Layout problem android

Hi

I have a simple page containg a listview and a button inside a stacklayout.

The button is defined this way :

        var buttonNext = new ImageButton
        {
            HeightRequest = 100,
            Text = " Next",
            Font = Font.BoldSystemFontOfSize(30),
            Source = ImageSource.FromResource("<namespac>.Select.png"),
            Orientation = ImageButton.ImageOrientation.ImageToLeft,
            ImageHeightRequest = 100,
            ImageWidthRequest = 100,
            VerticalOptions = LayoutOptions.EndAndExpand,
        };

The button should be positioned at the bottom of the screen. It does when the page initially loads.

But if I set the listview IsVisible to false during runtime it does not.

Why is this ?

This is an android problem.

Regards