In my app, a Service is started in the background to handle BLE communication with a BLE device. I have an Activity (StartActivity) on start of the app which searches the BLE device and when it found it, it starts the Service (BleService), hands the found Device to it and then binds to it to receive Broadcasts from BleService.  

BleService establishes the BLE connection, sets notifiers on different characteristics and reads them. As it got all the information it initially needs, a Broadcast is sent.  

This Broadcast causes StartActivity to switch to another Activity (MainActivity), which then binds again to BleService and reacts to BleService's Broadcasts.  

So far, so good. 

When I press the back button while in MainActivity, the app 'closes'. Now, when I restart the app (either by clicking on its icon or in the recent app list), the app gets back into StartActivity and can't connect to the BLE device. As the LED on my BLE device is constantly signalling me, it's connected, I think the first BleService is still running and connected to the BLE device.  

I checked this by adding a Log output to BleService's onDestroy() method and yes, onDestroy() isn't called. It is called, when I close my app through the recent app list. 

What should I do when closing my app through the use of the back button? 

**EDIT:** So I want to destillate my problem out of my question:  

When I close my app on pressing the back button in MainActivity and then start it through the recent app list or via its icon again, I get stuck in StartActivity. This is, because StartActivity can't find the BLE device, as it is still connected to the still running BleService.  

How can I avoid this?