Flutter shared_preferences 0.5.7在重新加载APP后无法获得值

Question

我使用https://pub.dev/packages/shared_preferences在我的颤振项目中，我发现有一些问题。简单地说，我可以在设置后获得值，但在重新加载此应用程序后无法获得值。

然后我创建了一个全新的项目来测试共享偏好插件，就像一个反演示一样，它是有效的。我可以在重新加载应用程序后获得值，但我在实际项目中编写了相同的代码，它不起作用，我只能在这个应用程序仍在运行时通过键获得值，重新加载后，SharedPreferences实例中什么都不包含。

我的真实项目很复杂，所以我只是把我的演示项目放在这里，并且两个项目中共享偏好插件的使用是相同的。我在同一台设备上运行两个项目。

任何帮助都是非常感谢的！

// main.dart
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final spKey = 'abc';
String value;
void getValue() async {
print('getValue()');
final sp = await SharedPreferences.getInstance();
if (sp.containsKey(spKey)) {
setState(() {
value = sp.getString(spKey);
});
}
}
void setValue() async {
print('setValue()');
final sp = await SharedPreferences.getInstance();
setState(() {
sp.setString(spKey, '123');
});
}
@override
Widget build(BuildContext context) {
print('build() value: $value');
if (value == null) {
getValue();
}
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You set value to:',
),
Text(
'$value',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: setValue,
tooltip: 'Increment',
child: Icon(Icons.refresh),
),
);
}
}

我的扑动医生是：

[✓] Flutter (Channel stable, v1.12.13+hotfix.9, on Mac OS X 10.14.6 18G103, locale en-CN)
• Flutter version 1.12.13+hotfix.9 at /Volumes/Transcend/Development/flutter
• Framework revision f139b11009 (5 weeks ago), 2020-03-30 13:57:30 -0700
• Engine revision af51afceb8
• Dart version 2.7.2
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
• Android SDK at /Volumes/Transcend/Development/AndroidSDK
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-29, build-tools 29.0.2
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
• All Android licenses accepted.
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.3.1, Build version 11C504
• CocoaPods version 1.9.0
[✓] Android Studio (version 3.6)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 45.1.1
• Dart plugin version 192.7761
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
[✓] VS Code (version 1.44.2)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.10.1
[✓] Connected device (1 available)
• Capt. Michael’s iPhone • 14717dae7626a115db93783c0f4a386e6c51783e • ios • iOS 12.4.5
• No issues found!

Answer 1

通过删除一些无用的代码来解决。