System.ArgumentException'kls' must not be IntPtr.Zero. Parameter name: kls

[acaliaro]

Hi Chris.
I have this problem

at Android.Runtime.JNIEnv.GetMethodID (IntPtr kls, System.String name, System.String signature) <0xaf5e7b48 + 0x0014c> in :0
at Android.Content.ISharedPreferencesInvoker.Edit () <0xaf5d6d20 + 0x0003f> in :0
at Acr.Notifications.NotificationsImpl.GetNextNotificationId () <0x9c478830 + 0x000bf> in :0
at Acr.Notifications.NotificationsImpl.Send (Acr.Notifications.Notification notification) <0x9c478380 + 0x0004b> in :0
at IWapp.App.m__1 (IWapp.App sender, System.String arg) <0x9c477c80 + 0x00193> in :0
at Xamarin.Forms.MessagingCenter+<>c__DisplayClass1_02[TSender,TArgs].<Subscribe>b__0 (System.Object sender, System.Object args) <0x9c477b58 + 0x000bb> in <filename unknown>:0 at Xamarin.Forms.MessagingCenter.InnerSend (System.String message, System.Type senderType, System.Type argType, System.Object sender, System.Object args) <0xaf9de070 + 0x00167> in <filename unknown>:0 at Xamarin.Forms.MessagingCenter.Send[TSender,TArgs] (Xamarin.Forms.TSender sender, System.String message, Xamarin.Forms.TArgs args) <0x9c477a88 + 0x00057> in <filename unknown>:0 at AltBeaconLibrary.Sample.Droid.Services.AltBeaconService.EnteredRegion (System.Object sender, AltBeaconLibrary.Sample.Droid.MonitorEventArgs e) <0x9c4776c0 + 0x000df> in <filename unknown>:0 at (wrapper delegate-invoke) System.EventHandler1[AltBeaconLibrary.Sample.Droid.MonitorEventArgs]:invoke_void_object_TEventArgs (object,AltBeaconLibrary.Sample.Droid.MonitorEventArgs)
at AltBeaconLibrary.Sample.Droid.MonitorNotifier.OnEnterRegionComplete (AltBeaconOrg.BoundBeacon.Region region) <0x9c477630 + 0x00067> in :0
at AltBeaconLibrary.Sample.Droid.MonitorNotifier.DidEnterRegion (AltBeaconOrg.BoundBeacon.Region region) <0x9c4775e8 + 0x0001b> in :0
at AltBeaconOrg.BoundBeacon.IMonitorNotifierInvoker.n_DidEnterRegion_Lorg_altbeacon_beacon_Region_ (IntPtr jnienv, IntPtr native__this, IntPtr native_region) <0x9c477528 + 0x00063> in :0
at (wrapper dynamic-method) System.Object:9996f0df-41f5-4bdc-95ea-96f5b8b96362 (intptr,intptr,intptr)