import 'package:flutter/widgets.dart';
import 'package:flutter_animator/flutter_animator.dart';

class TestAnimatedWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return RubberBand(
      child: Text(
        'Rubber',
        style: TextStyle(fontSize: 20),
      ),
    );
  }
}

import 'package:flutter/widgets.dart';
import 'package:flutter_animator/flutter_animator.dart';

class TestAnimatedWidget extends StatefulWidget {
  @override
  _TestAnimatedWidgetState createState() => _TestAnimatedWidgetState();
}
class _TestAnimatedWidgetState extends State<TestAnimatedWidget> {
  //Register a key in your state:
  GlobalKey<AnimatorWidgetState> _key = GlobalKey<AnimatorWidgetState>();
  
  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        Expanded(
            //Render the widget using the _key
            child: RubberBand(
              key: _key,
              child: Text(
                'Rubber',
                style: TextStyle(fontSize: 60),
              ),
            ),
        ),
        Padding(
            padding: EdgeInsets.fromLTRB(10, 10, 10, 30),
            child: IconButton(
              icon: Icon(
                Icons.play_arrow,
                color: Colors.green,
              ),
              //Use _key.currentState to forward/stop/reverse
              onPressed: () => _key.currentState.forward(),
            ),
        ),
      ],
    );
  }
}

import 'package:flutter/widgets.dart';

import '../../flutter_animator.dart';

///Firstly, we create an _AnimationDefinition_.
///This is the actual animation part, which gets driven by the _AnimatorWidget_.
class FadeInDownAnimation extends AnimationDefinition {
  FadeInDownAnimation({
  ///[AnimationPreferences] allows us to use the animation with different parameters for:
  ///offset, duration, autoPlay and an animationStatusListener.
    AnimationPreferences preferences = const AnimationPreferences(),
  }) : super(
          preferences: preferences,
          ///If you want to use the size of the widget, you need to define it here. (needsScreenSize is also available)
          needsWidgetSize: true,
          ///The opacity to use on the first render when using screenSize or widgetSize.
          ///In some cases 'flickering' may appear when this isn't set to 1.0 or 0.0 respectively.
          preRenderOpacity: 0.0,
        );

  ///Use the build function to actually render the animated values.
  ///Performance-wise it's better to use a FadeTransition for opacity animation.
  ///Use AnimatedBuilder to update te animation and it's values.
  @override
  Widget build(BuildContext context, Animator animator, Widget child) {
    return FadeTransition(
      ///Use animator.get([KEY]) to get to the Animation object.
      opacity: animator.get("opacity"),
      child: AnimatedBuilder(
        ///[Animator] exposes the AnimationController via animator.controller.
        animation: animator.controller,
        child: child,
        builder: (BuildContext context, Widget child) => Transform.translate(
          child: child,
          ///Use animator.get([KEY]).value to get the animated value.
          offset: Offset(0.0, animator.get("translateY").value),
        ),
      ),
    );
  }

  ///Inside the getDefinition method we return the actual animation.
  @override
  Map<String, TweenList> getDefinition({Size screenSize, Size widgetSize}) {
    return {
      ///Define a [KEY] and a list of Animated values from 0 to 100 percent.
      ///Please not that you can also define an animation curve inside the [TweenPercentage] class:
      ///TweenPercentage(percent: 0, value: 0.0, curve: Curves.ease),
      "opacity": TweenList<double>(
        [
          TweenPercentage(percent: 0, value: 0.0),
          TweenPercentage(percent: 100, value: 1.0),
        ],
      ),
      "translateY": TweenList<double>(
        [
          TweenPercentage(percent: 0, value: -widgetSize.height),
          TweenPercentage(percent: 100, value: 0.0),
        ],
      ),
    };
  }
}

///To use the AnimationDefinition we just created we could do the following:
///For a single animation:
/// AnimatorWidget(child: [child], definition: FadeInDownAnimation());
/// 
///For In & Out Animations:
///  InOutAnimation(child: [child), inDefinition: FadeInDownAnimation(), outDefinition: ...);
///