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kenzieschmollkenzieschmoll
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[shared_preferences] Fix a late initialized error with the example app (#8540)
The `_counter` future was throwing a late initialization error because it was accessed from the `FutureBuilder` in `build()` before it was initialized. This adds a completer `_preferencesReady` that we wait for before trying to build the `FutureBuilder` for `_counter`.
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4 files changed

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‎packages/shared_preferences/shared_preferences/CHANGELOG.md

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@@ -1,3 +1,6 @@
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## 2.5.3
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* Fixes a bug in the example app.
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## 2.5.2
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* Fixes `setState` returning `Future` on `example/main.dart` error in example code.

‎packages/shared_preferences/shared_preferences/example/lib/main.dart

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@@ -44,6 +44,10 @@ class SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
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late Future<int> _counter;
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int _externalCounter = 0;
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/// Completes when the preferences have been initialized, which happens after
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/// legacy preferences have been migrated.
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final Completer<void> _preferencesReady = Completer<void>();
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Future<void> _incrementCounter() async {
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final SharedPreferencesWithCache prefs = await _prefs;
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final int counter = (prefs.getInt('counter') ?? 0) + 1;
@@ -86,6 +90,7 @@ class SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
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return prefs.getInt('counter') ?? 0;
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});
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_getExternalCounter();
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_preferencesReady.complete();
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});
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}
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@@ -96,25 +101,30 @@ class SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
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title: const Text('SharedPreferencesWithCache Demo'),
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),
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body: Center(
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child: FutureBuilder<int>(
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future: _counter,
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builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
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switch (snapshot.connectionState) {
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case ConnectionState.none:
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case ConnectionState.waiting:
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return const CircularProgressIndicator();
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case ConnectionState.active:
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case ConnectionState.done:
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if (snapshot.hasError) {
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return Text('Error: ${snapshot.error}');
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} else {
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return Text(
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'Button tapped ${snapshot.data ?? 0 + _externalCounter} time${(snapshot.data ?? 0 + _externalCounter) == 1 ? '' : 's'}.\n\n'
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'This should persist across restarts.',
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);
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}
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}
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})),
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child: _WaitForInitialization(
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initialized: _preferencesReady.future,
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builder: (BuildContext context) => FutureBuilder<int>(
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future: _counter,
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builder: (BuildContext context, AsyncSnapshot<int> snapshot) {
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switch (snapshot.connectionState) {
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case ConnectionState.none:
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case ConnectionState.waiting:
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return const CircularProgressIndicator();
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case ConnectionState.active:
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case ConnectionState.done:
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if (snapshot.hasError) {
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return Text('Error: ${snapshot.error}');
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} else {
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return Text(
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'Button tapped ${snapshot.data ?? 0 + _externalCounter} time${(snapshot.data ?? 0 + _externalCounter) == 1 ? '' : 's'}.\n\n'
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'This should persist across restarts.',
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);
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}
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}
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},
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),
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),
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),
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floatingActionButton: FloatingActionButton(
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onPressed: _incrementCounter,
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tooltip: 'Increment',
@@ -123,3 +133,28 @@ class SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
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);
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}
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}
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/// Waits for the [initialized] future to complete before rendering [builder].
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class _WaitForInitialization extends StatelessWidget {
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const _WaitForInitialization({
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required this.initialized,
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required this.builder,
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});
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final Future<void> initialized;
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final WidgetBuilder builder;
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@override
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Widget build(BuildContext context) {
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return FutureBuilder<void>(
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future: initialized,
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builder: (BuildContext context, AsyncSnapshot<void> snapshot) {
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if (snapshot.connectionState == ConnectionState.waiting ||
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snapshot.connectionState == ConnectionState.none) {
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return const CircularProgressIndicator();
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}
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return builder(context);
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},
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);
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}
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}

‎packages/shared_preferences/shared_preferences/example/test/example_app_test.dart

