AsyncTask returning null

Question

I'm using jsoup to parse a html code, I'm using obviously an AsyncTask but it's returning null (javanullpointerexception).

private class LoadDocument extends AsyncTask<String, Void, Document>
    {

        ProgressDialog mProgressDialog;



        @Override
        protected void onPreExecute() {
            mProgressDialog = ProgressDialog.show(Parser.this, "Loading...", "Recuperation donnees...");
        }



        @Override
        protected Document doInBackground(String... url) {
            url[0] = urll;

                try {
                    document = Jsoup.connect(url[0])
                            .data("query", "Java")
                            .userAgent("Mozilla")
                            .cookie("auth", "token")
                            .timeout(10000)
                            .post();
                } catch (IOException e) {
                    e.printStackTrace();
                }



            return document;
        }

        @Override
        protected void onPostExecute(Document result) {
             document=result;
            mProgressDialog.dismiss();

        }


}

And then to execute a task and return the document:

urll= //the website
document=new LoadDocument().execute(urll).get();

I guess that document is always null. What's going wrong in my code? Thank you for helping.

code looking fine you can try to put log inside doInBackground and check what you are getting in document — ρяσѕρєя K, Dec 22 '12 at 17:55
@ρяσѕρєя K:i put `Log.d("DOCUMENTT",document.toString());` just before the return statement and it's not executed. — androniennn, Dec 22 '12 at 17:57

wtsang02 · Answer 1 · 2012-12-22T18:10:37.043

2

There's nothing wrong with the code. Please log it with Document.text(); Can you try changing the one line to check: doc = Jsoup.connect("http://stackoverflow.com").get(); then use Document.text() in your log.

edited Dec 22 '12 at 18:10

answered Dec 22 '12 at 17:57

wtsang02

18,603
10
49
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`Log.d("DOCUMENT",document.text());` just after the `execute(url).get()` and nothing is displayed. Compiler does not arrive in that line. – androniennn Dec 22 '12 at 18:00
Your using execute(url).post() , not .get(), there different. – wtsang02 Dec 22 '12 at 18:01
yes, in `doInBackground` I'm using post(), and to have the document I'm using get(). You can notice that in my code above. – androniennn Dec 22 '12 at 18:04
My bad, I though your .get() meaning the HTTP method. – wtsang02 Dec 22 '12 at 18:13

patheticpat · Answer 2 · 2012-12-22T17:55:43.170

1

AsyncTask.execute() doesn't return the result. Instead it returns a reference to the task itself. The result is only available to the onPostExecute method once the task completed.

edited Dec 22 '12 at 17:55

answered Dec 22 '12 at 17:49

patheticpat

861
6
11

And i think that `execute(URL).get()` returns result value, no ? – androniennn Dec 22 '12 at 17:55
Oops, you are right, `get()` waits for the task to finish and retrieves the result. Although this pretty much defeats the purpose of an `AsyncTask`. It doesn't make sense to start the work in the background and then block to wait until it finished. – patheticpat Dec 22 '12 at 17:59

score 0 · Answer 3 · answered Dec 22 '12 at 17:49

0

many can go wrong in that code:

url[0]

can be an empty string...

I would split that statement to:

Jsoup.connect(url[0])

+

.data("query", "Java")
                            .userAgent("Mozilla")
                            .cookie("auth", "token")
                            .timeout(10000)

.post();

at least

answered Dec 22 '12 at 17:49

But as you see i initalized url[0] to urll `url[0] = urll;` so url[0] has always some String on it. – androniennn Dec 22 '12 at 17:52

score 0 · Answer 4 · answered Dec 22 '12 at 18:00

0

Problem is somewhere inside your try catch block around the Jsoup code. Instead of printStackTrace, log something with Log.e, and then check your LogCat output.

answered Dec 22 '12 at 18:00

tom

18,953
4
35
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Believe me, there is not Log that's displayed, just the URL Log before execution. – androniennn Dec 22 '12 at 18:05
Don't know, perhaps that line is not correct :/ `document=new LoadDocument().execute(urll).get();` – androniennn Dec 22 '12 at 18:08

AsyncTask returning null

4 Answers4