[Nathan]

The documentation does not seem to state that the v-play navigation infrastructure will lazy-load pages. This is rather surprising for someone who’s used to standard QML, which will construct all components defined in the QML source at startup, unless they are wrapped in a Component{}. This leads to unexpected behavior such as getting a “ReferenceError: listPage is not defined” error from something like this:

App {
  Component.onCompleted: console.log(listPage.x)
  Navigation {
    NavigationItem {
      id: widgetsItem
      title: "Widgets"
      icon: IconType.calculator

      WidgetsPage { title: widgetsItem.title }
    }

    NavigationItem {
      title: "Simple List"
      icon: IconType.list

      NavigationStack { //this tab/navigation item uses stack-based sub-navigation
        SimpleListPage { id: listPage }
      }
    }
  }
}

 

This behavior should be documented in the Navigation and NavigationItem detailed description sections.

[GüntherFelgo Team]

Hi Nathan,
thank you for your feedback!
We will add it to the documentation. 😉

Our current implementation uses the Qt Quick TabView internally, which automatically comes with this lazy-loading mechanism.
Besides the Navigation, this also affects the TabControl component.

 

Cheers,
Günther

[Nathan]

Ahh, that makes sense. I also note that NavigationItem inherits Tab, which could have been a hint (since Qt’s Tab documentation emphasizes that Tabs are lazy-loaded), but I didn’t follow that link. It’s probably worth emphasizing on NavigationItem that it is lazy-loaded, and referencing the Tab docs for more info.

It appears that NavigationStack also lazy-loads its children, though, since in my original example (which was just a tweak from the example on the Navigation doc) I still can’t access listPage from an onSelected handler on its containing NavigationItem. I believe this is also the behavior of Qt Quick Controls’ StackView, if that’s what’s being used behind the scenes.

[GüntherFelgo Team]

You guessed right, we use the StackView internally.
Besides the Navigation/TabControl and the NavigationStack there aren’t any more items that lazy-load their content. So if you keep in mind that these types do you should be good to go.

Best,
Günther