I am working on converting my apps from UWP to Xamarin.Forms. A large number of my event handlers' second parameter was of type RoutedEventArgs (or a descendant of it). I often used the Handled property of this to control which controls' events were triggered. I am still very new to Xamarin.Forms, but it seems like it uses EventArgs instead (in the GestureRecognizers), which does not include this property. Is there anything I can do to gain functionality similar to that provided by RoutedEventArgs in Xamarin.Forms? Thanks.

I am using xamarin forms To create an app. in which i need to change TabbedPage tab bar color programmatically not by Xaml when tab page change but i can't help my self. var t = FindViewById(Resource.Id.sliding_tabs); method FindViewById return null

Hello,
I have the same issue as this one:
https://forums.xamarin.com/discussion/146590/showing-disable-xaml-generated-binding-debug-output-when-loading-a-page
https://forums.xamarin.com/discussion/147297/uwp-app-breaks-when-the-code-execution-comes-to-displayalert-line#latest
But the accepted answers does not work.

My solution works well on android, not with UWP.

From the main page, the app pushes async every pages well but pushing async the PositionsPage makes Redirect to App.g.i.cs:

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

This is the HomePage code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using AlmicantaratSharedProject.Ephemeris;

namespace AlmicantaratXF.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class HomePageXAML : ContentPage
    {
        public HomePageXAML()
        {
            InitializeComponent();
        }
        async void OnButtonTheoryClicked(object sender, EventArgs args)
        {
            await Navigation.PushAsync(new LessonTabPage(LessonTabPage.Lesson.theory));
        }
        async void OnButtonPracticeClicked(object sender, EventArgs args)
        {
            await Navigation.PushAsync(new LessonTabPage(LessonTabPage.Lesson.pratice));
        }
        async void OnButtonSettingsClicked(object sender, EventArgs args)
        {
            await Navigation.PushAsync(new SettingsPageXAML());
        }
        async void OnButtonPositionsClicked(object sender, EventArgs args)
        {
            Device.BeginInvokeOnMainThread(async () => //************ I added that to try to solve the problem
            {
                await Navigation.PushAsync(new PositionsPage()); //********** this is the line that redirects to the UnhandledException
            });
        }
        async void OnButtonStarsClicked(object sender, EventArgs args)
        {
            var watch = System.Diagnostics.Stopwatch.StartNew();
            string starname = App.StarsNames[1562].Designation(System.Globalization.CultureInfo.CurrentCulture);
            string stardesignation = App.StarsNames[2081].Designation(System.Globalization.CultureInfo.CurrentCulture);
            watch.Stop();
            await DisplayAlert("Stars", starname+" "+stardesignation, "OK");  // ************* There is no issue there...
        }
    }
}

I am trying to automate a website data extraction by dynamically creating a webview and loading the source url. I want the page and webview to be NOT to be displayed to the user. Unfortunately the events seems not working. Any help appreciated

Here is what I am trying to do:

ContentPage cp = new ContentPage();
    cp.Title = "My Page";
    StackLayout sl = new StackLayout();
    var webView = new WebView();

    sl.Children.Add(webView);
    cp.Content = sl;

    webView.Navigating += WebView_Navigating;
    webView.Navigated += WebView_Navigated;

    webView.Source = "https://www.google.com/";//just a sample i tried multiple urls including http


private async void WebView_Navigating(object sender, WebNavigatingEventArgs e)
{
    //event not firing!
}

private async void WebView_Navigated(object sender, WebNavigatedEventArgs e)
{
    //event not firing!
}

I created an interface IFirebaseDatabaseService that has that contains:
bool itemExists(string dbPath, string item);

I have implemented the following code for Android, can someone please help me with the code for iOS, i just can't get the most simple thing write, even with the examples in google. Well, as for the android code, I test it out with an item it doesn't exists multiple times, every time return false, okay. But with an item that did exist also returned false, I verified the path, and what I did next was to put Application.Current.MainPage.DisplayAlert("Result", exist.toString(), "OK"); just below the exists = sp.Exists(); line in the code below, and when being called by the interface still printed false, the DisplayAlert printed true
What am I doing wrong?

Android:
`public class ValueEventListener : Java.Lang.Object, IValueEventListener
{

public bool exists;
onDataChange(DataSnapshot sp)
{
    exists = sp.Exists();
}

}

public class FirebaseDatabaseService : IFirebaseDatabaseService
{
DatabaseReference databaseReference;
FirebaseDatabase database;

bool itemExists(string dbPath, string item)
{
    database = FirebaseDatabase.GetInstance(MainActivity.app).GetReference(dbPath);
    ValueEventListener v = new ValueEventListener();
           databaseReference.AddValueEventListener(v);
    return v.exists;
}

}`

I need to design the CollectionView with Header in XAML, how to do this?

