I am using Prism Through my app and I Created Custom View Toolbar and want to implement Navigation service anywhere I Called this Toolbar . I only find one example bud didn't work with me.

Content View

    <ContentView xmlns="http://xamarin.com/schemas/2014/forms" 
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
                 xmlns:prism="clr-namespace:Prism.Ioc;assembly=Prism.Forms"
                 xmlns:mvvm="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
                 x:Name="AppToolbarview" 
                 xmlns:local="clr-namespace:IFind.Views"
                 BackgroundColor="#20019C"
                 x:Class="IFind.Views.AppToolbar">
        <local:AppToolbar mvvm:ViewModelLocator.AutowirePartialView="{x:Reference AppToolbarview}" />
        <ContentView.Content>
                <ImageButton x:Name="backbtn" Grid.Row="0" HorizontalOptions="Start" HeightRequest="30" WidthRequest="25" VerticalOptions="CenterAndExpand" BackgroundColor="Transparent" Grid.Column="0" Source="back.png" Command="{Binding BackCommand}"  Aspect="AspectFit"></ImageButton>
        </ContentView.Content>
    </ContentView>

View Model

        public class AppToolbarViewModel : BindableBase
        {
            private INavigationService _navigationService;

            public DelegateCommand BackCommand => new DelegateCommand(Back);

            private void Back()
            {
                _navigationService.GoBackAsync();
            }

            public AppToolbarViewModel(INavigationService navigationService)
            {
                _navigationService = navigationService;
            }
        }

I tried this and Then tried to Register the service manually in app.cs

ViewModelLocationProvider.Register<AppToolbar,AppToolbarViewModel>();
but app crashing in page which contains Apptoolbar

Native Crash Reporting

Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries

used by your application.

No native Android stacktrace (see debuggerd output).

=================================================================

Basic Fault Address Reporting

Memory around native instruction pointer (0xcd19c3ca):0xcd19c3ba c0 5e 5f
Any help? many thanks

I need to create the above UI with Xamarin.Forms First I tried using the CarousalView with IndicatorView but the problem is CarousalView always centers the 1st item when I give it a PeekAreaInsert value. That's why i need to use CollectionView instead. But I'm not sure how I can achieve an IndicatorView like functionality with CollectionView. Any idea will be highly appreciated. Thanks

I would like to reset the Entry Box back to the Placeholder text after the Add Button is clicked. I cant seem to figure it out.

<Style x:Key="BaseStyle" 
       ApplyToDerivedTypes="True"
       TargetType="Element">
    <Setter Property="Shell.BackgroundColor"
            Value="#ffffff" />
    <Setter Property="Shell.ForegroundColor"
            Value="{StaticResource BodyTextColor}" />
    <Setter Property="Shell.TitleColor"
            Value="#ffffff" />
    <Setter Property="Shell.DisabledColor"
            Value="#B4FFFF" />
    <Setter Property="Shell.UnselectedColor"
            Value="#f4ebeb" />
  -- <Setter Property="Shell.TabBarTitleColor"
            Value="#ff0000"/>
   -- <Setter Property="Shell.TabBarForegroundColor"
            Value="#777777"/>
  --  <Setter Property="Shell.TabBarUnselectedColor"
            Value="#777777"/>
</Style>
<Style TargetType="TabBar" BasedOn="{StaticResource BaseStyle}" />

Hi,

I want to implement push notifications in my Xamarin form app 4.7. which should work even if app not run. kindly suggest me right way to implement push notifications in my XF app. I m try some plugins like CrossGeeks/FirebasePushNotificationPlugin but this not work on app close.

Thanks

Thus far, my experience trying to make Xamarin.Forms work on iOS has been a complete failure, and I am getting very close to giving up on this.

For the past week, I have tried, to no avail, to get push notifications working with both Azure and Firebase, and neither works no matter what I do.

So today, I was hoping to make some progress in at least getting the app to run on iOS, even if notifications can't work.

Alas, here I am, stuck again.

This time, it's on a really simple shell navigation.

The app flow is really basic, the shell is configured to display a "loading" view as the initial page. This page does a quick check to see if the user has already opened the app before, and if so, directs navigation to one page, and if not, to another.

The route in question is a global route registered as follows:

public partial class AppShell : Shell
{
    public AppShell()
    {
        InitializeComponent();
        Routing.RegisterRoute("login", typeof(Login));
        Routing.RegisterRoute("register", typeof(Register));
        Routing.RegisterRoute("botflow", typeof(BotFlow));
        Routing.RegisterRoute("document", typeof(Document));
    }
}

Specifically, the route being navigated to is the "register" route.

