The application is not currently visible to the user,
is not responding to user input, but is running in the background.

The application is visible and responding to user input.

The application is suspended momentarily.
This event is Android only.

For more details on the meaning of these states,
see the AppLifecycleStatus documentation.

Layouts

What is the equivalent of a StackLayout?

In Xamarin.Forms you can create a StackLayout
with an Orientation of horizontal or vertical.
Flutter has a similar approach,
however you would use the Row or Column widgets.

If you notice the two code samples are identical
except the Row and Column widget.
The children are the same and this feature
can be exploited to develop rich layouts
that can change overtime with the same children.

What is the equivalent of a Grid?