error: resource android:attr/fontVariationSettings not found

try to change the compileSdkVersion to:

compileSdkVersion 28

fontVariationSettings added in api level 28. Api doc here

This is caused by an incompatibility with the android support library that changed to version 28. I solved the problem by forcing the build to use a lower support library. //like build gradle

configurations.all {
        resolutionStrategy {
                force 'com.android.support:support-v4:27.1.0'
    }
} 

My project built successfully immediately after I changed this. Hope this might help you too. I lost a day of development because of this!.

For those that must keep compileSdkVersion 27 and are unable to upgrade to androidx yet, you must not upgrade to (or over) the versions of dependencies in the following links. These links are where the breaking change was introduced. You must find an earlier version that doesn't use androidx.

https://firebase.google.com/support/release-notes/android#update_-_june_17_2019

https://developers.google.com/android/guides/releases#june_17_2019

For instance, the following are compatible with compileSdkVersion 27:

dependencies {
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support:support-v4:27.1.1'
    implementation 'com.google.android.gms:play-services-maps:16.1.0'
    implementation 'com.google.android.gms:play-services-location:16.0.0'
    implementation 'com.google.firebase:firebase-core:16.0.9'
    implementation 'com.google.firebase:firebase-messaging:18.0.0'
}

The following will break with compileSdkVersion 27 and are only compatible with compileSdkVersion 28:

dependencies {
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:support-v4:28.0.0'
    implementation 'com.google.android.gms:play-services-maps:17.0.0'
    implementation 'com.google.android.gms:play-services-location:17.0.0'
    implementation 'com.google.firebase:firebase-core:17.0.0'
    implementation 'com.google.firebase:firebase-messaging:19.0.0'
}