Is there a way to update bounded data when I swipe back [PopAsync() ] - xamarin

Question

To provide some context, I'm writing a Xamarin.Forms application and utilizing data binding with INotifyPropertyChanged. Currently I have an inventory counter displayed on a button. The text on this button displays the bounded "Count" variable (e.g Current Inventory: 35). When I press the button, I push a screen onto the navigation stack which allows me to edit this "Count" variable. I use the class implementation like this
public class UserInventory : INotifyPropertyChanged
{
private int count = 0;
// Declare the event
public event PropertyChangedEventHandler PropertyChanged;
public int Count
{
get => Preferences.Get(nameof(Count),0);
set
{
if (count == value || value <1)
return;
Preferences.Set(nameof(Count), value);
//count = value;
//Application.Current.Properties["Count"] = count;
OnPropertyChanged(nameof(Count));
//OnPropertyChanged(nameof(displayName));
}
}
public UserInventory()
{
}
void OnPropertyChanged(string count)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(count));
}
}
I add this class in Xaml according to the tutorial on the Xamarin <ContentPage.BindingContext>
<local:UserInventory />
</ContentPage.BindingContext>
So the variables are bounded correctly and I have no issues seeing updates on the current page or when I push new pages. The issue is when I swipe back on iOS the previous screen with the button "Current Inventory: 35" does not update to reflect the new changes. If I push that screen the changes are reflected.
Is there anyway to ensure the bounded data is updated when you go back (PopAsync()) ?

Answer 1

Try overriding page's OnAppearing() method and call OnPropertyChanged from there.
Assuming 'UserInventory' the binded VM.....
public partial class Page1:ContentPage
{
public Page1()
{
InitializeComponent();
VM = (UserInventory)BindingContext;
}
public UserInventory VM { get; }
protected override void OnAppearing()
{
VM.Notify();
base.OnAppearing();
}
}
.
public class UserInventory: INotifyPropertyChanged
{
........
public void Notify()
{
OnPropertyChanged(nameof(Count));
}
}