how to stop asynctask when internet is connected but no internet access in android

String url = "http://xyzcloud.com/xyz/xyz.php";

this the url am trying to get the data from cloud,if internet is connected then async task will execute
i wrote this method for checking wether internet is connected or not, here in my mobile wifi is connetecd when am trying to execute it is giving exception

public boolean checkOnlineState()
    {
        boolean val = false;
        ConnectivityManager CManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo NInfo = CManager.getActiveNetworkInfo();

        if (NInfo != null && NInfo.isConnectedOrConnecting()) {
            try {
                if (InetAddress.getByName(url).isReachable(10000))
                {
                    // host reachable
                    val=true;
                    Log.e("checkOnlineState", "" + val);
                }
                else
                {

                    // host not reachable
                    val = false;
                    Log.e("checkOnlineState", "" + val);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return val;

    }