Request for Feature: different values for 'groupBy' and 'groupSeparatorBuilder()' about grouped_list

[Dimibe]

Hi @deezaster, there were several questions like yours, but I have some concerns because of backwards compatibility. I'm trying to provide an easy solution for this in the future. Currently there is a work around which you can try (only works if your data are real objects):

1. Group by the element itself then the element will available in the groupSeparator function.
2. Override the compareTo method in your element's class and group by the value you like.

Code from the Widget:

GroupedListView<Element, Element>(
          elements: _elements,
          groupBy: (element) => element,
          groupSeparatorBuilder: (Element element) => Text(
            element.groupName,
            textAlign: TextAlign.center,
            style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
          ),
          [...]
),

Code from the elements class:

class Element implements Comparable {
  String groupName;
  int groupIndex;
  String name;

  Element(this.groupIndex, this.groupName, this.name);

  @override
  int compareTo(other) {
    int compareResult = groupIndex.compareTo(other.groupIndex);
    // if result is 0 both items are in the same group, so sort them according their name.
    if (compareResult == 0) {
      compareResult = name.compareTo(other.name);
    }
    return compareResult;
  }

  @override
  bool operator ==(Object other) => other is Element && other.groupIndex == groupIndex;

  @override
  int get hashCode => groupIndex.hashCode;
}

The data for the list widget:

List _elements = <Element>[
  Element(1, 'Team One', 'John'),
  Element(2, 'Team Two', 'Will'),
  Element(1, 'Team One', 'Beth'),
  Element(2, 'Team Two', 'Miranda'),
  Element(3, 'Team Three', 'Mike'),
  Element(3, 'Team Three', 'Danny'),
];

The result:

I aware this is not a small solution but currently the only one which solves your request.

Hopefully this will help you

Best regards

[Dimibe]

@deezaster I've created a new package which depends on scrollable_positioned_list. In this package the groupSeparatorBuilder takes the whole element as argument.
Maybe you want to try it out: https://github.com/Dimibe/sticky_grouped_list