This will show an dialog error box if there is not network connectivity
ConnectivityManager connMgr = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
// fetch data
} else {
new AlertDialog.Builder(this)
.setTitle("Connection Failure")
.setMessage("Please Connect to the Internet")
.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
})
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
}