When are .NET MAUI (Xamarin Forms) pages/custom views destroyed? - xamarin.android

Question

I'm new to Xamarin/.NET MAUI application development. I started to develop a sample .NET MAUI application for Android device.
I'm trying to understand how/when a page and my custom view are destroyed (disposed of). I read some web pages but I can't really understand how things work in .NET MAUI (or Xamarin).
I have three pages: MainPage, SecondPage, TestMapPage.
SecondPage has a button that navigates to TestMapPage. It instantiates a TestMapPage object and passes it to Navigation.PushAsync().
TestMapPage contains a custom view TestMapView, which is rendered by my custom view renderer TestMapViewRenderer. I create a MapView object (from Naxam.Mapbox.Droid) in the renderer and show the map in TestMapPage. The map appears on the emulator and it works fine.
I thought that SecondPage, TestMapPage and TestMapView (and all the objects in TestMapViewRenderer) will be destroyed when I navigate back to MainPage. However, when I set a break point on Dispose() in the renderer and navigate back to SecondPage or MainPage in , it never gets hit.
My questions:
Are the SecondPage, TestMapPage, TestMapView and all the other objects in the view and view renderer like MapboxMap kept somewhere when I go back to MainPage?
When are pages and views destroyed/disposed of?
If those page objects are kept somewhere until the application shuts down, is it normal behaviour?
If not normal behaviour, how do I fix it?
I'm worried about memory leak...
MainPage.xaml.cs
public partial class MainPage : ContentPage
{
// ...
private async void OnGoToSecondPageClicked(object sender, EventArgs e)
{
await Navigation.PushAsync(new SecondPage());
}
}
SecondPage.xaml.cs
public partial class SecondPage : ContentPage
{
// ...
private async void OnMapShowClicked(object sender, EventArgs e)
{
await Navigation.PushAsync(new TestMapPage());
}
}
TestMapPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:MapTest"
x:Class="MapTest.TestMapPage">
<StackLayout Margin="5">
<local:TestMapView
x:Name="map"
VerticalOptions="FillAndExpand"
HorizontalOptions="CenterAndExpand"/>
</StackLayout>
</ContentPage>
TestMapView.cs
public class TestMapView : View { }
TestMapViewRenderer.cs
public partial class TestMapViewRenderer : ViewRenderer<TestMapView, Android.Views.View>
{
private MapboxMap map;
public TestMapViewRenderer(Context context) : base(context) {}
protected override void OnElementChanged(ElementChangedEventArgs<TestMapView> e)
{
base.OnElementChanged(e);
// ...
if (Control == null)
{
var mapView = new MapView(Context);
SetNativeControl(mapView);
mapView.GetMapAsync(this);
}
}
public void OnMapReady(MapboxMap map)
{
this.map = map;
this.map.SetStyle(Resources.GetString(Resource.String.mapbox_style_satellite), this);
}
protected override void Dispose(bool disposing)
{
// A breakpoint never hits on this line. Why?
base.Dispose(disposing);
}
// ...
}

Answer 1

as far as I know;
No, on each navigation you create new page instances, so, the page is created and kept in memory by .NET itself, once garbage collection hits a certain threshold, the memory will be free. Until then, the pages are in memory, but not meant to use somewhen in the future.
When GC decides, the Xamarin/MAUI doesn't care about views.
Unfortunately, yes.
It's normal, you can overcome by using what #ToolmakerSteve refers.