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// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/services.dart';
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import 'package:flutter_test/flutter_test.dart';
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import 'package:shared_preferences_example/main.dart';
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import 'package:shared_preferences_platform_interface/in_memory_shared_preferences_async.dart';
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import 'package:shared_preferences_platform_interface/shared_preferences_async_platform_interface.dart';
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import 'package:shared_preferences_platform_interface/types.dart';
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void main() {
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group('SharedPreferences example app', () {
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setUp(() {
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SharedPreferencesAsyncPlatform.instance = FakeSharedPreferencesAsync();
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});
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tearDown(() {
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SharedPreferencesAsyncPlatform.instance = null;
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});
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testWidgets('builds successfully', (WidgetTester tester) async {
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await tester.pumpWidget(const MyApp());
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});
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});
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}
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// Note: this code is duplicated in
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// shared_preferences/test/shared_preferences_async_test.dart. Since we cannot
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// import the relative path ../../test/shared_preferences_async_test.dart on the
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// web platform, we had to copy it here for use in this test library.
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base class FakeSharedPreferencesAsync extends SharedPreferencesAsyncPlatform {
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final InMemorySharedPreferencesAsync backend =
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InMemorySharedPreferencesAsync.empty();
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final List<MethodCall> log = <MethodCall>[];
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@override
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Future<bool> clear(
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ClearPreferencesParameters parameters, SharedPreferencesOptions options) {
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log.add(MethodCall('clear', <Object>[...?parameters.filter.allowList]));
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return backend.clear(parameters, options);
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}
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@override
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Future<bool?> getBool(String key, SharedPreferencesOptions options) {
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log.add(MethodCall('getBool', <String>[key]));
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return backend.getBool(key, options);
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}
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@override
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Future<double?> getDouble(String key, SharedPreferencesOptions options) {
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log.add(MethodCall('getDouble', <String>[key]));
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return backend.getDouble(key, options);
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}
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@override
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Future<int?> getInt(String key, SharedPreferencesOptions options) {
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log.add(MethodCall('getInt', <String>[key]));
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return backend.getInt(key, options);
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}
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@override
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Future<Set<String>> getKeys(
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GetPreferencesParameters parameters, SharedPreferencesOptions options) {
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log.add(MethodCall('getKeys', <String>[...?parameters.filter.allowList]));
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return backend.getKeys(parameters, options);
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}
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@override
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Future<Map<String, Object>> getPreferences(
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GetPreferencesParameters parameters, SharedPreferencesOptions options) {
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log.add(MethodCall(
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'getPreferences', <Object>[...?parameters.filter.allowList]));
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return backend.getPreferences(parameters, options);
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}
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@override
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Future<String?> getString(String key, SharedPreferencesOptions options) {
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log.add(MethodCall('getString', <String>[key]));
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return backend.getString(key, options);
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}
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@override
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Future<List<String>?> getStringList(
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String key, SharedPreferencesOptions options) {
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log.add(MethodCall('getStringList', <String>[key]));
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return backend.getStringList(key, options);
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}
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@override
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Future<bool> setBool(
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String key, bool value, SharedPreferencesOptions options) {
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log.add(MethodCall('setBool', <Object>[key, value]));
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return backend.setBool(key, value, options);
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}
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@override
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Future<bool> setDouble(
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String key, double value, SharedPreferencesOptions options) {
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log.add(MethodCall('setDouble', <Object>[key, value]));
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return backend.setDouble(key, value, options);
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}
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@override
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Future<bool> setInt(String key, int value, SharedPreferencesOptions options) {
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log.add(MethodCall('setInt', <Object>[key, value]));
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return backend.setInt(key, value, options);
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}
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@override
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Future<bool> setString(
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String key, String value, SharedPreferencesOptions options) {
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log.add(MethodCall('setString', <Object>[key, value]));
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return backend.setString(key, value, options);
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}
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@override
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Future<bool> setStringList(
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String key, List<String> value, SharedPreferencesOptions options) {
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log.add(MethodCall('setStringList', <Object>[key, value]));
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return backend.setStringList(key, value, options);
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}
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}

‎packages/shared_preferences/shared_preferences/pubspec.yaml

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@@ -3,7 +3,7 @@ description: Flutter plugin for reading and writing simple key-value pairs.
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Wraps NSUserDefaults on iOS and SharedPreferences on Android.
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repository: https://github.com/flutter/packages/tree/main/packages/shared_preferences/shared_preferences
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issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+shared_preferences%22
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version: 2.5.2
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version: 2.5.3
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environment:
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sdk: ^3.5.0

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