Flutter Animation animation development-the simplest animation introduction

In the following code, we have implemented an animation that changes the width and height of the green square from 100 to 500 within 5 seconds.

class AnimationRoute extends StatefulWidget {
  @override
  AnimationRouteState createState() => AnimationRouteState();
}

class AnimationRouteState extends State<AnimationRoute> with SingleTickerProviderStateMixin {

  Animation<double> animation;
  AnimationController controller;

  initState() {
    super.initState();
    // Controller sets the animation duration
         // vsync sets a TickerProvider, the current State is mixed with SingleTickerProviderStateMixin is a TickerProvider
    controller = AnimationController(
        duration: Duration(seconds: 5),
        vsync: this //
    );
         // Tween sets the interval value of animation, animate () method passes in an Animation, and AnimationController inherits Animation
    animation = new Tween(begin: 100.0, end: 500.0).animate(animation)
             // addListener listens to the callback of each frame of the animation, this call setState () to refresh the UI
      ..addListener(() {
        setState(()=>{});
      });
         // Start animation (forward execution)
    controller.forward();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
             // A square area is displayed here, which becomes larger as the animation is executed
      child: Container(
        color: Colors.green,
        width: animation.value,
        height: animation.value,
      ),
    );
  }

  @override
  void dispose() {
         // release resources
    controller.dispose();
    super.dispose();
  }
}

to sum up:

Create AnimationController and set the duration of the animation
Create Tween to animate the interval value
Call Tween.animate () and pass in the AnimationController created above
addListener () monitors the animation callback and calls setState () to refresh the UI
Call AnimationController.dispose () to release animation resources

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