將值從一個 class 傳遞到另一個 flutter

Question

我正在嘗試計算立方體的面積。 為此，我創建了一個 class，其中包含一個 slider 以獲取高度或寬度值。 但是我不知道如何將高度和寬度這兩個值聯合起來進行計算，或者如何將這個class的值傳遞到我的主頁。 如何將計算保存在變量中？

代碼主頁：

class HomePage extends StatefulWidget {
  const HomePage({super.key, required this.title});
  final String title;
  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  late double heightScreen, widthScreen;

  @override
  Widget build(BuildContext context) {
    heightScreen =
        MediaQuery.of(context).size.height - MediaQuery.of(context).padding.top;
    widthScreen = MediaQuery.of(context).size.width;
    return Scaffold(
      appBar: AppBar(
        title: const Text("Test "),
      ),
      body: Column(
        children: [
          SizedBox(
            height: 20,
          ),
          ChooseArea(slidString: "Height"),
          ChooseArea(slidString: "Width"),
        ],
      ),
    );
  }
}

選擇地區：

class ChooseArea extends StatefulWidget {
  ChooseArea({
    Key? key,
    required this.slidString,
  }) : super(key: key);

  final String slidString;

  @override
  State<ChooseArea> createState() => _ChooseAreaState();
}

class _ChooseAreaState extends State<ChooseArea> {
  double valueBottom = 1;
  @override
  Widget build(BuildContext context) {
    return Column(children: [
      Row(
        children: [
          Padding(
              padding: const EdgeInsets.only(left: 7),
              child: Text(widget.slidString))
        ],
      ),
      Row(children: [
        SizedBox(
          width: 250,
          child: Slider(
              value: valueBottom,
              label: "${valueBottom.toStringAsFixed(2)} m",
              divisions: 100,
              min: 1,
              max: 50,
              onChanged: (value) => setState(() => valueBottom = value)),
        ),
        SizedBox(width: 20),
        Text("${valueBottom.toStringAsFixed(2)} m")
      ])
    ]);
  }
}

Answer 1

您可以使用findAncestorStateOfType ，首先將您的HomePage更改為：

class HomePage extends StatefulWidget {
  const HomePage({super.key, required this.title});
  final String title;
  @override
  State<HomePage> createState() => HomePageState();

  static HomePageState? of(BuildContext context) =>
      context.findAncestorStateOfType<HomePageState>();
}

class HomePageState extends State<HomePage> {
  late double heightScreen, widthScreen;
  double? heightArea, widthArea;

  set heightValue(double value) {
    heightArea = value;
    print("heightArea = $heightArea");
  }

  set widthValue(double value) {
    widthArea = value;
    print("widthArea = $widthArea");
  }

  @override
  Widget build(BuildContext context) {
    heightScreen =
        MediaQuery.of(context).size.height - MediaQuery.of(context).padding.top;
    widthScreen = MediaQuery.of(context).size.width;
    return Scaffold(
      appBar: AppBar(
        title: const Text("Test "),
      ),
      body: Column(
        children: [
          SizedBox(
            height: 20,
          ),
          ChooseArea(slidString: "Height"),
          ChooseArea(slidString: "Width"),
        ],
      ),
    );
  }
}

然后將您的 ChooseArea 的onChanged更改為此：

Slider(
  value: valueBottom,
  label: "${valueBottom.toStringAsFixed(2)} m",
  divisions: 100,
  min: 1,
  max: 50,
  onChanged: (value) {
    if (widget.slidString == "Width") {
      HomePage.of(context)?.widthValue = value;
    } else {
      HomePage.of(context)?.heightValue = value;
    }
    setState(() => valueBottom = value);
  })