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Thread Focus Won't Stick In TPagePanel's OnChange Event
Sun, Feb 11 2018 10:19 PMPermanent Link

Frederick Chin

I have a TPagePanel with 2 TPages. Each TPage has several TEdits. What I want to do is when a user clicks the TPage or if the TPagePanel's ActivePage changes programmatically, I want focus to be on the first TEdit of that TPage.

In the TPagePanel's OnPageChange event, I have added the following code:-

if NewPage=Page1 then
  TEdit1.Setfocus
else if NewPage=Page2 then
  TEdit2.Setfocus;
Result:=True;

It seems that the Setfocus method is called but focus is lost for some reason. It seems that something else is happening after the OnPageChange event is called.

I believe that there should be an OnPageAfterChange event so that the setfocus call will stick.

Is my thought about a new event valid or am I putting the SetFocus call in the wrong place?

--
Frederick
Mon, Feb 12 2018 4:45 AMPermanent Link

Matthew Jones

Frederick Chin wrote:

> Is my thought about a new event valid or am I putting the SetFocus call in the wrong place?

I suspect that the event is happening before the page is made visible, so you can initialise it etc. Thus the focus will change, but the automatic code will then kick in and update it (or the edit is not visible so can't be focussed).

Probably worth putting in a load of event handlers to check the order, but I'd be looking at the OnShow for the TPage to see if that is after the switch.

--

Matthew Jones
Mon, Feb 12 2018 8:54 AMPermanent Link

Frederick Chin

"Matthew Jones" wrote:

/*
I suspect that the event is happening before the page is made visible, so you can initialise it etc. Thus the focus will change, but the automatic code will then kick in and update it (or the edit is not visible so can't be focussed).
*/

I think this is what is happening because I put a label to track the event and the label is updated but the focus is lost.

/*
Probably worth putting in a load of event handlers to check the order, but I'd be looking at the OnShow for the TPage to see if that is after the switch.
*/

I would prefer that the event control be handled by the TPagePanel so that there is one place for the page events.

As for the OnShow of the TPage, I did have some success. On my two TPages, the first object is a TEdit for the first page while there is a TCheckBox and TEdit in the second page.

In the OnShow event of the TPages, I put the code as follows:-

  if TPage(Sender).Name='FirstPage' then
     Edit1.Setfocus
  else if TPage(Sender).Name='SecondPage' then begin
     CheckBox1.Setfocus;
  end;

If I click on the first page, the edit box is focused but in the second page, EWB just refuses to set focus on the check box. I have no idea why. If I change the "CheckBox1.Setfocus" to "Edit2.Setfocus", the field is focused.

I tried to work around it by first focusing on the edit box and then call Edit2.Tab(True) which is supposed to perform a Shift+Tab to the check box. Again, no go.

--
Frederick
Mon, Feb 12 2018 9:04 AMPermanent Link

Matthew Jones

Frederick Chin wrote:

>    if TPage(Sender).Name='FirstPage' then

That would be better as

 if Sender = FirstPage then

so that changing the name gets a compile error. But I think you are just falling over the thorny issue of JavaScript and the DOM being awkward to sync. In one case I ended up using a timer to set the focus, but you end up getting awkward situations even then.

--

Matthew Jones
Mon, Feb 12 2018 9:10 AMPermanent Link

Frederick Chin

"Matthew Jones" wrote:

/*
That would be better as

 if Sender = FirstPage then
*/

Thanks for the tip.

/*
so that changing the name gets a compile error. But I think you are just falling over the thorny issue of JavaScript and the DOM being awkward to sync. In one case I ended up using a timer to set the focus, but you end up getting awkward situations even then.
*/

Ugh. Using a timer does sound messy and unwieldy. I'll gravitate for a single OnAfterChange event.

--
Frederick
Mon, Feb 12 2018 2:47 PMPermanent Link

Raul

Globestar Systems

Team Elevate Team Elevate

On 2/11/2018 10:19 PM, Frederick Chin wrote:
> It seems that the Setfocus method is called but focus is lost for some reason. It seems that something else is happening after the OnPageChange event is called.
>
> I believe that there should be an OnPageAfterChange event so that the setfocus call will stick.
>
> Is my thought about a new event valid or am I putting the SetFocus call in the wrong place?

Just a wild guess to try with

Create a new SetFocus procedure and call it from OnPageChange using the
async
(https://www.elevatesoft.com/manual?action=viewtopic&id=ewb2&topic=Asynchronous_Calls)

This woudl call it in async manner and might run after other framework
events run - worth  a quick test

Raul
Mon, Feb 12 2018 4:07 PMPermanent Link

Tim Young [Elevate Software]

Elevate Software, Inc.

Avatar

Email timyoung@elevatesoft.com

Frederick,

<< It seems that the Setfocus method is called but focus is lost for some reason. It seems that something else is happening after the OnPageChange event is called. >>

Yes, the OnPageChange event happens *before* anything happens with the pages, giving you an opportunity to prevent the page change.

OnShow is also a no-go because the tab click causes a focus call on the page that occurs *after* the new page is shown.

So, yes, there needs to be an OnPageChanged event or something similar for the TPage control, in addition to some more code to finesse the SetFocus method for the TPage control.  The existing behavior is present to allow for a TPage to behave like any container control in EWB where clicking on the container area causes the currently-focused control to lose focus, which is important for touch environments where you want to remove the soft keyboard from the screen.

I've attached a unit that makes these corrections, which you can use as a hotfix for now.

Tim Young
Elevate Software
www.elevatesoft.com



Attachments: WebPages.wbs
Mon, Feb 12 2018 8:32 PMPermanent Link

Frederick Chin

Tim,

/*
I've attached a unit that makes these corrections, which you can use as a hotfix for now.
*/

Thanks. The unit solves the focus issue.

--
Frederick
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