Activity of Android studio_ main.xml Unable to preview (gray page)

The activity_main.xml in Android Studio cannot be previewed (the gray page only displays the ActionBaroverLayout) and controls cannot be pulled into it. The styles.xml file is in the values file

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
</style>

To change to the preview state, add “base.” before the Theme in the