The code to perform the navigation is as follows:

public async Task ShellNavigateAsync(string route)
{
    await Task.Run(() =>
    {
        Application.Current.Dispatcher.BeginInvokeOnMainThread(async () =>
        {
            await Shell.Current.GoToAsync(route);
        });
    });
}

The call to await Shell.Current.GotToAsync(route) just hangs forever, and the navigation never takes place.

Hoping someone here can tell me the secret ingredients to make this work.

This code resides in the shared library, btw, and it is working flawlessly on Android. The same can't be said for iOS, sadly.

The multi-touch function on the Xamarin iOS simulator is great but I have bumped into what I hope is a silly (i.e. me being dense) problem. When I do a pinch, the two finger circles obviously have to go closer together. When they get as close as they can go, is there a way to move them apart again so that I can do another pinch gesture?

I have tried switching to Shallow Press and back to Multi-Touch but the circles stay where they were last left.

i have a Tabbed view like whatsup and the Main View is defined like this

<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage
    x:Class="WhatsApp.Views.MainView"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:views="clr-namespace:WhatsApp.Views"    
    Title="Trova"  NavigationPage.HasBackButton="False"  >

    <TabbedPage.Padding>
        <OnPlatform x:TypeArguments="Thickness" iOS="0, 20, 0, 0" />
    </TabbedPage.Padding> 
    <views:SearchMain  BackgroundColor="Transparent"/>
    <views:MatchesView />
    <views:ChatsView BackgroundColor="Transparent"  />
    <views:ViewsLikes BackgroundColor="Transparent" /> 
</TabbedPage>

The InitililizeComponent takes time ,

  try
            {
                InitializeComponent();
            }
            catch (Exception ex)
            {
                throw ex;
            }

i placed a try catch to check if there is no exception in the xaml.

What could be a problem

I have a horizontal collectionview with some item, I need an underline only for the selected item.

I tried like below:

MainPage.xaml.cs

public partial class MainPage : ContentPage
{
    public List<Category> categoryList { get; set; }
    public MainPage()
    {
        InitializeComponent();
        categoryList = new List<Category>();
        SetItems(true, false, false, false, false, false);
    }

    private void SetItems(bool v1, bool v2, bool v3, bool v4, bool v5, bool v6)
    {
        categoryList.Add(new Category() { Title = "itme1", IsSelected = v1 });
        categoryList.Add(new Category() { Title = "itme2", IsSelected = v2 });
        categoryList.Add(new Category() { Title = "itme3", IsSelected = v3 });
        categoryList.Add(new Category() { Title = "itme4", IsSelected = v4 });
        categoryList.Add(new Category() { Title = "itme5", IsSelected = v5 });
        categoryList.Add(new Category() { Title = "itme6", IsSelected = v6 });
        Category_collectionview.ItemsSource = categoryList;
    }

    public void CategoryTapped(object sender, SelectionChangedEventArgs e)
    {
        var selectedItem = (e.CurrentSelection.FirstOrDefault() as Category);
        if (selectedItem != null)
        {
            if (selectedItem.Title == "itme1")
            {
                SetItems(true, false, false, false, false, false);
            }
            else if (selectedItem.Title == "itme2")
            {
                SetItems(false, true, false, false, false, false);
            }
            else if (selectedItem.Title == "itme3")
            {
                SetItems(false, false, true, false, false, false);
            }
        }
        Category_collectionview.SelectedItem = null;
    }
}

public class Category 
{
    public string Title { get; set; }
    public bool IsSelected { get; set; }
}

MainPage.xaml

<CollectionView 
        SelectionMode="Single"
        SelectionChanged="CategoryTapped"
        x:Name="Category_collectionview"
        ItemsLayout="HorizontalList">
        <CollectionView.ItemTemplate>
            <DataTemplate>
                <StackLayout 
                    Orientation="Vertical"
                    Margin="5">

                    <Label
                        TextColor="Black"
                        HorizontalTextAlignment="Center"
                        VerticalTextAlignment="Center"
                        Text="{Binding Title}">
                        <Label.FontSize>
                            <OnIdiom x:TypeArguments="x:Double">
                                <OnIdiom.Phone>16</OnIdiom.Phone>
                                <OnIdiom.Tablet>32</OnIdiom.Tablet>
                                <OnIdiom.Desktop>16</OnIdiom.Desktop>
                            </OnIdiom>
                        </Label.FontSize>
                    </Label>

                    <BoxView 
                        HorizontalOptions="FillAndExpand"
                        BackgroundColor="Black"
                        IsVisible="{Binding IsSelected}"
                        HeightRequest="2"/>
                </StackLayout>
            </DataTemplate>
        </CollectionView.ItemTemplate>
    </CollectionView>

But the boxview is always on the first item, what I am missing here?

