InputDecoration errorText必须是常量

Question

[dart]无效的常量值.[dart]常量创建的参数必须是常量表达式.

我想制作DropdownButton,但errorText只接受常量变量.

[dart] Invalid constant value.
[dart] Arguments of a constant creation must be constant expressions.

常量变量意味着我不能用其他文本替换.

也许还有其他任何方式来进行DropdownButton验证吗？

String errorGender = null;

    var _inputGender = InputDecorator(
      decoration: const InputDecoration(labelText: 'Gender', errorText: errorGender),
      isEmpty: data['gender'] == null,
      child: DropdownButtonHideUnderline(
        child: ButtonTheme(
          alignedDropdown: true,
            child: DropdownButton(
              isDense: true,
              value: data['gender'],
              onChanged: (value) => setState(() => data['gender'] = value),
              items: _gender.map((value) {
                return DropdownMenuItem(
                  value: value,
                  child: Text(value[0].toUpperCase() + value.substring(1)),
                );
              }).toList()
            )
        )
      )
    );

Answer 1

const之前删除InputDecoration

decoration: InputDecoration(labelText: 'Gender', errorText: errorGender)