下拉选项未在 Flutter 中显示答案

【问题标题】：DropDown Selection Is Not Displaying In Flutter下拉选项未在 Flutter 中显示
【发布时间】：2023-01-08 01:17:39
【问题描述】：

选择项目后不显示下拉按钮菜单项当用户需要从可用项目列表中选择单个项目但 flutter 不显示所选项目时，

 

class TaskTitleDiaglogscreen extends StatefulWidget {
  const TaskTitleDiaglogscreen({
    super.key, });

  @override
  State<TaskTitleDiaglogscreen> createState() => _TaskTitleDiaglogscreenState();
}

class _TaskTitleDiaglogscreenState extends State<TaskTitleDiaglogscreen> {
 
  @override
  Widget build(BuildContext context) {
    final taskpriority = [
      'Urgent',
      'High priority',
      'Important',
      'Medium priority',
      'Not important',
      'Low priority',
    ];
    String? selecteditem;

    return AlertDialog(
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
      content: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          InputDecorator(
            decoration: InputDecoration(
              labelText: 'Select Priority',
              labelStyle: TextStyle(fontSize: 20),
              border:
                  OutlineInputBorder(borderRadius: BorderRadius.circular(20.0)),
              contentPadding: EdgeInsets.all(10),
            ),
            child: ButtonTheme(
              materialTapTargetSize: MaterialTapTargetSize.padded,
              child: DropdownButton(
                  value: selecteditem,
                  isExpanded: true,
                  icon: Icon(Icons.keyboard_double_arrow_down_rounded),
                  items: taskpriority.map(buildMenuitem).toList(),
                  onChanged: (value) {
                    setState(() {
                      selecteditem = value;
                    });
                    print(selecteditem);
                  }),
            ),
          )
        ],
      ),
    );
  }

  DropdownMenuItem<String> buildMenuitem(String priority) => DropdownMenuItem(
        value: priority,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Text(priority),
             CircleAvatar(
              radius: 10,
              backgroundColor: _getColor(priority),
            )
          ],
        ),
      );

  Color _getColor(String value) {
    switch (value) {
      case 'Urgent':
        return Colors.red;
      case 'High priority':
        return Color.fromARGB(255, 243, 144, 144);
      case 'Important':
        return Colors.green;
      case 'Medium priority':
        return Colors.lightGreenAccent;
      case 'Not important':
        return Colors.blue;
      case 'Low priority':
        return Colors.lightBlueAccent;
      default:
        return Colors.black;
    }
  }
}

当用户需要从当时可用项目的列表中选择单个项目时，使用下拉列表

【问题讨论】：

标签： flutter dart dropdown flutter-dropdownbutton

【解决方案1】：

您需要在构建方法之外定义变量，否则它将重新分配默认值。

class _TaskTitleDiaglogscreenState extends State<TaskTitleDiaglogscreen> {
  final taskpriority = [
    'Urgent',
    'High priority',
    'Important',
    'Medium priority',
    'Not important',
    'Low priority',
  ];
  String? selecteditem;
  @override
  Widget build(BuildContext context) {

【讨论】：