Async HTTP post android

Question

I am using an application where i just need to download a pair of coordinates for google maps from a mysql server. I can do this successfully using php and a normal httpost but my app freezes for a few seconds when i do it.

I read that you need to make httppost asycronous in order to avoid that freezing until the server finishes the prossess and sends the results.

The point is that i need that results in a json array like the normal httpost.

For example if i had this httppost.

HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://www.yoursite.com/script.php");

try {
    // Add your data
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
    nameValuePairs.add(new BasicNameValuePair("id", "12345"));
    nameValuePairs.add(new BasicNameValuePair("stringdata", "AndDev is Cool!"));
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

    // Execute HTTP Post Request
    HttpResponse response = httpclient.execute(httppost);
} catch (ClientProtocolException e) {
    // TODO Auto-generated catch block
} catch (IOException e) {
    // TODO Auto-generated catch block
}

String result11 = null;
// convert response to string
try {
    BufferedReader reader = new BufferedReader(new InputStreamReader(is11, "iso-8859-1"), 8);
    StringBuilder sb = new StringBuilder();
    sb.append(reader.readLine() + "\n");
    String line = "0";
    while ((line = reader.readLine()) != null) {
        sb.append(line + "\n");
    }
    is11.close();
    result11 = sb.toString();
} catch (Exception e) {
    Log.e("log_tag", "Error converting result " + e.toString());
}

// parsing data
try {
    JSONArray jArray1 = new JSONArray(result11);
} catch (JSONException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

How can i convert that to an asynchronous post so i can avoid the freeze ?

I have no idea how your code could even compile as it is, but please use EntityUtils.toString(response.getEntity()) instead of having your own BufferedReader-n-StringBuilder party. The former is less code, has correct error handling and obeys the character encoding sent by the server. — Philipp Reichart
– Philipp Reichart, Commented Mar 31, 2012 at 9:27

SecStone · Accepted Answer · 2012-03-31 09:13:41Z

There is a nice class AsyncTask which can be used to easily run asynchronous tasks. If you embed your code in such a subclass, you might end up with this:

public class FetchTask extends AsyncTask<Void, Void, JSONArray> {
    @Override
    protected JSONArray doInBackground(Void... params) {
        try {
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://www.yoursite.com/script.php");

            // Add your data
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
            nameValuePairs.add(new BasicNameValuePair("id", "12345"));
            nameValuePairs.add(new BasicNameValuePair("stringdata", "AndDev is Cool!"));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

            // Execute HTTP Post Request
            HttpResponse response = httpclient.execute(httppost);

            BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            sb.append(reader.readLine() + "\n");
            String line = "0";
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            reader.close();
            String result11 = sb.toString();

            // parsing data
            return new JSONArray(result11);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    @Override
    protected void onPostExecute(JSONArray result) {
        if (result != null) {
            // do something
        } else {
            // error occured
        }
    }
}

You can start the task using:

new FetchTask().execute();

Additional resources:

krishnakumarp · Accepted Answer · 2012-06-15 08:43:03Z

3

I suggest using android-async-http ( http://loopj.com/android-async-http/ ) library. It makes android async http calls simple and elegant.

answered Jun 15, 2012 at 8:43

krishnakumarp

9,3254 gold badges53 silver badges58 bronze badges

2 Comments

richey Over a year ago

unfortunately there are only few demos available that make it easier for a newbie to understand how to put everything together, like in this case to post data to an URL and to process a response utilizing JSON. I understand it's all there and seems to be very powerful and smart, but a few more examples would definitely help.

krishnakumarp Over a year ago

I've used it and found it easy to start with. I started with the code sample given in "Recommended Usage" section in loopj.com/android-async-http. I'd learn and do certain things along the way, such as persisting the cookies, making it work with SSL (trusted and untrusted), adding a check to see if the device is online or not etc. I feel all of these issues will have to be dealt with whether you use this library or Android API.

user932887 · Accepted Answer · 2012-03-31 09:12:44Z

Rather than just starting a new thread, it's a better idea to go with a full-fledged AsyncTask. It provides much greater control of things.

private class DoPostRequestAsync extends AsyncTask<URL, Void, String> {
     protected String doInBackground(URL url) {
        //Your download code here; work with the url parameter and then return the result
        //which if I remember correctly from your code, is a string.
        //This gets called and runs ON ANOTHER thread
     }

     protected void onPostExecute(String result) {
         //This gets called on the interface (main) thread!
         showDialog("Done! " + result);
     }
 }

Place the new class implementation inside of your desired Activity's class. For more info on AsyncTask please follow this link:

http://developer.android.com/reference/android/os/AsyncTask.html

Dave Chen · Accepted Answer · 2014-10-07 02:27:40Z

2

Assuming you want to do this on a button click:

public void onClick(View v) {
  new Thread(new Runnable() {
        public void run() {
            //your code here
        }
    }).start();
}

Basically, you are putting IO intensive operation in a separate thread (not your UI thread) so that the UI does not freeze.

edited Oct 7, 2014 at 2:27

Dave Chen

11k8 gold badges42 silver badges72 bronze badges

answered Mar 31, 2012 at 9:00

ACC

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1 Comment

user878813 Over a year ago

trying in a while and ill answer you. Thanks a lot for your response :)

koush · Accepted Answer · 2013-07-11 01:15:06Z

1

Use an async http library like ion. https://github.com/koush/ion

All the threading and asynchronous boilerplate will be handled for you.

This is your same code, asynchronous, using Ion. Much simpler:

Ion.with(context)
.load("http://www.yoursite.com/script.php")
.setBodyParameter("id", "12345")
.setBodyParameter("stringdata", "AndDev is Cool!")
.asJsonArray()
.setCallback(new FutureCallback<JsonArray> {
  void onCompleted(Exception e, JsonArray result) {
    // do something with the result/exception
  }
});

answered Jul 11, 2013 at 1:15

koush

2,96230 silver badges31 bronze badges

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