Android- download file + status bar notification slowing down phone

Question

I currently have an asynctask which downloads a mp3 from a server. When the user starts to download it, a status bar notification is created. This displays the prog

Answer 1

I had similar issue once, I solved it using CountDownTimer.

Similar to how @superfell suggested, you can call progress update of AsyncTask regularly while downloading file. And call the Notification Manager only at specific interval.

After calling start() of CountDownTimer, it will call onTick() function after every fixed interval of time, and will call onFinish() either when timer is timed out or when called explicitly. cancel() function will only cancel the timer and will not call onFinish() method.

class DownloadMaterial extends AsyncTask<String, String, String> {

    CountDownTimer cdt;
    int id = i;
    NotificationManager mNotifyManager;
    NotificationCompat.Builder mBuilder;

    @Override
    protected void onPreExecute() {
        /**
         * Create custom Count Down Timer
         */
        cdt = new CountDownTimer(100 * 60 * 1000, 500) {
            public void onTick(long millisUntilFinished) {
                mNotifyManager.notify(id, mBuilder.build());
            }

            public void onFinish() {
                mNotifyManager.notify(id, mBuilder.build());
            }
        };
    }

    @Override
    protected String doInBackground(String... strings) {
        /**
         * Start timer to update Notification
         * Set Progress to 20 after connection
         * Build Notification
         * Increment Progress
         * Download and Save file
         */
        try {
            mNotifyManager =
                    (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
            mBuilder = new NotificationCompat.Builder(context);
            mBuilder.setContentTitle("Downloading File")
                    .setContentText(file_name)
                    .setProgress(0, 100, false)
                    .setOngoing(true)
                    .setSmallIcon(R.mipmap.ic_launcher)
                    .setPriority(Notification.PRIORITY_LOW);

            // Initialize Objects here
            publishProgress("5");
            mNotifyManager.notify(id, mBuilder.build());
            cdt.start();

            // Create connection here
            publishProgress("20");

            // Download file here
            while ((count = input.read(data)) != -1) {
                total += count;
                publishProgress("" + (int) (20 + (total * 80 / fileLength)));
                output.write(data, 0, count);
            }
        } catch (Exception e) {
            return "Failed";
        }
        return "Success";
    }

    @Override
    protected void onProgressUpdate(String... values) {
        /**
         * Update Download Progress
         */
        mBuilder.setContentInfo(values[0] + "%")
                .setProgress(100, Integer.parseInt(values[0]), false);
    }

    @Override
    protected void onPostExecute(String s) {

        String title;
        if (s.equals("Success")) {
            title = "Downloaded";
        } else {
            title = "Error Occurred";
        }
        mBuilder.setContentTitle(title)
                .setContentInfo("")
                .setOngoing(false)
                .setProgress(0, 0, false);
        cdt.onFinish();
        cdt.cancel();
    }
}

It is a good practice to call onFinish() first and then call cancel().

Answer 2

I had the same issue that I was not able to update the progress bar notification even with an interval of 3 seconds so after hours of digging I came to realize the fact that whenever we update the notification the RemoteView object must be re-instantiated and re-initialized to the Notification object's contentView. After doing this I was able to update the Notification progress bar with an interval of 100ms-500ms for a very long period without facing any UI blocking.

Note: If you don't agree you can verify this answer by running this snippet after commenting out the marked line and see the difference. It may take about 5mins to start the severe UI blockage which will heat up your device and may stop functioning. I tried with an S3 mini with Android 4.2.2 and the updateNotification(....) method was called from a worker thread inside a service. and Moreover I already double checked it and don't know what happens when Notification.Builder is used for the same purpose.

Note: The reason to write this answer after 3 years of the question is because I wonder that I did not find even a single stackoverflow answer or other blog post handling this serious issue with this very simple solution.

I hope this answer will be helpful for other newbies like me. Enjoy.

Here is my copy pasted code that you can use directly.... I use the same code for updating a notification layout which contains two ProgressBars and four TextViews with a frequency of 500ms-100ms.

//long mMaxtTimeoutNanos = 1000000000 // 1000ms.
long mMinTimeNanos     = 100000000;//100ms minimum update limit. For fast downloads.
long mMaxtTimeoutNanos = 500000000;//500ms maximum update limit. For Slow downloads
long mLastTimeNanos = 0;
private void updateNotification(.....){
    // Max Limit
    if (mUpdateNotification || ((System.nanoTime()-mLastTimeNanos) > mMaxtTimeoutNanos)) {
        // Min Limit
        if (((System.nanoTime() - mLastTimeNanos) > mMinTimeNanos)) {
            mLastTimeNanos = System.nanoTime();
            // instantiate new RemoteViews object.
            // (comment out this line and instantiate somewhere
            // to verify that the above told answer is true)
            mRemoteView = new RemoteViews(getPackageName(),
                    R.layout.downloader_notification_layout);
            // Upate mRemoteView with changed data
            ...
            ...
            // Initialize the already existing Notification contentView
            // object with newly instatiated mRemoteView.
            mNotification.contentView = mRemoteView;
            mNotificationManager.notify(mNotificatoinId, mNotification);
            mUpdateNotification = false;
        }
    }
}

Answer 3

I saw similar results, you need to not push the update the notification so often, i changed mine to update only update a few times a second. (e.g. in onProgressUpdate keep track of the last time you called notify, and only call notify if you're past 100ms of the previous call, or if you're at the max value.

Answer 4

I too experienced this problem. I was updating the progress bar WAY too often (even when the progress didn't change), here's how I fixed that:

        // While loop from generic download method.
        int previousProgress = 0;
        while ((count = inputStream.read(buff)) != -1) {
            outputStream.write(buff, 0, count);
            totalBytesDownloaded += count;
            int prog = (int) (totalBytesDownloaded * 100 / contentLength);
            if (prog > previousProgress) {
                // Only post progress event if we've made progress.
                previousProgress = prog;
                myPostProgressMethod(prog);

            }
        }

Now the app runs great and the user still receives a progress notification.