Question

After reading a few posts and reading on the developers page about ASYNCTASK, I came up with the following code, and assigned it to a button:

private class TalkToServerTask extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        String response = "";
        try {
            InetAddress serverAddr = InetAddress.getByName(params[0]);
            Socket s = new Socket(serverAddr, Integer.valueOf(params[1]));

            PrintWriter out = new PrintWriter(new BufferedWriter(
                    new OutputStreamWriter(s.getOutputStream())), true);

            // WHERE YOU ISSUE THE COMMANDS

            out.println(params[2]);
            // BufferedReader input = new BufferedReader(
            // new InputStreamReader(s.getInputStream()));

            DataInputStream dataInputStream = null;
            dataInputStream = new DataInputStream(s.getInputStream());
            st = dataInputStream.readLine().toString();
            // String st = s.readLine();
            // st = input.readLine();
            // read line(s)

            s.close();
            return st;

        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return response;
    }

    @Override
    protected void onPostExecute(String result) {
        serverresponse = result;
    }

}

The idea being, that when a button is clicked, the ASyncTask sends the word “getDomains” to a console app running on my server, the server acts on this and sends back a string with the list of domains created on an email server.

I have verified that the server is receiving the command “getdomains”, and it in turn replies with a pipe-delimited string of domains. The problem being however, that I’ve set a Toast to pop up with the results of the socket transaction, and the toast shows nothing. If I hit the button again, the Toast shows the list of domains. To me, it seems as if the socket is first returning an empty

Here is the button code:

case R.id.btnDomains:
            SharedPreferences sp = PreferenceManager
                    .getDefaultSharedPreferences(this);
            IpAddress = sp.getString("ipaddress", "0.0.0.0");
            Serverport = sp.getString("tcpport", "12345");
            buttonpressed = "domains";
            // TalkToServerTask task = new TalkToServerTask();
            new TalkToServerTask().execute(IpAddress, Serverport, "getDomains");

            Intent buttonActivity = new Intent(MainActivity.this, Rules.class);
            buttonActivity.putExtra(MainActivity.DOMAINLIST, serverresponse);

            Toast.makeText(getApplicationContext(), serverresponse,
                    Toast.LENGTH_SHORT).show();

the variable “serverresponse” is what at first is showing empty, but then shows the list of servers.

Answer 1

As Thepoosh mentioned, AsyncTask is working on a separate thread.

Therefore the thread is being executed and didn’t get result yet when you first time press the button.

What you should do is to show the data in onPostExecute method. Also you should pass the context to your AsyncTask.

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

@Override
protected void onPostExecute(String result) {
    Intent buttonActivity = new Intent(context, Rules.class);
    buttonActivity.putExtra(MainActivity.DOMAINLIST, result);

    Toast.makeText(context.getApplicationContext(), result, Toast.LENGTH_SHORT).show();
}