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samples/background_isolate_channels/lib/main.dart

154 lines
4.8 KiB

// 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),
bottom: PreferredSize(
preferredSize: const Size.fromHeight(kToolbarHeight),
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 8.0),
child: SearchBar(
hintText: 'Search',
onChanged:
_database == null ? null : (query) => _refresh(query: query),
trailing: const [Icon(Icons.search), SizedBox(width: 8)],
),
),
),
),
body: 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),
),
);
}
}