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As per Firebase codelab Android tutorial,while adding com.google.firebase:firebase-auth:9.0.0 in build.gradle dependencies, getting below error:
Error:(28, 13) Failed to resolve: com.google.firebase:firebase-auth:9.0.0
See below screenshot:
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The 9.0.0 version of Firebase was built using Google Play services 9.0
While adding compile 'com.google.android.gms:play-services:9.0.0' into my build.gradle, gradle sync successfully.
I found my answer here.
来源：https://stackoverflow.com/questions/37382907/failed-to-resolve-com-google-firebasefirebase-auth9-0-0