Android Question Checking for a Null value in a string?

Sanxion · Mar 13, 2016

Guys

I am baffled as to the reason why this is not working:

B4X:

If MyNote <> Null And MyNote <> " " Then     
    etNote.Text = MyNote.Trim 
Else
    Msgbox("MyNote is null!","")
End If

Anybody know why the Null and empty string check is being ignored?

Thanks

klaus · Mar 13, 2016

What is not working ?
I suspect that this is wrong:
If MyNote <> Null And MyNote <> " " Then
I would use:
If MyNote <> Null And MyNote <> "" Then
In your code " " is the blank character and not an empty string.

Sanxion · Mar 13, 2016

klaus said:
What is not working ?
I suspect that this is wrong:
If MyNote <> NullAnd MyNote <> " " Then
I would use:
If MyNote <> NullAnd MyNote <> "" Then
In your code " " is the blank character and not an empty string.

I should have mentioned that at first I tried:

B4X:

If MyNote <> Null Then
       
        If MyNote <> "" Then   
           
            etNote.Text = MyNote.Trim   
       
        End If
    Else
       
        Msgbox("MyNote is null!","")
       
    End If

However, this line was still being executed: etNote.Text = MyNote.Trim

I therefore changed it to what I posted above and that has the same result. The point is that the first Null check does not work.

mc73 · Mar 13, 2016

Sanxion said:
The point is that the first Null check does not work.

Then, what is the etNote.text value? If for e.g. it is "null", which may happen if you're feeding from a database, then you should check for "null" instead of null.

Sanxion · Mar 13, 2016

mc73 said:
Then, what is the etNote.text value? If for e.g. it is "null", which may happen if you're feeding from a database, then you should check for "null" instead of null.

etNote.text value is 'null' - see the attached file

Ok...I am now checking for all three scenarios...

B4X:

If MyNote <> Null Then
       
        If MyNote <> "" Then
           
            If MyNote <> "null" Then   
               
                etNote.Text = MyNote.Trim   
           
            End If
           
        End If
       
    Else
       
        Msgbox("MyNote is null!","")
       
    End If

The result is the same?

Erel · Mar 13, 2016

What is the type of MyNote?

mc73 · Mar 13, 2016

If you see "null" you should check for "null" not null, since I guess myNote is a string.

Sanxion · Mar 13, 2016

Erel said:
What is the type of MyNote?

It is declared in Sub Globals:
Dim MyNote As String

Sanxion · Mar 13, 2016

mc73 said:
If you see "null" you should check for "null" not null, since I guess myNote is a string.

I am checking for "null" and null.

See the code above.

mc73 · Mar 13, 2016

I saw your code, this is why I replied! Just remove the <>null check!

Sanxion · Mar 13, 2016

mc73 said:
I saw your code, this is why I replied! Just remove the <>null check!

I just tried that...it didn't work...also I am not sure why the result would be any different if that was my first or third check.

mc73 · Mar 13, 2016

B4X:

if myNote="null" or myNote="" then
'doSomethingIfNeeded
log("null")
else
etNote.Text = MyNote.Trim 
end if

Sanxion · Mar 13, 2016

mc73 said:

B4X:

if myNote="null" or myNote="" then
'doSomethingIfNeeded
log("null")
else
etNote.Text = MyNote.Trim
end if

Thank-you MC73..I tried that and received the same result.

The value is still null and the checks are ignored.

Sanxion · Mar 13, 2016

I have 'resolved' the issue by checking for a null in the returned SQL via a Sub level variable - which does work. I then add an empty space if it is a null.

Mikonios · Jun 15, 2016

Version 3.82

B4X:

Sub CheckNewConDat(MisValNew() AsString, MisValDat() AsString, i AsInt) AsString
Dim MiVal As String = ""
Dim MiResult As String = ""

If MisValNew (16) <> MisValDat (16) OR MisValNew (17) <> MisValDat (17) OR MisValNew (19) <> MisValDat (19) OR _
MisValNew (20) <> MisValDat (20) OR MisValNew (23) <> MisValDat (23) OR MisValNew (24) <> MisValDat (24) OR _
MisValNew (28) <> MisValDat (28) Then
...

