implicitly animated count example

implicitly_animated_count.dart

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}
class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _count = 0;

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: Text("Animated Count example"),
      ),
      body: new Center(
        child: new AnimatedCount(
          count: _count,
          curve: Curves.ease,
          duration: Duration(seconds: 1),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            _count += 100;
          });
        },
        child: Icon(Icons.add),
      ),
    );
  }
}

class AnimatedCount extends ImplicitlyAnimatedWidget {
  final int count;

  AnimatedCount({
    Key key,
    @required this.count,
    @required Duration duration,
    Curve curve = Curves.linear
  }) : super(duration: duration, curve: curve, key: key);

  @override
  ImplicitlyAnimatedWidgetState<ImplicitlyAnimatedWidget> createState() => _AnimatedCountState();
}

class _AnimatedCountState extends AnimatedWidgetBaseState<AnimatedCount> {
  IntTween _count;

  @override
  Widget build(BuildContext context) {
    return new Text(_count.evaluate(animation).toString());
  }

  @override
  void forEachTween(TweenVisitor visitor) {
    _count = visitor(_count, widget.count, (dynamic value) => new IntTween(begin: value));
  }
}

Great work! And is it possible to use double values as well?

I got a solution for double values and negative double values .
For those who need, try this. and let me know if it is woking for you as well.

import 'package:flutter/material.dart';
import 'package:basic_utils/basic_utils.dart' as Utilss;

AnimatedCount(
    decimalValuesAsString: '23.25',
    animatedStyle: TextStyle(color: Colors.white),
    maxLines: 1,
    curve: Curves.ease,
    duration: Duration(milliseconds: 1200),
)

class AnimatedCount extends ImplicitlyAnimatedWidget {
  final String decimalValuesAsString;
  final TextStyle animatedStyle;
  final int maxLines;

  AnimatedCount({
    Key key,
    @required this.decimalValuesAsString,
    @required Duration duration,
    this.animatedStyle,
    this.maxLines,
    Curve curve = Curves.linear
  }) : super(duration: duration, curve: curve, key: key);

  @override
  ImplicitlyAnimatedWidgetState<ImplicitlyAnimatedWidget> createState() => _AnimatedCountState();
}

class _AnimatedCountState extends AnimatedWidgetBaseState<AnimatedCount> {
  IntTween _count;
  var decimalIndex;
  @override
  Widget build(BuildContext context) {
    String s = _count.evaluate(animation).toString();
    if(decimalIndex != -1) {
      s = Utilss.StringUtils.addCharAtPosition(s, ".", decimalIndex);
    }
    return new Text(s,style: widget.animatedStyle,maxLines: widget.maxLines,);
  }

  @override
  void forEachTween(TweenVisitor visitor) {
    decimalIndex = widget.decimalValuesAsString.toString().indexOf('.');
    if(decimalIndex != -1) {
      // decimal present
      var withoutDecimals = widget.decimalValuesAsString.toString().replaceAll('.', '');
      _count = visitor(_count, int.parse(withoutDecimals), (dynamic value) => new IntTween(begin: value));
    } else if (decimalIndex == -1) {
      // decimal not present
      _count = visitor(_count, int.parse(widget.decimalValuesAsString), (dynamic value) => new IntTween(begin: value));
    }
  }
}