Question

I’m trying to post data to URL by using Android App.

URL:

parameters:
“name” and “message”

I use the following code but it doesn’t work:

public void onClick(View v) {
    // Create a new HttpClient and Post Header

            // Create a new HttpClient and Post Header
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://comparch2011.appspot.com/");

            try {
                // Add your data
                List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
                nameValuePairs.add(new BasicNameValuePair("name", "DEV"));
                nameValuePairs.add(new BasicNameValuePair("message", "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
            }
     }

Answer 1

-first thing first : you should use adb logcat. It will give you real time logs of your phone on your computers, it is incredibly useful to know what is going on.

-I suspect that you are making these calls in an Activity and in this case the app is simply crashing because of that : their is a safeguard to prevent you from doing that. It raises errors ‘network on main thread’ when necessary (like here).
The problem is that Activities are ran on the main thread, the one that is also used for the UI. so when you make such a network call, all the UI is blocked until the function has returned (and since it is waiting for the website to respond it can take a couple of seconds, which is very bad for the usability of your app).

The solution is to use an AsyncTask . It is an easy to use class that will allow you to make asynchronous calls (ie calls that don’t block the UI).