For some reason when I leave a page and then navigate back to it. When I try to type in an Entry or select from a Picker, the value is not displayed on the UI. The keyboard still appears and I can see the text in the autocomplete but the UI remains blank.

This doesn't happen on Android 6.0

The page in question looks like this

    <Image x:Name="ImageUpload" Source="Upload"/>

    <Label x:Name="labelUpload" Text="" HorizontalOptions="Center"
        VerticalOptions="Center"/>

    <StackLayout Orientation="Vertical" Margin="20, 0, 20, 0">
        <ActivityIndicator x:Name="spinner" IsRunning="True" IsVisible="False"/>
        <ProgressBar x:Name="uploadProgress" IsVisible="False" Margin="30, 0, 30, 0" Progress="{Binding uploadProgress}"/>
        <Label HorizontalOptions="Center" x:Name="status"/>
    </StackLayout>

    <StackLayout Margin="20, 0,0,0" Orientation="Horizontal">
        <Label VerticalOptions="Center"  Text="Fail Reason"/>
        <Picker HorizontalOptions="FillAndExpand"  ItemsSource="{Binding Reasons}" x:Name="FailReason"></Picker>
    </StackLayout>
    <StackLayout Margin="20, 0,0,0" Orientation="Horizontal">
        <Label VerticalOptions="Center"  Text="Additional Comments"/>
        <Entry HorizontalOptions="FillAndExpand" x:Name="Comment" />
    </StackLayout>
    <Entry HorizontalOptions="FillAndExpand" x:Name="Comment" />


    <StackLayout Orientation="Horizontal" HorizontalOptions="Center">
        <Label VerticalOptions="Center" Text="Attach additional files"/>
        <Button Clicked="OpenFileExplorer" Text="Add"></Button>
    </StackLayout>

    <ListView x:Name="files" ItemsSource="{Binding files}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <ViewCell.ContextActions>
                        <MenuItem Clicked="RemoveImage" CommandParameter="{Binding .}" Text="Delete"/>
                    </ViewCell.ContextActions>
                    <StackLayout Orientation="Horizontal">
                        <Image  Source="{Binding thumbnail}"></Image>
                        <Label Text="{Binding fileName}" FontSize="18"/>
                    </StackLayout>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackLayout>

Hi,
I updated out app from Xamarin.Forms 2.4 to 2.5 and from Prism 6.3 to 7.0.

I have made some changes to App.cs and AppDelegate.cs / MainActivity.cs (as described on Prims page) but when I launch the app it crashes on the splash screen.

I added Xaml compilation option ([assembly: XamlCompilation(XamlCompilationOptions.Compile)]) and it gives me 1 error:

/Users/mj/Projects/DemoApp/DemoApp/Views/SideNavigationPage.xaml(3,3): 
Error: Position 7:3. Can not set the content of NavigationPage as it doesn't have a ContentPropertyAttribute (DemoApp)

SideNavigationPage Xaml code:

<?xml version="1.0" encoding="utf-8" ?>
<NavigationPage xmlns="link"
  xmlns:x="link"
  xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
  prism:ViewModelLocator.AutowireViewModel="True"
  x:Class="DemoApp.Views.SideBarNavigationPage">
    <StackLayout>
        <Label Text="{Binding Title}" VerticalOptions="Center" HorizontalOptions="Center" />
        <Button Command="{Binding NavigateCommand}" Text="Navigate" />
    </StackLayout>
</NavigationPage>

and xaml.cs

    using Prism.Navigation;
    using Xamarin.Forms;

    namespace DemoApp.Views
    {
        public partial class SideBarNavigationPage : NavigationPage, INavigationPageOptions, IDestructible
        {
            public SideBarNavigationPage()
            {
                InitializeComponent();
            }
            public bool ClearNavigationStackOnNavigation
            {
                get { return true; }
            }
            public void Destroy()
            {
            }
        }
    }

Is there anything else I need to change?

Hi,

I'm using the MVVM pattern with XamarinForms, so I create a model, assign it to the Xamarin Page (the page is a subclass of ContentPage) and because of the bindings declared in XAML everything gets registered beautifully.

