Can't bind IsBusy property - xaml

Question

I have Page with an Activity Indicator with the following code:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.ClientSearch" Title="Search">
<ContentPage.Content>
<StackLayout Orientation="Vertical">
<StackLayout.Children>
<SearchBar x:Name="txtSearchClient" TextChanged="OnTextChanged"></SearchBar>
<ActivityIndicator IsVisible="{Binding IsBusy}" IsRunning="{Binding IsBusy}" x:Name="indicadorCargando" />
<ListView x:Name="lstClients"></ListView>
</StackLayout.Children>
</StackLayout>
</ContentPage.Content>
</ContentPage>
In the partial class associated to this xaml, I have:
namespace MyApp
{
public partial class ClientSearch: ContentPage
{
public BusquedaClientes()
{
InitializeComponent();
}
async void OnTextChanged(object sender, TextChangedEventArgs e)
{
if (this.txtSearchClient.Text.Length >= 3)
{
var list_clients = App.ClientsManager.GetTasksAsync(txtSearchClient.Text);
this.IsBusy = true;
var template = new DataTemplate(typeof(TextCell));
template.SetBinding(TextCell.DetailProperty, "name_ct");
template.SetBinding(TextCell.TextProperty, "cod_ct");
lstClients.ItemTemplate = template;
lstClients.ItemsSource = await list_clients;
this.IsBusy = false;
}
}
}
}
As you can see, this.IsBusy is setting the Page property, so tried to bind to that property in the XAML. Unfortunetly it doesn't work:
<ActivityIndicator IsVisible="{Binding IsBusy}" IsRunning="{Binding IsBusy}" x:Name="indicadorCargando" />
How can I bind the values of the ActivityIndicator to the IsBusy page property?
I already know that setting the values like this:
this.IsBusy = true;
indicadorCargando.IsVisible=true;
indicadorCargando.IsRunning=true;
But I don't want to do that, I want to set one value instead of three.

Answer 1

You certainly could go the route of a separate view model, which is not a bad idea. However for the specific question, it doesn't look like you're setting the BindingContext anywhere, so it isn't going to get the IsBusy property that you want.
I haven't tried setting the BindingContext for a control to itself, but something like this ought to work:
<ActivityIndicator
IsVisible="{Binding IsBusy}"
IsRunning="{Binding IsBusy}"
x:Name="indicadorCargando"
BindingContext="{x:Reference indicadorCargando}" />

Answer 2

You need to give your page a name (x:Name="myPage") and then declare the binding using a reference to it using {Binding Source={x:Reference myPage}, Path=IsBusy} for the ActivityIndicator's IsVisible and IsRunning values. More info on this answer.

Answer 3

Here is how I would rewrite it:
public class ClientSearch : ContentPage
{
public ClientSearch()
{
BindingContext = new ClientSearchViewModel();
var stack = new StackLayout();
var searchBar = new SearchBar();
searchBar.SetBinding<ClientSearchViewModel>(SearchBar.TextProperty, x => x.Text);
var actInd = new ActivityIndicator();
actInd.SetBinding<ClientSearchViewModel>(ActivityIndicator.IsVisibleProperty, x => x.IsBusy);
actInd.SetBinding<ClientSearchViewModel>(ActivityIndicator.IsRunningProperty, x => x.IsBusy);
var lv = new ListView
{
ItemTemplate = new DataTemplate(() =>
{
var txtCell = new TextCell();
txtCell.SetBinding<MyItemModel>(TextCell.TextProperty, x => x.Name_Ct);
txtCell.SetBinding<MyItemModel>(TextCell.TextProperty, x => x.Cod_Ct);
return txtCell;
})
};
lv.SetBinding<ClientSearchViewModel>(ListView.ItemsSourceProperty, x => x.items);
stack.Children.Add(searchBar);
stack.Children.Add(actInd);
stack.Children.Add(lv);
Content = stack;
}
}
public class ClientSearchViewModel : BaseViewModel
{
public string Text { get; set; }
public bool IsBusy { get; set; }
public IEnumerable<MyItemModel> items { get; set; }
protected override async void OnPropertyChanged(string propertyName = null)
{
if (propertyName != nameof(Text) || Text.Length < 3) return;
IsBusy = true;
items = await App.ClientsManager.GetTasksAsync(Text);
IsBusy = false;
}
}
[ImplementPropertyChanged]
public abstract class BaseViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}