Informing about file transfers by a progress bar

We will implement file uploading in this recipe. The application will notify the user about the progress and will also display messages when the user starts uploading the file and when the upload has finished.

In this recipe, we first choose a file for upload. We click on the Upload button and then the file is going to be stored on the server.

How to do it…

Carry out the following steps:

1. The key part of the upload mechanism is the receiver. The receiver will implement more than the Receiver interface. We want to be notified about the progress, so we also implement ProgressListener. Then we want to be notified when the upload starts and ends, so we implement another two interfaces, StartedListener and FinishedListener.

   class UploadReceiver implements Receiver, ProgressListener, StartedListener, FinishedListener

2. We need access to the progress indicator from the upload receiver. So we make a reference from UploadReceiver to ProgressIndicator by creating...