As of version 28.0.0 of the Android SDK build tools the support library is being phased out in favour of Androidx. Jetifier attempts to bridge this gap by converting external packages to use Androidx.
When both Androidx and Jetifier are enabled in a project’s
gradle.properties (see below), jetifier (presumably) prevents the support library from being included in the project locally, and therefor into
# gradle.properties android.useAndroidX=true android.enableJetifier=true
The result is an error preventing compilation:
node_modules/react-native-gesture-handler/[...]/RNGestureHandlerEvent.java:3: error: package android.support.v4.util does not exist import android.support.v4.util.Pools; ^
This can be fixed by upgrading to androidx. Replacing the offending line (and anywhere else Pools is being imported) with
import androidx.core.util.Pools; would do the trick.
Of course that would cause people who are not on 28.x.x headaches. And this isn’t a problem if you aren’t using Jetifier (I can get it to compile past the error by turning it off, but am then faced with having to downgrade as whole).