We Keep Coding

Xamarin Android ForceDarkHelper What is it?

Periodically, the application begins to update itself. There is a constant call in the logs:
[ForceDarkHelper] updateByCheckExcludeList: pkg: com.companyname.manimobile activity: crc64d14753dcc52b83b4.MainActivity#a894c70
[ForceDarkHelper] updateByCheckExcludeList: pkg: com.companyname.manimobile activity: crc64d14753dcc52b83b4.MainActivity#a894c70
[ForceDarkHelper] updateByCheckExcludeList: pkg: com.companyname.manimobile activity: crc64d14753dcc52b83b4.MainActivity#a894c70
[ForceDarkHelper] updateByCheckExcludeList: pkg: com.companyname.manimobile activity: crc64d14753dcc52b83b4.MainActivity#a894c70
When this happens, if, for example, you open the menu , it closes itself, if something is filled in, it is cleared, the page is updated. There are no timers in the code. I'm testing the app on Xiaomi Redmi. I repeat sometimes it happens sometimes it doesn't. What is it?
I do not know what the problem is, but occasionally, it happens that the application throws the fingerprint to the page. It is intermittent. Sometimes everything works fine. That is, I go through the fingerprint, the next page opens, everything is normal and a second after 5 I am again thrown to the page where you need to enter the fingerprint.
Code for the authorization page:
public authentification()
{
try
{
InitializeComponent();
bool auth = CrossSettings.Current.GetValueOrDefault("authorized", false);
if (auth == false) { CheckAuth(); }
else
{
Application.Current.MainPage = new MasterLk();
}
}
catch { }
}
async void CheckAuth()
{
try
{
var avail = await CrossFingerprint.Current.IsAvailableAsync();
if (!avail)
{
CrossSettings.Current.GetValueOrDefault("authorized", true);
Application.Current.MainPage = new MasterLk();
}
else
{
var request = new AuthenticationRequestConfiguration("NeedAuth", "-");
var result = await CrossFingerprint.Current.AuthenticateAsync(request);
if (result.Authenticated)
{
CrossSettings.Current.GetValueOrDefault("authorized", true);
Application.Current.MainPage = new MasterLk();
}
else
{
CheckAuth();
}
}
}
catch { }
}
On the page where it throws it there is a ListView with a binding:
public class OrdersViewModel : BaseViewModel
{
private Table oldLoan;
private bool isRefreshing;
private readonly string clientId;
public bool IsRefreshing
{
get
{
return isRefreshing;
}
set
{
isRefreshing = value;
OnPropertyChanged("IsRefreshing");
}
}
public ICommand RefreshCommand { get; set; }
public ObservableCollection<Table> Loans { get; set; }
public void ShowOrHideLoan(Table loan)
{
if (oldLoan == loan)
{
loan.IsExpanded = !loan.IsExpanded;
Reload(loan);
}
else
{
if (oldLoan != null)
{
oldLoan.IsExpanded = false;
Reload(oldLoan);
}
loan.IsExpanded = true;
Reload(loan);
}
oldLoan = loan;
}
private void Reload(Table loan)
{
var index = Loans.IndexOf(loan);
Loans.Remove(loan);
Loans.Insert(index, loan);
}
public async Task LoadDataAsync()
{
IsRefreshing = true;
Loans.Clear();
try
{
var loans = await ConnectAPI.GetOrdersAsync(clientId);
await Task.Delay(1000);
foreach (var item in loans)
{
Loans.Add(item);
}
}
catch (Exception exc)
{
Console.WriteLine(exc.Message);
}
finally
{
oldLoan = null;
IsRefreshing = false;
}
}
public OrdersViewModel(string clientId)
{
IsRefreshing = false;
this.clientId = clientId;
Loans = new ObservableCollection<Table>();
RefreshCommand = new Command(async () =>
{
await LoadDataAsync();
});
Task.Run(async () => await LoadDataAsync());
}
}
That is, whenever the [ForceDarkHelper] updateByCheckExcludeList: pkg: com.companyname.manimobile activity: crc64d14753dcc52b83b4 event appears.MainActivity#a894c70
Throws it to the print page...
and if you stay on this page, it is updated after a while.

