[ImageJ-devel] Parameter decorator and supported classes

[MEYENHOFER Felix]

Hi 

during my first attempts of implementing a ij2 plugin I realised that the following point is not clear to me:
thanks to the widget demo of the imagej-tutorials I managed to define my UI in the ij2-way. Now during my further research to find a way to easily define an image input and getting the dialog with the Parameter decorator I found examples like

	@Parameter(type = ItemIO.INPUT)
	private ImgPlus<FloatType> img;
or 
	@Parameter(type = ItemIO.INPUT)
	private Dataset ds;

but when running such code I get a warning-dialog saying; “An ImgPlus is required, but none exists”
So I open an image and run  the plugin again. The same dialog appears again.
All the other types work well (String, File, etc.). Is this a bug or am I missing something.

Best regards, 

Felix