Re: [flexcoders] Re: Keeping DataGrid from scrolling to top on update to dataProvider

Sun, 09 Jul 2006 16:40:48 -0700

I'm calling a function to set the verticalScrollPosition in the onResult function of my service call, and it's setting the scroll position....

However, and maybe this is a bug in verticalScrollPosition(?), the DataGrid sets the scroll position (meaning that the scroll bar is in the 'remembered' place), but moves the entire content of the grid so that the first item in the list is still the one being displayed first.  So if I scroll up, there are blank items in the grid. 

That seems pretty silly. 

Maybe I'm doing something wrong though...?  

Deepa or anyone, do you have any recommendations, based on your knowledge of how the DG works behind the scenes?  

FYI: I'm also setting the selectedIndex in the same swoop, and I will soon be setting the column sorting at the same time as well.

Cheers

On 6/28/06, Jason Y. Kwong <[EMAIL PROTECTED]> wrote:

From my experiences, the grid takes a beat to update its visual appearance when its data gets updated.  After I know that the data has been updated, I normally use callLater() to set the scroll position.

On 6/28/06, djbrown_rotonews <[EMAIL PROTECTED]> wrote:
I'm still not having any luck. The reset event is being called
upstream and processed in my handler, with the proper value of
prevIndex calculated, but the grid still jumps to the top after the
data fill:

if (event.kind == CollectionEventKind.RESET) {
var prevIndex:int = this.dgDelays.verticalScrollPosition;
trace("prevIndex = ",prevIndex);
this.dgDelays.verticalScrollPosition=prevIndex;
}