However, if I can push and popping the same view on/off a NavigationPage (say 10 times) and then change a visual element (i.e. by typing in a bound text field), I get a console output for all the old bindings as well as the current binding. I have a base class for my MVVM models that includes the logging...

    public void PropChanged(String property) {
        if (PropertyChanged != null)
        {
            Console.WriteLine(this.GetType().ToString()+" PropChanged:" + property);
            PropertyChanged(this,new PropertyChangedEventArgs(property));
        }
    }

The only way I have so far been able to resolve the issue is to modify the Page to include an override OnDissapearing method, I tried to call UnapplyBindings() but that didn't help, however, setting the BindingContext to null has done the trick...

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

        // Only this seems to remove the bindings created from XAML from the ViewModel
        this.BindingContext = null; // <--- YAY!!! Bindings now removed

        this.ListDetailViewModel.Dispose(); // <-- Making sure the view model also tidies up
        this.ListDetailViewModel = null;

    }

My question is, shouldn't the ContentPage OnDisappearing be removing all the bindings anyway?

Although what I'm doing works, is this the right approach?

Given that ContentPage.UnapplyBindings doesn't remove the bindings, but setting ContentPage.BindingContext=null does, what the heck does UnapplyBindings actually do then?

You might have noticed that in addition, I delegate through to my view model to call Dispose which has some clean up code, is this 'okay', or should I simply have a method I call something like CleanUp - I'm not sure when the Dispose is 'meant' to be called, but it would seem it doesn't unless I manually invoke it.

Thanks.

Hello,
I pretty new in Xamarin Forms and I would like to do some kind of layouting.
I would like to use one ContentView to display different Controls on Phone / Tablet.

So basically the whole Layout should change if I e.g. using a Tablet.

Is there a way to handle this in XF?

Best regards,
Daniel

does it support using signal r client for signalr . net core. If not is there a possible solution of that for connecting the server to client in xamarin forms. I am currently using .net standard 2.0 for my xamarin forms application.

So I've tried to debug the application in my phone. And everything seem well. But then I got this error:
Start CloudDMS.DemoMobileApp.Android, Samsung SM-A300FU Player, .
Attempting connection to debug address: 192.168.64.101:37847.
Connected to: 192.168.64.101:37847.
Deploying \CloudDMS Work\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp.Android\CloudDMS.DemoMobileApp.Android.csproj...
Got device info: Samsung SM-A300FU Player (Android) @ 192.168.64.101:37847
Synchronizing files...
Building and running...
Built with 3 messages.
\CloudDMS Work\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\Interfaces\Notifications.cs(1,1): error: 'Resource.Drawable' does not contain a definition for 'icon'
\CloudDMS Work\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\Providers\contentProvider.cs(1,1): error: 'Resource.Drawable' does not contain a definition for 'icon'
\CloudDMS Work\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\CloudDMS.DemoMobileApp\Providers\ProjectProvider.cs(1,1): error: 'Resource.Drawable' does not contain a definition for 'icon'
Failed to debug your app.

Any solutions or ideas why do I get this error?

Hello,

I cannot update Xamarin.Android.Support.xxx packages from 26.1.0.1 to 27.0.2:

Install failed. Rolling back...
Package 'Xamarin.Android.Support.Fragment.27.0.2 :
Xamarin.Android.Support.Compat [27.0.2, 27.0.2],
Xamarin.Android.Support.Core.UI [27.0.2, 27.0.2],
Xamarin.Android.Support.Core.Utils [27.0.2, 27.0.2]' does not exist in project 'my.project'

The "Build" android package fails as follows:

This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Xamarin.Android.Support.Media.Compat.27.0.2\build\MonoAndroid81\Xamarin.Android.Support.Media.Compat.targets.
my.project
C:\mypath\mysolution\Droid\my.project.csproj
246

I'm running Visual Studio 2017 Version 15.6.2.

Thank you!

