demo/xinhuaribao/lib/provider/news_category_provider.dart

import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:news_app/http/http_util.dart';
import 'package:news_app/http/model_parser.dart';
import 'package:news_app/model/news_category_model.dart';

import '../constant/api_const.dart';
import 'network_provider.dart';

class NewsCategoryProvider extends Notifier<List<NewsCategoryModel>> {
  bool _hasConnectedOnce = false;

  @override
  List<NewsCategoryModel> build() {
    // 监听网络变化，在首次联网时触发加载
    ref.listen<AsyncValue<List<ConnectivityResult>>>(connectivityProvider, (
      previous,
      next,
    ) {
      final results = next.asData?.value ?? [];

      final hasNetwork =
          results.isNotEmpty && !results.contains(ConnectivityResult.none);

      if (hasNetwork && !_hasConnectedOnce) {
        _hasConnectedOnce = true;
        fetchNewsCategoryList();
      }
    });
    return List<NewsCategoryModel>.empty();
  }

  Future<void> fetchNewsCategoryList() async {
    final jsonData = await HttpUtil().get(apiNewsCategory);
    final newsItemList = ModelParser.parseList(
      jsonData,
      NewsCategoryModel.fromJson,
    );
    state = newsItemList;
  }
}