image_fade 0.4.0

A widget that displays a placeholder and optional progress indicator while an image loads, then cross-fades to the loaded image. Improves on FadeInImage.

example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:image_fade/image_fade.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.yellow,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, this.title}) : super(key: key);

  final String? title;

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

class _MyHomePageState extends State<MyHomePage> {
  // Sample images from Wikimedia Commons:
  static const List<String> _imgs = [
    'https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Almeida_Júnior_-_Saudade_%28Longing%29_-_Google_Art_Project.jpg/513px-Almeida_Júnior_-_Saudade_%28Longing%29_-_Google_Art_Project.jpg',
    'https://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Rafael_-_Retrato_de_um_Cardeal.jpg/786px-Rafael_-_Retrato_de_um_Cardeal.jpg',
    'https://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/James_McNeill_Whistler_-_La_Princesse_du_pays_de_la_porcelaine_-_brighter.jpg/580px-James_McNeill_Whistler_-_La_Princesse_du_pays_de_la_porcelaine_-_brighter.jpg',
    'https://upload.wikimedia.org/wikipedia/commons/thumb/0/01/Hans_Holbein_der_Jüngere_-_Der_Kaufmann_Georg_Gisze_-_Google_Art_Project.jpg/897px-Hans_Holbein_der_Jüngere_-_Der_Kaufmann_Georg_Gisze_-_Google_Art_Project.jpg',
    'https://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Pieter_Bruegel_the_Elder_-_The_Tower_of_Babel_%28Vienna%29_-_Google_Art_Project_-_edited.jpg/1280px-Pieter_Bruegel_the_Elder_-_The_Tower_of_Babel_%28Vienna%29_-_Google_Art_Project_-_edited.jpg',
  ];

  int _counter = 0;
  bool _clear = true;
  bool _error = false;

  void _incrementCounter() {
    setState(() {
      if (_clear || _error) {
        _clear = _error = false;
      } else {
        _counter = (_counter + 1) % _imgs.length;
      }
    });
  }

  void _clearImage() {
    setState(() {
      _clear = true;
      _error = false;
    });
  }

  void _testError() {
    setState(() {
      _error = true;
    });
  }

  @override
  Widget build(BuildContext context) {
    ImageProvider? image;
    if (_error) {
      image = NetworkImage('error.jpg');
    } else if (!_clear) {
      image = NetworkImage(_imgs[_counter]);
    }

    return Scaffold(
      appBar: AppBar(
        title: Text('Showing ' +
            (_error
                ? 'error'
                : _clear
                    ? 'placeholder'
                    : 'image #$_counter from Wikimedia')),
      ),
      body: Stack(children: <Widget>[
        Positioned.fill(
            child: ImageFade(
          image: image,
          placeholder: Container(
            color: Color(0xFFCFCDCA),
            child: Center(
                child: Icon(
              Icons.photo,
              color: Colors.white30,
              size: 128.0,
            )),
          ),
          alignment: Alignment.center,
          fit: BoxFit.cover,
          loadingBuilder:
              (BuildContext context, Widget child, ImageChunkEvent? event) {
            if (event == null) {
              return child;
            }
            return Center(
              child: CircularProgressIndicator(
                  value: event.expectedTotalBytes == null
                      ? 0.0
                      : event.cumulativeBytesLoaded /
                          event.expectedTotalBytes!),
            );
          },
          errorBuilder:
              (BuildContext context, Widget? child, dynamic exception) {
            return Container(
              color: Color(0xFF6F6D6A),
              child: Center(
                  child:
                      Icon(Icons.warning, color: Colors.black26, size: 128.0)),
            );
          },
        ))
      ]),
      floatingActionButton:
          Row(mainAxisAlignment: MainAxisAlignment.end, children: [
        FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Next',
          child: Icon(Icons.navigate_next),
        ),
        SizedBox(width: 10.0),
        FloatingActionButton(
          onPressed: _clearImage,
          tooltip: 'Clear',
          child: Icon(Icons.clear),
        ),
        SizedBox(width: 10.0),
        FloatingActionButton(
          onPressed: _testError,
          tooltip: 'Error',
          child: Icon(Icons.warning),
        ),
      ]),
    );
  }
}