title: Upload multiple images to server in a queue
body: <p><strong>Use case:</strong> Upload images in a queue in background to the server, images can be web urls or image file stored on the phone's memory.</p>
  
  <p><strong>What I want</strong> Limit the number of items in queue to 3 and show blurred images as placeholders for the actual images being uploaded in a recyclerview in an activity with a progress bar on each placeholder indicating how much of it has been uploaded. On top of every placeholder are three buttons to either pause, cancel or resume the upload of the image.</p>
  
  <p><strong>Current Situation:</strong> Right now, I was using <code>Multipart</code> in <code>Retrofit 1.9.0</code> to upload images and this service call was being done inside the activity.</p>
  
  <p>I am not able to figure out how to cancel, pause or resume a multipart-POST request using Retrofit or any other library in general and how to tie a UI event with an api service thread. I can update the UI from service, but how do I update something in the service from an event in UI (pause/resume/cancel)?</p>
  
  <p>How should I proceed with this use case? Do I need to use service? Can I show progress indicators in another activity based on the requests being executed in the service? What should be the architecture for this process?
  I don't need the code for it, but if there are some useful references related to this, I would like to read and test it out to finally derive my approach. </p>