我不确定我是否理解您的问题,但您可以对非原始元素列表进行排序,如下所示:
final List<Element> elements = [
Element(id: 1),
Element(id: 7),
Element(id: 2),
Element(id: 0)
];
elements.sort((a, b) => a.compareTo(b));
// or
elements.sort((a, b) => a.id > b.id ? 1 : -1);
这将是一个print(elements);
输出:
I/flutter ( 7351): [id: 0, id: 1, id: 2, id: 7]
这将是类Element
class Element {
final int id;
Element({this.id});
@override
String toString() => "id: $id";
int compareTo(Element other) => this.id > other.id ? 1 : -1;
}
编辑:要做到这一点异步,你可以这样做:
Future<List<Element>> asyncSort() async {
print("before sort: $elements");
elements = await compute(_sort, elements);
print("after sort: $elements");
return elements;
}
static List<Element> _sort(List<Element> list) {
list.sort((a, b) => a.compareTo(b));
return list;
}
print("before calling asyncSort(): $elements");
asyncSort();
print("after calling asyncSort(): $elements");
这将是输出:
I/flutter ( 7351): before calling asyncSort(): [id: 1, id: 7, id: 2, id: 0]
I/flutter ( 7351): before sort: [id: 1, id: 7, id: 2, id: 0]
I/flutter ( 7351): after calling asyncSort(): [id: 1, id: 7, id: 2, id: 0]
I/flutter ( 7351): after sort: [id: 0, id: 1, id: 2, id: 7]
Edit2:如果你想发送一个比较函数compute
,你可以使用一个Map
或一个List
参数与列表和比较函数并传递它而不是列表,因为compute
只接受一个参数。这是一个例子:
Future<List<Element>> asyncSort() async {
print("before sort: $elements");
Map args = {"list": elements, "compare": compare};
elements = await compute(_sortWith, args);
print("after sort: $elements");
return elements;
}
static List<Element> _sortWith(Map args) {
List<Element> list = args["list"];
Function(Element a, Element b) compare = args["compare"];
list.sort((a, b) => compare(a, b));
return list;
}
static int compare(Element a, Element b) {
return a.id > b.id ? 1 : -1;
}