Android Question Return to scrollposition in lazyload

[Phayao]

Hello everyone,

after some days experimenting, i was not able to solve an obvious trivial problem with lazyloading.
I have a B4X mainpage with a lazy load list of entries. Clicking on one entry goes to another page with the details of this entry.
When i go back to the mainpage, the list scrolls automatically to the highest (0) position. What i need is to open the main list with the clicked position of the list on top (or in the middle) of the screen.
I.a.w. the mainpage should remember the position of the clicked item and open at this position when coming back.
I tried by remembering the FirstIndex in the click event and start clv_layLoad at this index, but i get blank items until the indexed item comes down somewhere.

Sub clv_VisibleRangeChanged (FirstIndex As Int, LastIndex As Int)
    Dim id, npics, h As Int
    Dim id_title, title, datum As String
    Dim p As Boolean
    Dim pnl As B4XView

    ' FirstIndex = FIndex    ' global    <==== this is not working !
    ' LastIndex = LastIndex + FIndex
    ' Log("===== visible range changed from "&FirstIndex&" to "&LastIndex)

    For Each i As Int In PCLV.VisibleRangeChanged(FirstIndex, LastIndex)
        Dim item As CLVItem = clv.GetRawListItem(i)
        ' Dim pnl As B4XView  ' = xui.CreatePanel("")
        id_title = item.value.As(String)    '  Value is id : title instead of only id (numerical)
        id = id_title.SubString2(0, id_title.IndexOf(":"))
        title = id_title.Substring(id_title.IndexOf(":")+1)
        
        'title = SQL1.ExecQuerySingleResult("SElECT title FROM entries WHERE entry_id= "& id)
        datum =  SQL1.ExecQuerySingleResult("SElECT datum FROM entries WHERE entry_id= "& id)
        ' Log("row "& i &" id= "&id&" title= "&title)
        ' check pictures:
        npics = SQL1.ExecQuerySingleResult("SElECT count(*) FROM pictures WHERE entry_id = "& id)
        ' Log(npics &" pics for entry id = "& id)
        If npics > 0 Then    ' has pictures  -  no effect in lazyload !!
            h = 240dip    ' 240
            p = True
        Else
            h = 120dip    ' 120
            p = False
        End If
        pnl = CreateListItem(id, title, datum, p, clv.AsView.Width, h)  '   height has no influence !
        pnl.Tag = title    ' to use in hintrequest

        item.Panel.AddView(pnl, 0, 0, pnl.Width, h)

    Next
End Sub


Sub clv_ItemClick (Index As Int, Value As Object)    ' value is id : title
    Dim id_title As String = Value
    FIndex = Index    ' <==== remember when we come back
    Log("---- click on Index "& FIndex)
    Log("id_title = "& id_title)
    curID =  id_title.substring2(0,id_title.indexof(":"))    ' global to give to page 2

    Log("------ Click item nr "& Index &"  id = "& curID)
    
    B4XPages.ShowPage("Page 2")    ' ===> open detail page for this item

End Sub

Thanks for any idea in advance !

Chris

 

[Alexander Stolte]

When i go back to the mainpage, the list scrolls automatically to the highest (0) position.

Sounds to me like you have some event code in B4XPage_Appear that fills the list again? The list should not jump by itself just because you opened another page.

 

[Phayao]

Hi,

that's a good hint, you are right, the list is built each time the mainpage is called - i try to change the logic !
Thank you