Flutter 颤振-在Dart中，如何将变量和函数从一个类访问到另一个类（Diff文件）？

我有一个main.dart文件，其中包含两个函数和head变量：内置小部件。构建小部件的主体写在另一个名为food_List的文件中

主飞镖

食物清单

当相应的按钮在food_列表中单击时，我需要调用2函数，并且需要为food_列表中的文本获取声明的变量main.dart中的_cartNumber

---

如何做到这一点？任何建议都会很有帮助：

您可以按如下方式将函数传递给食物列表小部件：

    class FooldList extends StatefulWidget{
     final Function incCart;
     final Function decCart;
   //pass these in the constructor of FoodList}

    class FoodListState extends State<FoodList> {

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


      Widget _buildItemsForListView(BuildContext context, int index) {
        return Card(
            child: Row(

                              child: new Row(
                                  children: <Widget>[
                                    new FlatButton(
                                        onPressed: () => widget.decCart,
                                        child: new Text("-", style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        ))),
                                    new Text(// here the _cartNumber,
                                        style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        )),
                                    new FlatButton(
                                        onPressed: () => widget.incCart,
                                        child: new Text("+", style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        ))),
                                  ]
                              ),
                            ),
                          ),

            ));
      }



       @override
      Widget build(BuildContext context) {
        return Scaffold(
            body: ListView.builder(
              itemCount: 10,
              itemBuilder: _buildItemsForListView,
            ));
      }

    }

    class FoodList extends StatefulWidget {
      @override
      createState() => FoodListState();
    }

然后，大体上只需传递如下函数：

class _MrTabs extends State<MyApp> {


  int _cartNumber = 10;

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


  _cartNumIncrement() {
    _cartNumber += 1;
  }

  _cartNumDecrement() {
    _cartNumber -= 1;
  }

 @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home:......
      body:FooldList(incCart: _cartNumIncrement, decCart:_cartNumDecrement );
}

    class FooldList extends StatefulWidget{
     final Function incCart;
     final Function decCart;
   //pass these in the constructor of FoodList}

    class FoodListState extends State<FoodList> {

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


      Widget _buildItemsForListView(BuildContext context, int index) {
        return Card(
            child: Row(

                              child: new Row(
                                  children: <Widget>[
                                    new FlatButton(
                                        onPressed: () => widget.decCart,
                                        child: new Text("-", style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        ))),
                                    new Text(// here the _cartNumber,
                                        style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        )),
                                    new FlatButton(
                                        onPressed: () => widget.incCart,
                                        child: new Text("+", style: TextStyle(
                                          color: Colors.white, fontSize: 14,
                                        ))),
                                  ]
                              ),
                            ),
                          ),

            ));
      }



       @override
      Widget build(BuildContext context) {
        return Scaffold(
            body: ListView.builder(
              itemCount: 10,
              itemBuilder: _buildItemsForListView,
            ));
      }

    }

    class FoodList extends StatefulWidget {
      @override
      createState() => FoodListState();
    }

class _MrTabs extends State<MyApp> {


  int _cartNumber = 10;

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


  _cartNumIncrement() {
    _cartNumber += 1;
  }

  _cartNumDecrement() {
    _cartNumber -= 1;
  }

 @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home:......
      body:FooldList(incCart: _cartNumIncrement, decCart:_cartNumDecrement );
}