Default [Q] Android > create Telephone app that keeps focus on outgoing & incoming phoneCall

Using this simple example to create a PhoneCall application that dials out a hard coded # and monitors phone state.

Unfortunately, on making the phone call, we always switch to the actual built -in phone application.

I want to avoid this, or at the very least hide the dialer pad button. The user SHOULD NOT have the option to enter a phone#.

Does anyone know of a way to achieve this? i.e. keep the actual built-in phone application in the background (I would need to add buttons for speaker, and end call in the primary application)


alternatively, hide just the dial pad button in the native, built-in phone application?