Update Discovered Readers
This method will be called repeatedly until:
an error occurs
Terminal.discoverReaders is canceled
Terminal.connectBluetoothReader is called with a discovered reader
You should not cache the Reader objects in the readers list. In other words, after calling Terminal.connectBluetoothReader with a discovered reader, you should not attempt to cache and re-use the Reader object. The connectivity information associated with the discovered Reader object will become stale.
Your app should display an updating list of discovered readers if your user is connecting to a reader for the first time. Otherwise, you may automatically select a previously saved reader. Once a selection has been made, call the Terminal.connectBluetoothReader method to begin connecting to the reader.