How to import Shape class in XML

I think there aren't any problem in the code. Why don't you check these things.

1. Did you write the code in res/drawable/something.xml? You have to write your own file name at the something part.
2. There isn't <?xml version="1.0" encoding="utf-8"?> at the top.

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
</shape>

3. Do Clean, Rebuild Project.
4. Do Invalidate Cache/Restart.

right click on the drawable folder then new, select drawable resource file give any file name change that selector to shape and encode the file using UTF-8 like this

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="@color/white" />