Hello,
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Xamarin.Forms is only an UI framework, this function needs to achieved on each platform. On iOS, please register for user notifications to be able to set the application icon badge number:
//Register this in the Appdelegate
UIUserNotificationSettings settings = UIUserNotificationSettings.GetSettingsForTypes(UIUserNotificationType.Badge, null);
UIApplication.SharedApplication.RegisterUserNotificationSettings(settings);
Then use the UIApplication.SharedApplication.ApplicationIconBadgeNumber = number;
to set the badge number, you could DependencyService to call the function code in the shared project.
Unfortunately, the function is limited on Android. Android system doesn't allow changing of the application icon because it is sealed in the .apk tightly once the program is compiled. There is no way to change the icon to a 'drawable' programmatically.
Best Regards,
Jarvan Zhang
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