When building the widget tree you assign the Animation to an animated
property of a widget, such as the opacity of a FadeTransition, and tell the
controller to start the animation.

The following example shows how to write a FadeTransition that fades the
widget into a logo when you press the FloatingActionButton:

For more information, see
Animation & Motion widgets,
the Animations tutorial,
and the Animations overview.

How do I use a Canvas to draw/paint?

In Android, you would use the Canvas and Drawable to draw images and shapes
to the screen. Flutter has a similar Canvas API as well, since it is based
on the same low-level rendering engine, Skia. As a result, painting to a
canvas in Flutter is a very familiar task for Android developers.

Flutter has two classes that help you draw to the canvas: CustomPaint
and CustomPainter, the latter of which implements your algorithm to draw to
the canvas.