For example, we have a big Xamarin forms project, with 2000 page, and Prism MVVM framework, with DryIoc container, that has registered all 2000 pages.

This a lot of pages, added with DependencyService for example, navigationservice, dialogservice, can reduce navigation's speed and/or performance?
It can makes app run slow, for a lot of dependency?

Thanks!!

I tried https://stackoverflow.com/questions/59771557/xamarin-requesting-camera-permissions-in-webview this and many other solutions but nothing worked for me. It is working fine with mobile web browser but within my webview app it doesn't work. I tried creating a CustomRenderer as well as creating the Utils.cs file with Plugins.Permissions but nothing worked. Please help.

webView.Source = "https://test.webrtc.org/";

I'm trying to fill up or populate a ListView that is instantiated in PageA when the user clicks a button in PageB. I'm doing it sending a message with the MessageCenter in PageB and calling the MessageCenter.Subscribe() method in PageA (the Page where I want to add the new ViewCell or row to the ListView)... but it's not working.

I don't think that the problem is coming from the send/subscribe usage because I have alredy debugged the application and the collection (ObservableCollection) that i'm passing to the ListView.ItemSource property is indeed growning in size. Here you can see the class definitions:

PageA class definition:

PageA .xaml file:

PageB class definition:

I will appreciate a lot the help that you could provide!

I have created a Xamarin Forms App using Visual Studio 2019 on Windows 10, I connect to a remote Mac Mini when I want to build for iOS. I submit to the Apple App Store by creating an Archive within Visual Studio, then using remote desktop I open Xcode on the Mac Mini and then Window => Organizer I can select the Archive and click Distribute App which uploads it to the App Store.

Now however Apple are rejecting my App saying that it crashes on launch. This only started a few days ago, I have Xamarin Forms 4.7.0.1239 installed and the Mac mini has XCode 11.6. I assume this is automatically used to build.

I have a crash log from Apple, the start of the crash log is as follows:

Exception Type:  EXC_BAD_ACCESS (SIGABRT)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
VM Region Info: 0 is not in any region.  Bytes before following region: 4340170752
      REGION TYPE                      START - END             [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                 0000000102b1c000-0000000102fc8000 [ 4784K] r-x/r-x SM=COW  ...tlessMenu.iOS

Triggered by Thread:  0

Thread 0 name:  tid_407  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x00000001999fadf0 0x1999d4000 + 159216
1   libsystem_pthread.dylib         0x000000019991a948 0x199918000 + 10568
2   libsystem_c.dylib               0x00000001998a9c24 0x199834000 + 482340
3   libsystem_c.dylib               0x00000001998a9bb0 0x199834000 + 482224
4   ContactlessMenu.iOS             0x00000001048d9098 0x102b1c000 + 31183000

I don't understand this. Using 'iOS Crash Log Tool' I searched the folders on my Windows 10 machine and it gave me the following output:

Thread 0 Crashed:
0   libsystem_kernel.dylib          0x00000001999fadf0 0x1999d4000 + 159216
1   libsystem_pthread.dylib         0x000000019991a948 0x199918000 + 10568
2   libsystem_c.dylib               0x00000001998a9c24 0x199834000 + 482340
3   libsystem_c.dylib               0x00000001998a9bb0 0x199834000 + 482224
4   ContactlessMenu.iOS             0x00000001021a3d08 _xamarin_release_block_on_main_thread
5   ContactlessMenu.iOS             0x0000000102198f44 _xamarin_get_block_descriptor
6   ContactlessMenu.iOS             0x000000010205e950 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
7   ContactlessMenu.iOS             0x0000000101ff3988 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
8   ContactlessMenu.iOS             0x0000000101ff2370 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
9   ContactlessMenu.iOS             0x0000000101fe8150 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
10  ContactlessMenu.iOS             0x0000000100c4b7cc GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
11  ContactlessMenu.iOS             0x0000000100a0084c GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
12  ContactlessMenu.iOS             0x0000000100a06754 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
13  ContactlessMenu.iOS             0x0000000100d3d40c GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
14  ContactlessMenu.iOS             0x0000000100c0d4a0 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
15  ContactlessMenu.iOS             0x0000000102005588 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)
16  ContactlessMenu.iOS             0x00000001020c0a64 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)

Xcode does not show me crash logs for this version and when I click download debug symbols it says no dSYMs were found.

