Question

我已经为我的位置搜索代表构建了一个建议列表，该列表始终在顶部有一个将用户推送到新页面的项目。用户可以在这个新页面上选择地图上的位置并提交或返回搜索页面。如果用户提交了位置，则我要关闭基础位置搜索委托，并以所选位置作为结果。

为此，我在无状态建议列表窗口小部件中使用了回调，但是在onMapTapped回调的情况下，应用会引发异常：

class LocationSearchDelegate extends SearchDelegate<Location> {
  // ...
  @override
  Widget buildSuggestions(BuildContext context) {
    return _SuggestionList(
      query: query,
      onSelected: (Location suggestion) {
        result = suggestion;
        close(context, result);
      },
      onMapTapped: (Location location) {
        result = location;
        close(context, result); // <- Throws exception
      },
    );
  }
  // ...
}

例外：

Looking up a deactivated widget's ancestor is unsafe.
At this point the state of the widget's element tree is no longer stable. To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling inheritFromWidgetOfExactType() in the widget's didChangeDependencies() method.

由于导航到buildSuggestions，与此同时，ChooseOnMapPage方法的上下文变得过时了：

class _SuggestionList extends StatelessWidget {
  // ...
  void _handleOnChooseOnMapTap(BuildContext context) async {
    Location location = await Navigator.of(context).push(
      MaterialPageRoute<Location>(builder: (context) {
        return ChooseLocationPage();
      }),
    );
    onMapTapped(location);
  }
  // ...
}

解决方法

当前解决方法是显示结果，然后立即关闭搜索委托：

class LocationSearchDelegate extends SearchDelegate<Location> {
  // ...
  @override
  Widget buildSuggestions(BuildContext context) {
    return _SuggestionList(
      query: query,
      onSelected: (Location suggestion) {
        result = suggestion;
        close(context, result);
      },
      onMapTapped: (Location location) {
        result = location;
        showResults(context); // <- Throws NO exception
      },
    );
  }
  // ...
  @override
  Widget buildResults(BuildContext context) {
    Future.delayed(Duration.zero, () {
      close(context, result);
    });
    return Container();
  }
  // ...
}

我不喜欢这种解决方法，因此，有关如何解决此问题的任何建议？

如何使用陈旧的上下文关闭SearchDelegate？

0 个答案: