Cannot resolve symbol Theme, ThemeOverlay

Question

I updated my android studio to latest version - 3.0.1. Since then it complains 'Cannot resolve symbol' for Theme and ThemeOverlay in the following lines of code. App runs fine but they are marked in RED in the file.

styles.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"></style>
 <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

build.gradle is updated with the latest version

 dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
    }

Answer 1

Found Easiest Way

• Close project (File> Close Project)
• Import / Re-Open project again (NOT from Recent)

The error should be gone.

If(that_did_not_work)

• Open build.gradle, remove appcompact-v7 dependency and sync.
• Again add that dependency and sync.

Error Gone!

Answer 2

1)Close the project from the File menu.

2)Open the project again as existing Android Studio project.

This fix my problem.

Answer 3

1. In the app/build.gradle remove the line responsible for the appcompat package (something like implementation 'com.android.support:appcompat-v7:27.1.1')
2. Perform the Gradle sync. It will break and show a lot of errors
3. Bring the original line back
4. Perform the Gradle sync once again

This will magically solve the problem that for no reason appeared in the 3.0.1