I have found a Crash Log in XCode for an earlier version which seems to report the same thing. I realise this is a different version but it is very similar:

2 libsystem_c.dylib __abort
3 libsystem_c.dylib abort
4 ContactlessMenu.iOS xamarin_release_block_on_main_thread
5 ContactlessMenu.iOS _xamarin_get_block_descriptor
6 GMSx_absl::base_internal::AtomicHook<void (*)(char const*, int, char const*, char const*, char const*)>::DummyFunction(char const*, int, char const*, char const*, char const*)

Does this mean libsystem_c.dylib sent an Abort signal?

I think all the line with GMSx possibly refer to Google Maps.

I don't know how to collect the required files to create a proper symbolised crash log. I don't know the location of the files and if they are on the Windows computer or the Mac Mini?

If anyone has any pointers I would be very grateful.

I want to build a chatting App. So what are the requirments for it. I mean which server and database will be best for it?Any suggestion plz to build a chatting App?

I am implementing Dropbox API. I succeeded in both Android and iOS. But in UWP the app is crashing after entering credentials. I see the following two lines in Output window. Isn't Xamarin.Forms.UWP app configured to use .NET Core? If not how can I set it?

Actually after entering the credentials, it asks "Do you want to switch apps". It hangs if I say NO and crashes if I say Yes. I am using "com.companyname.appname:/oauth2redirect" as the Redirect URI and UWP Package Name is set to "com.companyname.appname".

The target process exited without raising a CoreCLR started event. Ensure that the target process is configured to use .NET Core. This may be expected if the target process did not run on .NET Core.
The program '[26140] WWAHost.exe' has exited with code 1 (0x1).

Following this MSD I have implemented WPS push notification support for my UWP application. In the case of Android, we have a

public override async void OnMessageReceived(RemoteMessage message)

method which is going to capture the pushed FCM notification and we are able to add Pending intents and have functionalities like navigating to a specific page on tap of a certain notification implemented. Likewise in the case of iOS, we have a

[Export("userNotificationCenter:didReceiveNotificationResponse:withCompletionHandler:")]
public void DidReceiveNotificationResponse(UNUserNotificationCenter center, UNNotificationResponse response, Action completionHandler)

to intercept any notification interaction from the user, such as taps, or action button interaction and handle them accordingly.

In UWP, we have a

toast.Activated

event, to which we can assign a handler to do whatever is it we want to achieve when the ToastNotification is interacted with.
Unfortunately, this requires me to actually create a ToastNotification to be able to assign an event handler to it.

But as stated in the Microsoft documentation, I need not have any method to intercept the push notification and create a ToastNotification. The Push notification banner is automatically displayed.

How do I capture the notification tapped by the user? As I will require to navigate to certain pages based on the notification tapped.

I'm trying to implement a base page where I have an Ad view rendered in all pages.
To accomplish these I created a ControlTemplate with the Ad in it and the content, the file is called BasePageControlTemplate:

<ResourceDictionary
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:navigationDrawer="clr-namespace:Syncfusion.SfNavigationDrawer.XForms;assembly=Syncfusion.SfNavigationDrawer.XForms"
    xmlns:state="clr-namespace:Xamarin.Forms.StateSquid;assembly=Xamarin.Forms.StateSquid"
    xmlns:xt="clr-namespace:Fighter_MoveList.MarkUpExtensions">
    <ControlTemplate x:Key="BasePageTemplate">
        <Grid RowSpacing="0">
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <StackLayout
                Grid.Row="0"
                state:StateLayout.CurrentState="{Binding PageState}"
                BindingContext="{Binding Source={RelativeSource TemplatedParent}, Path=BindingContext}">
                <ContentPresenter />
            </StackLayout>
            <ContentView Grid.Row="1" Content="{StaticResource AdControlViewMain}" />
        </Grid>
    </ControlTemplate>
</ResourceDictionary>

