主页 / coding / 问题 / 78854723
Accepted
Nibbles
Asked: 2024-08-10 06:05:10 +0800 CST

如何将变量传递给类？

  • 772

我想将路径名称保存为变量，转到类并显示路径名称（作为应用栏标题）。当我尝试执行此操作时，我收到以下代码行的错误“命名参数‘path’未定义”：

builder: (_, state) => ItemDetails(path: state.path),

您能给我指出正确的方向吗？这是代码：

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);

  runApp(MaterialApp.router(routerConfig: router));
}

final router = GoRouter(
  routes: [
    GoRoute(
      path: '/',
      builder: (_, __) => Scaffold(
        appBar: AppBar(title: const Text('Home Screen')),
      ),
      routes: [
        GoRoute(
          path: 'jobs/*',
          builder: (_, state) => ItemDetails(path: state.path),
          ),
      ],
    ),
  ],
);

class ItemDetails extends StatelessWidget {

  Map routeData = {};

  @override
  Widget build(BuildContext context) {
    routeData = ModalRoute
        .of(context)
        ?.settings
        .arguments as Map;

    final Query docRef = FirebaseFirestore.instance.collection("Collection_Name").where(
        "path", isEqualTo: path);

    return FutureBuilder<QuerySnapshot>(
      future: docRef. get (),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {

          return Scaffold(
            appBar: AppBar(
              title: Text(path),
            ),
            body: Center(child: CircularProgressIndicator()),
          );
        } else if (snapshot.hasError) {
          return Scaffold(
            appBar: AppBar(
              title: Text(path),
            ),
            body: Center(child: Text("Error: ${snapshot.error}")),
          );
        } else {
          var querySnapshot = snapshot.data!;
          var docs = querySnapshot.docs;
          final data = docs[0].data() as Map<String, dynamic>;

          final yourScrollController = ScrollController();
          return Scaffold(

              appBar: AppBar(
                title: Text(path),
              ),
flutter

1 个回答

  1. Best Answer

    您需要一个带有 ItemDetails 命名参数的构造函数：

    class ItemDetails extends StatelessWidget {
  // a new variable to store parameter received by constructor
  final String path;
  // constructor that has 1 named parameter called path
  ItemDetails({required this.path});
  
  Map routeData = {};

  @override
  Widget build(BuildContext context) {
  /// ... everything else
 }
}

    波浪括号{}表示有一个必需的参数path，并且在调用构造函数时必须用名称定义它。因此使用它的方式如下：

    ItemDetails(path: state.path)是正确的。

    但使用它如下：

    ItemDetails(state.path)是不正确的。

    附注：

    您还可以像这样定义位置参数：

    class ItemDetails extends StatelessWidget {
  // a new variable to store parameter received by constructor
  final String path;
  // constructor that has 1 positional parameter
  ItemDetails(this.path);
  
  Map routeData = {};

  @override
  Widget build(BuildContext context) {
  /// ... everything else
 }
}

    你可以这样称呼它：

    ItemDetails(state.path)

    这两种方法各有利弊，但对于您来说，差别并不大。

    • 2

相关问题