When a single value is "null" ::
in "debug" mode it works perfectly.
in "release" always the same error:

B4X:

15/06/2016: 124432: pocess: lastexception: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String.equals boolean (Object)' on a null object reference

Unable to resolve this problem

Erel · Jun 15, 2016

Please start a new thread for this question. Also describe how these two arrays are filled.

Mikonios · Jun 15, 2016

Solved with this inelegant modification that increases the response time on a DB with 10,000 records and 40 fields per record. ::::

B4X:

Sub CorrectNull(MyString As String) As String
    Try
        ' Force error
        If MyString.Length = 0 Then
            Dim MyNewStr As String = ""
        Else
            Dim MyNewStr As String = MyString
        End If
    Catch
        ' Capture the error
        Dim MyNewStr As String = ""
    End Try
    Return MyNewStr
End Sub

Sub CheckNewConDat(MisValNew() As String,  MisValDat() As String, i As Int) As String

    Dim MiVal As String = ""
    Dim MiResult As String = ""

    MisValNew(16) = CorrectNull(MisValNew(16)):        MisValDat(16) = CorrectNull(MisValDat(16))
    MisValNew(17) = CorrectNull(MisValNew(17)):        MisValDat(17) = CorrectNull(MisValDat(17))
    MisValNew(19) = CorrectNull(MisValNew(19)):        MisValDat(19) = CorrectNull(MisValDat(19))
    MisValNew(20) = CorrectNull(MisValNew(20)):        MisValDat(20) = CorrectNull(MisValDat(20))
    MisValNew(23) = CorrectNull(MisValNew(23)):        MisValDat(23) = CorrectNull(MisValDat(23))
    MisValNew(24) = CorrectNull(MisValNew(24)):        MisValDat(24) = CorrectNull(MisValDat(24))
    MisValNew(28) = CorrectNull(MisValNew(28)):        MisValDat(28) = CorrectNull(MisValDat(28))

    If MisValNew(16) <> MisValDat(16) OR MisValNew(17) <> MisValDat(17) OR MisValNew(19) <> MisValDat(19) OR _
        MisValNew(20) <> MisValDat(20) OR MisValNew(23) <> MisValDat(23) OR MisValNew(24) <> MisValDat(24) OR _
        MisValNew(28) <> MisValDat(28) Then
        MiResult = "UPDATE [10Datos] SET LstUpdte ='" &    MisValNew(13) & "', "

        MiResult = MiResult & "...='" &         MisValNew(16) & "', "
        MiResult = MiResult & "...='" &         MisValNew(17) & "', "
        MiResult = MiResult & "...='" &         MisValNew(19) & "', "
        MiResult = MiResult & "...='" &         MisValNew(20) & "', "
        MiResult = MiResult & "...='" &         MisValNew(23) & "', "
        MiResult = MiResult & "...='" &         MisValNew(24) & "', "
        MiResult = MiResult & "...='" &         MisValNew(28) & "' "

        MiResult = MiResult & "WHERE sLat = '" & MisValDat(0) & "' and sLng = '" & MisValDat(1) & "' "
        Try
            If Not(MisValNew(8) = Null) AND Not(MisValNew(8).Contains("'")) Then
                MiResult = MiResult & "AND Rotulo = '" & MisValNew(8) & "' "
            End If
        Catch
            LogMemory1("MiResult:" & i & "." & MiResult, "3")
        End Try

        MiResult = MiResult.Replace("=''", "=null")

    End If

    Return MiResult

'        LogMemory1("CheckNewConDat.lastexception: (" & i & ")." & LastException.Message, "3")

End Sub

Data Source :::

B4X:

    QryNew = "SELECT * FROM [" & TblNewName & "] WHERE sLat IS NOT NULL ORDER BY sLat"
    Dim LstResultNew As List
        LstResultNew = ExecuteMemoryTable(SQL1, QryNew, Null, 0)
    Dim MisValNew() As String = LstResultNew.Get(i)

Xample Image BBDD :::

Android Question Checking for a Null value in a string?

Sanxion

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