Pfthb

Before you hit the wall of text below, my main question is: What is a better way to structure this application?

In theory my app is kind of simple. I set up a VPN using a Bluetooth device or a USB device. USB takes precedence if both devices are available. The UI only displays availability and connected state of each device (as well as an event/debug log). This app will almost always run in the background.

I am new to Android AND Java so I've had some difficulty learning the nuances. But I have done a lot of reading and experimentation. Right now, my MainActivity holds the logic for managing custom USB and BT services that extend VpnService and this works pretty well. But I do have some issues related to the life-cycle of Activities and Services - mainly, I am having trouble handling ALL of the use cases which has led to robustness issues as I pair/connect/disconnect the BT/USB devices.

I am considering re-writing this application but can't think of a way to ensure I won't have the same issues. I have a pretty good handle on the life-cycle of Activity and Service components - so I was thinking that the app would be better structure if I moved the control-logic out of the UI activity into a persistent service that controls the USB and BT services. But I am struggling with making a decision on how to handle the various asynchronous device events that may occur while I am trying to handle blocking/async operations. The prime example here is when I am trying to connect to the (already paired) Bluetooth device and the USB device is attached. I need to make sure that the BT connect finishes, if it succeeds then I need to disconnect it (and wait for that to finish), then connect the USB device and start the VPN. Due to the unpredictability of the BT connect, I'd also like to be able to have a timeout on operations so that I can cancel them if they take longer than they should. Most of my attempts at this kind of functionality don't seem to work. I think that the events (intents) I am trying to send are blocked until operations finish.

So, hopefully you're still with me.. How would you structure this app? I have a lot of intent-filters (USB/BT device events) to manage and I need to carefully control the order of operations - letting each operation finish, check its result, and then figure out what to do next based on ALL events that have occurred up to the time that the decision is being made.

Thanks,
Stauff4