Android Question Bug? Error comparing two strings

makis_best · Jul 10, 2019

Hi

I try to compare a string with the content of one EditText
But the code refuse to continuous inside If / End If
The result of the Log is correct as you can see below.

siaka@gmail.com = siaka@gmail.com

Why?

B4X:

Dim EmailTxt As EditText
Dim Local_Email As String
Log(EmailTxt.Text & " = " & Local_Email)
If EmailTxt.Text = Local_Email Then
    Wait For (CallSub(Me, "ChangePass")) Complete (Result As Boolean)
        ........
End If

makis_best · Jul 11, 2019

I convert both strings to Unicode for checking and I be back

emexes · Jul 11, 2019

I have gotten this far to reproducing the symptoms:

B4X:

Dim bc As ByteConverter
 
Dim Bob1 As String = "siaka" & Chr(65312) & "gmail.com"
Dim Bob2 As String = "siaka" & Chr(64) & "gmail.com"
 
Log(Bob1.Length & " " & Bob1)
Log(Bob2.Length & " " & Bob2)
Log((Bob1 = Bob2))

produces this log:

Erel · Jul 11, 2019

What is the output of:

B4X:

Dim bc As ByteConverter
Log(bc.HexFromBytes(Text1.GetBytes("UTF8"))
Log(bc.HexFromBytes(Text2.GetBytes("UTF8"))

Erel · Jul 11, 2019

emexes said:
I have gotten this far to reproducing the symptoms

This is expected. The two strings are different.

emexes · Jul 11, 2019

Erel said:
This is expected. The two strings are different.

Agreed. But they look the same on my screen:

Not that it matters - my theory of different-character-same-appearance falls over when I use .CompareTo, which apparently returns a different result to using the "=" operator.

Erel · Jul 11, 2019

emexes said:
when I use .CompareTo, which apparently returns a different result to using the "=" operator

Are you sure? Can you post an example?

emexes · Jul 11, 2019

Now I am thinking perhaps the one Unicode character can end up being different byte patterns, depending upon the encoding used.

Erel · Jul 11, 2019

Strings are not affected by encodings. Strings = list of unicode code points. Encoding is relevant when you convert the code points to bytes.

emexes · Jul 11, 2019

Erel said:
Are you sure?

That made me lol: this caper has me so confused that I'm not even sure that 1+1=2 any more!

Can you post an example?

This post: https://www.b4x.com/android/forum/threads/bug-error-comparing-two-strings.107534/#post-672338

q: Did using the .CompareTo method fix the problem where it was occurring in your app?
a: Yes... With the .CompareTo working fine....

makis_best · Jul 11, 2019

@Erel The EmailTxt.Text return 7369616B6140676D61696C2E636F6D And The Local_Email return 7369616B614040676D61696C2E636F6D

I think something is hidden somewhere.... I need to check the database field

Erel · Jul 11, 2019

The proper way to continue is by waiting for the output of the code in post #23.

Erel · Jul 11, 2019

7369616B6140676D61696C2E636F6D
7369616B614040676D61696C2E636F6D

There is an extra non-printable character here.

You can remove it with:

B4X:

Text2 = Text2.Replace(Chr(0x04), "")

makis_best · Jul 11, 2019

True....

I have to find why.... for the moment I use Replace.
and I be back when I have news

emexes · Jul 11, 2019

makis_best said:
@Erel The EmailTxt.Text return 7369616B6140676D61696C2E636F6D And The Local_Email return 7369616B614040676D61696C2E636F6D

There's your problem, then:

B4X:

7369616B6140  676D61696C2E636F6D
7369616B614040676D61696C2E636F6D

I think something is hidden somewhere....

Agreed.

emexes · Jul 11, 2019

Erel said:
7369616B6140676D61696C2E636F6D
7369616B614040676D61696C2E636F6D

There is an extra non-printable character here.

Actually, it is an extra printable character '@'

But why is the double "@@" not displayed? Hmm.

Erel · Jul 11, 2019

0x04 is not a printable character. You can test it with:

B4X:

Log("a" & Chr(0x04) & "b") 'ab

It is a control character (EOT): https://unicode.org/charts/PDF/U0000.pdf

emexes · Jul 11, 2019

Erel said:
0x04 is not a printable character. You can test it with:

B4X:

Log("a" & Chr(0x04) & "b") 'ab

It is a control character: https://www.utf8-chartable.de/unicode-utf8-table.pl

Agreed, but the ...04... in the hex dump is not on a 2-hex-digit byte boundary.

emexes · Jul 11, 2019

B4X:

7369616B6140  676D61696C2E636F6D
7369616B614040676D61696C2E636F6D

makis_best · Jul 11, 2019

OK.... I find it.... After that post I go to sleep... I haven't sleep all night looking what is going on.
I did 4 steps.
1) I alter database field from string to TEXT.
2) I check the code and then Log(EmailTxt.Text.Length & " " & Local_Email.Length) Return siaka@gmail.com = siaka@ gmail.com Space after @
3) I alter database field from TEXT to string.
4) I run the code again and executed correctly.
No error using If Local_Email = EmailTxt.Text Then.....

Problem solved after alter the field twice.....

Very strange!!!!!
I can understand it.
But now everything seems to work perfect.

emexes · Jul 11, 2019

There is still the issue of why .CompareTo worked when "=" did not. You're probably right to let it go; when things are not making sense, it is easy to mix up what happened when, and simpler to let it be.

I still have a theory about character encodings that might reproduce the symptoms. You are using non-ASCII characters, which should be no problem, but... I'll keep looking for another half-hour, otherwise I won't be able to sleep all night either!

Android Question Bug? Error comparing two strings

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