我希望你丢失了SetState() .并且你忘记在defaultFormField上添加控制器

onPressed: () {
            showTimePicker(context: context, initialTime: TimeOfDay.now())
                .then((dynamic value) {
              setState(() {
                _controller.text = value.format(context);
              });

              print(value.format(context).toString());
            });

完整小部件

import 'package:flutter/material.dart';

Widget defaultFormField({
  required TextEditingController controller,
  required TextInputType type,
  Function? validate,
  required dynamic label,
  required IconData prefix,
  IconData? suffix,
  bool isPassword = false,
  Function? suffixPressed,
  VoidCallback? onTap,
  Color colorField = Colors.black54,
}) =>
    TextFormField(
      controller: controller,
      keyboardType: type,
      obscureText: isPassword,
      onTap: onTap,
      validator: (value) {
        return validate!(value);
      },
      decoration: InputDecoration(
        hintText: label,
        border: OutlineInputBorder(),
        focusedBorder:
            OutlineInputBorder(borderSide: BorderSide(color: colorField)),
        prefixIcon: Icon(
          prefix,
          color: colorField,
        ),
        suffixIcon: IconButton(
          onPressed: () {
            suffixPressed!();
          },
          icon: Icon(suffix),
        ),
      ),
    );

class HomeLayout extends StatefulWidget {
  @override
  _HomeLayoutState createState() => _HomeLayoutState();
}

class _HomeLayoutState extends State<HomeLayout> {
  int currentIndex = 0;
  List<Widget> screens = [
    NewTasksScreen(),
    // DoneTasksScreen(),
    // ArchivedTasksScreen(),
  ];
  List<String> titles = ['New Tasks', 'Done Tasks', 'Archived Tasks'];
  // late Database database;
  var scaffoldKey = GlobalKey<ScaffoldState>();
  bool isBottomSheetShown = false;
  IconData febIcon = Icons.edit;
  var titleController = TextEditingController();
  final timeController = TextEditingController();
  var backgroundFloatBottom = Colors.deepPurpleAccent;
  String toolTip = 'Add';
  @override
  void initState() {
    // TODO : DATABASE SQFLITE
    super.initState();
    // createDatabase();
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: scaffoldKey,
      appBar: AppBar(
        title: Text(titles[currentIndex]),
        backgroundColor: Colors.deepPurpleAccent,
        elevation: 5,
        shadowColor: Colors.black,
      ),
      body: screens[currentIndex],
      floatingActionButton: FloatingActionButton(
        backgroundColor: backgroundFloatBottom,
        tooltip: toolTip,
        onPressed: () {
          if (isBottomSheetShown) {
            Navigator.pop(context);
            isBottomSheetShown = false;
            setState(() {
              febIcon = Icons.edit;
              toolTip = 'Add';
            });
          } else {
            scaffoldKey.currentState!.showBottomSheet((context) => Container(
                  color: Colors.grey[50],
                  padding: EdgeInsets.all(20),
                  child: Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      defaultFormField(
                          controller: titleController,
                          type: TextInputType.text,
                          label: 'Task Title',
                          prefix: Icons.title,
                          colorField: Colors.deepPurpleAccent,
                          validate: (String value) {
                            if (value.isEmpty) {
                              return 'Title Must Not Be Empty';
                            }
                            return null;
                          }),
                      SizedBox(height: 15),
                      defaultFormField(
                          controller: timeController,
                          type: TextInputType.datetime,
                          label: 'Task Time',
                          colorField: Colors.deepPurpleAccent,
                          prefix: Icons.watch_later_outlined,
                          onTap: () async {
                            await showTimePicker(
                                    context: context,
                                    initialTime: TimeOfDay.now())
                                .then((dynamic value) {
                              setState(() {
                                timeController.text = value.format(context);
                              });

                              print(value.format(context).toString());
                            });
                          },
                          validate: (String value) {
                            if (value.isEmpty) {
                              return 'Time Must Not Be Empty';
                            }
                            return null;
                          })
                    ],
                  ),
                ));
            isBottomSheetShown = true;
            setState(() {
              febIcon = Icons.close;
              backgroundFloatBottom = Colors.deepPurpleAccent;
              toolTip = 'Close';
            });
          }
        },
        child: Icon(febIcon),
        hoverColor: Colors.deepPurple,
      ),
      bottomNavigationBar: BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        selectedItemColor: Colors.deepPurpleAccent,
        currentIndex: currentIndex,
        onTap: (index) {
          setState(() {
            currentIndex = index;
          });
        },
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.menu),
            label: 'Tasks',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.done_all),
            label: 'Done',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.archive_outlined),
            label: 'Archived',
          ),
        ],
      ),
    );
  }
}

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

  @override
  _NewTasksScreenState createState() => _NewTasksScreenState();
}

class _NewTasksScreenState extends State<NewTasksScreen> {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Text("NewTasksScreen"),
    );
  }
}