--- In flexcoders@yahoogroups.com, "Deepa Subramaniam"
<[EMAIL PROTECTED]> wrote:
>
> I'm sorry, I totally misspoke. I meant to say RESET in my
explanation
> below.
>
>
>
> When your collection is filled with new data after a fill() call
to your
> DataService, the component bound to that collection will receive a
> CollectionEvent with kind = RESET. Internally, we re-populate the
> component with the new data and reset the scroll position to 0.
>
>
> What you can do is add your own collectionChange event handler to
your
> collection and upon receiving a RESET, reset the
verticalScrollPosition
> to whatever value you've been tracking.
>
>
>
> private function acHandler(event:CollectionEvent):void
>
>     {
>
>                 if ( event.kind == CollectionEventKind.RESET)
>
>                         dg.verticalScrollPosition = vPos;
>
>     }
>
>
>
> There's no need to use the scrollToIndex() method; by setting the
> verticalScrollPosition property directly, the scrollbar and
content are
> update as if the user scrolled to that index.
>
>
>
> Best,
>
> deepa
>
> ________________________________
>
> From: flexcoders@yahoogroups.com
[mailto: flexcoders@yahoogroups.com] On
> Behalf Of djbrown_rotonews
> Sent: Wednesday, June 28, 2006 7:21 AM
> To: flexcoders@yahoogroups.com
> Subject: [flexcoders] Re: Keeping DataGrid from scrolling to top on
> update to dataProvider
>
>
>
> I added a collectionChange event to my XMLListCollection (that's
the
> dataProvider for the grid) as follows:
>
> public function preserveScrollPosition(event:CollectionEvent):void
{
>
> var prevIndex:int = this.dgDelays.verticalScrollPosition;
> trace("prevIndex = ",prevIndex);
> this.dgDelays.scrollToIndex(prevIndex);
>
> }
>
> and the trace info does give me the value of the currentScroll,
but
> the grid still goes back to the top after the data is populated.
>
> is refresh() still being called after this guy?
>
> --- In flexcoders@yahoogroups.com <mailto:flexcoders%
40yahoogroups.com>
> , "Deepa Subramaniam"
> <dsubrama@> wrote:
> >
> > When the actual data comes in, the DataGrid encounters a REFRESH
> > collectionChange event and if you look in
> > ListBase.collectionChangeHandler's REFRESH case, you'll see that
> the
> > verticalScrollPosition is set to 0.
> >
> > What you need to do is set the scroll position *after* the data
> has come
> > in and the DataGrid has processed the REFRESH event.
> >
> > -deepa
> >
> > -----Original Message-----
> > From: flexcoders@yahoogroups.com <mailto:flexcoders%
40yahoogroups.com>
>
> [mailto:flexcoders@yahoogroups.com <mailto:flexcoders%
40yahoogroups.com>
> ] On
> > Behalf Of djbrown_rotonews
> > Sent: Tuesday, June 27, 2006 12:42 PM
> > To: flexcoders@yahoogroups.com <mailto: flexcoders%
40yahoogroups.com>
> > Subject: [flexcoders] Re: Keeping DataGrid from scrolling to top
on
> > update to dataProvider
> >
> > I actually tried this (my dataProvider for the grid is an
> > XMLListCollection being populated by a jsp. The grid has custom
> item
> > renderers if that's relevant).
> >
> > anyhow, I have an "update" button which will call the jsp and
get
> > new results when clicked. I've set it up so the click() method
> > correctly captures the scroll position, calls the jsp, and then
> sets
> > the scrollToIndex to the previous value of the scroll position.
It
> > works great while the "busy cursor" is displayed, but it reverts
> > back to scrolled all the way at the top once the actual data
comes
> > in from the jsp (it takes about 3 seconds to update the grid
with
> > the new data).
> >
> > any ideas on where the scroll position is being reset?
> >
> > --- In flexcoders@yahoogroups.com
> <mailto: flexcoders%40yahoogroups.com> , "Deepa Subramaniam"
> > <dsubrama@> wrote:
> > >
> > > Hi Jordan -
> > >
> > >
> > >
> > > You can keep track of the verticalScrollPosition property in
your
> > > DataGrid and upon receving UPDATES, re-set the
> > verticalScrollPosition to
> > > the previous value and the DataGrid will jump to the last
scroll
> > > position and show the correct content.
> > >
> > >
> > >
> > > -deepa
> > >
> > >
> > >
> > > ________________________________
> > >
> > > From: flexcoders@yahoogroups.com
> <mailto:flexcoders%40yahoogroups.com>
> > [mailto: flexcoders@yahoogroups.com
> <mailto:flexcoders%40yahoogroups.com> ] On
> > > Behalf Of Jordan Snyder
> > > Sent: Monday, June 26, 2006 7:34 PM
> > > To: flexcoders@yahoogroups.com <mailto: flexcoders%
40yahoogroups.com>
>
> > > Subject: [flexcoders] Keeping DataGrid from scrolling to top
on
> > update
> > > to dataProvider
> > >
> > >
> > >
> > > Hello All,
> > >
> > > I am working on an app in which I poll the server quite
> frequently
> > to
> > > get new information. The information comes to me in an XML
> format
> > that
> > > I simply assign as the dataProvider for a DataGrid component.
> > >
> > > I have to keep in consideration the fact that the user may
have
> > selected
> > > a certain row, and may want to delete that row even after an
> > update to
> > > the dataProvider is made, so I keep track of the selectedIndex
> > property
> > > and reselect upon an update.
> > >
> > > But if the user has not selected a row, the DataGrid will
> > automatically
> > > scroll to the top upon an update, even if the user has
scrolled
> to
> > the
> > > bottom of the grid.
> > >
> > > Is there a way around this? I found a way to scrollToIndex(),
> but
> > no
> > > way of getting the currently viewed items. It may have
> something
> > to do
> > > with the various renderer properties available on the
DataGrid,
> > but I
> > > have a very limited understanding of this, so it's over my
head.
> > >
> > > Surely this problem has been run into before, but I can't seem
> to
> > find
> > > the right combination of search terms to figure out a method
of
> > solving
> > > it.
> > >
> > > Does anyone have any ideas or proven methods for the problem?
> Any
> > help
> > > would be greatly appreciated.
> > >
> > > Thank you,
> > >
> > > Jordan Snyder
> > > jordan.snyder@
> > > www.jordansnyder.com
> > >
> >
> >
> >
> >
> >
> >
> >
> >
> > --
> > Flexcoders Mailing List
> > FAQ:
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> >
>






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