Add scheduled notifications example. (xamarin#679)

Author: davidbritch

LocalNotifications/LocalNotifications/LocalNotifications.Android/AlarmHandler.cs

@@ -0,0 +1,19 @@
+using Android.Content;
+
+namespace LocalNotifications.Droid
+{
+    [BroadcastReceiver(Enabled = true, Label = "Local Notifications Broadcast Receiver")]
+    public class AlarmHandler : BroadcastReceiver
+    {
+        public override void OnReceive(Context context, Intent intent)
+        {
+            if (intent?.Extras != null)
+            {
+                string title = intent.GetStringExtra(AndroidNotificationManager.TitleKey);
+                string message = intent.GetStringExtra(AndroidNotificationManager.MessageKey);
+
+                AndroidNotificationManager.Instance.Show(title, message);
+            }
+        }
+    }
+}

LocalNotifications/LocalNotifications/LocalNotifications.Android/AndroidNotificationManager.cs

@@ -15,36 +15,33 @@ public class AndroidNotificationManager : INotificationManager
         const string channelId = "default";
         const string channelName = "Default";
         const string channelDescription = "The default channel for notifications.";
-        const int pendingIntentId = 0;
 
         public const string TitleKey = "title";
         public const string MessageKey = "message";
 
         bool channelInitialized = false;
-        int messageId = -1;
+        int messageId = 0;
+        int pendingIntentId = 0;
+
         NotificationManager manager;
 
         public event EventHandler NotificationReceived;
 
+        public static AndroidNotificationManager Instance { get; private set; }
+
         public void Initialize()
         {
             CreateNotificationChannel();
+            Instance = this;
         }
 
-        public int ScheduleNotification(string title, string message)
+        public void Show(string title, string message)
         {
-            if (!channelInitialized)
-            {
-                CreateNotificationChannel();
-            }
-
-            messageId++;
-
             Intent intent = new Intent(AndroidApp.Context, typeof(MainActivity));
             intent.PutExtra(TitleKey, title);
             intent.PutExtra(MessageKey, message);
 
-            PendingIntent pendingIntent = PendingIntent.GetActivity(AndroidApp.Context, pendingIntentId, intent, PendingIntentFlags.OneShot);
+            PendingIntent pendingIntent = PendingIntent.GetActivity(AndroidApp.Context, pendingIntentId++, intent, PendingIntentFlags.UpdateCurrent);
 
             NotificationCompat.Builder builder = new NotificationCompat.Builder(AndroidApp.Context, channelId)
                 .SetContentIntent(pendingIntent)
@@ -55,9 +52,31 @@ public int ScheduleNotification(string title, string message)
                 .SetDefaults((int)NotificationDefaults.Sound | (int)NotificationDefaults.Vibrate);
 
             Notification notification = builder.Build();
-            manager.Notify(messageId, notification);
+            manager.Notify(messageId++, notification);
+        }
 
-            return messageId;
+        public void SendNotification(string title, string message, DateTime? notifyTime = null)
+        {
+            if (!channelInitialized)
+            {
+                CreateNotificationChannel();
+            }
+
+            if (notifyTime != null)
+            {
+                Intent intent = new Intent(AndroidApp.Context, typeof(AlarmHandler));
+                intent.PutExtra(TitleKey, title);
+                intent.PutExtra(MessageKey, message);
+
+                PendingIntent pendingIntent = PendingIntent.GetBroadcast(AndroidApp.Context, pendingIntentId++, intent, PendingIntentFlags.CancelCurrent);
+                long triggerTime = GetNotifyTime(notifyTime.Value);
+                AlarmManager alarmManager = GetAlarmManager();
+                alarmManager.Set(AlarmType.RtcWakeup, triggerTime, pendingIntent);
+            }
+            else
+            {
+                Show(title, message);
+            }
         }
 
         public void ReceiveNotification(string title, string message)
@@ -86,5 +105,19 @@ void CreateNotificationChannel()
 
             channelInitialized = true;
         }
+
+        AlarmManager GetAlarmManager()
+        {
+            AlarmManager alarmManager = Android.App.Application.Context.GetSystemService(Context.AlarmService) as AlarmManager;
+            return alarmManager;
+        }
+
+        long GetNotifyTime(DateTime notifyTime)
+        {
+            DateTime utcTime = TimeZoneInfo.ConvertTimeToUtc(notifyTime);
+            double epochDiff = (new DateTime(1970, 1, 1) - DateTime.MinValue).TotalSeconds;
+            long utcAlarmTime = utcTime.AddSeconds(-epochDiff).Ticks / 10000;
+            return utcAlarmTime; // milliseconds
+        }
     }
 }

