main.dart

import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:oktoast/oktoast.dart';
import 'package:photo_manager/photo_manager.dart';
import 'package:provider/provider.dart';

import 'model/photo_provider.dart';
import 'page/index_page.dart';
import 'widget/image_item_widget.dart';

final PhotoProvider provider = PhotoProvider();

void main() {
  runZonedGuarded(
    () => runApp(const _SimpleExampleApp()),
    (Object e, StackTrace s) {
      if (kDebugMode) {
        FlutterError.reportError(FlutterErrorDetails(exception: e, stack: s));
      }
      showToast('$e\n$s', textAlign: TextAlign.start);
    },
  );
  SystemChrome.setSystemUIOverlayStyle(
    const SystemUiOverlayStyle(
      statusBarColor: Colors.transparent,
      systemNavigationBarColor: Colors.transparent,
    ),
  );
}

class _SimpleExampleApp extends StatelessWidget {
  const _SimpleExampleApp();

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<PhotoProvider>.value(
      value: provider, // This is for the advanced usages.
      child: MaterialApp(
        title: 'Photo Manager Example',
        theme: ThemeData(
          colorSchemeSeed: Colors.blue,
        ),
        builder: (context, child) {
          if (child == null) {
            return const SizedBox.shrink();
          }
          return Banner(
            message: 'Debug',
            location: BannerLocation.bottomStart,
            child: OKToast(child: child),
          );
        },
        home: const _SimpleExamplePage(),
        debugShowCheckedModeBanner: false,
      ),
    );
  }
}

class _SimpleExamplePage extends StatefulWidget {
  const _SimpleExamplePage();

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

class _SimpleExamplePageState extends State<_SimpleExamplePage> {
  /// Customize your own filter options.
  final FilterOptionGroup _filterOptionGroup = FilterOptionGroup(
    imageOption: const FilterOption(
      sizeConstraint: SizeConstraint(ignoreSize: true),
    ),
  );
  final int _sizePerPage = 50;

  AssetPathEntity? _path;
  List<AssetEntity>? _entities;
  int _totalEntitiesCount = 0;

  int _page = 0;
  bool _isLoading = false;
  bool _isLoadingMore = false;
  bool _hasMoreToLoad = true;

  Future<void> _requestAssets() async {
    setState(() {
      _isLoading = true;
    });
    // Request permissions.
    final PermissionState ps = await PhotoManager.requestPermissionExtend();
    if (!mounted) {
      return;
    }
    // Further requests can be only proceed with authorized or limited.
    if (!ps.hasAccess) {
      setState(() {
        _isLoading = false;
      });
      showToast('Permission is not accessible.');
      return;
    }
    // Obtain assets using the path entity.
    final List<AssetPathEntity> paths = await PhotoManager.getAssetPathList(
      onlyAll: true,
      filterOption: _filterOptionGroup,
    );
    if (!mounted) {
      return;
    }
    // Return if not paths found.
    if (paths.isEmpty) {
      setState(() {
        _isLoading = false;
      });
      showToast('No paths found.');
      return;
    }
    setState(() {
      _path = paths.first;
    });
    _totalEntitiesCount = await _path!.assetCountAsync;
    final List<AssetEntity> entities = await _path!.getAssetListPaged(
      page: 0,
      size: _sizePerPage,
    );
    if (!mounted) {
      return;
    }
    setState(() {
      _entities = entities;
      _isLoading = false;
      _hasMoreToLoad = _entities!.length < _totalEntitiesCount;
    });
  }

  Future<void> _loadMoreAsset() async {
    final List<AssetEntity> entities = await _path!.getAssetListPaged(
      page: _page + 1,
      size: _sizePerPage,
    );
    if (!mounted) {
      return;
    }
    setState(() {
      _entities!.addAll(entities);
      _page++;
      _hasMoreToLoad = _entities!.length < _totalEntitiesCount;
      _isLoadingMore = false;
    });
  }

  Widget _buildBody(BuildContext context) {
    if (_isLoading) {
      return const Center(child: CircularProgressIndicator.adaptive());
    }
    if (_path == null) {
      return const Center(child: Text('Request paths first.'));
    }
    if (_entities?.isNotEmpty != true) {
      return const Center(child: Text('No assets found on this device.'));
    }
    return GridView.custom(
      gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: 4,
      ),
      childrenDelegate: SliverChildBuilderDelegate(
        (BuildContext context, int index) {
          if (index == _entities!.length - 8 &&
              !_isLoadingMore &&
              _hasMoreToLoad) {
            _loadMoreAsset();
          }
          final AssetEntity entity = _entities![index];
          return ImageItemWidget(
            key: ValueKey<int>(index),
            entity: entity,
            option: const ThumbnailOption(size: ThumbnailSize.square(200)),
          );
        },
        childCount: _entities!.length,
        findChildIndexCallback: (Key key) {
          // Re-use elements.
          if (key is ValueKey<int>) {
            return key.value;
          }
          return null;
        },
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('photo_manager')),
      body: Column(
        children: <Widget>[
          const Padding(
            padding: EdgeInsets.all(8.0),
            child: Text(
              'This page will only obtain the first page of assets '
              'under the primary album (a.k.a. Recent). '
              'If you want more filtering assets, '
              'head over to "Advanced usages".',
            ),
          ),
          Expanded(child: _buildBody(context)),
        ],
      ),
      persistentFooterButtons: <TextButton>[
        TextButton(
          onPressed: () {
            Navigator.of(context).push<void>(
              MaterialPageRoute<void>(builder: (_) => const IndexPage()),
            );
          },
          child: const Text('Advanced usages'),
        ),
      ],
      floatingActionButton: FloatingActionButton(
        onPressed: _requestAssets,
        child: const Icon(Icons.developer_board),
      ),
    );
  }
}