[Qt-qml] Using Loader to switch between List View items

[Paul Isaacs]

Hi Eduardo - a huge thanks to you for your detailed and clear explanation.
An excellent tutorial to a programming novice.

Paul Isaacs
Principal Applications Engineer
Sound Devices LLC
www.sounddevices.com


On 5/11/10 3:29 PM, Eduardo Fleury wrote:
> Hi there.
>
> On Tue, May 11, 2010 at 11:37 AM, Paul Isaacs 
> <paul_isaacs at sounddevices.com <mailto:paul_isaacs at sounddevices.com>> 
> wrote:
> > I am using a main List View to list/switch between 3 separate pages.
> > Each page is defined by its own .qml file.
>
> Ok that's fine.
>
> > Each loaded page defines a mouse area in order to return back to the
> > main List View.
>
> The idea is OK but there is an issue with the implementation.
>
> So you have:
>
> *1) The main screen (MainList.qml)* with:
>  A. some stuff on it, including a list and some text.
>  B. a Loader, to show secondary screens
>
> Then when you choose an option, B is filled with:
>
> *2) A secondary screen (List1.qml)*
>  A. some stuff on it, including a text
>  B. a button to go back
>  C. a _Loader_
>
> Ok, the problem here is with 2.C. In this case you don't want to open 
> another instance of MainList inside your secondary list... In fact you 
> want to hide List1 so that the _original_ MainList can be seen again, 
> isn't it?
>
> With the original implementation you were creating several layers of 
> Loaders... MainList on top of List1 on top of MainList on top of List1 
> on top of MainList, and so on...
>
> "So, probably memory will be exhausted sometime, right?"
>
> Yes... but there is another problem...
>
> If the_* original instance of MainList is still there, hidden bellow 
> the onion of layers, it means it is still grabbing keyboard arrow 
> events.*_ That means the second instance of MainList, which is created 
> when we go back from List1, won't get any events..
>
> If you change "visible = false" to "opacity = 0.5" or something like 
> that you will be able to see thru the problem...
>
> Attached is a new version of your code that works fine. I've 
> documented all my changes inline and recommend you start reading from 
> List1.qml.
>
> Let me know if anything is unclear.
>
> Best regards,
> -- 
> Eduardo M. Fleury
> OpenBossa - INdT
> http://eduardofleury.com/
> http://www.openbossa.org/
>
>
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