LocalNotifications/LocalNotifications/LocalNotifications.Android/LocalNotifications.Android.csproj

@@ -15,7 +15,6 @@
     <AndroidManifest>Properties\AndroidManifest.xml</AndroidManifest>
     <MonoAndroidResourcePrefix>Resources</MonoAndroidResourcePrefix>
     <MonoAndroidAssetsPrefix>Assets</MonoAndroidAssetsPrefix>
-    <AndroidUseLatestPlatformSdk>false</AndroidUseLatestPlatformSdk>
     <TargetFrameworkVersion>v9.0</TargetFrameworkVersion>
     <AndroidEnableSGenConcurrent>true</AndroidEnableSGenConcurrent>
     <AndroidUseAapt2>true</AndroidUseAapt2>
@@ -60,6 +59,7 @@
     <Compile Include="MainActivity.cs" />
     <Compile Include="Resources\Resource.designer.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="AlarmHandler.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Resources\AboutResources.txt" />
@@ -87,7 +87,7 @@
   <ItemGroup />
   <ItemGroup>
     <ProjectReference Include="..\LocalNotifications\LocalNotifications.csproj">
-      <Project>{48AB845E-F987-41F0-B81A-1C178087A374}</Project>
+      <Project>{A7BE66D7-177D-4188-87A1-E6948B3D1C7C}</Project>
       <Name>LocalNotifications</Name>
     </ProjectReference>
   </ItemGroup>

LocalNotifications/LocalNotifications/LocalNotifications.Android/MainActivity.cs

@@ -36,8 +36,8 @@ void CreateNotificationFromIntent(Intent intent)
         {
             if (intent?.Extras != null)
             {
-                string title = intent.Extras.GetString(AndroidNotificationManager.TitleKey);
-                string message = intent.Extras.GetString(AndroidNotificationManager.MessageKey);
+                string title = intent.GetStringExtra(AndroidNotificationManager.TitleKey);
+                string message = intent.GetStringExtra(AndroidNotificationManager.MessageKey);
 
                 DependencyService.Get<INotificationManager>().ReceiveNotification(title, message);
             }

LocalNotifications/LocalNotifications/LocalNotifications.Android/Properties/AndroidManifest.xml

@@ -1,6 +1,6 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.companyname.localnotifications">
-    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="28" />
-    <application android:label="LocalNotifications.Android"></application>
-    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+	<uses-sdk android:minSdkVersion="21" />
+	<application android:label="LocalNotifications.Android"></application>
+	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 </manifest>

LocalNotifications/LocalNotifications/LocalNotifications.iOS/iOSNotificationManager.cs

@@ -1,4 +1,5 @@
 using System;
+using Foundation;
 using UserNotifications;
 using Xamarin.Forms;
 
@@ -7,7 +8,7 @@ namespace LocalNotifications.iOS
 {
     public class iOSNotificationManager : INotificationManager
     {
-        int messageId = -1;
+        int messageId = 0;
 
         bool hasNotificationsPermission;
 
@@ -22,12 +23,12 @@ public void Initialize()
             });
         }
 
-        public int ScheduleNotification(string title, string message)
+        public void SendNotification(string title, string message, DateTime? notifyTime = null)
         {
             // EARLY OUT: app doesn't have permissions
-            if(!hasNotificationsPermission)
+            if (!hasNotificationsPermission)
             {
-                return -1;
+                return;
             }
 
             messageId++;
@@ -38,11 +39,19 @@ public int ScheduleNotification(string title, string message)
                 Subtitle = "",
                 Body = message,
                 Badge = 1
-            };
+            };            
 
