Download a JSON string from a website with AsyncTask

Question

I have an android application and using AsyncTask I want to download a JSON file from a website.

So far I have

public class DownloaderTask extends AsyncTask<String, Void, String[]> {

private MyActivity myactivity;
private Context context;
private String rawFeed[] = new String[3];

DownloaderTask(MyActivity parent) {

    myactivity = parent;
    context = parent.getApplicationContext();
}

@Override
protected String[] doInBackground(String... params) {

    boolean complete = false;
    InputStream input = null;
    OutputStream output = null;
    HttpURLConnection connection = null;

    for (int i = 0; i < params.length; i++) {

        try {
            URL url = new URL(params[i]);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();

            input = connection.getInputStream();
        }
        catch (Exception e) {

        }
    }

    return rawFeed;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected void onPostExecute(String[] strings) {

    if (myactivity != null) {

        myactivity.setRefreshed(strings);
    }
}

Im not sure how to continue from here

The website I'm downloading from is : https://d396qusza40orc.cloudfront.net/android%2FLabs%2FUserNotifications%2Ftaylorswift.txt

and when you go to the site it's just a page with a bunch of text on it, a JSON file.

The parameters that get passed into the AsyncTask is an array of 3 strings, each string containing the URL that I need to download from

AsyncTasks have issues, mainly around the lifecycle of an App. Have you tried using the library Volley for this? You could even use GSON (if you need deserialising) inside a subclassed Volley class. See this SO post http://stackoverflow.com/questions/24537875/making-a-gson-request-using-volley — Graham Smith, Nov 04 '14 at 16:26
I want to use AsyncTask to get familiar with function of it. What kind of issues? Are they so bad that people generally don't use it? @GrahamSmith — masterCoder, Nov 04 '14 at 16:31

score 1 · Accepted Answer · answered Nov 04 '14 at 16:32

1

To read all the contents of an input stream I use:

String inputStreamToString(InputStream is)
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(is));
    StringBuilder stringBuilder = new StringBuilder();
    String line = null;
    try
    {
        while ((line = reader.readLine()) != null)
        {
            stringBuilder.append(line);
        }
        is.close();
    }
    catch (IOException e)
    { }
    return stringBuilder.toString();
}

Then, to parse it as a JSON you just can user the Java JSONObject constructing it with that string.

answered Nov 04 '14 at 16:32

JML

611
3
9

so getting an InputStream, the following code would read the contents? – masterCoder Nov 04 '14 at 16:35
if the content is text, yes (not sure what is the behaviour of this method if trying to read something else, preobably it'll work and generate a nonsense string) – JML Nov 04 '14 at 16:39
what if it's in a for loop? Where would you place the is.close()? – masterCoder Nov 04 '14 at 16:41
in your case, inside each interation of the loop, as you are opoening a new connection and getting a new InputStream in each iteration. Normally, you should add a finally statement after the catch, and (if the input isn't null) close it there, to asure that it's closed not matter the result of the try-catch – JML Nov 04 '14 at 16:44
pretty sure my asynctask returned a null string array...going to look into it in more depth in a bit – masterCoder Nov 04 '14 at 16:51
i forgot to assign the reader to my string, after that it worked! – masterCoder Nov 04 '14 at 19:05

Download a JSON string from a website with AsyncTask

1 Answers1