Xamarin.Forms定时本地通知不显示且无报错问题求助

架构老林

2026-8-11

排查Xamarin.Forms定时本地通知无法显示的问题

我按照教程实现了Xamarin.Forms定时重复本地通知，但通知完全不显示，也没有任何错误或异常抛出。以下是全部相关代码，请帮忙定位问题：

Android平台实现代码（LocalNotification.cs）

using System;
using System.IO;
using System.Xml.Serialization;
using Android.App;
using Android.Content;
using Android.Media;
using AndroidX.Core.App;
using Java.Lang;
using Test.Droid;
using Test.Models;
using Test.Views;

[assembly: Xamarin.Forms.Dependency(typeof(LocalNotificationService))]

namespace Test.Droid
{

    public class LocalNotificationService : ILocalNotificationService
    {
        int _notificationIconId { get; set; }
        readonly DateTime _jan1st1970 = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        internal string _randomNumber;

        public void LocalNotification(string title, string body, int id, DateTime notifyTime)
        {

            //long repeateDay = 1000 * 60 * 60 * 24;    
            long repeateForMinute = 60000; // In milliseconds   
            long totalMilliSeconds = (long)(notifyTime.ToUniversalTime() - _jan1st1970).TotalMilliseconds;
            if (totalMilliSeconds < JavaSystem.CurrentTimeMillis())
            {
                totalMilliSeconds = totalMilliSeconds + repeateForMinute;
            }

            var intent = CreateIntent(id);
            var localNotification = new LocalNotification();
            localNotification.Title = title;
            localNotification.Body = body;
            localNotification.Id = id;
            localNotification.NotifyTime = notifyTime;

            if (_notificationIconId != 0)
            {
                localNotification.IconId = _notificationIconId;
            }
            else
            {
                localNotification.IconId = Resource.Drawable.icon;
            }

            var serializedNotification = SerializeNotification(localNotification);
            intent.PutExtra(ScheduledAlarmHandler.LocalNotificationKey, serializedNotification);

            Random generator = new Random();
            _randomNumber = generator.Next(100000, 999999).ToString("D6");

            var pendingIntent = PendingIntent.GetBroadcast(Application.Context, Convert.ToInt32(_randomNumber), intent, PendingIntentFlags.Immutable);
            var alarmManager = GetAlarmManager();
            alarmManager.SetRepeating(AlarmType.RtcWakeup, totalMilliSeconds, repeateForMinute, pendingIntent);
        }

        public void Cancel(int id)
        {

            var intent = CreateIntent(id);
            var pendingIntent = PendingIntent.GetBroadcast(Application.Context, Convert.ToInt32(_randomNumber), intent, PendingIntentFlags.Immutable);
            var alarmManager = GetAlarmManager();
            alarmManager.Cancel(pendingIntent);
            var notificationManager = NotificationManagerCompat.From(Application.Context);
            notificationManager.CancelAll();
            notificationManager.Cancel(id);
        }

        public static Intent GetLauncherActivity()
        {

            var packageName = Application.Context.PackageName;
            return Application.Context.PackageManager.GetLaunchIntentForPackage(packageName);
        }


        private Intent CreateIntent(int id)
        {

            return new Intent(Application.Context, typeof(ScheduledAlarmHandler))
                .SetAction("LocalNotifierIntent" + id);
        }

        private AlarmManager GetAlarmManager()
        {

            var alarmManager = Application.Context.GetSystemService(Context.AlarmService) as AlarmManager;
            return alarmManager;
        }

        private string SerializeNotification(LocalNotification notification)
        {

            var xmlSerializer = new XmlSerializer(notification.GetType());

            using (var stringWriter = new StringWriter())
            {
                xmlSerializer.Serialize(stringWriter, notification);
                return stringWriter.ToString();
            }
        }
    }

    [BroadcastReceiver(Enabled = true, Label = "Local Notifications Broadcast Receiver")]
    public class ScheduledAlarmHandler : BroadcastReceiver
    {

        public const string LocalNotificationKey = "LocalNotification";

        [Obsolete]
        public override void OnReceive(Context context, Intent intent)
        {
            var extra = intent.GetStringExtra(LocalNotificationKey);
            var notification = DeserializeNotification(extra);
            //Generating notification    
            var builder = new NotificationCompat.Builder(Application.Context)
                .SetContentTitle(notification.Title)
                .SetContentText(notification.Body)
                .SetSmallIcon(notification.IconId)
                .SetSound(RingtoneManager.GetDefaultUri(RingtoneType.Ringtone))
                .SetAutoCancel(true);

            var resultIntent = LocalNotificationService.GetLauncherActivity();
            resultIntent.SetFlags(ActivityFlags.NewTask | ActivityFlags.ClearTask);
            var stackBuilder = AndroidX.Core.App.TaskStackBuilder.Create(Android.App.Application.Context);

            stackBuilder.AddNextIntent(resultIntent);