Hi Dear Reader, I have created a simple XF project in VS 2019 - latest upgrades, with Xamarin Forms (latest stable) using a Blank template. When I tried to add a LauncScreen.storyboard (becasue none was created in the template) I got the messages below.
When I created a new Tabbed project (including UWP) it created a LaunchScreen.storyboard, but when I double clicked it, the editor was opened but I got a similar set of errors.

Any ideas as to what is wrong with my installation?
Where can I find a site that has current instructions for creating a Launch screen in Xamarin Forms - iOS?
Thanks!
Will

System.AggregateException: One or more errors occurred. ---> System.AggregateException: One or more errors occurred. ---> MonoTouch.Design.Client.InvalidSessionException: Error in the application.
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest(CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 235
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest[TResponse](CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 252
at MonoTouch.Design.Client.ServerProcessConnection.CreateSession() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 111
at MonoTouch.Design.Client.ServerProcessConnection.b__28_0() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 116
at System.Threading.Tasks.Task1.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of stack trace from previous location where exception was thrown --- at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject) --- End of inner exception stack trace --- at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions) at System.Threading.Tasks.Task1.GetResultCore(Boolean waitCompletionNotification)
at System.Threading.Tasks.Task1.get_Result() at MonoTouch.Design.Client.IPhoneDesignerSession.<>c__DisplayClass289_11.b__1(Task1 t) in E:\A\_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 2073 at System.Threading.Tasks.ContinuationResultTaskFromResultTask2.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at System.Threading.Tasks.Task.Wait()
at MonoTouch.Design.Client.IPhoneDesignerSession.<>c__DisplayClass289_01.<EnsureSession>b__0() in E:\A\_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 2139 at System.Threading.Tasks.Task1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MonoTouch.Design.Client.IPhoneDesignerSession.d__191.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 748
--- End of stack trace from previous location where exception was thrown ---
at MonoTouch.Design.Client.IPhoneDesignerSession.d__191.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 755
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MonoTouch.Design.Client.IPhoneDesignerSession.d__190.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 733
--- End of stack trace from previous location where exception was thrown ---
at MonoTouch.Design.Client.IPhoneDesignerSession.d__190.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 741
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at MonoTouch.Design.Client.IPhoneDesignerSession.d__186.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 622
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MonoTouch.Design.Tasks.d__1.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Shared\TaskExtensions.cs:line 28
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MonoTouch.Design.Client.IPhoneDesignerSession.d__185.MoveNext() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 574
---> (Inner Exception #0) System.AggregateException: One or more errors occurred. ---> MonoTouch.Design.Client.InvalidSessionException: Error in the application.
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest(CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 235
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest[TResponse](CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 252
at MonoTouch.Design.Client.ServerProcessConnection.CreateSession() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 111
at MonoTouch.Design.Client.ServerProcessConnection.b__28_0() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 116
at System.Threading.Tasks.Task1.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of stack trace from previous location where exception was thrown --- at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject) --- End of inner exception stack trace --- at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions) at System.Threading.Tasks.Task1.GetResultCore(Boolean waitCompletionNotification)
at System.Threading.Tasks.Task1.get_Result() at MonoTouch.Design.Client.IPhoneDesignerSession.<>c__DisplayClass289_11.b__1(Task1 t) in E:\A\_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\IPhoneDesignerSession.cs:line 2073 at System.Threading.Tasks.ContinuationResultTaskFromResultTask2.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
---> (Inner Exception #0) MonoTouch.Design.Client.InvalidSessionException: Error in the application.
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest(CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 235
at MonoTouch.Design.Client.ServerProcessConnection.SendRequest[TResponse](CommandRequest req, Boolean throwIfNotRunning) in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 252
at MonoTouch.Design.Client.ServerProcessConnection.CreateSession() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 111
at MonoTouch.Design.Client.ServerProcessConnection.b__28_0() in E:\A_work\129\s\Xamarin.Designer.iOS\MonoTouch.Design.Client\Connection\ServerProcessConnection.cs:line 116
at System.Threading.Tasks.Task`1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)<---
<---

and the listing goes on and on - way too long for this post...

I created questions.db file using DB Browser and want to read data from it in my Xamarin Forms application. That sounds pretty simple, right, but I'm 10+ hours stuck googling. Most answers just link to "Xamarin.Forms Local Databases" in microsoft docs.

