I wasn't able to compile
cert4android due to error
Not enough information to infer parameter T (which appears at every call of
findViewById). According to https://stackoverflow.com/questions/44461571/error-on-findviewbyid-after-upgrading-to-compile-sdk-version (and others), the API of
findViewById has changed in Android O. However, the gradle file of cert4android targets API 26 (which is Android O).
After changing the calls, I'm able to compile, now. You can find my changes here (I planned to do a merge request, but those aren't permitted in your repository):