Hello,
Vaadin Designer 2 can open HTML files but only those that follow Vaadin Framework’s
declarative format
. Java files can’t be opened in Designer.
You can create a Designer compatible HTML file by creating a new “Vaadin 8 Design” file from Eclipse’s new File menu. Please follow the steps in the documentation:
https://vaadin.com/docs/v8/designer/designer-getting-started.html
Hope this helps!