[Interest] Stack view and lazy loading of big Qml files

[VStevenP]

Hi Nuno,
You might wish to consider using a ListView whose delegate is a Component which contains a Loader.
That way, app pages are just delegate instances created and managed by the ListView.  You can use the cacheBuffer property of the ListView to manage how many delegates (pages) are instantiated a.k.a. loaded.
My group is using this technique to handle loading and unloading of related application pages.  It's easy to flick between the related pages this way, helping to ensure that nearby pages are loaded and cached, and therefore quickly available to the user, while other pages which are not neighboring pages can be loaded later as needed by the ListView.
I don't think you'll want to load all your application pages at the start.  Here's why:  The QML engine can sometimes keep up to 4 copies of your pages.  This was explained at QtDevDays, but I can't recall the exact details.  Any way, if your app pages use decent size graphics, the amount of actual RAM used by a page can be up to 4X that at certain times.  Therefore, it makes sense to have an evolved page loading strategy, so you don't use excessive RAM in tablet and embedded environments, where RAM resource may be more scarce.
Steve PavaoKorg R&D
      From: "interest-request at qt-project.org" <interest-request at qt-project.org>
 To: interest at qt-project.org 
 Sent: Tuesday, December 30, 2014 6:00 AM
 Subject: Interest Digest, Vol 39, Issue 60


   
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Message: 2
Date: Tue, 30 Dec 2014 09:10:12 +0000
From: Nuno Santos <nunosantos at imaginando.pt>
Subject: [Interest] Stack view and lazy loading of big Qml files
To: Interests Qt <interest at qt-project.org>
Message-ID: <756C12DE-64F5-4E60-9322-80882481FFEC at imaginando.pt>
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Hi,

I have a stack view which will be used to load the main content of application views.

Currently, when I select a new view, I pass the url of the correspondent Qml file. I use the replace method because in fact i?m only interested in the transition animation.

The problem is that in arm devices like android and ipad, the transition is not immediate due to the fact that the Qml being loaded are quite heavy.

The app users won?t understand that so I wanted to load all the views without showing them and instead of passing the url I would pass the id of the component. 

My questions are: 

What is the best way of doing that?
Where should I keep the elements without having them rendered on the screen?
Is there any other way of making this?

Thanks in advance,

Regards,

Nuno Santos

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