DragDropLayout doesn't work in Eclipse

I'm trying to use a horizontal DragDropLayout (https://vaadin.com/directory#!addon/dragdroplayouts) for a Vaadin project following the demo. However, I can't drag any of its components when I run the project. I have set both the drag mode and the drop handler for the layout as well as the drop ratio. According to pom.xml the of Vaadin and DragDropLayout versions should be compatible (7.1.1 and 1.3.2). Is there anything I'm missing?

Did you compile the widgetset?

I tried to do that, but Eclipse gave me the following error message:

Select a widgetset file(..widgetset.gwt.xml) or a Vaadin project to compile.

The closest file I could find in the project was called "AppWidgetset.gtw.xml".I tried to compile the widgetset while selecting the file, but I only got a NullPointerException.

Alright, I think we now know where the issue is.

How did you create the project, with Maven, Gradle or with the Vaadin Plugin wizard?

I created it through Maven and picked the Vaadin archetype.

Could you try building the widgetset by running mvn vaadin:compile in a terminal,  or alternatively, in eclipse by right clicking on the project and selecting Run as... -> Maven build... and run the vaadin:compile goal. Do you get any errors?

John Ahlroos: Could you try building the widgetset by running mvn vaadin:compile in a terminal,  or alternatively, in eclipse by right clicking on the project and selecting Run as... -> Maven build... and run the vaadin:compile goal. Do you get any errors?

This worked for me. Thanks!

We get a null pointer exception doing any widgetset compilations for 7.7.1 on Windows Eclipse.  Mac Eclipse can compile, but not on Windows, so it seems there's some issue with the vaadin plugin or 7.7.1 for Windows builds.

David Wall: We get a null pointer exception doing any widgetset compilations for 7.7.1 on Windows Eclipse.  Mac Eclipse can compile, but not on Windows, so it seems there's some issue with the vaadin plugin or 7.7.1 for Windows builds.

Seems to be a bug in the widgetset compiler https://dev.vaadin.com/ticket/20316