Flutter支持Preferences（Shared Preferences and NSUserDefaults） 、文件、和Sqlite3。若想使用這個(gè)功能需要引入官方倉(cāng)庫(kù)的相應(yīng)插件，下面詳細(xì)介紹這三種存儲(chǔ)方式的使用方法。

Preferences

等同iOS的NSUserDefaults和Android的SharedPreferences。

導(dǎo)入插件

1. 打開(kāi)項(xiàng)目的pubspec.yaml配置，在dependencies節(jié)點(diǎn)下新增配置:
   shared_preferences: ^0.4.1
2. 點(diǎn)擊開(kāi)發(fā)工具提示的packages get按鈕或者在命令行輸入flutter packages get來(lái)同步第三方插件
3. 在Dart文件中引入插件
   import 'package:shared_preferences/shared_preferences.dart';

Flutter支持的全部插件: https://github.com/flutter/plugins

使用示例

setUserName() async{
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setString(mUserName,"小明");
}

getUserName() async{
    SharedPreferences prefs = await SharedPreferences.getInstance();
    userName = prefs.getString(mUserName);
}

displayUserName() {
    Future<String> userName = getUserName();
    userName.then((String userName) {
           Scaffold.of(context).showSnackBar(
                    SnackBar(content: Text("數(shù)據(jù)獲取成功：$userName")));
    });
}

文件存儲(chǔ)

導(dǎo)入插件

1. 打開(kāi)項(xiàng)目的pubspec.yaml配置，在dependencies節(jié)點(diǎn)下新增配置:
   path_provider: ^0.4.0
2. 點(diǎn)擊開(kāi)發(fā)工具提示的packages get按鈕或者在命令行輸入flutter packages get來(lái)同步第三方插件
3. 在Dart文件中引入插件
   import 'package:path_provider/path_provider.dart';

使用示例

獲取文件路徑方法：

1. 獲取應(yīng)用緩存目錄: getTemporaryDirectory
   • 類似iOS的NSTemporaryDirectory和Android的getCacheDir
2. 獲取應(yīng)用文件目錄: getApplicationDocumentsDirectory
   • 類似iOS的NSDocumentDirectory和Android上的AppData目錄
   • 應(yīng)用程序被刪除時(shí)，系統(tǒng)會(huì)清除目錄
3. 存儲(chǔ)卡: getExternalStorageDirectory
   • 僅支持Android平臺(tái)

// 找到正確的本地路徑
Future<String> get _localPath async {
  final directory = await getApplicationDocumentsDirectory();
  return directory.path;
}

// 創(chuàng)建對(duì)文件位置的引用
Future<File> get _localFile async {
  final path = await _localPath;
  return new File('$path/counter.txt');
}

// 將數(shù)據(jù)寫(xiě)入文件
Future<File> writeCounter(int counter) async {
  final file = await _localFile;
  // Write the file
  return file.writeAsString('$counter');
}

// 從文件中讀取數(shù)據(jù)
Future<int> readCounter() async {
  try {
    final file = await _localFile;
    // Read the file
    String contents = await file.readAsString();

    return int.parse(contents);
  } catch (e) {
    // If we encounter an error, return 0
    return 0;
  }
}

Sqfite

SQLite plugin for Flutter. Get the default databases location. On Android, it is typically data/data/<package_name>/databases, On iOS, it is the Documents directory.

導(dǎo)入插件

1. 打開(kāi)項(xiàng)目的pubspec.yaml配置，在dependencies節(jié)點(diǎn)下新增配置:
   sqflite: ^1.0.0
2. 點(diǎn)擊開(kāi)發(fā)工具提示的packages get按鈕或者在命令行輸入flutter packages get來(lái)同步第三方插件
3. 在Dart文件中引入插件
   import 'package:sqflite/sqflite.dart';

使用示例

// 獲取數(shù)據(jù)庫(kù)文件的存儲(chǔ)路徑
var databasesPath = await getDatabasesPath();
String path = join(databasesPath, 'demo.db');

// 創(chuàng)建數(shù)據(jù)庫(kù)表
db = await openDatabase(path, version: 1,
       onCreate: (Database db, int version) async {
   await db.execute('''
        CREATE TABLE $tableBook (
            $columnId INTEGER PRIMARY KEY, 
            $columnName TEXT, 
            $columnAuthor TEXT, 
            $columnPrice REAL, 
            $columnPublishingHouse TEXT)
          ''');
    });

// 插入數(shù)據(jù)
Future<int> rawInsert(String sql, [List<dynamic> arguments]);

Future<int> insert(String table, Map<String, dynamic> values,
      {String nullColumnHack, ConflictAlgorithm conflictAlgorithm});

// 查詢數(shù)據(jù)
Future<List<Map<String, dynamic>>> rawQuery(String sql,
      [List<dynamic> arguments]);

Future<List<Map<String, dynamic>>> query(String table,
      {bool distinct,
      List<String> columns,
      String where,
      List<dynamic> whereArgs,
      String groupBy,
      String having,
      String orderBy,
      int limit,
      int offset});

// 更新數(shù)據(jù)
Future<int> rawUpdate(String sql, [List<dynamic> arguments]);

Future<int> update(String table, Map<String, dynamic> values,
      {String where,
      List<dynamic> whereArgs,
      ConflictAlgorithm conflictAlgorithm});

// 刪除
Future<int> rawDelete(String sql, [List<dynamic> arguments]);

Future<int> delete(String table, {String where, List<dynamic> whereArgs});

// 關(guān)閉數(shù)據(jù)庫(kù)
Future close() async => db.close();

參考文檔

Flutter中的本地存儲(chǔ)
Flutter數(shù)據(jù)存儲(chǔ)之shared_preferences
Flutter 構(gòu)建完整應(yīng)用手冊(cè)-持久化
Flutter持久化存儲(chǔ)之?dāng)?shù)據(jù)庫(kù)存儲(chǔ)

轉(zhuǎn)載：Flutter 本地存儲(chǔ)