Flutter/Dart - 未处理的异常：“String”类型不是“index”的“int”类型的子类型

Question

我是 Flutter 的初学者，目前正在学习构建任务计划器的教程 (https://www.youtube.com/watch?v=xJSestoFlJ8&list=PLF9bFmu3NqWqchwS3DO9MDSl15IiHQWcr&index=9)

在手动重写代码（数据库等）后，当我重新启动应用程序以在调试控制台中显示我保存到数据库中的项目时，我在使用 initstate 和 setstate 时收到错误提示

Unhandled Exception: type 'String' is not a subtype of type 'int' of 'index'

这是与错误相关的代码

final TextEditingController _textEditingController = TextEditingController();
  var db = DatabaseHelper();

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

    _readTaskList();
  }

  void _handleSubmitted(String text) async {
    _textEditingController.clear();

    Tasks tasksItem = Tasks(text, DateTime.now().toIso8601String());
    int savedItemId = await db.saveItem(tasksItem);

    print("Item saved ID: $savedItemId");

  }

_readTaskList() async {
    List items = await db.getItems();
    items.forEach((item) {
      Tasks tasksItem = Tasks.map(items);
      print("DB Items: ${tasksItem.itemName}");
    });
  }

这里是完整的调试控制台日志

E/flutter ( 8249): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'String' is not a subtype of type 'int' of 'index'
E/flutter ( 8249): #0      new Tasks.map 
package:gatorblocks_rbt/models/tasks.dart:12
E/flutter ( 8249): #1      _TaskPlannerState._readTaskList.<anonymous closure> 
package:gatorblocks_rbt/pages/taskPlanner.dart:105
E/flutter ( 8249): #2      List.forEach  (dart:core-patch/growable_array.dart:285:8)
E/flutter ( 8249): #3      _TaskPlannerState._readTaskList 
package:gatorblocks_rbt/pages/taskPlanner.dart:104
E/flutter ( 8249): <asynchronous suspension>
E/flutter ( 8249): #4      _TaskPlannerState.initState 
package:gatorblocks_rbt/pages/taskPlanner.dart:24
E/flutter ( 8249): #5      StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4355
E/flutter ( 8249): #6      ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 8249): #7      Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #8      Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #9      SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 8249): #10     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #11     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #12     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 8249): #13     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 8249): #14     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4206
E/flutter ( 8249): #15     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 8249): #16     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #17     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #18     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 8249): #19     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #20     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #21     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 8249): #22     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #23     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #24     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 8249): #25     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 8249): #26     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4206
E/flutter ( 8249): #27     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4381
E/flutter ( 8249): #28     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 8249): #29     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #30     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #31     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 8249): #32     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #33     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #34     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5445
E/flutter ( 8249): #35     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #36     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #37     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 8249): #38     Element.rebuild 
package:flutter/…/widgets/framework.dart:3947
E/flutter ( 8249): #39     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:4206
E/flutter ( 8249): #40     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4381
E/flutter ( 8249): #41     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:4201
E/flutter ( 8249): #42     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3194
E/flutter ( 8249): #43     Element.updateChild 
package:flutter/…/widgets/framework.dart:2988
E/flutter ( 8249): #44     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:4243
E/flutter ( 8249): #45     Element.rebuild (package:flutte

Here is a screenshot

该应用程序运行良好，没有崩溃或任何问题，只是无法正确显示我保存到数据库中的项目。

Answer 1

您收到错误是因为您将int 放入接受String 的Text 小部件。

您可以通过使用 toString() 方法转换 int 来解决这个问题。

检查以下代码：将其替换为您的 handleSubmitted 函数：

  void _handleSubmitted(String text) async {
    _textEditingController.clear();

    Tasks tasksItem = Tasks(text, DateTime.now().toIso8601String());
    int savedItemId = await db.saveItem(tasksItem);

    // convert savedItemId to a string using toString() method
    print("Item saved ID: $savedItemId.toString()");

  }

我希望这会有所帮助。

更新 浏览完您的代码后，我可以看到您正在尝试访问您未在 Tasks 构造函数中定义的字段 id。 为什么你会收到错误： Type String is not a subtype of int index

希望这能解决您的错误。