Maui Shell Flyout IsPresentedChanged event

Question

Xamarin forms to Maui migration question...

The FlyoutPage in XF has the IsPresentedChanged event that fires when the Flyout menu is displayed/hidden.

Is there an equivalent for Maui Shell Flyout? I can't find anything in the docs.

As a supplement I have a ContentView set as the Shell.FlyoutContent and I can accomplish my requirement (amend a property on the ContentView when the Flyout menu becomes visible) via an OnAppearing event on the ContentView.

Thanks in advance.

Answer 1

The Shell doesn't have a such event. But you can detect the Shell.FlyoutIsPresented Property changed by your custom event.

  public AppShell()
  {
      InitializeComponent();
      PropertyChanged += Changed;
  }   

  private void Changed(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
  {
      if(e.PropertyName == "FlyoutIsPresented")
      {
          if(FlyoutIsPresented)
          {

          }else
          {
          }
      }
  }

Answer 2

If you're using the MVVM Community Toolkit then you can rely on two-way binding and the source generated OnXXXChanged / OnXXXChanging methods.

In your ViewModel:

[ObservableProperty]
bool _isFlyoutPresented;

In your View (XAML):

<Shell FlyoutIsPresented="{x:Binding IsFlyoutPresented, Mode=TwoWay}" />

Now you can react to the changes in your ViewModel:

partial void OnIsFlyoutPresentedChanging(bool oldValue, bool newValue)
{
    // ...
}

Setting the IsFlyoutPresented property will now trigger the flyout. You can tell if it's open by checking the value in IsFlyoutPresented.