Cant able to sync the variables inside a Threads android

Question

Boolean timer = false;

@Override
        protected Boolean doInBackground(String... params) {
            // TODO Auto-generated method stub
            downloadmanagerstart();
            System.out.println("return");

            boolean downloading = true;

            while (downloading) {
                DownloadManager.Query q = new DownloadManager.Query();
                q.setFilterById(download_id);

                Cursor cursor = downloadManager.query(q);
                cursor.moveToFirst();
                int bytes_downloaded = cursor
                        .getInt(cursor
                                .getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                int bytes_total = cursor
                        .getInt(cursor
                                .getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
                if (cursor.getInt(cursor
                        .getColumnIndex(DownloadManager.COLUMN_STATUS)) == DownloadManager.STATUS_SUCCESSFUL) {
                    downloading = false;
                }
                cursor.close();
                publishProgress(bytes_downloaded, bytes_total);
            }
            return true;
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            // TODO Auto-generated method stub

            final int bytes_downloaded = values[0];
            System.out.println(bytes_downloaded
                    + " Downloaded 1");

            int bytes_total = values[1];
            int dl_progress = (int) ((bytes_downloaded * 100l) / bytes_total);
            String totaldownload_str = android.text.format.Formatter
                    .formatFileSize(MainActivity.this, bytes_downloaded);
            current_tvm.setText(totaldownload_str);
            mProgressBar.setProgress((int) dl_progress);

            if (!timer) {
                Thread thread = new Thread() {
                    @Override
                    public void run() {

                        t = new Timer();
                        t.scheduleAtFixedRate(new TimerTask() {

                            @Override
                            public void run() {
                                // TODO Auto-generated method stub
                                runOnUiThread(new Runnable() {
                                    public void run() {

                                        System.out.println(bytes_downloaded
                                                + " Downloaded 2");
                                    }
                                });

                            }
                        }, 0, 1000);

                    }
                };
                thread.start();
                timer = true;
            }
        }

As you can see I have put two System.out.println(bytes_downloaded+ " Downloaded 1"); in onProgress andSystem.out.println(bytes_downloaded+ " Downloaded 2"); inside a thread on onProgress. The vale of bytes_downloaded is always 0 inside the thread why is this happening. I wanted it to be sync every second with the value bytes_downloaded in onProgress. thanks in advance.

Answer 1

Its 0 because its a final variable. Once its set, it can't change. So it will always be what you initially set it to. If you want to pass data like that use a member variable of the class (with synchronization if necessary), not a final or method level variable.

Additionally, this approach isn't needed. onProgressUpdate is already run on the UI thread- that's the point of the function. Why would you want to delay the UI update more, and why would you use such a convoluted way of doing so? I think you really don't understand the concepts of how threads, timers, and AsyncTasks work, because this code makes 0 sense.