flutter_offline_sync_engine 1.0.0

Optimistic UI offline-first data synchronization engine for Flutter with configurable conflict resolution strategies.

example/lib/main.dart

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

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Offline Sync Engine Demo',
      theme: ThemeData.dark(useMaterial3: true),
      home: const SyncScreen(),
    );
  }
}

class SyncScreen extends StatefulWidget {
  const SyncScreen({super.key});

  @override
  State<SyncScreen> createState() => _SyncScreenState();
}

class _SyncScreenState extends State<SyncScreen> {
  late final OfflineSyncEngine _engine;
  final List<String> _localItems = ['Initial Item 1', 'Initial Item 2'];

  @override
  void initState() {
    super.initState();
    _engine = OfflineSyncEngine(
      actionHandler: (action) async {
        // Simulate network API delay
        await Future<void>.delayed(const Duration(milliseconds: 600));
        return true; // Sync success
      },
    );
  }

  void _addItem() {
    final newItem = 'Offline Item #${_localItems.length + 1}';
    setState(() {
      _localItems.add(newItem);
    });

    _engine.recordMutation(SyncAction(
      id: 'mutation_${DateTime.now().millisecondsSinceEpoch}',
      entityType: 'items',
      actionType: SyncActionType.create,
      payload: {'title': newItem},
    ));
  }

  Future<void> _syncNow() async {
    final synced = await _engine.synchronize();
    if (mounted) {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Successfully synced $synced pending items!')),
      );
      setState(() {});
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('flutter_offline_sync_engine Demo'),
        actions: [
          IconButton(
            icon: const Icon(Icons.sync),
            onPressed: _engine.pendingCount > 0 ? _syncNow : null,
          ),
        ],
      ),
      body: Column(
        children: [
          StreamBuilder<SyncStatus>(
            stream: _engine.statusStream,
            initialData: _engine.currentStatus,
            builder: (context, snapshot) {
              final status = snapshot.data ?? SyncStatus.idle;
              return Container(
                width: double.infinity,
                padding: const EdgeInsets.all(12),
                color: status == SyncStatus.syncing
                    ? Colors.orange
                    : status == SyncStatus.success
                        ? Colors.green.shade800
                        : Colors.blueGrey.shade800,
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    Text('Engine Status: ${status.name.toUpperCase()}'),
                    Text('Pending Queue: ${_engine.pendingCount}'),
                  ],
                ),
              );
            },
          ),
          Expanded(
            child: ListView.builder(
              itemCount: _localItems.length,
              itemBuilder: (context, index) => ListTile(
                leading: const Icon(Icons.check_circle_outline),
                title: Text(_localItems[index]),
              ),
            ),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: _addItem,
        icon: const Icon(Icons.add),
        label: const Text('Add Offline Item'),
      ),
    );
  }
}