标签: flutter-dropdownbutton

在这里，我创建了一个 DropdownItemMenu，它从 firebase 集合中获取元素，但它显示了一个错误

\n

未为类型“BuildContext”定义方法“showSnackBar”

\n

Container(\n                    margin: EdgeInsets.only(left: 16, right: 16),\n                    height: MediaQuery.of(context).size.height * 0.10,\n                    child: Card(\n                      child: Padding(\n                        padding: const EdgeInsets.all(8.0),\n                        child: DropdownButton<String>(\n                          isExpanded: false,\n                          style: TextStyle(\n                              fontSize: 14, color: Colors.blueGrey),\n                          icon: const Icon(Icons.keyboard_arrow_down),\n                          underline: Container(color: Colors.transparent),\n                          onChanged: (serieValue) {\n                            final snackBar = SnackBar(\n                                content: Text(\n                              'S\xc3\xa9rie selectionn\xc3\xa9e est $serieValue',\n                              style: TextStyle(\n                                  fontWeight: FontWeight.bold,\n                                  fontSize: 14,\n                                  color: Color(0xff11b719)),\n                            ));\n                            Scaffold.of(context.showSnackBar(snackBar));\n\n\n                            setState(() {\n                              selectedIndexSerie = serieValue;\n                            });\n                          },\n                          value: selectedIndexSerie,\n                          hint: Text(\n                            'Selectionner une s\xc3\xa9rie',\n                            style: …

我尝试选择DropdownButton item这样的：

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:dropdown_test_sample/main.dart';

void main() {
  testWidgets('Select Dropdown item test', (WidgetTester tester) async {
    // Build our app and trigger a frame.
    await tester.pumpWidget(const SampleApp());

    final dropdown = find.byKey(const ValueKey('dropdown'));

    await tester.tap(dropdown);
    await tester.pumpAndSettle();

    final dropdownItem = find.byKey(const ValueKey('First item key'));

    await tester.tap(dropdownItem);
    await tester.pumpAndSettle();
  });
}

但不幸的是，它抛出了这个异常：

似乎有某种东西不断使用相同的DropdownButton item密钥创建相同的密钥，从而使小部件测试失败，因为tester.tap()无法同时“点击”两个小部件。

这是小部件的完整实现DropdownButton：

import 'package:flutter/material.dart';

void main() {
  runApp(const SampleApp());
}

class SampleApp extends StatelessWidget {
  const SampleApp({Key? key}) …

所以我在我的应用程序中创建了一个 DropdownButton。问题是，每当我单击下拉菜单时，应用程序就会崩溃。我很困惑，因为当我在单击 DropdownButton 之前单击其他小部件（如 TextFormFields）时，它似乎工作正常。

错误信息： 'package:flutter/src/material/dropdown.dart': Failed assertion: line 581 pos 12: 'menuHeight == menuBottom - menuTop': is not true.

这是我的下拉按钮：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

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

class DropDownTry extends StatefulWidget {
  const DropDownTry({Key? key}) : super(key: …

当我尝试使用 flutter DropdownButton Widget 时，我在控制台中收到此错误。

package:flutter/src/material/dropdown.dart': 断言失败: 第 1252 行 pos 12: 'widget.items!.where((DropdownMenuItem item) => item.value == widget.value).length == 1' : 不是真的。

有一个很长的回溯...这里我添加了小代码示例，它将重现此错误...任何人都可以简单地复制粘贴到main.dart文件中

// flutter import
 import 'package:flutter/material.dart';

void main() {
  runApp(const BugReportApp());
}

class BugReportApp extends StatefulWidget {
  const BugReportApp({Key? key}) : super(key: key);

  @override
  State<BugReportApp> createState() => _BugReportAppState();
}

class _BugReportAppState extends State<BugReportApp> {
  final TextEditingController _dropdownController = TextEditingController();
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Bug Report',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Flex(direction: …

我希望你一切都好。我有一个小问题，我想根据另一个 DropdownButton 的值动态更改 DropdownButton 的值。

好吧，我将解释我的处境以及问题所在：

首先我有一个包含 3 个元素的StudyCycle列表；

final _studyCycles = const <StudyCycle>[
    StudyCycle(cycle: Cycles.elementary, classrooms: <ClassroomsLevels>[
      ClassroomsLevels.cp,
      ClassroomsLevels.ce1,
      ClassroomsLevels.ce2,
      ClassroomsLevels.cm1,
      ClassroomsLevels.cm2,
    ]),
    StudyCycle(cycle: Cycles.primary, classrooms: <ClassroomsLevels>[
      ClassroomsLevels.sixth,
      ClassroomsLevels.fifth,
      ClassroomsLevels.fourth,
      ClassroomsLevels.third,
    ]),
    StudyCycle(cycle: Cycles.secondary, classrooms: <ClassroomsLevels>[
      ClassroomsLevels.second,
      ClassroomsLevels.first,
      ClassroomsLevels.terminal,
    ])
  ];

此StudyCycle列表用于构建第一个 DropdownButton

 DropdownButton<StudyCycle>(
          value: _selectedStudyCycle,
          items: List<DropdownMenuItem<StudyCycle>>.generate(
            _studyCycles.length,
            (index) => DropdownMenuItem<StudyCycle>(
              value: _studyCycles[index],
              child: Text(_studyCycles[index].cycle.toString()),
            ),
          ),
          hint: const Text('Your Study Cycle'),
          onChanged: (StudyCycle? studyCycle) {
            if (studyCycle != _selectedStudyCycle) {
              if (_selectedStudyCycle != null) …

有没有办法在执行 onTap 函数时关闭包含所有 DropdownMenuItems的DropdownButton的选择菜单（DropdownMenuItem 内的 GestureDetector）？

这是我对 Alperen Baskaya 方法的实现（稍微简化的版本，以便于理解）。然而，这种方法还不起作用，我不确定是因为我错误地实施了它，还是因为该方法不适用于我的问题。

class _BoatSelectionState extends State<BoatSelection> {
  FocusNode focusNode;
  
  @override
  void initState() {
    super.initState();
    focusNode = FocusNode();
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        Expanded(
          child: 
            DropdownButtonHideUnderline(
              child: DropdownButton<Boat>(
                focusNode: focusNode,
                icon: Icon(
                  Icons.keyboard_arrow_down_rounded,
                  color: Colors.black,
                ),
                isExpanded: true,
                value: selectedBoat,
                onChanged: (Boat _boat) => Provider.of<BoatStreamsCubit>(context, listen: false).setBoat(_boat),
                selectedItemBuilder: (BuildContext context) {
                  return widget.boats.map<Widget>((Boat boat) {
                    return Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        BoatClassLogo(boat: boat),
                        Expanded(
                          child: …