如何在Flutter上基于多个类别有效地过滤列表？

Question

假设我有一个显示加油站列表的屏幕，像这样。

共有3个下拉菜单：左侧用于根据品牌（壳牌，星号等）进行过滤，中间用于根据距离进行排序（升序和降序），右侧用于根据设施进行过滤（ATM，厕所等）。如果3个下拉菜单中的所有下拉列表均显示“全部”，则将显示原始列表。否则...一些情况。

仅过滤“ Esso”：

过滤具有ATM的“ Esso”：

更改这些下拉菜单的值时，列表必须相应地处于filterend位置。到目前为止，我已经完成了处理设施下拉菜单的工作。它有很多嵌套的if-else块，很容易让我感到困惑，例如：

 else if (dropdownBrand == "All" && dropdownDistance != "All"){
   if (dropdownDistance == "Near to far"){

     _displayedList = _petrolList;
     _displayedList.sort((a,b) => a.price.compareTo(b.price));
     _displayedList = _displayedList
         .where((PetrolItem item) => item.facilities.toString().toLowerCase() == dropdownFacilities.toString().toLowerCase())
         .toList();
   }
   else {
     _displayedList = _petrolList;
     _displayedList.sort((a,b) => b.price.compareTo(a.price));
     _displayedList = _displayedList
          .where((PetrolItem item) => item.facilities.toString().toLowerCase() == dropdownFacilities.toString().toLowerCase())
          .toList();
   }
}
else if (dropdownBrand != "All" && dropdownDistance == "All"){
  _displayedList = _petrolList;
  _displayedList = _displayedList
      .where((PetrolItem item) => item.brand.toString().toLowerCase() == dropdownBrand.toString().toLowerCase() && item.facilities.toString().toLowerCase() == dropdownFacilities.toString().toLowerCase())
      .toList();
}
else if (dropdownBrand == "All" && dropdownDistance == "All"){
  _displayedList = _petrolList;
  _displayedList = _displayedList
      .where((PetrolItem item) => item.facilities.toString().toLowerCase() == dropdownFacilities.toString().toLowerCase())
      .toList();
}

完整代码：here

如何简化排序和过滤代码？

Answer 1

尝试如下所示：

_displayedList = getListByBrand(brand:_selectedBrand)
_displayedList = getListByFacility(facility: _selectedFacility)
_displayedList = getListListByDistance(distance: _selectedDistance)


List<outlet> getListByBrand(String brand) {
    if (brand == '') {

        return _displayedList ;
    } else {
        // Apply your filter here.
        return _filteredList ;

    }

}

List<outlet> getListByFacility(String facility) {
    if (facility == '') {

        return _displayedList ;
    } else {
        // Apply your filter here.
        return _filteredList ;

    }

}

ist<outlet> getListListByDistance(String distance) {
    if (distance == '') {

        return _displayedList ;
    } else {
        // Apply your filter here.
        return _filteredList ;

    }

}