I have a StackLayout that I'm populating child views with as I iterate through my ObservableCollection.

Why? Why would you do this through C#, micromanagement and brute force?
Why not use a container like FlexLayout and bind - that's the point of having an ObservableCollection to begin with.

Everything after that line in your post... Is a by-product of trying to do it like that.

There's really just no reason to build all that from C# like its a 1990's WinForms program.

@jezh said:
Besides, you can also use Xam.Plugins.Settings of JamesMontemagno.
It supports: Int, Int64, Double, String, DateTime, Bool, Float, Decimal, Guid

For more details: github.com/jamesmontemagno/SettingsPlugin

Hope it can help you.

Or instead of using Xam.Plugins.Settings you could use Xamarin.Essentials

Xamarin.Essentials.Preferences.Set("logged", true);
Xamarin.Essentials.Preferences.Get("logged", false);
Xamarin.Essentials.Preferences.ContainsKey("logged");

I ran into lots of different problems trying to implement this using the previously mentioned methods so i did this a different way. My way involves no custom renderers, no back button overriding and no platform specific code.

I simply embedded my TabbedPage in a NavigationPage and then when i add my tabs to the TabbedPage i pass an action to the necessary tabs which allows them to push a page onto the NavigationPage. Tested and works on both iOS and Android.

public class TabControllerPage : TabbedPage
{
    public TabControllerPage()
    {
        // This hides the navigation page's navigation bar as it is not needed
        NavigationPage.SetHasNavigationBar(this, false);

        // Create tab page and pass PushPage action to it
        var testPage = new TestPage {
            PushPage = (page) => {
                Navigation.PushAsync(page, true);
            }
        };

        // Add as many tabs as you like here
        AddTab(testPage, "Tab 1", true, "tab_1_icon.png");
    }

    void AddTab(Page page, string title, bool inNav, string icon = null)
    {
        // This sets the NavigationBar title
        page.Title = title;

        if (inNav)
        {
            var navigationPage = new NavigationPage(page);
            if (icon != null)
            {
                navigationPage.Icon = icon;
            }
            // This sets the tab labels
            navigationPage.Title = title;
            Children.Add(navigationPage);
        }
        else
        {
            Children.Add(page);
        }
    }
}

public partial class TestPage : ContentPage
{
    public Action<ContentPage> PushPage;

    public TestPage()
    {
        InitializeComponent();
    }

    // Call this method when ever you need to push a page onto the navigation page and hide the tabbed page.
    void NavigateToPage(ContentPage page)
    {
        PushPage?.Invoke(page);
    }
}

@Liêm_Nguyễn

You need to create the Widget in the android project, not in the PCL project.
Here is the tutorial:https://developer.xamarin.com/samples/monodroid/SimpleWidget/

In addition to the bugs, there are many pending PRs that don't seem to be going anywhere. I also agree that most bugs don't get fixed (including the ones tagged with /blocker, /critical, and /high-impact). This could be explained by the fact that the team is probably currently busy with the 4.0 release but more importantly they have spread themselves out too thin with many things (iOS, Android, UWP, Tizen, WPF, and MacOS in addition to XAML, CollectionView, Shell, Material, etc.)

They could probably hire 15 new devs for $2M per annum and resolve issues at a faster rate. This kind of money is insignificant for a company the size of Microsoft - not to mention the ultimate goal for them is to attract as many developers as possible to Visual Studio and Azure.

Flutter is probably the best choice right now for cross platform, but that means we give up C#/.NET.

Remove the selected index, Set RequestItem.Category value, it will work. Set your RequestItem.Category property to OnPropertyChanged.

If not clear, refer this sample,

<Picker x:Name="CategoryPicker"                 
ItemsSource="{Binding Categories, Mode=TwoWay}"
SelectedItem="{Binding Path= CategorySeletedItem, Mode=TwoWay}" 
HorizontalOptions="FillAndExpand"
Title="Escolha uma Categoria"
SelectedIndexChanged="CategoryPicker_SelectedIndexChanged"
ItemDisplayBinding="{Binding Name}"
Margin="10,20,10,0"/>

Code behind

 private List<Category> categories;
        public List<Category> Categories
        {
            get { return categories; }
            set { categories = value; }
        }

        private Category categorySeletedItem;
        public Category CategorySeletedItem
        {
            get { return categorySeletedItem; }
            set { categorySeletedItem = value; OnPropertyChanged(); }
        }

        public MainPage()
        {
            InitializeComponent();                       

            Categories = new List<Category>();
            for (int i = 0; i < 10; i++)
                Categories.Add(new Category { Name = "Name" + i });

            CategorySeletedItem = Categories.FirstOrDefault();

            BindingContext = this;
        }