInBackground(String... arg0) {
        // TODO Auto-generated method stub

        Oto test = new Oto();

        try {
            brojevi_varijabla = test.brojevi_739();
            if (Integer.valueOf(brojevi_varijabla[0]) > 10) {
                Tbroj1.setText("" + brojevi_varijabla[0]);
            } else {
                Tbroj1.setText(" " + brojevi_varijabla[0]);
            }

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }
}

public class Oto {

    public String[] brojevi_739() throws Exception {

        int i = 0;
        int uvjet = 0;
        int varijabla = 0;
        char[] znak = { '>', '<' };
        BufferedReader in = null;
        String data[] = null;
        String provjera = "date-info";
        int[] polje = new int[2];

        try {
            HttpClient klijent = new DefaultHttpClient();
            URI webstranica = new URI(
                    "https://www.aaa.bb");
            HttpGet zahtjev = new HttpGet();
            zahtjev.setURI(webstranica);
            HttpResponse odgovor = klijent.execute(zahtjev);
            in = new BufferedReader(new InputStreamReader(odgovor
                    .getEntity().getContent()));
            StringBuffer brojevi = new StringBuffer("");
            String brojevi_string = null;
            String neki_string = null;
            String red = "";

            in.skip(21000);
            while ((red = in.readLine()) != null) {
                varijabla = red.indexOf(provjera);

                if (varijabla != -1) {

                    // 1. KOLO
                    if (uvjet == 0) { // onda sadrži taj
                                        // substring
                                        // !!!!
                        red = in.readLine(); // sada string red sadrži ono
                                                // što
                                                // želim, još moram samo to
                                                // izrezati!!
                        do {
                            if (i == 0) {
                                varijabla = red.indexOf(znak[i]);
                            }

                            else {
                                varijabla = red.indexOf(znak[i], polje[0]);
                            }

                            if (varijabla != -1) // ako taj znak postoji u
                                                    // stringu
                            {
                                if (i == 0) {
                                    polje[i] = varijabla + 1;
                                }

                                else {
                                    polje[i] = varijabla;
                                }
                                i++;
                            }

                        } while (i <= 1);

                        neki_string = red.substring(polje[0], polje[1]);
                        Tkolo.setText(neki_string);

                        provjera = "Dobitna kombinacija";
                        uvjet++;
                        continue;
                    }


                }
            }

            in.close();

            brojevi_string = brojevi.toString();

            data = brojevi_string.split("\n");

            return data;

        } finally {
            if (in != null) {
                try {
                    in.close();
                    return data;
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }


}}

Answer 1

What you are doing wrong is Tbroj1.setText() inside the doInBackground() method. What you have to do is to use the onPostExecute method to post your data on the UI:

public class loadData extends AsyncTask<String, Integer, Boolean> {
 protected Long doInBackground(String... arg0) {
     Oto test = new Oto();
     Boolean result = false;

    try {
        brojevi_varijabla = test.brojevi_739();
        result = true;
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return result;
 }


 protected void onPostExecute(Boolean result) {
     if(result){
        if (Integer.valueOf(brojevi_varijabla[0]) > 10) {
            Tbroj1.setText("" + brojevi_varijabla[0]);
        } else {
            Tbroj1.setText(" " + brojevi_varijabla[0]);
        }
     }

 }
}

Answer 2

Actually, You are trying to update UI in doInBackGround() of your AsyncTask, so its not allowed (doInBack.. runs in non UI Thread..), So put the UI updation code in onPostExecute() of AsyncTask..

Try this and let me know what happen..

public class loadData extends AsyncTask<String, Integer, String> {

    @Override
    protected String doInBackground(String... arg0) {
        // TODO Auto-generated method stub
        Oto test = new Oto();
        try {
            brojevi_varijabla = test.brojevi_739();       
            if(brojevi_varijabla != null)
            return brojevi_varijabla[0];
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

 @Override
    protected void onPostExecute(String result)
    {
        if(result != null)
          {
            if (Integer.valueOf(result) > 10) {
                Tbroj1.setText("" + result;
            } else {
                Tbroj1.setText(" " + result);
            }
          }
     }
}

Answer 3

You can't manipulate UI elements directly on a non-UI (background) thread, which is where doInBackground() always runs. The usual way of using AsyncTask is to get the data in doInBackground(), return it as a value, and then process the UI changes in onPostExecute(). For example:

public class loadData extends AsyncTask<String, Integer, String> {

@Override
protected String doInBackground(String... arg0) {
    Oto test = new Oto();

    try {
        brojevi_varijabla = test.brojevi_739();
        if (Integer.valueOf(brojevi_varijabla[0]) > 10) {
            return "" + brojevi_varijabla[0];
        } else {
            return " " + brojevi_varijabla[0];
        }

    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return null;
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    if (result != null) Tbroj1.setText(result);
}

}

Answer 4

use onPostExecute(Void result1) {}

to catch the result and perform the action required over there