小编Ste*_*cis的帖子

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) …