Flutter：RangeError（索引）：无效值：不在包含范围 0..27：28

Question

大家好，我是 flutter 初学者，在练习滑动以关闭选项时，我已经完成了下面提到的代码，在删除了一些产品后，我收到了以下错误，我试图解决问题但不能，请给我宝贵的建议。

下面附上代码和错误供大家参考。

======== widgets库捕获异常================================ ======================= 以下 RangeError 被抛出构建： RangeError (index): 无效值：不在包含范围 0..27: 28

抛出异常时，这是堆栈： #0 List.[] (飞镖:core-patch/growable_array.飞镖:254:60) #1 MyHome.build。（包：flutterswipedismiss/main.dart:34:27） #2 SliverChildBuilderDelegate.build（包：flutter/src/widgets/sliver.dart:455:22） #3 SliverMultiBoxAdaptorElement._build（包：flutter/src/widgets/sliver.dart:1201:28） #4 SliverMultiBoxAdaptorElement.createChild。（包：flutter/src/widgets/sliver.dart:1214:55） ...

...

Main.dart

  import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHome(),
    );
  }
}

class MyHome extends StatelessWidget {
  final List<String> items =
      List<String>.generate(30, (i) => "Product ${i + 1}");
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Delete panna sidela thallu"),
      ),
      body: ListView.builder(
        itemCount: items.length,
        itemBuilder: (context, int index) {
          return Dismissible(
            key: Key(items[index]),
            onDismissed: (direction) {
              items.removeAt(index);
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(
                  content: Text("Item Dismissed."),
                ),
              );
            },
            background: Container(
              color: Colors.red,
            ),
            child: ListTile(
              title: Text("${items[index]}"),
            ),
          );
        },
      ),
    );
  }
}

Answer 1

我无法理解问题的原因，但我能够通过将 MyHome 小部件转换为 StatefulWidget 并在删除项目时调用 setState 来修复它。

这是新代码：

class MyHome extends StatefulWidget {
  @override
  _MyHomeState createState() => _MyHomeState();
}

class _MyHomeState extends State<MyHome> {
  final List<String> items =
      List<String>.generate(30, (i) => "Product ${i + 1}");
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Delete panna sidela thallu"),
      ),
      body: ListView.builder(
        itemCount: items.length,
        itemBuilder: (context, int index) {
          return Dismissible(
            key: Key(items[index]),
            onDismissed: (direction) {
              setState(() {
                items.removeAt(index);
              });
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(
                  content: Text("Item Dismissed."),
                ),
              );
            },
            background: Container(
              color: Colors.red,
            ),
            child: ListTile(
              title: Text("${items[index]}"),
            ),
          );
        },
      ),
    );
  }
}

Flutter：RangeError（索引）：无效值：不在包含范围 0..27：28

Flutter : RangeError (index): Invalid value: Not in inclusive range 0..27: 28

android

slide

dismiss

dart

flutter

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