Which explains nothing about the manually created database file, where to put it etc.

Some unofficial guides tell to put .db file to Resources/Assets folder for IOS/Droid, which seems right and I did.

I also added interfaces and [assembly: Dependency(typeof(DatabaseService))].... thing for android/ios, but failed. Everyone seems to use slightly different syntax, i haven't seen something for that in official docs, I'm completely lost.

Sorry for not posting any code, I'm not even sure which path to take, that's why I'm not diving into exact syntax right now.

In my Xamarin Forms app, when I debug to a remoted iPhone Simulator on a Windows machine I am starting to see the following messages in the launch Output window. Is this something that I need to be concerned about?

testapp.iOS[4814:67911] SecTaskLoadEntitlements failed error=22 cs_flags=200, pid=4814
testapp.iOS[4814:67911] SecTaskCopyDebugDescription: testapp.iOS[4814]/0#-1 LF=0
testapp.iOS[4814:67911] SecTaskLoadEntitlements failed error=22 cs_flags=200, pid=4814
testapp.iOS[4814:67911] SecTaskCopyDebugDescription: testapp.iOS[4814]/0#-1 LF=0

Hey all,
I just updated my xamarin forms version from 4.2 to 4.3.

When I try to run my UWP application, I get a splash screen and I get the following exception

$exception {"Could not find Windows Runtime type 'Microsoft.UI.Xaml.Controls.XamlControlsResources'.":"Microsoft.UI.Xaml.Controls.XamlControlsResources"} System.TypeLoadException

in my uwp's app.xaml.cs Xamarin.Forms.Forms.Init(e)
I went through the process of cleaning my solution, reinstalled the nugut packages, and deleting my bin and object folders. Still no luck.

After some research, this is from the Microsoft.UI.Xaml.dll which should be packaged in UWP by default.

Has anyone experience this issue before?

Is there any way to create this kind of UI (Like spinner) ?
Any idea would be appreciated.
Thanks.

Hi Devs,
I am implementing Azure Push Notifications in my xamarin.forms app. I have created a notification hub on azure. Test send works fine on physical iOS device but when it comes to send notification from one device to other registered devices, server returns Error 404 Not found. Below is the code for my backend service that send the code:

``` using Microsoft.Azure.NotificationHubs;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web.Http;

namespace PNS_Backend.Controllers
{
    [RoutePrefix("PushNotifications")]
    public class PushNotifController : ApiController
    {
        [HttpPost]
        [Route("")]
        public async Task<IHttpActionResult> SendNotificationAsync([FromBody] string message)
        {
            // Get the settings for the server project.
            HttpConfiguration config = this.Configuration;
            try
            {
                await SendNotification(message, null);
            }
            catch (Exception ex)
            {
                // Write the failure result to the logs.
                config.Services.GetTraceWriter().Error(ex.Message, null, "Push.SendAsync Error");
                return BadRequest(ex.Message);
            }

            return Ok();
        }


        [HttpPost]
        [Route("{installationid}")]
        public async Task<IHttpActionResult> SendNotificationAsync(string installationId, [FromBody] string message)
        {
            // Get the settings for the server project.
            HttpConfiguration config = this.Configuration;
            try
            {
                await SendNotification(message, installationId);
            }
            catch (Exception ex)
            {
                // Write the failure result to the logs.
                config.Services.GetTraceWriter().Error(ex.Message, null, "Push.SendAsync Error");
                return BadRequest(ex.Message);
            }

            return Ok();
        }


        async Task<NotificationOutcome> SendNotification(string message, string installationId)
        {
            // Get the settings for the server project.
            HttpConfiguration config = this.Configuration;


            // The name of the Notification Hub from the overview page.
            string notificationHubName = "gopns_hub";
            // Use "DefaultFullSharedAccessSignature" from the portal's Access Policies.
            string notificationHubConnection = "Endpoint=sb://sampleaddress.windows.net/;SharedAccessKeyName=DefaultFullSharedAccessSignature;SharedAccessKey=n1wtqS1Phy+xHZ00OZrrPIDoy9YAnYyMpMsKnN5lRX8=";

            // Create a new Notification Hub client.
            var hub = NotificationHubClient.CreateClientFromConnectionString(
                notificationHubConnection,
                notificationHubName,
                // Don't use this in RELEASE builds. The number of devices is limited.
                // If TRUE, the send method will return the devices a message was
                // delivered to.
                enableTestSend: false);

            // Sending the message so that all template registrations that contain "messageParam"
            // will receive the notifications. This includes APNS, GCM, WNS, and MPNS template registrations.
            var templateParams = new Dictionary<string, string>
            {
                ["messageParam"] = message
            };

            // Send the push notification and log the results.

            NotificationOutcome result = null;
            if (string.IsNullOrWhiteSpace(installationId))
            {
                result = await hub.SendTemplateNotificationAsync(templateParams).ConfigureAwait(false);
            }
            else
            {
                result = await hub.SendTemplateNotificationAsync(templateParams, "$InstallationId:{" + installationId + "}").ConfigureAwait(false);
            }


            // Write the success result to the logs.
            config.Services.GetTraceWriter().Info(result.State.ToString());
            return result;
        }
    }
}``

Also, below is the code for my Xamarin.Forms button that tries to send the message:
```public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
_client.BaseAddress = new Uri(App.MobileServiceUrl);
_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
_client.Timeout = TimeSpan.FromSeconds(120);
}

