Can an Android AsyncTask doInBackground be synchronized to serialize the task execution?

Question

Is it possible to make AsyncTask.doInBackground synchronized - or achieve the same result in another way?

Answer 1

public class RestAsyncTask1 extends AsyncTask {

    private AsyncTaskCompleteListener callback;
    private Context context;
    private String method;
    private static final AtomicInteger PROGRESS_NUM = new AtomicInteger(0);
    private static ProgressDialog PROGRESS_DIALOG;

    public RestAsyncTask1(Context context, AsyncTaskCompleteListener callback, String method) {
        this.callback = callback;
        this.context = context;
        this.method = method;
    }

    public static String format(String url, String... params) {
        String[] encoded = new String[params.length];

        for (int i = 0; i < params.length; i++) {
            encoded[i] = Uri.encode(params[i]);
        }

        return String.format(url, (String[]) encoded);
    }

    @Override
    protected void onPreExecute() {
        int x = PROGRESS_NUM.getAndIncrement();

        if (x == 0) {
            String title = "M_yug";
            PROGRESS_DIALOG = new ProgressDialog(context);
           // PROGRESS_DIALOG.setTitle(title);
            PROGRESS_DIALOG.setIndeterminate(true);
            PROGRESS_DIALOG.setCancelable(false);
            PROGRESS_DIALOG.setOnCancelListener(null);
            PROGRESS_DIALOG.setMessage("Loading. Please wait...");
            PROGRESS_DIALOG.show();
        }
    }

    @Override
    protected String doInBackground(String... params) {
        String url = params[0];
        String response = null;
        HttpURLConnection connection = null;

        if (params.length > 1) {
            if (method.equals(Method.GET)) {
                url = format(url, (String[]) Arrays.copyOfRange(params, 1, params.length));
            } else if (params.length > 2) {
                url = format(url, (String[]) Arrays.copyOfRange(params, 1, params.length - 1));
            }

            try {
                URL call = new URL(url);
                connection = (HttpURLConnection) call.openConnection();
                connection.setRequestProperty("Content-Type", "application/json");
                //connection.setRequestProperty("M-Yug", Utilities.VERSION);
                connection.setRequestMethod(method);
                connection.setDoOutput(true);

                if (method.equals("POST")) {
                    BufferedOutputStream outputStream = new BufferedOutputStream(connection.getOutputStream());
                    outputStream.write(params[params.length - 1].getBytes());
                    outputStream.flush();
                }

                int status = connection.getResponseCode();

                if (status == HttpURLConnection.HTTP_OK) {
                    InputStream is = connection.getInputStream();
                    response = readValue(is);
                } else if (status == 400) {
                    InputStream is = connection.getErrorStream();
                    BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                    StringBuilder builder = new StringBuilder();
                    String line;

                    while ((line = reader.readLine()) != null) {
                        builder.append(line);
                    }

                    reader.close();
                    Toast.makeText(context, "" + builder.toString(), Toast.LENGTH_SHORT).show();
                }

                connection.disconnect();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (connection != null) {
                    connection.disconnect();
                }
            }
        }

        return response;
    }

    @Override
    protected void onPostExecute(String s) {
        int x = PROGRESS_NUM.decrementAndGet();

        if (x == 0 && PROGRESS_DIALOG != null && PROGRESS_DIALOG.isShowing()) {
            PROGRESS_DIALOG.dismiss();
        }

        if (s!=null) {
            String resopnse=s.toString();
            callback.onSuccess(resopnse);
        } else {
           Toast.makeText(context,"Server Not Responding",Toast.LENGTH_SHORT).show();
        }
    }

    private String readValue(InputStream is) {
        BufferedReader br = null;
        StringBuilder sb = new StringBuilder();
        String line;

        try {
            br = new BufferedReader(new InputStreamReader(is));

            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
        } catch (Exception e) {
        }

        return sb.toString();
    }

    enum Method {
        GET, POST
    }
}