Android Studio - XML Editor autocomplete not working with support libraries

Question

I just started using the new android.support.design library. When using any of the widgets inside the XML editor I stop getting the XML autocomplete suggestions!

For example,

<android.support.design.widget.CoordinatorLayout
    android:id="@+id/header_root"
    android:layout_width="match_parent"
    android:layout_height="200dp">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/primary_dark" />

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:src="@drawable/ic_action_add"
        android:layout_marginLeft="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginTop="56dp"
        app:fabSize="normal"
        app:layout_anchor="@id/header_root"
        app:layout_anchorGravity="bottom|right|end" />

</android.support.design.widget.CoordinatorLayout>

None of the tags will show the autocomplete popup, like when I start typing "android:i" no popup appears, the only suggestion I get is shown in the following picture.

I have tried cleaning my project, restarting the pc, restarting Android Studio.. nothing is working!

Answer 1

If NONE of the above answers worked, ...

Just navigate to your android studio installation directory, i.e,

yourDrive:/.AndroidStudio3.3/system

and DELETE THE CACHE FOLDER ( first close android studio, if its running ).

Then start Android Studio again. Done.

P.S I am using android studio 4.0