    HttpClient _client = new HttpClient();

    protected override void OnAppearing()
    {
        base.OnAppearing();

        MessagingCenter.Subscribe<object, string>(this, App.NotificationReceivedKey, OnMessageReceived);
        btnSend.Clicked += OnBtnSendClicked;
    }

    void OnMessageReceived(object sender, string msg)
    {
        Device.BeginInvokeOnMainThread(() => {
            lblMsg.Text = msg;
        });
    }

    async void OnBtnSendClicked(object sender, EventArgs e)
    {
        Debug.WriteLine($"Sending message: " + txtMsg.Text);

        var content = new StringContent("\"" + txtMsg.Text + "\"", Encoding.UTF8, "application/json");
        var result = await _client.PostAsync("PushNotifications", content); // At this line, I get Error 404 as a result and message is not sent.
        Debug.WriteLine("Send result: " + result.IsSuccessStatusCode);
    }

    protected override void OnDisappearing()
    {
        base.OnDisappearing();
        MessagingCenter.Unsubscribe<object>(this, App.NotificationReceivedKey);
    }
}```

This line : var result = await _client.PostAsync("PushNotifications", content);
gives me the Error 404 when i call PostAsync on client object.
Can you guys check it and suggest some solutions?
Thanks

Hello Guy's,
Here is a screen shot link !

My question is that how we achive that thing on list binding.
one more thing is that while listview is bind and load more data when scroll upwork so more data is load and image is show after some time , now again scroll down ward image is blink and old image is show for some time then show original image which bind that cell.

• How to increase "Appshell" Performance to open master page and hide it task some time to show and hide when doing this process is look stuck for a time and then hide or show .

Thank's

Xamarin.Forms: I have used a ListView and created a DataTemplate as custom ViewCell with Grid inside the same.
In my Grid I have created 3 Columns with picker inside first column and Entry as second and third column.
Whenever I click upon entry cell or TextChanged event is triggered, Picker in other column is also focused and picker item selection pop up is displayed.

Hello,

I am implementing Firebase Crashlytics in xamarin forms.I want to log exceptions occurred in try/catch block to firebase.
I am using below line of code to track exception in xamarin android which are reflected as Non-fatal error on firebase portal (Which is achieved).
Android native code-
public void TrackException(Exception exception)
{
Crashlytics.Crashlytics.LogException(Java.Lang.Throwable.FromException(exception));
}

I am using dependency service to call above code in xamarin forms PCL project.
try
{
}
catch(Exception ex)
{
DependencyService.Get().TrackException(ex);
}

Similarly for xamarin.iOS I have method Crashlytics.SharedInstance.RecordError(objNSError);
How can I convert Exception to NSError object in xamarin?

Thanks,
Payal

I am having some issues with setting the status bar color and the selected tab underline color in xamarin forms, especially android.

Status Bar
I thought that setting the colorPrimaryDark would set the status bar background color:
<item name="colorPrimaryDark">@color/primaryDark</item>

Which i set to yellow as a test, but instead it look black, with no text. If I swipe down from the top of the screen then somehow the text (time, battery, carrier etc show).

Tab Underline
I do this but the tab underline is still white:

  <!--Selected tab underline-->
  <style name="AppCompatDialogStyle" parent="Theme.AppCompat.Light.Dialog">
    <item name="colorAccent">@color/accent</item>
  </style>

How can I fix this? How do I set the tab underline color and the status bar color in android and iOS?
Thanks

How to add an application to TestFlight using Xamarin Forms?

I'm using a collection view and it works great ( horizontal ), but I would like it to continuously scroll and start from 0 if the user scrolls all the way to the right.

Has anyone done this yet or that new territory?

Hello everyone. How i use collection view with infinite scrolling