            Random random = new Random();
            int randomNumber = random.Next(9999 - 1000) + 1000;

            var resultPendingIntent =
                stackBuilder.GetPendingIntent(randomNumber, (int)PendingIntentFlags.Immutable);
            builder.SetContentIntent(resultPendingIntent);
            // Sending notification    
            var notificationManager = NotificationManagerCompat.From(Application.Context);
            notificationManager.Notify(randomNumber, builder.Build());
        }

        private LocalNotification DeserializeNotification(string notificationString)
        {

            var xmlSerializer = new XmlSerializer(typeof(LocalNotification));
            using (var stringReader = new StringReader(notificationString))
            {
                var notification = (LocalNotification)xmlSerializer.Deserialize(stringReader);
                return notification;
            }
        }
    }
}

XAML页面（LocalNotification.xaml）

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="Test.Views.LocalNotificationPage"
             BackgroundColor="#533F95">
    <ContentPage.Content>
        <Grid VerticalOptions="FillAndExpand" Padding="25,40,25,30" RowSpacing="20">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <Grid Grid.Row="0">
                <StackLayout HorizontalOptions="FillAndExpand" Orientation="Horizontal">
                    <Label Text="Notifications ON/OFF" TextColor="White" FontSize="16" HorizontalOptions="StartAndExpand" VerticalOptions="Center"/>
                    <Switch IsToggled="{Binding NotificationONOFF}" HorizontalOptions="EndAndExpand" VerticalOptions="Center"/>
                </StackLayout>
            </Grid>
            <Grid Grid.Row="1">
                <StackLayout HorizontalOptions="FillAndExpand" Orientation="Horizontal">
                    <Label Text="SET TIME" HorizontalOptions="StartAndExpand" FontSize="15" TextColor="White" VerticalOptions="Center"/>
                    <TimePicker HorizontalOptions="EndAndExpand" Time="{Binding SelectedTime}" TextColor="White" BackgroundColor="Transparent" Format="t"/>
                </StackLayout>
            </Grid>
            <Grid Grid.Row="2">
                <StackLayout HorizontalOptions="FillAndExpand" Orientation="Horizontal">
                    <Label Text="SET DATE" TextColor="White" FontSize="15" VerticalOptions="Center" HorizontalOptions="StartAndExpand"/>
                    <DatePicker HorizontalOptions="EndAndExpand" Date="{Binding SelectedDate}" TextColor="White"  BackgroundColor="Transparent" Format="MM-dd-yyyy"/>
                </StackLayout>
            </Grid>
            <Grid Grid.Row="3">
                <StackLayout HorizontalOptions="FillAndExpand" Spacing="10">
                    <Label Text="Enter Message" FontSize="15" HorizontalOptions="StartAndExpand" TextColor="White" VerticalOptions="Center"/>
                    <Editor HeightRequest="120" Text="{Binding MessageText}" TextColor="Purple" BackgroundColor="White" HorizontalOptions="FillAndExpand"/>
                </StackLayout>
            </Grid>
            <Grid Grid.Row="4">
                <Button Text="Save" Command="{Binding SaveCommand}" FontSize="15" TextColor="White" BackgroundColor="Purple"  HorizontalOptions="FillAndExpand" BorderRadius="15"/>
            </Grid>
        </Grid>
    </ContentPage.Content>
</ContentPage>

页面代码-behind（LocalNotification.xaml.cs）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace Test.Views
{
   
    public partial class LocalNotificationPage : ContentPage
    {
        public LocalNotificationPage()
        {
            InitializeComponent();
            BindingContext = new LocalNotificationPageViewModel();
        }
    }
}

ViewModel（LocalNotificationviewmode.cs）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Text;
using Xamarin.Forms;