-            // Local notifications can be time or location based
-            // Create a time-based trigger, interval is in seconds and must be greater than 0
-            var trigger = UNTimeIntervalNotificationTrigger.CreateTrigger(0.25, false);
+            UNNotificationTrigger trigger;
+            if (notifyTime != null)
+            {
+                // Create a calendar-based trigger.
+                trigger = UNCalendarNotificationTrigger.CreateTrigger(GetNSDateComponents(notifyTime.Value), false);
+            }
+            else
+            {
+                // Create a time-based trigger, interval is in seconds and must be greater than 0.
+                trigger = UNTimeIntervalNotificationTrigger.CreateTrigger(0.25, false);
+            }                      
 
             var request = UNNotificationRequest.FromIdentifier(messageId.ToString(), content, trigger);
             UNUserNotificationCenter.Current.AddNotificationRequest(request, (err) =>
@@ -52,8 +61,6 @@ public int ScheduleNotification(string title, string message)
                     throw new Exception($"Failed to schedule notification: {err}");
                 }
             });
-
-            return messageId;
         }
 
         public void ReceiveNotification(string title, string message)
@@ -65,5 +72,18 @@ public void ReceiveNotification(string title, string message)
             };
             NotificationReceived?.Invoke(null, args);
         }
+
+        NSDateComponents GetNSDateComponents(DateTime dateTime)
+        {
+            return new NSDateComponents
+            {
+                Month = dateTime.Month,
+                Day = dateTime.Day,
+                Year = dateTime.Year,
+                Hour = dateTime.Hour,
+                Minute = dateTime.Minute,
+                Second = dateTime.Second
+            };
+        }
     }
 }

LocalNotifications/LocalNotifications/LocalNotifications/App.xaml.cs

@@ -8,7 +8,7 @@ public App()
         {
             InitializeComponent();
 
-            // use the dependency service to get a platform-specific implementation and initialize it
+            // Use the dependency service to get a platform-specific implementation and initialize it.
             DependencyService.Get<INotificationManager>().Initialize();
 
             MainPage = new MainPage();

LocalNotifications/LocalNotifications/LocalNotifications/INotificationManager.cs

@@ -5,11 +5,8 @@ namespace LocalNotifications
     public interface INotificationManager
     {
         event EventHandler NotificationReceived;
-
         void Initialize();
-
-        int ScheduleNotification(string title, string message);
-
+        void SendNotification(string title, string message, DateTime? notifyTime = null);
         void ReceiveNotification(string title, string message);
     }
 }

LocalNotifications/LocalNotifications/LocalNotifications/MainPage.xaml

@@ -9,13 +9,21 @@
              Padding="10">
     <StackLayout Margin="0,35,0,0"
                  x:Name="stackLayout">
-        <Label Text="Click the button to create a local notification."
+        <Label Text="Click the button below to create a local notification."
                TextColor="Red"
                HorizontalOptions="Center"
                VerticalOptions="Start" />
         <Button Text="Create Notification"
                 HorizontalOptions="Center"
                 VerticalOptions="Start"
-                Clicked="OnScheduleClick"/>
+                Clicked="OnSendClick" />
+        <Label Text="Click the button below to schedule a local notification for in 10 seconds time."
+               TextColor="Red"
+               HorizontalOptions="Center"
+               VerticalOptions="Start" />
+        <Button Text="Create Notification"
+                HorizontalOptions="Center"
+                VerticalOptions="Start"
+                Clicked="OnScheduleClick" />
     </StackLayout>
 </ContentPage>

LocalNotifications/LocalNotifications/LocalNotifications/MainPage.xaml.cs

@@ -20,12 +20,20 @@ public MainPage()
             };
         }
 
+        void OnSendClick(object sender, EventArgs e)
+        {
+            notificationNumber++;
+            string title = $"Local Notification #{notificationNumber}";
+            string message = $"You have now received {notificationNumber} notifications!";
+            notificationManager.SendNotification(title, message);
+        }
+
         void OnScheduleClick(object sender, EventArgs e)
         {
             notificationNumber++;
             string title = $"Local Notification #{notificationNumber}";
             string message = $"You have now received {notificationNumber} notifications!";
-            notificationManager.ScheduleNotification(title, message);
+            notificationManager.SendNotification(title, message, DateTime.Now.AddSeconds(10));
         }
 
         void ShowNotification(string title, string message)