Android Cannot resolve symbol '?attr/selectableItemBackground'

Answer 1

2 options:

Option 1

Another possible reason is: Google's maven repository is not set for the build script.

Open your project's main build.gradle add this line:

buildscript {
    repositories {
        google()  <-- this
        // Be also sure that google() is before jcenter()
    }
}

Without this, it may not be able to download the Android Studio Gradle plugin 3.0+. It's not distributed in jCenter but in the Google's maven repository.

Option 2

Run this command in root of project and resync project

Linux:

rm .idea/libraries/Gradle__com_android_support_*.xml

Windows:

del .idea\libraries\Gradle__com_android_support_*.xml