If you show 2 BiometricPrompts back-to-back on a Pixel 4 (which uses face unlock), the second prompt will be immediately dismissed. This does not happen on devices that use fingerprint, like a Pixel 2.

I've attached a sample project that reproduces the issue. You can configure the delay between the first prompt being dismissed and the second being shown - with a delay of 400ms the issue reliably reproduces, and with a delay of 600ms it does not.

Here's a video of the sample on a Pixel 4: https://i.imgur.com/4sCWOm0.mp4

Here's a video of the sample on a Pixel 2: https://i.imgur.com/5dDI4zO.mp4

I believe it's caused by this postDelayed, which has a 500ms delay for face unlock and runs after the second prompt has been shown when 2 are shown back-to-back.

Note that this is a bug in the framework, not in the androidx.biometric library, but there doesn't seems to be a relevant component for framework biometrics (and it should be possible to work around this in androidx).

BUILD INFO:

Device type: Pixel 4
OS version: 10
Biometric library version: 1.0.1

STEPS TO REPRODUCE:

Install the sample.
Perform face unlock with the default 0 delay between prompts.

EXPECTED RESULTS: Both prompts work correctly.

OBSERVED RESULTS: The second prompt is immediately dismissed.

NUMBER OF TIMES YOU WERE ABLE TO REPRODUCE: 3/3

Issue 157783075

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