SQLite insert turns inserted values into 1, 2, 3 when they should be String like qpzMH7

I use the following code to insert data into a table

    SQLiteDatabase db = this.getWritableDatabase();
    String CREATE_FOLLOWING_TABLE = "CREATE TABLE IF NOT EXISTS " + FOLLOWING_TABLE_NAME + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_USER_ID + " TEXT)";
    db.execSQL("DROP TABLE IF EXISTS " + FOLLOWING_TABLE_NAME);
    db.execSQL(CREATE_FOLLOWING_TABLE);


    String sql = "INSERT INTO " + FOLLOWING_TABLE_NAME + " (" + KEY_USER_ID + ") VALUES(?)";
    db.beginTransaction();
    SQLiteStatement stmt = db.compileStatement(sql);
    for(String id : userIds) { // userIds is ArrayList<String>
        stmt.bindString(1, id);
        stmt.execute();
        stmt.clearBindings();
    }
    db.setTransactionSuccessful();
    db.endTransaction();
    db.close();

I confirmed that the userIds ArrayList contains String values which are like qWz17mh. However, after running the above code, I get the following in the table

_id    userid
  1    1
  2    2
  3    3
  4    4
  5    5
  6    6

I don't know why this is happening. My suspicion lies in the insert syntax. What do you think is wrong? Thanks in advance!