MIUI 12 has made an intelligent dark theme. The system itself repaints the applications if they do not support the dark theme. Apparently this service is ForceDarkHelper. And ExcludeList is in the settings a list of applications that cannot be repainted

Touch Id with Xamarin Forms Application

We are trying to use Touch Id with iOS using our Xamarin Forms application.
In our Xamarin Forms Application, in the App.Xaml.cs constructor we are using an interface to reference the iOS native touch id implementation:
bool _authenticatedWithTouchID = DependencyService.Get<ITouchID>().AuthenticateUserIDWithTouchID();
if (_authenticatedWithTouchID)
{
MainPage = new NavigationPage(new MainPage());
}
else
{
MainPage = new NavigationPage(new LoginPage());
}
This is the interface signature within Forms Application:
public interface ITouchID
{
bool AuthenticateUserIDWithTouchID();
}
This is the implementation of the interface within the iOS project:
[assembly: Dependency(typeof(TouchID))]
namespace GetIn.iOS
{
public class TouchID : ITouchID
{
public bool AuthenticateUserIDWithTouchID()
{
bool outcome = false;
var context = new LAContext();
if (context.CanEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, out NSError AuthError))
{
var replyHandler = new LAContextReplyHandler((success, error) => {
Device.BeginInvokeOnMainThread(() => {
if (success)
{
outcome = true;
}
else
{
outcome = false;
}
});
});
context.EvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, "Logging with touch ID", replyHandler);
};
return outcome;
}
}
}
We get a response from the outcome variable (which is true if user is authenticated) but that is not being passed back to the forms application.
We have also tried using async tasks with no luck.
Is there a recommended way we do this? We are trying to keep this as simple as possible.

You need to change your code to handle asynchronous behavior.
public class TouchID : ITouchID
{
public Task<bool> AuthenticateUserIDWithTouchID()
{
var taskSource = new TaskCompletionSource<bool>();
var context = new LAContext();
if (context.CanEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, out NSError AuthError))
{
var replyHandler = new LAContextReplyHandler((success, error) => {
taskSource.SetResult(success);
});
context.EvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, "Logging with touch ID", replyHandler);
};
return taskSource.Task;
}
}
Remember add the using on top
using System.Threading.Tasks;
And change your interface declaration
public interface ITouchID
{
Task<bool> AuthenticateUserIDWithTouchID();
}
And finally your Xamarin.Forms code...
var touchId = DependencyService.Get<ITouchID>();
var _authenticatedWithTouchID = await touchId.AuthenticateUserIDWithTouchID();
if (_authenticatedWithTouchID)
{
MainPage = new NavigationPage(new MainPage());
}
else
{
MainPage = new NavigationPage(new LoginPage());
}

Managed to get this working by using the async changes above (although you can do this without using the async method), and then doing the following:
By moving and adapting the following code from the app.xaml.cs to our MainPage.xaml.cs (our tabbed page) constructor.
var touchId = DependencyService.Get<ITouchID>();
var _authenticatedWithTouchID = await
touchId.AuthenticateUserIDWithTouchID();
if (_authenticatedWithTouchID)
{
//Do Nothing as on this page
}
else
{
//Go back to login page
Navigation.InsertPageBefore(new LoginPage(), this);
await Navigation.PopAsync();
}