Hi, I am developing Tabs in my application. When I am starting FirstPage from Tab1, It is hiding all the Tab's and showing page in full screen. How can I get Tabs in all screens of the app.
My code

  <?xml version="1.0" encoding="utf-8" ?>
    <TabbedPage  xmlns="http://xamarin.com/schemas/2014/forms"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                 x:Class="TabbedApp.MainPage"
                 xmlns:local="clr-namespace:TabbedApp">
        <local:DairyTabs></local:DairyTabs>
        <ContentPage Title="Tab 2">
            <StackLayout>
                <Label Text="Tab 2"   
                HorizontalTextAlignment="Center"  
                HorizontalOptions="FillAndExpand"  
                Margin="5" />
            </StackLayout>
        </ContentPage>
   </TabbedPage>

Code for starting Page2

btnDemo.Clicked +=async delegate {
                await Navigation.PushModalAsync(new Page2());
            };

See below images for more clarification

Hello,

I want to set icons in tabbed page and I'm using this code but everytime i get null exception on this line if (actionBar.TabCount > 0) and also app crash when i go from login screen to this main screen https://forums.xamarin.com/discussion/comment/151236/#Comment_151236

Code is
`public partial class Main : TabbedPage {
public Main() {
InitializeComponent();
NavigationPage.SetHasNavigationBar(this, false);

        if (Device.OS == TargetPlatform.iOS)
        {
            Children.Add(new NavigationPage(new Timer() { Title = "Ikas" }));
            Children.Add(new NavigationPage(new Views.Reports.ReportsPage() { Title = "Dkas" }));
            Children.Add(new NavigationPage(new Profile() { Title = "Zkas" }));
        }
        else
        {
            Children.Add(new Timer() { Title = "Ikas", Icon = "ic_ikas" });
            Children.Add(new Views.Reports.ReportsPage() { Title = "Dkas", Icon = "ic_dkas" });
            Children.Add(new Profile() { Title = "Zkas", Icon = "ic_zkas" });
        }
    }

}`

and custom renderer

using Android.App; using Android.Widget; using Xamarin.Forms; using Xamarin.Forms.Platform.Android; using Android.Graphics.Drawables; using System; using Android.Graphics; using Android.Runtime; using System.ComponentModel; using Android.Views;
[assembly: ExportRenderer(typeof(TabbedPage), typeof(CTabbedPageRenderer))]
namespace somenamespace
{
public class (CTabbedPageRenderer))]: TabbedRenderer
{

`    private Activity activity;
    private TabbedPage _tabbedPage;
    private const string COLOR = "#FFFFFF";


    protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
    {
        base.OnElementChanged(e);

        activity = this.Context as Activity;
        _tabbedPage = e.NewElement as TabbedPage;


    }

    protected override void DispatchDraw(Canvas canvas)
    {

        ActionBar actionBar = activity.ActionBar;


        if (actionBar.TabCount > 0)
        {
            ColorDrawable colorDrawable = new ColorDrawable(global::Android.Graphics.Color.ParseColor(COLOR));
            actionBar.SetStackedBackgroundDrawable(colorDrawable);
            ActionBarTabsSetup(actionBar);
        }

        base.DispatchDraw(canvas);
    }

    private void ActionBarTabsSetup(ActionBar actionBar)
    {
        try
        {
            //_tabbedPage.Children[0].IC
            for (int i = 0; i < actionBar.TabCount; i++)
            {
                Android.App.ActionBar.Tab dashboardTab = actionBar.GetTabAt(i);
                if (TabIsEmpty(dashboardTab))
                {

                    int id = Resources.GetIdentifier(_tabbedPage.Children[i].Icon.File, "drawable", Context.PackageName);
                    TabSetup(dashboardTab, id);
                }

            }

        }
        catch (Exception)
        {

        }

    }

    private bool TabIsEmpty(ActionBar.Tab tab)
    {
        if (tab != null)
            if (tab.CustomView == null)
                return true;
        return false;
    }

    private void TabSetup(ActionBar.Tab tab, int resourceID)
    {
        ImageView iv = new ImageView(activity);
        iv.SetImageResource(resourceID);
        iv.SetPadding(0, 10, 0, 0);

        tab.SetCustomView(iv);
    }
}

}`
Can some one help me?

