How to change in ButtonStyle

[NafissaBHJ]

In the DropDownButton I want to change the background color to transparent, but I can't change the buttonStyle as the ButtonStyle doesn't change, or am I missing on something?
thank you

[bdlukaa]

You can wrap your DropDownButton with a ButtonTheme. I filed #1139 to add the .style property to the drop down button widget.