Dart 'The function isn' t defined' 尽管已定义

Question

如何在 onTap() 中正确访问 _runThisFunction(...)？

...

class _DealList extends State<DealList> with AutomaticKeepAliveClientMixin {

  void _runThisFunction() async {
    print('Run me')
  }

  @override
  Widget build(BuildContext context) {
    super.build(context);
    return FutureBuilder(
      future: _loadingDeals,
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        return snapshot.connectionState == ConnectionState.done
            ? RefreshIndicator(
                onRefresh: _handleRefresh,
                child: ListView.builder(
                  physics: const AlwaysScrollableScrollPhysics(),
                  itemCount: snapshot.data['deals'].length,
                  itemBuilder: (context, index) {
                    final Map deal = snapshot.data['deals'][index];

                    return _getDealItem(deal, context);
                  },
                ),
              )
            : Center(
                child: CircularProgressIndicator(),
              );
      },
    );
  }
}

Container _getDealItem(Map deal, context) {
  return new Container(
    height: 90.0,
    child: Material(
      child: InkWell(
        child: _getDealRow(deal), // <-- this renders the row with the `deal` object
        onTap: () {
          // Below call fails
          // 'The function isn't defined'
          _runThisFunction();

        },
      ),
    ),
  );
}

Answer 1

原因是您超出了范围。
小提示:“函数” 一词始终表示您尝试调用的函数不是 class 的一部分和关键字 "method" 向您表明您尝试调用的函数是某个类的一部分。

在您的例子中，_runThisFunction 定义在 _DealList 的内部，但您正试图从外部调用它。
您需要将 _getDealItem 移入 _DealList 或将 _runThisFunction 移出。

/// In this case both methods [_runThisFunction()] and [_getDealItem()] are defined inside [_DealList].
class _DealList extends State<DealList> with AutomaticKeepAliveClientMixin {
   void _runThisFunction() ...

   Container _getDealItem() ...
}

---

/// In this case both functions are defined globally.
void _runThisFunction() ...

Container _getDealItem() ...

您需要确保您也将相同的逻辑应用于 _getDealRow 和其他嵌套调用。