在我的数据库帮助器类中添加DROP DATABASE函数后，出现了DATABASE READ ONLY的错误，我可能会尝试删除所需的表，但我想知道我在这里做错了什么，我尝试删除DROP函数及其之后的工作

以下是错误消息：android.database.sqlite.SQLiteReadOnlyDatabaseException：尝试写入只读数据库(代码1032SQLITE_READONLY_DBMOVED[1032])

public class logdb extends SQLiteOpenHelper{
Context c;
SQLiteDatabase db=this.getWritableDatabase();
public logdb(@Nullable Context context)
{
    super(context, "login.db", null, 1);
    this.c = context;
    try
    {
        String st = "create table if not exists user(email text,password text,username text)";
        db.execSQL(st);
    }
    catch(Exception e){

    }
}

@Override
public void onCreate(SQLiteDatabase db) {}

public void createuser()
{
    try
    {
        String st = "create table if not exists user(email text,password text,username text)";
        db.execSQL(st);
    }
    catch(Exception e)
    {

    }
}
public String drop(){
    try
    {
        c.deleteDatabase("login.db");
           //adding this line is turning the database into read only

    }
    catch(Exception e )
    {

    }
    return " No here error ";
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {}

public void oninsert(ContentValues cv)
{
    try
    {
        db.execSQL("insert into user values('"+cv.get("email")+"','"+cv.get("password")+"','"+cv.get("username")+"')");
    }
    catch(Exception e)
    {

    }
}

public String getusername(){
    Cursor c = db.rawQuery("select * from user",null);

    if(c.getCount()!=0)
    {
        c.moveToNext();
        return c.getString(2);
    }
    return c.getString(2);
}

}