Code of the Ad:

<views:AdControlView
            x:Key="AdControlViewMain"
            AdUnit="XXX"
            BackgroundColor="{StaticResource AccentColor}" />

This works at first, the flow is from left to right (Notice the bar on the bottom, thats de ad):

However, when navigating back from the back arrow in the toolbar the previous page looks like this (Notice the bar on the bottom is not seen anymore):

Why does this happen?
I do have the controlTemplate in both pages:
RosterPage:

<pages:BasePage
    x:Class="Fighter_MoveList.Views.RosterPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:d="http://xamarin.com/schemas/2014/forms/design"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:models="clr-namespace:Fighter_MoveList.Models"
    xmlns:pages="clr-namespace:Fighter_MoveList.Views"
    xmlns:pviews="clr-namespace:Xamarin.Forms.PancakeView;assembly=Xamarin.Forms.PancakeView"
    xmlns:views="clr-namespace:Fighter_MoveList.ContentViews"
    xmlns:vm="clr-namespace:Fighter_MoveList.ViewModels"
    xmlns:xt="clr-namespace:Fighter_MoveList.MarkUpExtensions"
    Title="{xt:Translate roster_title}"
    x:DataType="vm:RosterViewModel"
    ControlTemplate="{StaticResource BasePageTemplate}"
    mc:Ignorable="d">
    <ContentPage.ToolbarItems>
        <ToolbarItem Clicked="InfoItem_Clicked" IconImageSource="info" />
    </ContentPage.ToolbarItems>
    <ContentPage.Content>
        ...
    </ContentPage.Content>
</pages:BasePage>

FighterDetailPage:

<pages:BasePage
    x:Class="Fighter_MoveList.Views.FighterDetailPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:models="clr-namespace:Fighter_MoveList.Models"
    xmlns:pages="clr-namespace:Fighter_MoveList.Views"
    xmlns:sfBorder="clr-namespace:Syncfusion.XForms.Border;assembly=Syncfusion.Core.XForms"
    xmlns:views="clr-namespace:Fighter_MoveList.ContentViews"
    xmlns:vm="clr-namespace:Fighter_MoveList.ViewModels"
    xmlns:xt="clr-namespace:Fighter_MoveList.MarkUpExtensions"
    Title="{Binding Title}"
    x:DataType="vm:FighterDetailViewModel"
    ControlTemplate="{StaticResource BasePageTemplate}">
    <pages:BasePage.Resources>
        <Thickness x:Key="FooterSpacing" Top="100" />
    </pages:BasePage.Resources>
    ...
</pages:BasePage>

I don't know if its related, but I'm using shell for navigation:
Routing.RegisterRoute(nameof(FighterDetailPage), typeof(FighterDetailPage));
This is how i go to it:
await Shell.Current.GoToAsync($"{nameof(FighterDetailPage)}?FighterId={selectedItem}");

I don't know if im missing something when using ControlTemplate.
Thanks in anticipation.

Hi Everyone,

I need help with this issue. I recently installed VS 2019 Version 16.6.0 on a barely new computer. I am a newbie to Xamarin development.
I created a new Mobile App (Xamarin Forms) project, once the project has completed loading in Visual Studio, I get the following error:

Error NU1202 Package System.Numerics.Vectors 4.5.0 is not compatible with netstandard2.0 (.NETStandard,Version=v2.0). Package System.Numerics.Vectors 4.5.0 supports:
- monoandroid10 (MonoAndroid,Version=v1.0)
- monotouch10 (MonoTouch,Version=v1.0)
- netcoreapp2.0 (.NETCoreApp,Version=v2.0)
- uap10.0.16299 (UAP,Version=v10.0.16299)
- xamarinios10 (Xamarin.iOS,Version=v1.0)
- xamarinmac20 (Xamarin.Mac,Version=v2.0)
- xamarintvos10 (Xamarin.TVOS,Version=v1.0)
- xamarinwatchos10 (Xamarin.WatchOS,Version=v1.0) Holla \Projects\Mobile\Holla\Holla\Holla\Holla.csproj _1

This is strange as am new to Xamarin. I can't even build the project. I noticed in the solution explorer the screenshot below:

I tried to delete the Xamarin Essentials package from Solution Explorer and then re-installed using the package manage, it failed, popping up same error.
I have read a lot of online articles but, none could help to fix this problem. I will appreciate any assistance from the community please.
Thank you.