13.5. Flutter Animations: Widget Animations

In the world of application development, animations play a crucial role in creating intuitive and attractive user interfaces. In Flutter, an open source framework from Google, animations are handled in an exceptionally effective and diverse way. In this chapter, we'll explore widget animations in Flutter and how you can use them to improve the user experience in your apps.

What are widget animations?

Widget animations in Flutter are sequences of images that create the illusion of movement. They can be used to bring an application to life, improving the user experience and making the user interface more intuitive. Animations can range from simple color changes to complex motion sequences.

How do widget animations work in Flutter?

In Flutter, animations are created using two main components: Animation objects and animated widgets. The Animation object is an abstraction that generates a sequence of numbers over time. These numbers can be used to change any property of a widget, such as its position, color or size.

Animated widgets, on the other hand, are normal widgets that are rebuilt with new values ​​whenever the Animation object changes. This allows animated widgets to change appearance over time, creating the illusion of movement.

How to create widget animations in Flutter?

Creating widget animations in Flutter involves several steps. First, you need to create an Animation object. This can be done using the AnimationController class, which lets you control the duration and progression of the animation.

Next, you need to create an animated widget. This can be done using one of the many animated widget classes provided by Flutter, such as AnimatedOpacity, AnimatedPositioned, or AnimatedContainer.

Finally, you need to bind the Animation object to the animated widget. This is done by passing the Animation object as a parameter to the animated widget's constructor.

Example Widget Animation

Let's create a simple animation that makes a widget move from one side of the screen to the other. First, we create the Animation object:

AnimationController controller;
Animation animation;

@override
void initState() {
  super.initState();

  controller = AnimationController(
    duration: const Duration(seconds: 2),
    vsync: this,
  );

  animation = Tween(begin: 0, end: 100).animate(controller)
    ..addListener(() {
      setState(() {
        // The state that has changed here is the animation object's value.
      });
    });

  controller.forward();
}

Next, we create the animated widget. In this case, we'll use AnimatedBuilder, which lets you create custom animations:

AnimatedBuilder(
  animation: animation,
  builder: (BuildContext context, Widget child) {
    return Transform.translate(
      offset: Offset(animation.value, 0),
      child: child,
    );
  },
  child: Container(width: 100, height: 100, color: Colors.red),
)

This will create an animation that moves a red container from one side of the screen to the other in two seconds.

Conclusion

Widget animations in Flutter are a powerful tool to improve the user experience in your apps. With a basic understanding of how they work, you can create complex and compelling animations that will bring your app to life. Remember, the key to creating good animations is to experiment and have fun in the process!