Async task within MvvmCross Command not returning

I am building a small project using MvvMCross within a Xamarin PCL project and having issue with an async Task that I am calling within a command that is bound to a button.
I have a fake web service where-in I simply call Task.Delay(3000). When the process gets to this point it simply sits and does nothing.
I originally had the command call using the .wait() call but read somewhere that this was a blocking call and cant be miced with "async / wait"
Could someone help and possible give me a hint as to where I am going wrong on the command binding please ?
https://bitbucket.org/johncogan/exevaxamarinapp is the public git repo, the specific command is
public ICommand SaveProfile
within the ProfileViewModel.cs file.
The specific code is:
public ICommand SaveProfile
{
get
{
return new MvxCommand(() =>
{
if (_profile.IsValidData())
{
// Wait for task to compelte, do UI updates here
// TODO Throbber / Spinner
EnumWebServiceResult taskResult;
Mvx.Resolve<IProfileWebService>().SendProfileToServer(_profile).Wait();
if(_profileWebService.getLastResponseResult() == true){
taskResult = EnumWebServiceResult.SUCCESS;
}else{
taskResult = EnumWebServiceResult.FAILED_UNKNOWN;
}
//_profileWebService.SendProfileToServer(_profile).Wait();
// Close(this);
}
});
}
}
The web service class () is:
using System;
using System.Threading.Tasks;
using ExevaXamarinApp.Models;
namespace ExevaXamarinApp.Services
{
public class FakeProfileWebService : IProfileWebService
{
public int _delayPeriod { get; private set; }
public bool? lastResult;
/// <summary>
/// Initializes a new instance of the <see cref="T:ExevaXamarinApp.Enumerations.FakeProfileWebService"/> class.
/// </summary>
/// 3 second delay to simulate a remote request
public FakeProfileWebService()
{
_delayPeriod = 3000;
lastResult = null;
}
private Task Sleep()
{
return Task.Delay(3000);
}
public bool? getLastResponseResult(){
return lastResult;
}
/// <summary>
/// Sends the profile to server asynchronously
/// </summary>
/// <returns>EnumWebServiceResultFlag value</returns>
/// <param name="profileObject">Profile model object</param>
public async Task SendProfileToServer(Profile profileObject)
{
// Validate arguments before attempting to use web serivce
if (profileObject.IsValidData())
{
// TODO: Return ENUM FLAG that represents the state of the result
await Sleep();
lastResult = true;
}else{
lastResult = false;
}
}
}
}

Please try this:
public ICommand SaveProfile
{
get
{
return new MvxCommand(async () => // async added
{
if (_profile.IsValidData())
{
// Wait for task to compelte, do UI updates here
// TODO Throbber / Spinner
EnumWebServiceResult taskResult;
await Mvx.Resolve<IProfileWebService>().SendProfileToServer(_profile).ConfigureAwait(false); // await, confi.. added
if(_profileWebService.getLastResponseResult() == true){
taskResult = EnumWebServiceResult.SUCCESS;
}else{
taskResult = EnumWebServiceResult.FAILED_UNKNOWN;
}
//_profileWebService.SendProfileToServer(_profile).Wait();
// Close(this);
}
});
}
}
private async Task Sleep() // async added
{
return await Task.Delay(3000).ConfigureAwait(false); // await, confi... added
}
public async Task SendProfileToServer(Profile profileObject)
{
// Validate arguments before attempting to use web serivce
if (profileObject.IsValidData())
{
// TODO: Return ENUM FLAG that represents the state of the result
await Sleep().ConfigureAwait(false); // await, confi... added
lastResult = true;
}else{
lastResult = false;
}
}
The problem is, that the context from the UI and the async cause a deadlock.

