Odtnhj

I'm developing another sample where Messaging Center send status messages not coupled from device code to my view models.

At this point I used:

• A alert message;


• Label in my view;


• A method by dependency injection from native code(interfaced and created before).

To notice the events before try in View models... etc

For it I used a static view instance in my share application constructor (App.xaml) where in view constructor I Subscript the status.

App (shared)

public partial class App : Application
 {
 public static ConnectViewModel CVM get; set; // Connection View Model
 #region MasterDetailPage
 public static MasterDetailPage MDP;
 public static NavigationPage NAV = null;
 public static MainView _mainpage;
 #endregion

 public App ()
 
 InitializeComponent();
 InitializeApplication();
 NAV = new NavigationPage(new StarterView()) BarBackgroundColor = Color.FromHex("701424"), BarTextColor = Color.White ; ;
 MDP = new MasterDetailPage();
 MDP.BackgroundColor = Xamarin.Forms.Color.FromHex("701424");
 _mainpage = new MainView();
 MDP.Master = _mainpage;
 MDP.Detail = NAV;
 MainPage = MDP;
 MainPage.Title = "H2X";

 
 private void InitializeApplication()
 

 if (CVM == null)
 
 CVM = new ConnectViewModel();
 
 

(View shared)

public MainView ()
 
 InitializeComponent ();

 string a="Test";
 #region MessegeCenter

 MessagingCenter.Subscribe<string,string>("APP", "Message_Received", async (sender,arg) => 
 
 string b = a;
 a = $"arg";

 try
 
 * await DisplayAlert(App.BM_Status, "Ok", "OK");*
 catch(Exception e)
 
 string a = e.Message;
 
 * generic_label_of_my_view = generic_label_of_my_view + "+";//It's not async one*
 *string test = App.CVM.All_conn.Msg_Reciever();//Injection - It's not async one*

 );
 #endregion

 

Into the specific platform code (Device - UWP):

• I create a timer that sends messages after some time instanced in mainpage constructor.


• A HID device that notice me when some msg comes from USB.

The dispatcherTimer

void dispatcherTimer_Tick(object sender, object e)
 
 DateTimeOffset time = DateTimeOffset.Now;
 TimeSpan span = time - lastTime;
 lastTime = time;
 //Time since last tick should be very very close to Interval
 TimerLog.Text += timesTicked + "t time since last tick: " + span.ToString() + "n";
 timesTicked++;
 if (timesTicked > timesToTick)
 
 MessagingCenter.Send<string,string>("APP","Message_Received","MR");
 
 

The HIDInit and HID InputReport event

 public async void HID_Init()
 


 var selector = HidDevice.GetDeviceSelector(a_Id, b_Id, c_ID, d_ID);
 var devices = await DeviceInformation.FindAllAsync(selector);

 if (devices.Any())
 
 // At this point the device is available to communicate with
 // So we can send/receive HID reports from it generically


 console_text = "HID devices found: " + devices.Count;

 device = await HidDevice.FromIdAsync(devices.ElementAt(0).Id, FileAccessMode.ReadWrite);

 if (device != null)
 
 // At this point the device is available to communicate with
 // create my input caller/event
 device.InputReportReceived += inputReportReceived;//invoke caller

 deviceWatcher = DeviceInformation.CreateWatcher(selector);
 deviceWatcher.Removed += deviceRemovedEventHandler;//checa se nada foi removido
 deviceWatcher.Start();
 
 else
 
 // There were no HID devices that met the selector criteria
 throw new Exception("MUTT HID device not found");
 

 
 else
 
 // There were no HID devices that met the selector criteria
 console_text = "HID device not found";
 
 

 private void inputReportReceived(HidDevice sender, HidInputReportReceivedEventArgs args)
 
 var bbytes = new byte[10];
 wait_streaming = true;
 DataReader dataReader = DataReader.FromBuffer(args.Report.Data);
 dataReader.ReadBytes(bbytes);

 console_text += System.Text.Encoding.ASCII.GetString(bbytes, 2, bbytes[1]);

 is_read = false;

 wait_streaming = false;

 MessagingCenter.Send<string,string>("App","Message_Received","MR");

 

When I run any case with Dispatchertimer "works".

When I run by the Hidinputreport event with the alertmessage creates a system.exception in alertmessege line.

This is the "System.Exception"

if DEBUG && !DISABLE_XAML_GENERATED_BREAK_ON_UNHANDLED_EXCEPTION
 UnhandledException += (sender, e) =>
 
 if (global::System.Diagnostics.Debugger.IsAttached) global::System.Diagnostics.Debugger.Break();
 ;
endif

When I run by the Hidinputreport event with the Label a marshalled interface crash with other thread in my call from messegingCenter in native code.

System.Exception: 'The application call a marshalled interface for another thread.

 (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD))'

When I run the injection, works but I'm afraid that this Thread troubles make some semantical bug in my project cause I need to call INofifyPropertyChanged in shared code to print in my view the message but ...

Can I call it into the sender into Messeging Center Subscripte ?

How can I correct the other troubles with Threads ? Manual Reset Events ? EventWaitHandle ? (Inheritance:Object->MarshalByRefObject->WaitHandle->EventWaitHandle) ... so invasive way :/

I'm sorry if I ask some stupid question or show stupit code here ... but I don't know how to organize it WELL

Thank you in advance

Guilherme