如何检查sqlite db文件对我的android应用程序是否有效？

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

public class MyDatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 1;

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建数据库表格的代码
    }

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

MyDatabaseHelper dbHelper = new MyDatabaseHelper(context);
SQLiteDatabase db = dbHelper.getReadableDatabase();

Cursor cursor = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table' AND name='mytable'", null);
if (cursor.getCount() > 0) {
    // 表格存在
} else {
    // 表格不存在
}
cursor.close();

db.close();