Cannot resolve symbol AppCompatActivity - Support v7 libraries aren't recognized?
For me, Even after upgrading to appcompat-v7:22.1.0, in which AppCompatActivty is added,the problem was not resolved for me, Android Studio was giving same problem
Cannot resolve symbol 'AppCompatActivity'
Sometimes clearing the android studio caches help.
In android studio I just cleared the caches and restarted with the following option--
File->Invalidate Caches/Restart
If you use androidX instead of android, you needchange
import android.support.v7.app.AppCompatActivity;to
import androidx.appcompat.app.AppCompatActivity;and change
<android.support.constraint.ConstraintLayout>to
<androidx.constraintlayout.widget.ConstraintLayout>
1.Delete the .idea folder
2.Close and reopen the project
3.File - > Sync Project With Gradle Files
This worked for me