Implicitly animated widgets

Flutter has a whole set of widgets that have animation built directly into them. This is great, but these animated widgets also mirror lots of widgets we have already seen, allowing a very easy drop replacement in your widget tree to get some great animations.

These widgets work by animating any changes to their internal state. For example, if a widget has been drawn to the screen in one color, and then a setState property changes the widget's color, then the change in color is animated rather than a single frame color switch. Let's first take a look at the AnimatedContainer widget, and then we will explore the other implicitly animated widgets available.

AnimatedContainer

The first widget to look at, and probably the most powerful, is the AnimatedContainer widget. This is very similar to the Container widget we first saw in Chapter 5, Widgets – Building Layouts in Flutter, but adds some key properties that allow it to animate changes...