I have a problem when i include the object
Widgetset ‘com.vaadin.v7.Vaadin7WidgetSet’ does not contain an implementation for org.tepi.imageviewer.ImageViewer. Check the connector’s @Connect mapping, the widgetset’s GWT module description file and re-compile your widgetset. In case you have downloaded a vaadin add-on package, you might want to refer to
I use vaadin 8.4 compatibility