How to perform AsyncTask for checking internet connection

Question

I have the following code, and what I'm trying to do is to programmatically check if there is an internet connection or not.
Since I'm getting a NetworkOnMainThreadException, and have been advised to use AsyncTask.
I want to perform network operation on hasActiveInternetConnection(Context context)and return true if connected to a network, else false .
How do I do this using AsyncTask?

 public class NetworkUtil extends AsyncTask<String, Void, String>{
        Context context;

        public NetworkUtil(Context context){
            this.context = context;
         }

    private ProgressDialog dialog;

    @Override
    protected void onPreExecute() {

        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... arg0) {
        if (new CheckNetwork(context).isNetworkAvailable()) 
        {
             try {
                 HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection());
                 urlc.setRequestProperty("User-Agent", "Test");
                 urlc.setRequestProperty("Connection", "close");
                 urlc.setConnectTimeout(1500); 
                 urlc.connect();
                 boolean url= (urlc.getResponseCode() == 200);
                 String str = String.valueOf(url);
                 return str;
             } catch (IOException e) {

             }
         } 


            // your get/post related code..like HttpPost = new HttpPost(url);
         else {
            Toast.makeText(context, "no internet!", Toast.LENGTH_SHORT).show();
        }


        return null;
    }
    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        if (dialog.isShowing()) {
            dialog.dismiss();
        }
    }
    }

Answer 1

use this class for checking internet connectivity...

public class CheckNetwork {
private Context context;

public CheckNetwork(Context context) {
    this.context = context;
}

public boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager = (ConnectivityManager) context
            .getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager
            .getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}

}

then.....

use the this ASynTask for httppost.

public class NetworkUtil extends AsyncTask<String, Void, String> {

private ProgressDialog dialog;

@Override
protected void onPreExecute() {
    dialog = new ProgressDialog(YourActivity.this);
    dialog.setMessage("Loading...");
    dialog.setCancelable(false);
    dialog.show();
    super.onPreExecute();
}

@Override
protected String doInBackground(String... arg0) {
    if (new CheckNetwork(YourActivity.this).isNetworkAvailable()) {
        // your get/post related code..like HttpPost = new HttpPost(url);
    } else {
        // No Internet 
        // Toast.makeText(YourActivity.this, "no internet!", Toast.LENGTH_SHORT).show();
    }
    return null;
}
@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    if (dialog.isShowing()) {
        dialog.dismiss();
    }
}

Answer 2

Your AsyncTask should look like this:

 private class NetworkUtilTask extends AsyncTask<Void, Void, Boolean>{
    Context context;

    public NetworkUtilTask(Context context){
        this.context = context;
     }

     protected Boolean doInBackground(Void... params) {
         return hasActiveInternetConnection(this.context);
     }
     protected void onPostExecute(Boolean hasActiveConnection) {
         Log.d(LOG_TAG,"Success=" + hasActiveConnection);
     }
 }

You would then execute it like the following:

NetworkUtilTask netTask = new NetworkUtilTask(context);
netTask.execute();

Answer 3

There is no way to get an Internet connexion state, you will always have the network connection state.

But I found a pretty nice answer here: you send a request to google.com !! :) you can also try to ping to google by unix commandes if you want !!

here the guy is using a thread , and waiting a little bit for the answer, then returning a boolean . you do your staff in the handler . this is his code :

public static void isNetworkAvailable(final Handler handler, final int timeout) {
    // ask fo message '0' (not connected) or '1' (connected) on 'handler'
    // the answer must be send before before within the 'timeout' (in milliseconds)

    new Thread() {
        private boolean responded = false;   
        @Override
        public void run() { 
            // set 'responded' to TRUE if is able to connect with google mobile (responds fast) 
            new Thread() {      
                @Override
                public void run() {
                    HttpGet requestForTest = new HttpGet("http://m.google.com");
                    try {
                        new DefaultHttpClient().execute(requestForTest); // can last...
                        responded = true;
                    } 
                    catch (Exception e) {
                    }
                } 
            }.start();

            try {
                int waited = 0;
                while(!responded && (waited < timeout)) {
                    sleep(100);
                    if(!responded ) { 
                        waited += 100;
                    }
                }
            } 
            catch(InterruptedException e) {} // do nothing 
            finally { 
                if (!responded) { handler.sendEmptyMessage(0); } 
                else { handler.sendEmptyMessage(1); }
            }
        }
    }.start();
}

Then, I define the handler:

Handler h = new Handler() {
    @Override
    public void handleMessage(Message msg) {

        if (msg.what != 1) { // code if not connected

        } else { // code if connected

        }   
    }
};

...and launch the test:

isNetworkAvailable(h,2000); // get the answser within 2000 ms