We installed the Vaadin designer 2 but we cannot open our java files where the UI is located.
Error:
Vaadin Designer only supports HTML files.
If I would like to open html file then I got this error message:
org.eclipse.ui.internal.ErrorEditorPart cannot be cast to com.vaadin.designer2.eclipse.editors.VaadinEditor
Here is the answer:
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