Btukfyl

I am trying to add a tabbed page as shown in the xamarin documentation but I keep getting the following error, System.NullReferenceException "Object reference not set to an instance of an object." Do I need to declare a new object for each page or is this done automatically when using xaml?

Here is my StackTrace,

  at Xamarin.Forms.Platform.Android.AppCompat.Platform.LayoutRootPage(Xamarin.Forms.P age page, Int32 width, Int32 height) [0x0005d] in   C:BuildAgentworkaad494dc9bc9783Xamarin.Forms.Platform.AndroidAppCompatPlat form.cs:279 

  at Xamarin.Forms.Platform.Android.AppCompat.Platform.Xamarin.Forms.Platform.Android.IPlatformLayout.OnLayout (Boolean changed, Int32 l, Int32 t, Int32 r, Int32 b) [0x00003] in C:BuildAgentworkaad494dc9bc9783Xamarin.Forms.Platform.AndroidAppCompatPlatform.cs:196 

  at Xamarin.Forms.Platform.Android.PlatformRenderer.OnLayout (Boolean changed, Int32 l, Int32 t, Int32 r, Int32 b) [0x0000e] in C:BuildAgentworkaad494dc9bc9783Xamarin.Forms.Platform.AndroidPlatformRenderer.cs:73 

  at Android.Views.ViewGroup.n_OnLayout_ZIIII (IntPtr jnienv, IntPtr native__this, Boolean changed, Int32 l, Int32 t, Int32 r, Int32 b) [0x00009] in /Users/builder/data/lanes/3415/7db2aac3/source/monodroid/src/Mono.Android/platforms/android-23/src/generated/Android.Views.ViewGroup.cs:3427 

  at (wrapper dynamic-method) System.Object:d59f31f1-b9b6-40ea-9254-a422fe409750 (intptr,intptr,bool,int,int,int,int)

Here is my code,

using Xamarin.Forms;

namespace BSi.Mobile.Events.Views

{

    public partial class MainMasterDetailPage : MasterDetailPage

    {

        public MainMasterDetailPage()

        {

            InitializeComponent();

        }

    }

}



<?xml version="1.0" encoding="utf-8" ?>

<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"

              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"

              xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"

              xmlns:local="clr-namespace:BSi.Mobile.Events.Views;assembly=BSi.Mobile.Events"

              prism:ViewModelLocator.AutowireViewModel="True"

              x:Class="BSi.Mobile.Events.Views.MainMasterDetailPage">

    <MasterDetailPage.Master>

       <ContentPage Title="Default" Padding="10">

          <StackLayout>

             <Button Text="Home" Command="{Binding MenuSelectedCommand}"  CommandParameter="NavigationPageMainPage"/>

             <Button Text="Event Schedule" Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPageEventPage"/>

             <Button Text="Floor Plan" Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPageFloorPlanPage"/>

             <Button Text="Sponsor/Media Partners" Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPageSponsorsPage"/>

             <Button Text="Where To Eat" Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPageFoodNearbyPage"/>

          </StackLayout>

       </ContentPage>

   </MasterDetailPage.Master>

   <MasterDetailPage.Detail>

       <TabbedPage>

           <TabbedPage.Children>

              <local:MainPage Title="Info" Icon="http://icons.iconarchive.com/icons/graphicloads/100-flat/256/home-icon.png"/>

              <local:EventPage Title="Sessions" Icon="http://icons.iconarchive.com/icons/graphicloads/100-flat/256/home-icon.png"/>

              <local:SpeakersPage Title="Speakers" Icon="http://icons.iconarchive.com/icons/graphicloads/100-flat/256/home-icon.png"/>

              <local:ExhibitsPage Title="Exhibits" Icon="http://icons.iconarchive.com/icons/graphicloads/100-flat/256/home-icon.png"/>

           </TabbedPage.Children>

       </TabbedPage>

   </MasterDetailPage.Detail>

</MasterDetailPage>

UPDATE:

I made some changes as suggested by SushiHangover, I now recieve no errors but my tabbed menu is not appearing.

You can add TabbedPage Children like this in XAML:

<MasterDetailPage.Detail>

    <TabbedPage>

        <TabbedPage.Children>

            <ContentPage Title="Page 1" Icon="ja.png" />

            <ContentPage Title="Page 2" Icon="ja.png" />

            <ContentPage Title="Page 3" Icon="ja.png" />

        </TabbedPage.Children>

    </TabbedPage>

</MasterDetailPage.Detail>

Just substitute your "local" custom pages for ContentPage

Or via code:

public TabsPage ()

{

    this.Children.Add (new ContentPage () { Title = "Page 1", Icon = "ja.png" });

    this.Children.Add (new ContentPage () { Title = "Page 2", Icon = "ja.png" });

    this.Children.Add (new ContentPage () { Title = "Page 3", Icon = "ja.png" });

}

The answer was to use command parameter that is relative to the pages to be displayed in the tabbed page.

