1.初始化flutter_local_notifications插件。

final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
    FlutterLocalNotificationsPlugin();

Future<void> initializeNotifications() async {
  const AndroidInitializationSettings initializationSettingsAndroid =
      AndroidInitializationSettings("@mipmap/ic_launcher");

  const InitializationSettings initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid);

  await flutterLocalNotificationsPlugin.initialize(initializationSettings);
}

2.在main函数中调用初始化操作

Future<void> main() async {
  //初始化操作
  WidgetsFlutterBinding.ensureInitialized();
  initializeNotifications();
  tz.initializeTimeZones();
  
  //获取当前设备所处时区
  final String currentTimeZone = await FlutterTimezone.getLocalTimezone();
  Tool.currentTimeZone=currentTimeZone;
  runApp(const MyApp();
}

3.写一个NotificationHelper类

import 'package:flutter/cupertino.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:timezone/timezone.dart' as tz;

import '../main.dart';
import '../tools/tool.dart';

class NotificationHelper extends StatefulWidget {
  String name;
  String body;
  int hour;
  int min;
  int id;

  NotificationHelper(
      {super.key,
      required this.name,
      required this.body,
      required this.hour,
      required this.min,
      required this.id});

  Future<void> scheduleNotification() async {
    const AndroidNotificationDetails androidPlatformChannelSpecifics =
        AndroidNotificationDetails(
      'channel_id',
      'channel_name',
      'channel_description',
      importance: Importance.max,
      priority: Priority.high,
    );
    const NotificationDetails platformChannelSpecifics =
        NotificationDetails(android: androidPlatformChannelSpecifics);

    final now = DateTime.now();
    //推送的时间
    final scheduledDate = DateTime(now.year, now.month, now.day, hour, min);

    await flutterLocalNotificationsPlugin.zonedSchedule(
    //id唯一
      id,
      name,
      type,
      //计算推送时间
      _nextInstanceOfTime(scheduledDate),
      platformChannelSpecifics,
      androidAllowWhileIdle: true,
      uiLocalNotificationDateInterpretation:
          UILocalNotificationDateInterpretation.absoluteTime,
      //每周重复一次
      // matchDateTimeComponents: DateTimeComponents.dayOfWeekAndTime
      //每天重复一次
      //matchDateTimeComponents: DateTimeComponents.time
      //每个月重复一次
      //matchDateTimeComponents: DateTimeComponents.dayOfMonthAndTime);
      //每年重复一次
      //matchDateTimeComponents: DateTimeComponents.dateAndTime
    );
  }

  tz.TZDateTime _nextInstanceOfTime(DateTime scheduledTime) {
    //获取手机当前时区的时间
    tz.TZDateTime now = tz.TZDateTime.now(tz.getLocation(Tool.currentTimeZone));

    tz.TZDateTime scheduledDate = tz.TZDateTime(
      tz.getLocation(Tool.currentTimeZone),
      now.year,
      now.month,
      now.day,
      scheduledTime.hour,
      scheduledTime.minute,
    );

  if (scheduledDate.isBefore(now)) {
    scheduledDate = scheduledDate.add(const Duration(days:1));
    }
    return scheduledDate;
  }

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    throw UnimplementedError();
  }
}

4.调用

NotificationHelper(
  name: xx,
  body:xx,
  hour: xx,
  min: xx,
  id: xx,
).scheduleNotification();