photo_gallery/example/lib/main.dart

import 'dart:async';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:photo_gallery/photo_gallery.dart';
import 'package:transparent_image/transparent_image.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  List _collections;
  bool _loading = false;

  @override
  void initState() {
    super.initState();
    _loading = true;
    initAsync();
  }

  Future<void> initAsync() async {
    if (await _promptPermissionSetting()) {
      List<Album> collections =
          await PhotoGallery.listAlbums(mediumType: MediumType.image);
      setState(() {
        _collections = collections;
        _loading = false;
      });
    }
    setState(() {
      _loading = false;
    });
  }

  Future<bool> _promptPermissionSetting() async {
    if (Platform.isIOS &&
            await Permission.storage.request().isGranted &&
            await Permission.photos.request().isGranted ||
        Platform.isAndroid && await Permission.storage.request().isGranted) {
      return true;
    }
    return false;
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Photo gallery example'),
        ),
        body: _loading
            ? Center(
                child: CircularProgressIndicator(),
              )
            : LayoutBuilder(
                builder: (context, constraints) {
                  double gridWidth = (constraints.maxWidth - 20) / 3;
                  double gridHeight = gridWidth + 33;
                  double ratio = gridWidth / gridHeight;
                  return Container(
                    padding: EdgeInsets.all(5),
                    child: GridView.count(
                      childAspectRatio: ratio,
                      crossAxisCount: 3,
                      mainAxisSpacing: 5.0,
                      crossAxisSpacing: 5.0,
                      children: <Widget>[
                        ...?_collections?.map(
                          (collection) => GestureDetector(
                            onTap: () => Navigator.of(context).push(
                                MaterialPageRoute(
                                    builder: (context) =>
                                        CollectionPage(collection))),
                            child: Column(
                              children: <Widget>[
                                ClipRRect(
                                  borderRadius: BorderRadius.circular(5.0),
                                  child: Container(
                                    color: Colors.grey[300],
                                    height: gridWidth,
                                    width: gridWidth,
                                    child: FadeInImage(
                                      fit: BoxFit.cover,
                                      placeholder:
                                          MemoryImage(kTransparentImage),
                                      image: AlbumThumbnailProvider(
                                        albumId: collection.id,
                                        highQuality: true,
                                      ),
                                    ),
                                  ),
                                ),
                                Container(
                                  alignment: Alignment.topLeft,
                                  padding: EdgeInsets.only(left: 2.0),
                                  child: Text(
                                    collection.name,
                                    maxLines: 1,
                                    textAlign: TextAlign.start,
                                    style: TextStyle(
                                      height: 1.2,
                                      fontSize: 16,
                                    ),
                                  ),
                                ),
                                Container(
                                  alignment: Alignment.topLeft,
                                  padding: EdgeInsets.only(left: 2.0),
                                  child: Text(
                                    collection.count.toString(),
                                    textAlign: TextAlign.start,
                                    style: TextStyle(
                                      height: 1.2,
                                      fontSize: 12,
                                    ),
                                  ),
                                ),
                              ],
                            ),
                          ),
                        ),
                      ],
                    ),
                  );
                },
              ),
      ),
    );
  }
}

class CollectionPage extends StatefulWidget {
  final Album collection;

  CollectionPage(Album collection) : collection = collection;

  @override
  State<StatefulWidget> createState() => CollectionPageState();
}

class CollectionPageState extends State<CollectionPage> {
  List<Medium> _media;

  @override
  void initState() {
    super.initState();
    initAsync();
  }

  void initAsync() async {
    MediaPage mediaPage = await widget.collection.listMedia();
    setState(() {
      _media = mediaPage.items;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          leading: IconButton(
            icon: Icon(Icons.arrow_back_ios),
            onPressed: () => Navigator.of(context).pop(),
          ),
          title: Text(widget.collection.name),
        ),
        body: GridView.count(
          crossAxisCount: 3,
          mainAxisSpacing: 1.0,
          crossAxisSpacing: 1.0,
          children: <Widget>[
            ...?_media?.map(
              (media) => GestureDetector(
                onTap: () => Navigator.of(context).push(
                    MaterialPageRoute(builder: (context) => ViewerPage(media))),
                child: Container(
                  color: Colors.grey[300],
                  child: FadeInImage(
                    fit: BoxFit.cover,
                    placeholder: MemoryImage(kTransparentImage),
                    image: ThumbnailProvider(
                      mediumId: media.id,
                      highQuality: true,
                    ),
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class ViewerPage extends StatelessWidget {
  final Medium media;

  ViewerPage(Medium media) : media = media;

  @override
  Widget build(BuildContext context) {
    DateTime date = media.creationDate ?? media.modifiedDate;
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          leading: IconButton(
            onPressed: () => Navigator.of(context).pop(),
            icon: Icon(Icons.arrow_back_ios),
          ),
          title: Text(date?.toLocal().toString()),
        ),
        body: Container(
          alignment: Alignment.center,
          child: FadeInImage(
            fit: BoxFit.cover,
            placeholder: MemoryImage(kTransparentImage),
            image: PhotoProvider(mediumId: media.id),
          ),
        ),
      ),
    );
  }
}