Flutter initState 不运行调用的方法

Question

我确定我遗漏了一些非常明显的东西，但是我无法理解为什么会发生这种情况。

我调用了一个名为 readJSON 的方法，它将 JSON 文件读入对象。我使用长度来呈现页面，每个页面都有一个基于主对象索引的复选框列表。

我已使用：https://github.com/afzalali15/onboarding_demo 在我的应用程序中构建此入职任务。

*请注意，当我实现这个时，我看到热重载工作得非常好。当我关闭 VSCode 并稍后再次打开时，readJSON 方法永远不会运行。

class _OnboardingPageState extends State<OnboardingPage> {
  List<OnboardingTodo> onboardingTasks = [];
  final _controller = OnboardingController();
  String response = '';

  bool value = false;

  Future<void> readJson() async {
    response = await rootBundle.loadString('assets/cfg/onboarding_tasks.json');
    final onboardingTodo = onboardingTodoFromJson(response);
    onboardingTasks.addAll(onboardingTodo.values);
    print("onboarding length - " + onboardingTasks.length.toString());
  }

  @override
  void initState() {
    readJson();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Stack(
          children: [
            PageView.builder(
              controller: _controller.pageController,
              onPageChanged: _controller.selectedPageIndex,
              itemCount: onboardingTasks.length,
              itemBuilder: (context, index) {
                return Container(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      Image.asset(
                        _controller.onboardingPages[index].imageAsset,
                        height: 100,
                        width: 100,
                      ),
                      SizedBox(height: 32),
                      Text(
                        _controller.onboardingPages[index].title,
                        style: TextStyle(
                            fontSize: 24, fontWeight: FontWeight.w500),
                      ),
                      SizedBox(height: 32),
                      Expanded(
                        child: Container(
                          child: ListView.builder(
                            padding: const EdgeInsets.all(8),
                            itemCount: onboardingTasks[index].tasks.length,
                            itemBuilder:
                                (BuildContext context, int chkBoxindex) {
                              return CheckboxListTile(
                                controlAffinity:
                                    ListTileControlAffinity.leading,
                                value: value,
                                title: Text(
                                    '${onboardingTasks[index].tasks[chkBoxindex].title}'),
                                onChanged: (bool newVal) {
                                  setState(() {
                                    value = newVal;
                                  });
                                },
                              );
                            },
                          ),
                        ),
                      ),
                    ],
                  ),
                );
              },
            ),
            // The dots showing the index of the pages
            ...
            // The next/end button
            ...
          ],
        ),
      ),
    );
  }
}

感谢任何帮助或建议。谢谢

Answer 1

试试void initState() { super.initState(); WidgetsBinding.instance .addPostFrameCallback((_) => readJson();); } 或使用 Loader 之类的

bool loading = true;
  Future<void> readJson() async {
    setState(() => loading = true);
    response = await rootBundle.loadString('assets/cfg/onboarding_tasks.json');
    final onboardingTodo = onboardingTodoFromJson(response);
    onboardingTasks.addAll(onboardingTodo.values);
    print("onboarding length - " + onboardingTasks.length.toString());
    setState(() => loading = false);
  }

并将加载器放入 UI 中

itemBuilder: (context, index) {
                return loading ? YourProgressIndicatorWidget : Container(child: ......
}