namespace Test.Views
{
    public class LocalNotificationPageViewModel : INotifyPropertyChanged
    {
        Command _saveCommand;
        public Command SaveCommand
        {
            get
            {
                return _saveCommand;
            }
            set
            {
                SetProperty(ref _saveCommand, value);
            }
        }
        bool _notificationONOFF;
        public bool NotificationONOFF
        {
            get
            {
                return _notificationONOFF;
            }
            set
            {
                SetProperty(ref _notificationONOFF, value);
                Switch_Toggled();
            }
        }
        void Switch_Toggled()
        {
            if (NotificationONOFF == false)
            {
                MessageText = string.Empty;
                SelectedTime = DateTime.Now.TimeOfDay;
                SelectedDate = DateTime.Today;
                DependencyService.Get<ILocalNotificationService>().Cancel(0);
            }
        }
        DateTime _selectedDate = DateTime.Today;
        public DateTime SelectedDate
        {
            get
            {
                return _selectedDate;
            }
            set
            {
                SetProperty(ref _selectedDate, value);
            }
        }
        TimeSpan _selectedTime = DateTime.Now.TimeOfDay;
        public TimeSpan SelectedTime
        {
            get
            {
                return _selectedTime;
            }
            set
            {
                SetProperty(ref _selectedTime, value);
            }
        }
        string _messageText;
        public string MessageText
        {
            get
            {
                return _messageText;
            }
            set
            {
                SetProperty(ref _messageText, value);
            }
        }
        public LocalNotificationPageViewModel()
        {
            SaveCommand = new Command(() => SaveLocalNotification());
        }
        void SaveLocalNotification()
        {
            if (NotificationONOFF == true)
            {
                var date = (SelectedDate.Date.Month.ToString("00") + "-" + SelectedDate.Date.Day.ToString("00") + "-" + SelectedDate.Date.Year.ToString());
                var time = Convert.ToDateTime(SelectedTime.ToString()).ToString("HH:mm");
                var dateTime = date + " " + time;
                var selectedDateTime = DateTime.ParseExact(dateTime, "MM-dd-yyyy HH:mm", CultureInfo.InvariantCulture);
                if (!string.IsNullOrEmpty(MessageText))
                {
                    DependencyService.Get<ILocalNotificationService>().Cancel(0);
                    DependencyService.Get <ILocalNotificationService>().LocalNotification("Local Notification", MessageText, 0, selectedDateTime);
                    App.Current.MainPage.DisplayAlert("LocalNotificationDemo", "Notification details saved successfully ", "Ok");
                }
                else
                {
                    App.Current.MainPage.DisplayAlert("LocalNotificationDemo", "Please enter meassage", "OK");
                }
            }
            else
            {
                App.Current.MainPage.DisplayAlert("LocalNotificationDemo", "Please switch on notification", "OK");
            }
        }
        protected bool SetProperty<T>(ref T backingStore, T value, [CallerMemberName] string propertyName = "", Action onChanged = null)
        {
            if (EqualityComparer<T>.Default.Equals(backingStore, value))
                return false;
            backingStore = value;
            onChanged?.Invoke();
            OnPropertyChanged(propertyName);
            return true;
        }
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
        {
            var changed = PropertyChanged;
            if (changed == null)
                return;
            changed.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

服务接口（Ilocalnotificationservice.cs）

using System;
using System.Collections.Generic;
using System.Text;

namespace Test.Views
{
    public interface ILocalNotificationService
    {
        void LocalNotification(string title, string body, int id, DateTime notifyTime);
        void Cancel(int id);
    }
}

核心问题排查与修复建议

缺失Android通知渠道（API 26+强制要求）
Android 8.0及以上版本必须创建通知渠道才能显示通知，你的代码完全没有渠道创建逻辑。在ScheduledAlarmHandler的OnReceive方法开头添加以下代码：

if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
{
    var channelId = "LocalNotificationChannel";
    var channelName = "本地通知";
    var channelDescription = "定时重复通知渠道";
    var channel = new NotificationChannel(channelId, channelName, NotificationImportance.Default)
    {
        Description = channelDescription
    };
    var notificationManager = context.GetSystemService(Context.NotificationService) as NotificationManager;
    notificationManager.CreateNotificationChannel(channel);
    builder.SetChannelId(channelId);
}

PendingIntent请求码逻辑错误
你使用随机数作为PendingIntent的请求码，导致应用重启后Cancel方法无法找到对应的PendingIntent，同时可能覆盖旧的闹钟任务。建议直接使用通知ID作为请求码：

// 在LocalNotification方法中
var pendingIntent = PendingIntent.GetBroadcast(Application.Context, id, intent, PendingIntentFlags.Immutable);
// 在Cancel方法中
var pendingIntent = PendingIntent.GetBroadcast(Application.Context, id, intent, PendingIntentFlags.Immutable);

AlarmManager重复闹钟兼容性问题
Android 6.0+的Doze模式会限制SetRepeating的精准度，若需要可靠的重复通知，建议使用SetExactAndAllowWhileIdle，并在每次触发后重新设置下一次闹钟。
图标资源有效性验证
确保Resource.Drawable.icon存在于Android项目中，且符合通知图标规范（透明背景、尺寸合规），无效图标会导致通知无法显示。

DateTime转换逻辑简化
ViewModel中拼接日期时间的方式容易出错，可简化为：

var selectedDateTime = new DateTime(SelectedDate.Year, SelectedDate.Month, SelectedDate.Day, 
                                   SelectedTime.Hours, SelectedTime.Minutes, SelectedTime.Seconds);

内容的提问来源于stack exchange，提问作者Vired

Xamarin.Forms定时本地通知不显示且无报错问题求助

Android平台实现代码（LocalNotification.cs） #

XAML页面（LocalNotification.xaml） #

页面代码-behind（LocalNotification.xaml.cs） #

ViewModel（LocalNotificationviewmode.cs） #

服务接口（Ilocalnotificationservice.cs） #