Now its fixed for good. That was easier than I thought

(cherry picked from commit 2076818220)

mastodon/src/main/java/org/joinmastodon/android/GlobalUserPreferences.java

@@ -32,6 +32,7 @@ public class GlobalUserPreferences{
 	public static boolean enableDeleteNotifications;
 	public static boolean relocatePublishButton;
 	public static boolean reduceMotion;
+	public static boolean keepOnlyLatestNotification;
 	public static String publishButtonText;
 	public static ThemePreference theme;
 	public static ColorPreference color;
@@ -70,6 +71,7 @@ public class GlobalUserPreferences{
 		voteButtonForSingleChoice=prefs.getBoolean("voteButtonForSingleChoice", true);
 		enableDeleteNotifications=prefs.getBoolean("enableDeleteNotifications", true);
 		reduceMotion=prefs.getBoolean("reduceMotion", false);
+		keepOnlyLatestNotification=prefs.getBoolean("keepOnlyLatestNotification", false);
 		theme=ThemePreference.values()[prefs.getInt("theme", 0)];
 		recentLanguages=fromJson(prefs.getString("recentLanguages", "{}"), recentLanguagesType, new HashMap<>());
 		recentEmojis=fromJson(prefs.getString("recentEmojis", "{}"), recentEmojisType, new HashMap<>());
@@ -105,6 +107,7 @@ public class GlobalUserPreferences{
 				.putBoolean("uniformNotificationIcon", uniformNotificationIcon)
 				.putBoolean("enableDeleteNotifications", enableDeleteNotifications)
 				.putBoolean("reduceMotion", reduceMotion)
+				.putBoolean("keepOnlyLatestNotification", keepOnlyLatestNotification)
 				.putString("publishButtonText", publishButtonText)
 				.putInt("theme", theme.ordinal())
 				.putString("color", color.name())

mastodon/src/main/java/org/joinmastodon/android/PushNotificationReceiver.java

@@ -38,6 +38,8 @@ public class PushNotificationReceiver extends BroadcastReceiver{
 
 	public static final int NOTIFICATION_ID=178;
 
+	private static int notificationID;
+
 	@Override
 	public void onReceive(Context context, Intent intent){
 		if(BuildConfig.DEBUG){
@@ -125,17 +127,21 @@ public class PushNotificationReceiver extends BroadcastReceiver{
 					.setDefaults(Notification.DEFAULT_SOUND | Notification.DEFAULT_VIBRATE);
 		}
 		Drawable avatar=ImageCache.getInstance(context).get(new UrlImageLoaderRequest(pn.icon, V.dp(50), V.dp(50)));
+
+		notificationID = GlobalUserPreferences.keepOnlyLatestNotification ? NOTIFICATION_ID : (int)System.currentTimeMillis();
+
 		Intent contentIntent=new Intent(context, MainActivity.class);
 		contentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 		contentIntent.putExtra("fromNotification", true);
 		contentIntent.putExtra("accountID", accountID);
+		contentIntent.putExtra("notificationID", notificationID);
 		if(notification!=null){
 			contentIntent.putExtra("notification", Parcels.wrap(notification));
 		}
 		builder.setContentTitle(pn.title)
 				.setContentText(pn.body)
 				.setStyle(new Notification.BigTextStyle().bigText(pn.body))
-				.setContentIntent(PendingIntent.getActivity(context, accountID.hashCode() & 0xFFFF, contentIntent, PendingIntent.FLAG_IMMUTABLE | PendingIntent.FLAG_UPDATE_CURRENT))
+				.setContentIntent(PendingIntent.getActivity(context, notificationID, contentIntent, PendingIntent.FLAG_IMMUTABLE | PendingIntent.FLAG_UPDATE_CURRENT))
 				.setWhen(notification==null ? System.currentTimeMillis() : notification.createdAt.toEpochMilli())
 				.setShowWhen(true)
 				.setCategory(Notification.CATEGORY_SOCIAL)
@@ -160,6 +166,6 @@ public class PushNotificationReceiver extends BroadcastReceiver{
 		if(AccountSessionManager.getInstance().getLoggedInAccounts().size()>1){
 			builder.setSubText(accountName);
 		}
-		nm.notify(accountID, NOTIFICATION_ID, builder.build());
+		nm.notify(accountID, notificationID, builder.build());
 	}
 }

