子控件的build方法设置了父控件的状态后触发的回调不会触发其父控件的build方法

Question

我有一个父小部件（为此片段）MainLayout，和一个子小部件ChildChild。我想在执行其build方法后，在子级父级窗口小部件的AppBar的操作中添加一个IconButton。父级的AppBar中显示的操作以其状态存储。

我使用的方法存在问题：子控件的build方法设置其父控件的状态后触发的回调不会触发其父控件的构建方法，但状态（的父级）已更改。结果，搜索图标未安装在MainLayout的AppBar的动作中。

为什么要采用这种方式以及如何解决？

下面的代码是我的孩子和父母小部件外观的示例：

child_widget.dart：

class ChildWidget extends StatelessWidget {
  // Add a search button in the AppBar of MainLayout widget.
  void _updateAppBar(BuildContext context) async {
    InheritedMainLayout.of(context).appBar.updateActions(<Widget>[
            IconButton(
              icon: Icon(Icons.search),
              onPressed: () => showSearch(
                context: context,
                delegate: SearchPageDelegate(),
              ),
            ),
          ]);
  }

  @override
  Widget build(BuildContext context) {
    _updateAppBar(context);
    return Container(
      width: 100,
      height: 100,
      color: Colors.blue,
    );
  }
}

parent_widget.dart：

class ParentWidget extends StatefulWidget {
  @override
  _ParentWidgetState createState() => new _ParentWidgetState();
}

class _ParentWidgetState extends State<ParentWidget> {
  // This is the method that is passed as a parameter to the ChildWidget to update the actions of the AppBar.
  void _updateAppBarActions(List<Widget> actions) =>
    setState(() => _appBarActions = actions);

  @override
  Widget build(BuildContext context) {
    return InheritedMainLayout( // The inherited widget used to use the _updateAppBarActions method in the child widget
      appBar: new AppBarConfig(
        actions: _appBarActions,
      ),
      child: Scaffold(
        appBar: AppBar(
          title: Text("Title of the App"),
          actions: _appBarActions, // Actions showed in the AppBar are from the state, _appBarActions
        ),
        body: Padding(
          padding: EdgeInsets.all(20.0),
          child: _currentChild, // Here is loaded the builded widget called ChildWidget.
        ),
        drawer: AppDrawer(
          items: _drawerItems,
          onTap: _onChangePage,
        ),
      ),
    );
  }
}