Nick's .NET Travels

Continually looking for the yellow brick road so I can catch me a wizard....

Navigation, View Models, Pages, Frames and Universal Windows Applications

Over the past couple of month Microsoft has been laying the groundwork to get developers excited about the upcoming universal application model that will ship with Windows 10. The promise of a single executable that will just run anywhere seems to be the holy grail. However, just because an application will run anywhere, on any devices, doesn’t mean that the user experience is optimized. Take for example a simple list-details windows phone application which presents a list of items, which, when an item is tapped, navigates to a new page with the details of the item. On a desktop with a large screen it doesn’t make sense to navigate to a separate page in order to display the details of the item. Instead, the screen can be split with the list on the left and the details of the selected item displayed on the right.

The simple app navigation model I discussed previously assumes simple navigation between view models, and thus between pages on the Windows platform. However, it’s not that simple; as we just saw instead of navigating to a new page, the selected item is presented in full on the right side. This means we need to contemplate a more complex set of navigation rules, allowing for different navigation paths through the application dependent on available screen real estate. In fact to handle the scenario with a list on the left and details on the right, it may be necessary to consider sub-views with corresponding sub view-models.

Taking this example, let’s assume that we start off with two pages: ListPage and DetailsPage. When we have more space we want to extend the ListPage to include details for the selected item. It doesn’t make sense to duplicate the layout, which would result in a maintenance headache. Instead what we can do is to start extracting portions of the UI into usercontrols that can be reused. For example we might have ListControl, which displays the list of items, and DetailsControl, which not surprisingly displays the details of the item. Clearly these map to the existing ListPage and DetailsPage but now in the case of larger screens we have two options: we can either add the DetailsControl to the ListPage so that, space permitting, the details can be displayed on the right; or, we can create a completely different ListAndDetailsPage which as you’d imagine has both the ListControl and DetailsControl. Now a distinction could be made between phone and desktop platforms to navigate to the appropriate page.

The last challenge is how to handle resizing Windows – in Windows 8/8.1 this problem didn’t really exist. Well it did if you included snap/split mode but very few developers really went to any lengths to refactor their UX and it really only resized the display width-wise. In Windows 10, users will be able to more dynamically adjust the size of the Window and it is up to us application developers/designers to determine how the application behaves. Take the list-details example – with a minimal window, the application should almost mirror the UX of the phone. However, since we have the ListAndDetailsPage the UX will have to adjust the layout, rather than simply navigating to a new page.

There’s clearly a lot to think about and the holy grail of a single application is still going to take a lot of refinement to get right – time to find yourself a great UX person to add to the team!

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