Previously, FingerprintManager could be used to handle fingerprint authentication, and did not depend on an Activity in order to go through a system dialog. It could be used from anywhere, as any of the sensor managers.
Now, Google have released the support library version in https://developer.android.com/reference/androidx/biometrics/BiometricPrompt and deprecated FingerprintManager. They wish all apps to go through the same unified system dialog.
Big problem is - the whole thing is strongly coupled to FragmentActivity.
I wish to use this fingerprint authentication in an AccessibilityService (display over other apps).
What can be done?
Some options I'm considering:
UPDATE
Accepted commonsware's answer below. I am able to succesfully launch an Activity on top of apps when getting accessibility events, and start using BiometricPrompt. BiometricPrompt has other problems though, and it seems like a very half-baked API that never went through stress testing - but that's beyond the scope of this question.
Go back to the old FingerprintManager despite becoming deprecated
That may not work well on newer devices. I suspect that it also will not work well on devices whose biometric security is not a fingerprint.
Implement some transparent Activity that will somehow pop up above other apps, just to satisfy the API's requirement for FragmentActivity.
If I were in your shoes, I would go this route. Use Theme.Translucent.NoTitleBar for this.
Note that I cannot guarantee that this will work from an AccessibilityService, and displaying any form of UI will result in new accessibility events that you would need to filter out.