mastodon/src/main/java/org/joinmastodon/android/fragments/SettingsFragment.java

@@ -243,6 +243,10 @@ public class SettingsFragment extends MastodonToolbarFragment{
 		items.add(new SwitchItem(R.string.notify_reblog, R.drawable.ic_fluent_arrow_repeat_all_24_regular, pushSubscription.alerts.reblog, i->onNotificationsChanged(PushNotification.Type.REBLOG, i.checked)));
 		items.add(new SwitchItem(R.string.notify_mention, R.drawable.ic_fluent_mention_24_regular, pushSubscription.alerts.mention, i->onNotificationsChanged(PushNotification.Type.MENTION, i.checked)));
 		items.add(new SwitchItem(R.string.sk_notify_posts, R.drawable.ic_fluent_alert_24_regular, pushSubscription.alerts.status, i->onNotificationsChanged(PushNotification.Type.STATUS, i.checked)));
+		items.add(new SwitchItem(R.string.sk_keep_only_latest_notification, R.drawable.ic_fluent_custom_alert_latest_24_regular, GlobalUserPreferences.keepOnlyLatestNotification, i->{
+			GlobalUserPreferences.keepOnlyLatestNotification=i.checked;
+			GlobalUserPreferences.save();
+		}));
 
 		items.add(new HeaderItem(R.string.settings_account));
 		items.add(new TextItem(R.string.sk_settings_profile, ()->UiUtils.launchWebBrowser(getActivity(), "https://"+session.domain+"/settings/profile"), R.drawable.ic_fluent_open_24_regular));

mastodon/src/main/res/drawable/ic_fluent_custom_alert_latest_24_regular.xml

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@color/fluent_default_icon_tint"
+        android:pathData="M12,1.996C7.852,1.996 4.5,5.341 4.5,9.496L4.5,13.594L3.129,16.752A1.251,1.251 0,0 0,4.275 18.5L9,18.5L9.006,18.68A3,3 0,0 0,15 18.502L19.736,18.5A1.25,1.25 0,0 0,20.881 16.75L19.5,13.594L19.5,12.668A6.5,6.5 0,0 1,18 12.955L18,13.906L19.354,17L4.656,17L6,13.906L6,9.496C6,6.253 8.549,3.631 11.754,3.502A6.5,6.5 0,0 1,12.793 2.051A7.49,7.49 0,0 0,12 1.996zM13.5,18.5L13.494,18.646A1.5,1.5 0,0 1,10.5 18.502L13.5,18.5z" />
+    <path
+        android:fillColor="@color/fluent_default_icon_tint"
+        android:pathData="m17.5,2.189a4.311,4.311 0,1 0,4.282 3.809c-0.04,-0.35 0.213,-0.687 0.565,-0.687 0.306,0 0.576,0.213 0.612,0.517A5.5,5.5 0,1 1,20.918 2.191V1.891a0.595,0.595 0,1 1,1.19 0v1.604l0.02,0.031h-0.02V3.675A0.595,0.595 0,0 1,21.513 4.27h-1.784a0.595,0.595 0,1 1,0 -1.189h0.396a4.292,4.292 0,0 0,-2.626 -0.892z" />
+</vector>

mastodon/src/main/res/values/strings_sk.xml

@@ -136,4 +136,5 @@
     <string name="sk_emoji_recent">Recently used</string>
     <string name="sk_clear_recent_emoji">Clear recently used emoji</string>
     <string name="sk_disable_relocate_publish_button_to_enable_customization">Disable "Relocate publish button" to allow customization</string>
+    <string name="sk_keep_only_latest_notification">Keep only latest notification</string>
 </resources>