[DUG] ListView - Scroll Event

[Jolyon Smith]

Why not use the OnSelectItem() event and simply ignore the events where the
"Selected" parameter is FALSE ?

The only possible complication I foresee then is if you need to support the
user selecting "nothing" (i.e. un-selecting any current selection and
leaving the control with no selected item).


On 28 July 2014 08:08, Eric A <eaa603 at hotmail.com> wrote:

> Yes, could do that, with the understanding that it will result in some
> extra overhead due to fetching two lots of child records if I don't detect
> which is the last non-nil item notified.  That's what I meant by "messy".
>
> ------------------------------
> From: robo555 at gmail.com
> Date: Sun, 27 Jul 2014 20:57:40 +0200
>
> To: delphi at listserver.123.net.nz
> Subject: Re: [DUG] ListView - Scroll Event
>
> So you just need to use the OnChange event, and check the item is not nil.
> From memory I don't think you need to check whether item is different to
> previous item.
>
> Robo
>
>
> On Sun, Jul 27, 2014 at 8:52 PM, Eric A <eaa603 at hotmail.com> wrote:
>
> Yes, multiple OnChange events are generated on the ListView control, for
> both mouse clicks and navigation key depressions, as follows:
>
> a) First mouse click or down arrow/PgDn key depression:
> - Item = new selection
>
> b) subsequent mouse clicks or down arrow/PgDn key depressions:
> - Item - current selection
> - Item= nil
> - Item = new selection
>
> Seems messy ...
>
> ------------------------------
> From: robo555 at gmail.com
> Date: Sun, 27 Jul 2014 12:28:33 +0200
> To: delphi at listserver.123.net.nz
>
> Subject: Re: [DUG] ListView - Scroll Event
>
> From memory, when a record changes, first an event gets fired where
> selected item is nil, then a second event gets fire where selected item is
> the new item.
>
>
> On Sun, Jul 27, 2014 at 11:07 AM, Eric A <eaa603 at hotmail.com> wrote:
>
> (Delphi 7)
>
> I  wish to detect the user selecting a row (item) in a ListView component
> to display child records for  the item in another control.
>
> There is no "OnScroll" event for this control.  I can use the "OnClick"
> event OK for a selection cia the mouse, but how do I detect when a user
> scrolls on to a record by using the arrow keys (or PgUp, PgDn or moving the
> scrollbar ?
>
> I have tried the using the OnChange event but it seems that there are two
> events generated for each movement by the arrow keys.
>
> Does anyone have a code snippet to accomplish this?
>
> Eric.
>
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