Creating a Loading view in .NET Core / Change view without returning c#

I am working on a website created in .NET Core (using the full .NET Framework) that uses background tasks to get a devices list.
I want to display a loading "view" like this while the task is getting data from another PC (using GET requests) and then, when the task is completed I want to display the table with the devices. How can I do that?
Here is a little piece of my code:
public class DeviceController : Controller {
public IActionResult Index() {
if (DataSyncronizer.getDeviceListTask.Status == TaskStatus.Running) {
// TODO Show the loading screen here.
// return this.View("Loading");
}
if (DataSyncronizer.getDeviceListTask.Status == TaskStatus.Faulted) {
ViewData["ErrorTitle"] = "Errore di sincronizzazione";
ViewData["ErrorText"] = "Cannot get devices";
return this.View("Error");
}
if (DataSyncronizer.getDeviceListTask.Status == TaskStatus.Canceled) {
ViewData["ErrorTitle"] = "Errore di sincronizzazione";
ViewData["ErrorText"] = "";
return this.View("Error");
}
return this.View(DataSyncronizer.Devices);
}
And this is the function that gets the device list:
public static class DataSyncronizer {
public static Task<List<Device>> getDeviceListTask { get; private set; }
public static List<Device> Devices = new List<Device>();
public static Task UpdateDevices() {
getDeviceListTask = new Task<List<Device>>(() =>
Device.GetMyDevicesList(meUser));
getDeviceListTask.ContinueWith((result) => {
DataSyncronizer.Devices = result.Result;
}, TaskScheduler.Current);
getDeviceListTask.Start();
return getDeviceListTask;
}
}

You could display the loader right before you call UpdateDevices().
add this to the end of your TASK
.ContinueWith(t => "Function to hide loader");
Example
var webTask = Task.Run(() =>
{
try
{
wcf.UploadMotionDynamicRaw(bytes); //my web service
}
catch (Exception ex)
{
//deal with error
}
}).ContinueWith(t => "Function to hide loader");

How do I run my Task in my ViewModel inside my ContentPage?

I have a task in my viewmodel that looks like this:
ICommand getWeather;
public ICommand GetWeatherCommand =>
getWeather ??
(getWeather = new Command(async () => await ExecuteGetWeatherCommand()));
public async Task ExecuteGetWeatherCommand()
{
if (IsBusy)
return;
IsBusy = true;
try
{
WeatherRoot weatherRoot = null;
var units = IsImperial ? Units.Imperial : Units.Metric;
if (UseGPS)
{
//Get weather by GPS
var local = await CrossGeolocator.Current.GetPositionAsync(10000);
weatherRoot = await WeatherService.GetWeather(local.Latitude, local.Longitude, units);
}
else
{
//Get weather by city
weatherRoot = await WeatherService.GetWeather(Location.Trim(), units);
}
//Get forecast based on cityId
Forecast = await WeatherService.GetForecast(weatherRoot.CityId, units);
var unit = IsImperial ? "F" : "C";
Temp = $"Temp: {weatherRoot?.MainWeather?.Temperature ?? 0}°{unit}";
Condition = $"{weatherRoot.Name}: {weatherRoot?.Weather?[0]?.Description ?? string.Empty}";
}
catch (Exception ex)
{
Temp = "Unable to get Weather";
//Xamarin.Insights.Report(ex);
}
finally
{
IsBusy = false;
}
}
How can I reach that Task and make it execute the function properly?
My goal is for it to execute right when the user enters the contentpage (StartPage). Right now I use this code below but the Command does not execute.
public StartPage ()
{
InitializeComponent ();
loadCommand ();
}
async Task loadCommand ()
{
var thep = new WeatherViewModel ();
await thep.ExecuteGetWeatherCommand ();
}
I bind the command into my listview:
RefreshCommand="{Binding GetWeatherCommand}"
With my current code the Task does not execute. What am I missing?

Firstly, your naming convention is odd, theTask is not a Task, so you probably should not call it one. Secondly, because you are calling loadCommand in your constructor and not awaiting it, its possible for the constructor to complete before the function is completed. In general, you want to avoid async in your constructor.
Stephen Cleary has a great article on async in constructors here: http://blog.stephencleary.com/2013/01/async-oop-2-constructors.html
What may be appropriate is attaching a handler to the Appearing event of your page, and do the async work there. Without more context it is a little hard to say if this is the best approach for your use case.
For instance:
public StartPage ()
{
InitializeComponent ();
Appearing += async (sender, args) => await loadCommand();
}
async Task loadCommand ()
{
var viewModel = new StartPageViewModel();
await viewModel.ExecuteCommand();
}