如何从房间SQLite数据库中检索数据？

// 导入必要的类
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.content.Context;

// 创建帮助类
public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 1;

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建表格的SQL语句
        String createTableQuery = "CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, name TEXT)";
        db.execSQL(createTableQuery);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 升级数据库的操作
    }

    // 检索数据的方法
    public Cursor retrieveData() {
        SQLiteDatabase db = getReadableDatabase();
        String query = "SELECT * FROM mytable";
        return db.rawQuery(query, null);
    }
}

// 在需要检索数据的地方使用
DatabaseHelper dbHelper = new DatabaseHelper(context);
Cursor cursor = dbHelper.retrieveData();

// 遍历查询结果
if (cursor != null && cursor.moveToFirst()) {
    do {
        int id = cursor.getInt(cursor.getColumnIndex("id"));
        String name = cursor.getString(cursor.getColumnIndex("name"));
        // 处理数据
    } while (cursor.moveToNext());
}

// 关闭游标和数据库连接
cursor.close();
dbHelper.close();