理想情况下你需要两样东西

1. Package 在状态构建器中的警报对话框，用于更新其状态。
   1.对话框关闭后重置enabled和note的值。因此，等待对话框关闭并根据您的需要重置值。
   下面是修改后的代码：

class _DeleteCrewMemberWidgetState extends State<DeleteCrewMemberWidget> {
  var note = '';
  bool enabled = false;
  @override
  Widget build(BuildContext context) {
    //No longer needed here
    //bool enabled = note.length >= 10;
    delete() {
      Navigator.pop(context, 'OK');
    }

    /// print(enabled);
    return IconButton(
        icon: Icon(Icons.remove_circle),
        onPressed: () async {
          String? input = await showDialog<String>(
            context: context,
            builder: (BuildContext context) => StatefulBuilder(
              builder: (context, setState) {
                return AlertDialog(
                  title: const Text('Delete Some Name'),
                  content: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      const Text(
                          'Please enter a reason for not needing this crew member.'),
                      TextField(
                        maxLines: 4,
                        onChanged: (value) {
                          if (value.length >= 10) {
                            enabled = true;
                          } else {
                            enabled = false;
                          }
                          print(value);
                          setState(() {});
                        },
                        decoration: const InputDecoration(
                          border: OutlineInputBorder(),
                          hintText: 'Enter your reason here',
                        ),
                      ),
                    ],
                  ),
                  actions: <Widget>[
                    TextButton(
                      onPressed: () => Navigator.pop(context, 'Cancel'),
                      child: const Text('Cancel'),
                    ),
                    TextButton(
                      onPressed: enabled ? () => delete() : null,
                      child: const Text('OK'),
                    ),
                  ],
                );
              },
            ),
          );

          //You can add a conditional here to check the return String and enable disable likewise
          note = '';
          enabled = false;

          setState(() {});
        });
  }
}

注意：您并不总是需要用setState Package 变量来进行更新，只需调用setState就会自动用更新后的变量更新widget树。

我不知道我是否理解正确，但禁用“确定”按钮，直到用户输入原因：

onPressed: enabled ? () => note.length >= 10 ? delete() : null : null,

验证码：

class _DeleteCrewMemberWidgetState extends State<DeleteCrewMemberWidget> {
  var note = '';

  @override
  Widget build(BuildContext context) {
    bool enabled = note.length >= 10;

    // delete this member
    delete() {
      Navigator.pop(context, 'OK');
    }

    print(enabled);
    return IconButton(
      icon: Icon(Icons.remove_circle),
      onPressed: () => showDialog<String>(
        context: context,
        builder: (BuildContext context) => AlertDialog(
          title: Text('Delete ${widget.position.name}'),
          content: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Text(
                  'Please enter a reason for not needing this crew member.'),
              TextField(
                maxLines: 4,
                onChanged: (value) => setState(() {
                  note = value;
                  print(note);
                }),
                decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter your reason here',
                ),
              ),
            ],
          ),
          actions: <Widget>[
            TextButton(
              onPressed: () => Navigator.pop(context, 'Cancel'),
              child: const Text('Cancel'),
            ),
            TextButton(
              onPressed: enabled ? () => note.length >= 10 ? delete() : null : null,
              child: const Text('OK'),
            ),
          ],
        ),
      ),
    );
  }
}

看看我能不能帮你解决这个问题。

这是TextEditingController的更正：

class _DeleteCrewMemberWidgetState extends State<DeleteCrewMemberWidget> {

  final noteController = TextEditingController();
  bool noteIsValid = false;

  @override
  void dispose() {
    noteController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {

    // delete this member
    delete() {
      Navigator.pop(context, 'OK');
    }

    return IconButton(
      icon: Icon(Icons.remove_circle),
      onPressed: () => showDialog<String>(
        context: context,
        builder: (BuildContext context) => AlertDialog(
          title: Text('Delete ${widget.position.name}'),
          content: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Text(
                  'Please enter a reason for not needing this crew member.'),
              TextField(
                controller: noteController,
                maxLines: 4,
                decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter your reason here',
                ),
              ),
            ],
          ),
          actions: <Widget>[
            TextButton(
              onPressed: () => Navigator.pop(context, 'Cancel'),
              child: const Text('Cancel'),
            ),
            TextButton(
              onPressed: noteIsValid ? () => delete() : null,
              child: const Text('OK'),
            ),
          ],
        ),
      ),
    );
  }

  @override
  void initState() {
    super.initState();
    noteController.addListener(() {
      setState(() {
        noteIsValid = noteController.text.length >= 10;
      });
    });
  }
}