Android Question Unable to clear a listview

Serge Bertet · Aug 4, 2018

hi,

do I need to loop over all items to clear an whole listview?
it looks like only the selected item is cleared with the clear method.
With

B4X:

PlayListView.Clear

or

B4X:

    Do While PlayListView.Size > 0
        PlayListView.RemoveAt(0)
    Loop

I always have new text over old text in some cells.
So looking for a way clear and refresh (refill) a listview with new values.

Thx

Computersmith64 · Aug 4, 2018

Clear should remove all items from the list. Can you post all the related code?

- Colin.

Serge Bertet · Aug 4, 2018

Here is the code used to refresh the listview:

B4X:

Sub ShowList
    PlayListView.Clear
    csr = Starter.db.ExecQuery("SELECT * FROM 'playlists' ORDER BY `playlistname` ASC")
    If csr.RowCount > 0 Then
        For i = 0 To csr.RowCount-1
            csr.Position = i
            PlayListView.AddSingleLine2(csr.GetString("playlistname"), csr.GetInt("ID"))
        Next
    End If
    ActionPanel.visible = False
End Sub

Hope that helps to help me.

Serge

Computersmith64 · Aug 4, 2018

Serge Bertet said:

Here is the code used to refresh the listview:

B4X:

Sub ShowList
    PlayListView.Clear
    csr = Starter.db.ExecQuery("SELECT * FROM 'playlists' ORDER BY `playlistname` ASC")
    If csr.RowCount > 0 Then
        For i = 0 To csr.RowCount-1
            csr.Position = i
            PlayListView.AddSingleLine2(csr.GetString("playlistname"), csr.GetInt("ID"))
        Next
    End If
    ActionPanel.visible = False
End Sub

Hope that helps to help me.

Serge

So what happens when you run this code? The if statement is redundant btw. If there are no records in the cursor, the for loop won't execute.

- Colin

Serge Bertet · Aug 4, 2018

Yes, you'r rigth, the If is not needed here, but it is waiting for an Else ....
When I execute this code I can see the old text overwritted with the new one and at the end both (old ans new) are visible.
When I run step by step using the debugger it looks like only le last selected item is erased.
Android version on my test tablet is 4.2.1
Also used:

B4X:

    Do While PlayListView.Size > 0
        PlayListView.RemoveAt(0)
    Loop

with no result.

Serge

LucaMs · Aug 4, 2018

Your code should work; at least you can add a Sleep(0) after PlayListView.Clear, to allow the GUI refreshing.

[I suggest to use names like lvPlay (where the prefix lv means ListView, of course, so you "save" characters) and, mainly, to use xCustomListview]

klaus · Aug 4, 2018

Can you post a small project showing the problem, or post your project.
The ListView.Clear method clears all items.
So, the problem seems to be somewhere else in your code.

Mahares · Aug 4, 2018

klaus said:
So, the problem seems to be somewhere else in your code

Could it be that he is not closing the cursor before he generates the new list, so it is doubling up the items:
csr.close

klaus · Aug 4, 2018

I dont think so. But he could try it.

Serge Bertet · Aug 4, 2018

As per LucaMs advice I switched to xCutomListView but there is stil a ListView in another activity.
Yes I never close the cursor, maybe the problem is here, thx Mahares, i'll try.
.. and try with a delay ... I can see my tablet slowing down debug after debug until I restart.
For now I'm stuck with syntaxes containing $ I don't know what it is used for .... even "Beginners Guide" and "B4x Langage Basic" don't talk about that ... but this is matter for another thread.
Thx for all
Serge

LucaMs · Aug 4, 2018

Serge Bertet said:
For now I'm stuck with syntaxes containing $ I don't know what it is used for .... even "Beginners Guide" and "B4x Langage Basic" don't talk about that

https://www.b4x.com/android/forum/threads/b4x-smart-string-literal.50135/#content

BTW, if you want use it to create query strings, I highly recommend you to use the "versions 2" of the SQL queries (parametrized queries):

Starter.db.ExecQuery2(...

(also: ExecNonQuery2 and ExecQuerySingleResult2).

Serge Bertet · Aug 4, 2018

In fact it is in an example for CustomListView (CustomListView.b4a) found on this web site

B4X:

    For i = 1 To 3
        clv2.Add(CreateListItem($"Item #${i}"$, clv2.AsView.Width, 70dip), 70dip, $"Item #${i}"$)
    Next

I'll check your link.

klaus · Aug 4, 2018

It is always difficult to help with small code snippets.
It is always much more efficient to post a small project showing the problem, or even post the whole project (at least for me).
Most of the time, the problem is not in the code snippet but somewhere else in the code.

In your last post you refer to CustomListView, but you should use xCustomListView.

LucaMs · Aug 4, 2018

klaus said:
In your last post you refer to CustomListView, but you should use xCustomListView.

"Unfortunately" its classe name is CustomListView.

Android Question Unable to clear a listview

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