To make a class private, start its name with an underscore (_).

So far you’ve learned how to generate a sequence of numbers over time.
Nothing has been rendered to the screen. To render with an
Animation object, store the Animation object as a
member of your widget, then use its value to decide how to draw.

Consider the following app that draws the Flutter logo without animation:

App source: animate0

The following shows the same code modified to animate the
logo to grow from nothing to full size.
When defining an AnimationController, you must pass in a
vsync object. The vsync parameter is described in the
AnimationController section.

The changes from the non-animated example are highlighted:

{animate0 → animate1}/lib/main.dart

@@ -9,16 +9,39 @@

9
9

State<LogoApp> createState() => _LogoAppState();