list - 从 getX dart 包中为 Flutter 应用程序排序 RxList

Question

我无法按给定属性对可观察的 RxList 进行排序。当我使用 BloC 方法时，排序工作正常，使用一个简单的列表。

最近我将状态管理更改为 GetX ( https://github.com/jonataslaw/getx ) 包，因为我看到了几个优点(不需要上下文、页面转换等)。

这里有两种情况，我的不好，之前没有说明，让我放小 cucumber 的

场景 1:

Given user in Posts Screen
When user Pull down to get Newest posts
Then user get the newly fetched posts on top of the previous loaded list

场景 2:

Given user in Posts Screen
When user reaches the end of the list
Then user get more posts at the end of the previous loaded list

post_model.dart

class Post {
  final int id;
  final String title;
  final DateTime date;
  final User user;

Post({
    @required this.id,
    @required this.title,
    @required this.date,
    this.user});
 
}

post_controller.dart

import 'dart:async';

import 'package:get/state_manager.dart';
import 'package:blog/models/post.dart';
import 'package:blog/services/posts_api.dart';

class PostsController extends GetxController {
  int _page = 0;

  ---------HERE OBS LIST-----------
  RxList posts = [].obs;

  @override
  void onReady() {
    super.onReady();
    this.loadPosts();
  }

  Future<void> loadPosts({isRefreshLoad = false}) async {
    int pager;
    if (isRefreshLoad) {
      pager = 1;
    } else {
      increment();
      pager = this._page;
    }

    Map<String, String> arguments = {'page': '$pager'};
    final List<Post> newPosts =
        await PostsApi.instance.getPosts(arguments: arguments);

    // remove duplicates
    posts.addAll(
      newPosts.where(
        (newPosts) => posts.every((post) => newPosts.id != post.id),
      ),
    );

    //----------HERE'S THE EXCEPTION----------
    posts.sort((a, b) => b.id.compareTo(a.id));
    update(['posts']);
  }
}

错误

flutter: [GETX] PostsController has been initialized
[VERBOSE-2:ui_dart_state.cc(166)] Unhandled Exception: type 'Post' is not a subtype of type 'List<dynamic>'
#0      RxList.remove 
package:get/…/rx/rx_impl.dart:333

PostsScreen.dart

Scaffold(
                backgroundColor: Color.fromRGBO(58, 66, 86, 1.0),
                appBar: AppBarWidget(
                  drawerOpen: drawerPosition,
                  appBarVisible: _isVisible,
                  drawerVisible: true,
                ),
                body: ColorfulSafeArea(
                  overflowRules: OverflowRules.only(left: true, bottom: true),
                  child: GetBuilder<PostsController>(
                    id: 'posts',
                    init: PostsController(),
                    builder: (_postsController) {
                      _postsControllerGlobal = _postsController;
                      // Scenario 1 - Triggers when user pull down to get new posts
                      return RefreshIndicator( 
                        onRefresh: () {
                          return _postsController.loadPosts(
                              isRefreshLoad: true);
                        },
                        child: StreamBuilderWidget(
                          stream: _postsController.posts.stream,
                         // Scenario 2 Triggers when scroll controller reaches end of list
                          scrollController: _scrollController,                               isDrawerOpen: _isDrawerOpen,
                          widgetType: 'PostItemWidget',
                        ),
                      );
                    },
                  ),
                ),
              ),

----在此处输入代码------

我需要一种方法，无论触发器是 PullDown 还是到达列表的最后末尾，在它们被添加到流后始终按日期 desc 顺序对获取的帖子列表进行重新排序，以便始终显示项目按发布顺序。

希望有人能帮帮我。

Answer 1

经过几天的努力，我发现它要简单得多，而且由于我缺乏知识。

由于列表是可观察的，只需将其转换为列表就足以完成排序:

普通列表

• newPosts.sort((a, b) => b.date.compareTo(a.date));

可观察列表

• newPosts.toList().sort((a, b) => b.date.compareTo(a.date));

谢谢!