buttonAlignedDropdown property
final
If true, then a DropdownButton menu's width will match the ButtonBar button's width.
If false, then the dropdown's menu will be wider than its button. In either case the dropdown button will line up the leading edge of the menu's value with the leading edge of the values displayed by the menu items.
This will override the surrounding ButtonThemeData.alignedDropdown setting for buttons contained in the ButtonBar.
This property only affects DropdownButton contained in a ButtonBar and its menu.
Implementation
final bool? buttonAlignedDropdown;