opacity blinking

blinkingwidget.dart

///
/// pmatatias 
///

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const appTitle = 'Opacity Demo';
    return const MaterialApp(
      title: appTitle,
      home: MyHomePage(title: appTitle),
    );
  }
}

class BlinkingWidget extends AnimatedWidget {
  const BlinkingWidget({
    super.key,
    required AnimationController controller,
    this.child,
  }) : super(listenable: controller);
  final Widget? child;

  Animation<double> get _opacity => listenable as Animation<double>;

  @override
  Widget build(BuildContext context) {
    return AnimatedOpacity(
      // If the widget is visible, animate to 0.0 (invisible).
      // If the widget is hidden, animate to 1.0 (fully visible).
      opacity: _opacity.value > 0.5 ? 1.0 : 0.0,
      duration: const Duration(milliseconds: 1000),
      // The green box must be a child of the AnimatedOpacity widget.
      child: child ??
          Container(
            width: 200,
            height: 200,
            color: Colors.green,
          ),
    );
  }
}

// The StatefulWidget's job is to take data and create a State class.
// In this case, the widget takes a title, and creates a _MyHomePageState.
class MyHomePage extends StatefulWidget {
  const MyHomePage({
    super.key,
    required this.title,
  });

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

// The State class is responsible for two things: holding some data you can
// update and building the UI using that data.
class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  late final AnimationController _controller = AnimationController(
    duration: const Duration(milliseconds: 3000),
    vsync: this,
  )..repeat();

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
          padding: const EdgeInsets.all(20),
          child: Column(children: [
            BlinkingWidget(controller: _controller),
            SizedBox(height:30),
            BlinkingWidget(
                controller: _controller,
                child: LinearProgressIndicator(
                  value: 730 / 785,
                  minHeight: 30,
                ),),
          ])),
    );
  }
}