external keyboard – Android menu navigation without touchscreen input

I’m working on a smart glasses project that is using an Intrinsyc Open-q 2500 SOM that utilises a Snapdragon processor, running a custom Android SDK (Oreo 8.1) made for smart watches.

To navigate through the Android UI, as well as applications, we are hoping to use an external touch sensor (IQS223) which will output high for a short period when a gesture is detected. E.g If a swipe forward is detected it will set pin1 (connected to GPIO1 of SOM) to high for 80ms, or if a TAP is detected it will set pin2 (connected to GPIO2 of SOM) to high for 80ms.

I’ve read it is possible to connect navigate/control an application via an external keyboard. All interactive widgets are focusable, meaning that the selected widget is highlighted (via a glow or appearance change). Therefore, It seems I should be able to fire a keyboard event on detection of a GPIO input change, and use that event to trigger an action. E.g. on detection of a high input on GPIO1 I’d fire a “Enter” keypress event.

My question is how would I go about doing this for the main Android UI (navigation of settings, selecting an app from main menu etc.)?
i.e I want to set the main Android UI to be focusable (if possible) so I can navigate/control the device by simulating keypresses, which are fired when an input level changes on a certain GPIO pin.

Is there an alternate method to achieving this?