<?xml version="1.0" encoding="utf-8"?>

<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"

              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"

              xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"

              prism:ViewModelLocator.AutowireViewModel="True"

              x:Class="BSi.Mobile.Events.Views.MainMasterDetailPage">

<MasterDetailPage.Master>

   <ContentPage Title="Default">

     <StackLayout>

       <StackLayout BackgroundColor="{StaticResource iconGray}" Padding="15"      HeightRequest="100">

         <Image Source="canfitpro_logo2" HeightRequest="60" HorizontalOptions="Start" VerticalOptions="EndAndExpand" />

       </StackLayout>

       <TableView Intent="Form" HasUnevenRows="True">

         <TableRoot>

           <TableSection Title="Vancouver Fitness Expo">

             <ViewCell>

              <StackLayout Margin="15, 10, 10, 10" Orientation="Horizontal">

                 <StackLayout.GestureRecognizers>

                   <TapGestureRecognizer Command="{Binding MenuSelectedCommand}" CommandParameter="EventTabbedPage/NavigationPage/MainPage"/>

                 </StackLayout.GestureRecognizers>

                 <Image Source="icon_home_circle" HeightRequest="40"/>

                 <Label Text="Home" VerticalTextAlignment="Center" Margin="20, 0, 0, 0" Style="{DynamicResource SubtitleStyle}"/>

               </StackLayout>

             </ViewCell>

             <ViewCell>

               <StackLayout Margin="15, 10, 10, 10" Orientation="Horizontal">

                 <StackLayout.GestureRecognizers>

                   <TapGestureRecognizer Command="{Binding MenuSelectedCommand}" CommandParameter="EventTabbedPage/NavigationEventPage"/>

                 </StackLayout.GestureRecognizers>

                 <Image Source="icon_sessions_circle" HeightRequest="40"/>

                 <Label Text="Sessions" VerticalTextAlignment="Center" Margin="20, 0, 0, 0" Style="{DynamicResource SubtitleStyle}"/>

               </StackLayout>

             </ViewCell>

           </TableSection>

           <TableSection Title="Resources">

             <ViewCell>

               <StackLayout Margin="15, 10, 10, 10" Orientation="Horizontal">

                 <StackLayout.GestureRecognizers>

                   <TapGestureRecognizer Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPage/FloorPlanPage"/>

                 </StackLayout.GestureRecognizers>

                 <Image Source="icon_floormap_circle" HeightRequest="40"/>

                 <Label Text="Floor Plan" VerticalTextAlignment="Center" Margin="20, 0, 0, 0" Style="{DynamicResource SubtitleStyle}"/>

               </StackLayout>

             </ViewCell>

             <ViewCell>

               <StackLayout Margin="15, 10, 10, 10" Orientation="Horizontal">

                 <StackLayout.GestureRecognizers>

                   <TapGestureRecognizer Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPage/SponsorsPage"/>

                 </StackLayout.GestureRecognizers>

                 <Image Source="icon_partners_circle" HeightRequest="40"/>

                 <Label Text="Sponsor / Media Partners" VerticalTextAlignment="Center" Margin="20, 0, 0, 0" Style="{DynamicResource SubtitleStyle}"/>

               </StackLayout>

             </ViewCell>

             <ViewCell>

               <StackLayout Margin="15, 10, 10, 10" Orientation="Horizontal">

                 <StackLayout.GestureRecognizers>

                   <TapGestureRecognizer Command="{Binding MenuSelectedCommand}" CommandParameter="NavigationPage/FoodNearbyPage"/>

                 </StackLayout.GestureRecognizers>

                 <Image Source="icon_restaurant_circle" HeightRequest="40"/>

                 <Label Text="Where To Eat" VerticalTextAlignment="Center" Margin="20, 0, 0, 0" Style="{DynamicResource SubtitleStyle}"/>

               </StackLayout>

             </ViewCell>

           </TableSection>

         </TableRoot>        

       </TableView>        

     </StackLayout>

   </ContentPage>

  </MasterDetailPage.Master>

</MasterDetailPage>