Android Local Storage

Introduction

In any mobile application, the ability to store data locally is crucial for providing a seamless user experience. Android offers various options for storing data locally, such as SharedPreferences, SQLite database, and file storage. In this blog post, we'll explore the concept of local storage in Android and demonstrate how to implement a UserTable using a SQLite database.

Local Storage Options in Android

SharedPreferences

SharedPreferences is a key-value storage mechanism provided by Android for storing simple data types, such as booleans, strings, integers, floats, and longs. It is ideal for storing small amounts of data that needs to be persisted across application sessions. Here's an example of how to store and retrieve data using SharedPreferences:

// Storing data
SharedPreferences.Editor editor = getSharedPreferences("MyPrefs", MODE_PRIVATE).edit();
editor.putString("username", "John");
editor.putInt("age", 25);
editor.apply();

// Retrieving data
SharedPreferences prefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
String username = prefs.getString("username", "");
int age = prefs.getInt("age", 0);

SQLite Database

SQLite is a lightweight relational database management system embedded in Android. It provides a structured storage solution for storing and retrieving large amounts of structured data. Here's an example of how to create a UserTable using SQLite database:

public class UserTableHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "users.db";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "user";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_NAME = "name";
    private static final String COLUMN_EMAIL = "email";
    // ... other columns

    public UserTableHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + " (" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_NAME + " TEXT, " +
                COLUMN_EMAIL + " TEXT)"; +
                // ... other columns
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Handle database upgrade if version changes
    }

    public void addUser(User user) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, user.getName());
        values.put(COLUMN_EMAIL, user.getEmail());
        // ... set other values
        db.insert(TABLE_NAME, null, values);
        db.close();
    }

    public List<User> getAllUsers() {
        List<User> userList = new ArrayList<>();
        String selectQuery = "SELECT * FROM " + TABLE_NAME;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        if (cursor.moveToFirst()) {
            do {
                User user = new User();
                user.setId(cursor.getInt(cursor.getColumnIndex(COLUMN_ID)));
                user.setName(cursor.getString(cursor.getColumnIndex(COLUMN_NAME)));
                user.setEmail(cursor.getString(cursor.getColumnIndex(COLUMN_EMAIL)));
                // ... set other values
                userList.add(user);
            } while (cursor.moveToNext());
        }
        cursor.close();
        db.close();
        return userList;
    }

    // ... other database operations
}

Conclusion

Local storage is an essential feature in Android development, enabling us to persist and retrieve user data efficiently. In this blog post, we explored two common options for local storage: SharedPreferences and SQLite database. We demonstrated how to store and retrieve data using these mechanisms and provided a complete code example for implementing a UserTable using SQLite. By using these techniques, you can enhance your Android application's functionality and deliver a better user experience.

本文来自极简博客，作者：算法架构师，转载请注明原文链接：Android Local Storage