Flutter 3.7.0

background_isolate_channels/analysis_options.yaml

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+include: ../analysis_options.yaml

background_isolate_channels/lib/main.dart

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+// Copyright 2022 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io' show Directory;
+
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+import 'package:path/path.dart' as path;
+import 'package:path_provider/path_provider.dart' as path_provider;
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:uuid/uuid.dart' as uuid;
+
+import 'simple_database.dart';
+
+///////////////////////////////////////////////////////////////////////////////
+// This is the UI which will present the contents of the [SimpleDatabase]. To
+// see where Background Isolate Channels are used see simple_database.dart.
+///////////////////////////////////////////////////////////////////////////////
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Background Isolate Channels',
+      theme: ThemeData(
+        primarySwatch: Colors.blue,
+      ),
+      home: const MyHomePage(title: 'Background Isolate Channels'),
+    );
+  }
+}
+
+class MyHomePage extends StatefulWidget {
+  const MyHomePage({super.key, required this.title});
+
+  final String title;
+
+  @override
+  State<MyHomePage> createState() {
+    return _MyHomePageState();
+  }
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  /// The database that is running on a background [Isolate]. This is nullable
+  /// because acquiring a [SimpleDatabase] is an asynchronous operation. This
+  /// value is `null` until the database is initialized.
+  SimpleDatabase? _database;
+
+  /// Local cache of the query results returned by the [SimpleDatabase] for the
+  /// UI to render from. It is nullable since querying the results is
+  /// asynchronous. The value is `null` before any result has been received.
+  List<String>? _entries;
+
+  /// What is searched for in the [SimpleDatabase].
+  String _query = '';
+
+  @override
+  void initState() {
+    // Write the value to [SharedPreferences] which will get read on the
+    // [SimpleDatabase]'s isolate. For this example the value is always true
+    // just for demonstration purposes.
+    final Future<void> sharedPreferencesSet = SharedPreferences.getInstance()
+        .then(
+            (sharedPreferences) => sharedPreferences.setBool('isDebug', true));
+    final Future<Directory> tempDirFuture =
+        path_provider.getTemporaryDirectory();
+
+    // Wait until the [SharedPreferences] value is set and the temporary
+    // directory is received before opening the database. If
+    // [sharedPreferencesSet] does not happen before opening the
+    // [SimpleDatabase] there has to be a way to refresh
+    // [_SimpleDatabaseServer]'s [SharedPreferences] cached values.
+    Future.wait([sharedPreferencesSet, tempDirFuture]).then((values) {
+      final Directory? tempDir = values[1] as Directory?;
+      final String dbPath = path.join(tempDir!.path, 'database.db');
+      SimpleDatabase.open(dbPath).then((database) {
+        setState(() {
+          _database = database;
+        });
+        _refresh();
+      });
+    });
+    super.initState();
+  }
+
+  @override
+  void dispose() {
+    _database?.stop();
+    super.dispose();
+  }
+
+  /// Performs a find on [SimpleDatabase] with [query] and updates the listed
+  /// contents.
+  void _refresh({String? query}) {
+    if (query != null) {
+      _query = query;
+    }
+    _database!.find(_query).toList().then((entries) {
+      setState(() {
+        _entries = entries;
+      });
+    });
+  }
+
+  /// Adds a UUID and a timestamp to the [SimpleDatabase].
+  void _addDate() {
+    final DateTime now = DateTime.now();
+    final DateFormat formatter =
+        DateFormat('EEEE MMMM d, HH:mm:ss\n${const uuid.Uuid().v4()}');
+    final String formatted = formatter.format(now);
+    _database!.addEntry(formatted).then((_) => _refresh());
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(widget.title),
+      ),
+      body: Column(
+        children: [
+          TextField(
+            onChanged:
+                _database == null ? null : (query) => _refresh(query: query),
+            decoration: const InputDecoration(
+              labelText: 'Search',
+              suffixIcon: Icon(Icons.search),
+            ),
+          ),
+          Expanded(
+            child: ListView.builder(
+              itemBuilder: (context, index) {
+                return ListTile(title: Text(_entries![index]));
+              },
+              itemCount: _entries?.length ?? 0,
+            ),
+          ),
+        ],
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: _database == null ? null : _addDate,
+        tooltip: 'Add',
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+}