我正在尝试在flutter中进行下拉选择输入!我想从future的列表引用中获取数据。我不确定该怎么做，因为这会给我错误:代码如下:dropdownButtonHideUnderline(FormFieldStatestate){returnFutureBuilder(future:Global.payCountriesRef.getData(),builder:(BuildContextcontext,AsyncSnapshotsnap){if(snap.hasData){Listcountries=snap.data;returnnewDropdownButtonHideUnder
