Error

ERROR: Missing classes detected while running R8. Please add the missing classes or apply additional keep rules that are generated in /Users/xxx/yyy/app/build/outputs/mapping/release/missing_rules.txt. ERROR: R8: Missing class com.facebook.infer.annotation.Nullsafe$Mode (referenced from: com.facebook.ads.NativeAdBase) ...

Solution

Just add -ignorewarnings to proguard-rules.pro as described in the Android 8 release notes.