Add backup/restore functionality to example app

docs/pages/docs/Examples/existing_databases.md

@@ -60,7 +60,7 @@ LazyDatabase _openConnection() {
         await file.writeAsBytes(buffer.asUint8List(blob.offsetInBytes, blob.lengthInBytes));
     }
 
-    return NativeDatabase.createInBackground(file);;
+    return NativeDatabase.createInBackground(file);
   });
 }
 ```

examples/app/lib/database/connection/native.dart

@@ -5,17 +5,16 @@ import 'package:drift/native.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:path/path.dart' as p;
 
+Future<File> get databaseFile async {
+  // We use `path_provider` to find a suitable path to store our data in.
+  final appDir = await getApplicationDocumentsDirectory();
+  final dbPath = p.join(appDir.path, 'todos.db');
+  return File(dbPath);
+}
+
 /// Obtains a database connection for running drift in a Dart VM.
 DatabaseConnection connect() {
   return DatabaseConnection.delayed(Future(() async {
-    // Background isolates can't use platform channels, so let's use
-    // `path_provider` in the main isolate and just send the result containing
-    // the path over to the background isolate.
-
-    // We use `path_provider` to find a suitable path to store our data in.
-    final appDir = await getApplicationDocumentsDirectory();
-    final dbPath = p.join(appDir.path, 'todos.db');
-
-    return NativeDatabase.createBackgroundConnection(File(dbPath));
+    return NativeDatabase.createBackgroundConnection(await databaseFile);
   }));
 }

examples/app/lib/database/database.dart

@@ -119,7 +119,7 @@ class AppDatabase extends _$AppDatabase {
     });
   }
 
-  static Provider<AppDatabase> provider = Provider((ref) {
+  static final StateProvider<AppDatabase> provider = StateProvider((ref) {
     final database = AppDatabase();
     ref.onDispose(database.close);
 

examples/app/lib/screens/backup/backup.dart

@@ -0,0 +1 @@
+export 'unsupported.dart' if (dart.library.ffi) 'supported.dart';

examples/app/lib/screens/backup/supported.dart

@@ -0,0 +1,94 @@
+import 'dart:io';
+
+import 'package:app/database/connection/native.dart';
+import 'package:app/database/database.dart';
+import 'package:drift/drift.dart';
+import 'package:file_picker/file_picker.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+import 'package:sqlite3/sqlite3.dart';
+
+class BackupIcon extends StatelessWidget {
+  const BackupIcon({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return IconButton(
+      onPressed: () =>
+          showDialog(context: context, builder: (_) => const BackupDialog()),
+      icon: const Icon(Icons.save),
+      tooltip: 'Backup',
+    );
+  }
+}
+
+class BackupDialog extends ConsumerWidget {
+  const BackupDialog({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return AlertDialog(
+      title: const Text('Database backup'),
+      content: const Text(
+        'Here, you can save the database to a file or restore a created '
+        'backup.',
+      ),
+      actions: [
+        TextButton(
+          onPressed: () {
+            createDatabaseBackup(ref.read(AppDatabase.provider));
+          },
+          child: const Text('Save'),
+        ),
+        TextButton(
+          onPressed: () async {
+            final db = ref.read(AppDatabase.provider);
+            await db.close();
+
+            // Open the selected database file
+            final backupFile = await FilePicker.platform.pickFiles();
+            if (backupFile == null) return;
+            final backupDb = sqlite3.open(backupFile.files.single.path!);
+
+            // Vacuum it into a temporary location first to make sure it's working.
+            final tempPath = await getTemporaryDirectory();
+            final tempDb = p.join(tempPath.path, 'import.db');
+            backupDb
+              ..execute('VACUUM INTO ?', [tempDb])
+              ..dispose();
+
+            // Then replace the existing database file with it.
+            final tempDbFile = File(tempDb);
+            await tempDbFile.copy((await databaseFile).path);
+            await tempDbFile.delete();
+
+            // And now, re-open the database!
+            ref.read(AppDatabase.provider.notifier).state = AppDatabase();
+          },
+          child: const Text('Restore'),
+        ),
+      ],
+    );
+  }
+}
+
+Future<void> createDatabaseBackup(DatabaseConnectionUser database) async {
+  final choosenDirectory = await FilePicker.platform.getDirectoryPath();
+  if (choosenDirectory == null) return;
+
+  final parent = Directory(choosenDirectory);
+  final file = File(p.join(choosenDirectory, 'drift_example_backup.db'));
+
+  // Make sure the directory of the file exists
+  if (!await parent.exists()) {
+    await parent.create(recursive: true);
+  }
+  // However, the file itself must not exist
+  if (await file.exists()) {
+    await file.delete();
+  }
+
+  await database.customStatement('VACUUM INTO ?', [file.absolute.path]);
+}

examples/app/lib/screens/backup/unsupported.dart

@@ -0,0 +1,10 @@
+import 'package:flutter/material.dart';
+
+class BackupIcon extends StatelessWidget {
+  const BackupIcon({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return const SizedBox.shrink();
+  }
+}

examples/app/lib/screens/home.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
 import '../database/database.dart';
+import 'backup/backup.dart';
 import 'home/card.dart';
 import 'home/drawer.dart';
 import 'home/state.dart';
@@ -48,6 +49,7 @@ class _HomePageState extends ConsumerState<HomePage> {
       appBar: AppBar(
         title: const Text('Drift Todo list'),
         actions: [
+          const BackupIcon(),
           IconButton(
             onPressed: () => context.go('/search'),
             icon: const Icon(Icons.search),

examples/app/pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
   flutter:
     sdk: flutter
   drift:
+  file_picker: ^5.2.5
   flutter_colorpicker: ^1.0.3
   flutter_riverpod: ^1.0.3
   go_router: ^3.0.6