Wish B4X Table RowID begins with 1 and not with 0 why

klaus · Apr 30, 2020

Hi Erel,
I have begun to use the B4A Table CustomView.
In the B4XTable1.CellClicked (ColumnId As String, RowId As Long) routine the RowID begins with 1, why?
We are all used that indexes begin with 0, why does it begin here with 1?
Trying

B4X:

mp = bxtTable.GetRow()
Log(mp.Get(ColumnId))

Returns null.
I put Wish as the prefix, because I would like to have this index coherent with all the others.

LucaMs · Apr 30, 2020

klaus said:
We are all used that indexes begin with 0, why does it begin here with 1?

Row 0 is the column header.

klaus · Apr 30, 2020

No!
Look at the code example in my post!
Log(mp.Get(ColumnId)) returns null !?

LucaMs · Apr 30, 2020

klaus said:
No!
Look at the code example in my post!
Log(mp.Get(ColumnId)) returns null !?

Erel said:
Note that we start from cell #1. This is the second cell in the list. The first cell is the header (which you can customize as well).

[From here]

klaus · Apr 30, 2020

Well, I read the original thread of the B4XTable and didn't find anything about the RowID beginning with 1.
I will live with it, but I find it a bit disturbing.

LucaMs · Apr 30, 2020

klaus said:
Well, I read the original thread of the B4XTable and didn't find anything about the RowID beginning with 1.
I will live with it, but I find it a bit disturbing.

Maybe you're right anyway, about the CellClicked event, it shouldn't return the RowID 0.

klaus · Apr 30, 2020

... it shouldn't return the RowID 0.

No, it doesn't return 0.
It returns the correct value!
I use it with a SQLite database and I memorize the rowids of the database rows in a List, there the first index is 0.
To read in the database the selected row i need to use CurrentIndex = RowId - 1.

LucaMs · Apr 30, 2020

Usually, also an autoincremented field index starts with 1 (I'm not sure but you cannot start with 0, there).

But you are referring to the rowID of the table that I never use (or rarely, just for rare specific reasons).

LucaMs · Apr 30, 2020

LucaMs said:
Usually, also an autoincremented field index starts with 1 (I'm not sure but you cannot start with 0, there).

But you are referring to the rowID of the table that I never use (or rarely, just for rare specific reasons).

Even the "internal" SQLite rowID starts with 1!

klaus · Apr 30, 2020

Well, we could argue a lot about this.
Anyway, now I know it and have to use it as it is, no problem.

LucaMs · Apr 30, 2020

I've noticed that you're somewhat reluctant to give me a "Like", Klaus.
Who knows, maybe every now and then, among the many nonsense I write, sometimes an exact thing will happen ?.

It is not important, of course: I am unable to eat them ?

Mahares · Apr 30, 2020

klaus said:
Look at the code example in my post!

LucaMS is correct. If I click on the 10th row of the data here is what I get:

B4X:

 Log($"rowId: ${RowId} "$  )   '10 which is row # clicked. Note that header cell is 0, then cell 1 then 2, etc.   
   Dim mp As Map
    mp.Initialize
    mp = B4XTable1.GetRow(RowId)
    Log(mp)   'shows: col name and  the number 10 if I clicked the 10th row excluding the header row

My stored data column name is: Entry and the cell content for the 10th row is 10, since my data starts with 1, then 2, then 3, etc.

Erel · May 1, 2020

There are two things worth clearing:

1. The RowId is a random unique value. Don't assume that it starts from 1. The only thing that you can assume is that RowId = 0 means an empty row. I use it all the time in the DataUpdated event.

If you want to get the visible row number then you must use B4XTable.VisibleRowIds.

2. You need to add 1 when you want to get the "CellLayout" of a visible row from Column.CellLayouts. It happens because the first layout is the header layout.

Example that marks rows where the value of a column is larger than 10:

B4X:

Sub B4XTable1_DataUpdated
    For i = 0 To B4XTable1.VisibleRowIds.Size - 1
        Dim RowId As Long = B4XTable1.VisibleRowIds.Get(i)
        If RowId > 0 Then 'non-empty row
            Dim Value As Double = B4XTable1.GetRow(RowId).Get(numberColumn.Id)
            If Value > 10 Then
                SetRowColor(i, xui.Color_LightGray)
                Continue '<----
            End If
        End If
        SetRowColor(i, xui.Color_White)
    Next
End Sub

Sub SetRowColor (RowIndex As Int, Clr As Int)
    For Each c As B4XTableColumn In B4XTable1.VisibleColumns
        Dim pnl As B4XView = c.CellsLayouts.Get(RowIndex + 1) '+1 because of the header
        pnl.Color = Clr
    Next
End Sub

Erel · May 1, 2020

@klaus I don't understand the code that you posted in the first post.

This code will never return null:

B4X:

Sub B4XTable1_CellClicked (ColumnId As String, RowId As Long)
    Dim m As Map = B4XTable1.GetRow(RowId)
    Log(m.Get(ColumnId))
End Sub

It will print the clicked cell value.

klaus · May 1, 2020

Don't worry, in my real code I use only the RowID and it works.
I simply supposed that ColumnId and RowID were the indexes of the column and the row and not IDs with a different meaning.
The reason of this thread was the wish to be coherent with all B4X objects having indexes beginning with 0.

Erel · May 1, 2020

The answer is that RowId is not an index. It is a random id that identifies each row.

LucaMs · May 1, 2020

Erel said:
The answer is that RowId is not an index. It is a random id that identifies each row.

I think you are talking about the B4XTable RowID, not the SQLite rowid, right?
It is better to distinguish well between these two, in this thread.

klaus · May 1, 2020

Erel said:
The answer is that RowId is not an index. It is a random id that identifies each row.

That's what I understood after your previous posts, it's like database RowIds..

Mahares · May 1, 2020

Erel said:
ColumnId As String

Calling a column name or column header ColumnID is also a bit confusing because you always think of ID as a number when it comes to database. It should have been named: ColumnHeader or ColumnName
The same here: B4XTable1.GetRow(RowId).Get(numberColumn.Id) Id is normally reserved for a number but here it is the column content. It should have been named: ColumnContent or ColumnValue

Erel · May 3, 2020

Mahares said:
Calling a column name or column header ColumnID is also a bit confusing because you always think of ID as a number when it comes to database. It should have been named: ColumnHeader or ColumnName
The same here: B4XTable1.GetRow(RowId).Get(numberColumn.Id) Id is normally reserved for a number but here it is the column content. It should have been named: ColumnContent or ColumnValue

1. It has nothing to do with this thread.

2. Don't confuse ID with an index. ID doesn't need to be a number. There is an important distinction between the column title and its id. In most cases they are the same but they don't need to be the same. The ID is an internal field that the user never sees.

Wish B4X Table RowID begins with 1 and not with 0 why

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