Hi,

I know how to store data using Application.Current.Properties.

I want to save a list of data to local DB and retrieve those data. For that which method is suitable?

Hello,

I have a very simple project. I'm trying to test AppLinkEntry (Deeplink).

I have a very simple test code, creating a simple LinkEntry :

                var url = $"https://www.mywebsite.com";

                var entry = new AppLinkEntry
                {
                    Title = "Welcome to MainPage",
                    Description = "This is the main page item",
                    AppLinkUri = new System.Uri(url),
                    IsLinkActive = true,
                    Thumbnail = ImageSource.FromFile("appIcon80.png")
                };

                entry.KeyValues.Add("contentType", "item");
                entry.KeyValues.Add("appName", "XamarinDeepLinks");
                entry.KeyValues.Add("companyName", "Test");


                Application.Current.AppLinks.RegisterLink(entry);

This code is executed during the OnAppearing() of a page.

But, when I'm trying to look for my link on ios simulator, it is not appearing... Nothing.

Do you notice the same issue ? I'm using 2.5.0.xxx Xamarin.Forms.

Many thanks for your feedback.

Marc

I implemented local DB in my project and I am using following code for select all the items from local DB. MyCommunities is my model class.

public List<MyCommunities> GetItems()
    {
        lock (locker)
        {
            return (from i in database.Table<MyCommunities>() select i).ToList();
        }
    }

I am using following code for taking an item from local DB with a particular officename(it only return one item):

public MyCommunities GetItemByOfficename(string office)
    {
        lock (locker)
        {
            return database.Table<MyCommunities>().FirstOrDefault(x => x.Officename == office);
        }
    }

I am trying to select all the items from local DB having a particular userid(It should be a list of Mycommunities). Don't know how to add userid when parsing.

Thanks in advance

Hi,

I'm looking to add crash reporting capability to my xamarin.forms app - are there any recommended modules / plugins that could be used for this?

I have a Master Detail page.
Detail page is created in NavigationPage container.
On detail page I have a button.
On Click I'm doing the follow:

await Detail.Navigation.PushAsync(GetNextPage());

And after this my app hangs.

This does not hang if I remove await.
From documentation it is a bit not clear what exactly await PushAsync means. Will it wait until the pushed page is closed, or until it will initialize and show?

Unable to sync firebase chat to local database.
I am using _lstChat.ItemsSource = db.subChat(data.Key); for direct bind firebase chat to list.
But When I want to save locally
var dd = db.subChat(data.Key);
App.Database.SaveItemAsync2(dd); I am getting 0 in dd. Actually its take 3-4 second to bind. So want to maintain all chat locally and background sync through sqlite to Firebase.

public ObservableCollection<Chat> subChat(string _roomKEY)
    {

        return fbClient.Child("ChatApp/"+_roomKEY+"/Message")
                       .AsObservable<Chat>()
                       .AsObservableCollection<Chat>();
    }

        <ViewCell>
                        <ViewCell.View>
                            <Grid Padding="5">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition/>
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto"/>
                                </Grid.RowDefinitions>
                                <Label Text="Description" VerticalOptions="Start"/>
                                <Label x:Name="lblRulesDesc" Grid.Column="1" LineBreakMode="WordWrap"/>
                            </Grid>
                        </ViewCell.View>
                    </ViewCell>

