是否可以访问flutter应用程序的android共享首选项？

Question

我正在将我当前的 Android 应用程序更新为 flutter。是否可以使用flutter上的shared_preferences插件访问android应用程序中使用的sharedPreferences。

因此，当用户更新应用程序时，他们会直接登录。

Answer 1

您可以使用这个包native_shared_preferences， 有一些方法可以帮助您喜欢（containsKey（），getKeys（））。

这个包native_shared_preferences存储时不给键添加前缀。与此包shared_preferences不同，它总是为使用它存储的每个变量添加前缀

前缀：“flutter_”

Answer 2

这是我从本机应用程序获取必要的令牌和一个 int 值的方法。

首先，您需要 path_provider 来查找必要的文件，plist_parser 用于 iO，因为 iO 将用户默认值存储为 .plist 文件，以及 xml 来读取 Android 中具有共享首选项的 .xml 文件。

如何查找 iO 原生值：

if (Platform.isIOS) {
  // Find the dir of the app.
  final appDocumentsDir = await getLibraryDirectory();
    // Create a list of contents in this dir, which includes files and dirs. 
    List contents = appDocumentsDir.listSync();
    // Find in the list the dir with user preferences
    Directory? prefsDir = contents.firstWhereOrNull((element) => element is Directory && element.path.contains('Preferences'));
    if (prefsDir != null) {
      // Get contents of the dir named 'Preferences'
      List subContents = prefsDir.listSync();
      // Find .plist file with package name of your app.
      File? prefsFile = subContents.firstWhereOrNull((element) => element is File && element.path.contains('com.your_app.plist'));
      if (prefsFile != null) {
        // Parse the file 
        final plist = PlistParser().parseBinaryFileSync(prefsFile.path);
        // With loop find necessary items
        for (final item in plist.entries) {
          if (item.key == 'access_token') {
            print('${item.value as String}');
            // your code to handle the value 
          }
          if (item.key == 'city_id') {
            print('${item.value as int}');
            // your code to handle the value 
          }
          // An example to get stored data of Swift struct 
          if (item.key == 'selectedCity') {
            // Create decoder
            const asciiDecoder = AsciiDecoder();
            // Get ASCII value, which stored like [56, 104, 92 ...]
            final asciiValues = item.value;
            // Convert it to string.
            // It returns json string
            final cityJson = asciiDecoder.convert(asciiValues);
            // Convert json to the class with its factory.
            // You may use https://app.quicktype.io to convert JSON
            // to Flutter class and create necessary factories
            final city = City.fromRawJson(cityJson);
            // your code to handle the object of this class
          }
        }
      }
    }
  }

如何从 Android 中的共享首选项中获取值。

import 'package:xml/xml.dart' as xml;
// Name it somehow you like for example 'xml' as far as it conflicts with dart.io
// You will need dart.io for Platform

if (Platform.isAndroid) {
  // Find the dir of you app by package name
  final appDocumentsDir = Directory('/data/data/com.your_app');
  // Create a list of contents in this dir, which includes files and dirs. 
  List contents = appDocumentsDir.listSync();
  // Find in the list the dir with shared preferences
  Directory? prefsDir = contents.firstWhereOrNull((element) => element is Directory && element.path.contains('shared_prefs'));
  if (prefsDir != null) {
    // Get contents of the dir named shared_prefs
    List subContents = prefsDir.listSync();
    // Find .xml file with shared preferences.
    // Check the name of this file in native code, or
    // find it in Device Explorer of Android Studio.
    File? prefsFile = subContents.firstWhereOrNull((element) => element is File && element.path.contains('your_name.xml'));
    if (prefsFile != null) {
        // Create XML document
        final document = xml.XmlDocument.parse(prefsFile.readAsStringSync());
        // Loop from root to children
        for (final items in document.children) {
          // Loop for each child
          for (final item in items.childElements) {
            // Read item as Sting
            final itemString = item.outerXml;
            // Check for your name in prefs
            if (itemString.contains('access_token')) {
              // If prefs store it as String it will look like
              // '<string name="access_token">the token value</string>'
              // Get the value in this key
              final value = item.innerXml;
              // your code to handle the value
            }
            // For int or float you need to do something different.
            // Because prefs store it like '<int name="city_id" value="3" />'
            if (itemString.contains('city_id')) {
              // 'item.attributes' will return a list like 
              // [name="city_id", value="3"]
              // and you need to get second value and parse it to int
              final cityId = int.parse(item.attributes[1].value);
              // You code to handle the value 'cityId'
            }
          }
        }
      } 
    } 
  } 
}

.firstWhereOrNull 是来自 getX 非常有用的库的函数。 或者您可以使用下面的扩展。

extension IterableX<T> on Iterable<T> {
  T? firstWhereOrNull(bool Function(T) test) {
  T? firstItem;
  for (var item in this) {
    if (test(item)) {
      firstItem = item;
      break;
    }
  }
  return firstItem;
  }
}