System.Net.Http.HttpRequestException: An error occurred while sending the request ---> System.Net.WebException: Error getting response stream (ReadDone2): ReceiveFailure ---> System.Exception: at System.Net.WebConnection.HandleError (System.Net.WebExceptionStatus st, System.Exception e, System.String where) [0x00031] in <33c5603ad293441aaed2769dd871c706>:0
at System.Net.WebConnection.ReadDone (System.IAsyncResult result) [0x00056] in <33c5603ad293441aaed2769dd871c706>:0
at System.Net.Sockets.SocketAsyncResult+<>c.b__27_0 (System.Object state) [0x00000] in <33c5603ad293441aaed2769dd871c706>:0
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem () [0x00015] in <2722d81e5b26475cb5f475fea055f291>:0
at System.Threading.ThreadPoolWorkQueue.Dispatch () [0x00074] in <2722d81e5b26475cb5f475fea055f291>:0
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback () [0x00000] in <2722d81e5b26475cb5f475fea055f291>:0
at System.Net.WebConnection.HandleError (System.Net.WebExceptionStatus st, System.Exception e, System.String where) [0x00031] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/System/System.Net/WebConnection.cs:439
--- End of inner exception stack trace ---
at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) [0x00059] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/System/System.Net/HttpWebRequest.cs:1033
at System.Threading.Tasks.TaskFactory1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func2[T,TResult] endFunction, System.Action1[T] endAction, System.Threading.Tasks.Task1[TResult] promise, System.Boolean requiresSynchronization) [0x0000f] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/threading/Tasks/FutureFactory.cs:550
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:152
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:535 at System.Net.Http.HttpClientHandler+<SendAsync>d__64.MoveNext () [0x003d3] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/System.Net.Http/System.Net.Http/HttpClientHandler.cs:402 --- End of inner exception stack trace --- at System.Net.Http.HttpClientHandler+<SendAsync>d__64.MoveNext () [0x0046c] in /Users/builder/data/lanes/5533/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/System.Net.Http/System.Net.Http/HttpClientHandler.cs:406 --- End of stack trace from previous location where exception was thrown --- at Xamarin.UITest.Shared.Http.HttpClient.SendData (System.String endpoint, System.String method, System.Net.Http.HttpContent content, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy, System.Nullable1[T] timeOut) [0x000ea] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.Shared.Http.HttpClient.Post (System.String endpoint, System.String arguments, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy, System.Nullable1[T] timeOut) [0x00017] in <0ea59db5aaf943039918d5008bfc5053>:0 at Xamarin.UITest.Shared.Http.HttpClient.Post (System.String endpoint, System.Object arguments, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy, System.Nullable1[T] timeOut) [0x00019] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.iOS.HttpCalabashConnection.Map (System.Object arguments) [0x00000] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.iOS.iOSGestures.InternalQuery[T] (Xamarin.UITest.Queries.AppQuery query, System.Object[] args, System.String methodName) [0x00046] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.iOS.iOSGestures.Query (Xamarin.UITest.Queries.AppQuery query) [0x0000d] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.iOS.iOSApp+c__AnonStorey1C+c__AnonStorey1D.<>m__0 () [0x00000] in <0ea59db5aaf943039918d5008bfc5053>:0
at Xamarin.UITest.Shared.WaitForHelper.WaitForAnyOrDefault[T] (System.Func1[TResult] query, T[] defaultValue, System.Nullable1[T] timeout, System.Nullable1[T] retryFrequency, System.Nullable1[T] postTimeout) [0x00023] in <0ea59db5aaf943039918d5008bfc5053>:0

I'm getting crashes with the unhandled exception "A geolocation error occured: PositionUnavailable"

But the only place that I think I am calling anything geolocation related is the following:
try { await geolocator.GetPositionAsync(timeout: 10000, cancelToken: cancelSource.Token, includeHeading: true) .ContinueWith(t => { // Some code to set the center }); } catch (XLabs.Platform.Services.Geolocation.GeolocationException) { // we just ignore it... }

I guess my questions are, is this going to catch the exception (and if so, why isn't unhandled)
and is there something else that is trying to use the location and thus throwing this exception?

Hi developers

i have some problem here when try to binding string list to picker
get result 0.

i'm try this
https://blog.xamarin.com/new-bindable-picker-control-for-xamarin-forms/
and some other

but still get 0 value in picker list

thanks in advance

Hi,

How can I use the System.Data.SqlClient namespace in my Xamarin Forms in my Visual Studio for Mac?

It doesn't seem to be understanding it?

Kindly help..

Thanks,
Jassim