UWP: Dynamic UI 1/2

If you are new to C#/UWP programming then one of the furthest things that may have crossed your mind is a UI that is dynamic and fluid based on the screen size or the device form factor your application is running on. However this concept is very important and is super easy to implement. So I thought I might do a little write up about this and help some people out. I know I may not have all the information presented here but I would like this to be a starting point that others can build on and hopefully this post is useful to some.

When I first started working on developing UWP applications I tried to have the core functionality working for a desktop PC, i.e. anything from a 12” screen sized device and up; and I did not really consider other form factors like mobile devices or the HoloLens. But the more I work on UWP applications and how simple it is to implement this functionality I ask myself, why not consider it up front? Microsoft actually has some really useful information and even provides a worthwhile example, see here. Plus there are numerous StackOverflow questions with answers and blogs/articles that discuss this exact topic. So now when I work on any UWP application I consider what UI elements need to be placed where for the various form factors and screen sizes.

If you use the link provided above then it will already place you to the correct spot in the article that outlines how to modify the UI layout based on screen sizes/form factors. The method to have your UI change based on your form factor or screen size I will be discussing is the use of Setters, StateTriggers, and AdaptiveTriggers.

Setters, StateTriggers and AdaptiveTriggers

Some of the advantages of using the new Setters designed for Windows 10 over the Storyboards that you would have had to previously use are:

1. No more GoToState method call in your code: there is no C# code that needs to be written when using the new Setters; your application will dynamically change layouts when the state condition is met.
2. Cleaner XAML Code: syntactically the XAML for using the Setters is cleaner and easier to read. The Storyboard objects could sometimes get very complex and large I found.
3. No empty DefaultState: the properties in your XAML outside the Setters appear as your default properties and the Setter values will not be triggered until the state condition is met. You do not need to define an empty DefaultState.

Using the Setters, StateTriggers, and AdaptiveTriggers are extremely easy as well. The Microsoft article provides a solid example but I am going to provide two more for reference. In the first example I will showcase the change in font size when the screen changes size, and the second example will showcase rearranging of TextBlock objects when changing screen sizes and on a small form factor device like a mobile.

Example 1: TextBlock Font Size Change

This was actually one of my very first attempts to have the UI dynamically change with a changing screen size and form factor. Below is the XAML code that I wrote to get the font size to change for a TextBlock object that is displayed to the user; some of the unnecessary XAML code has been omitted.

<Page>
  <ScrollViewer>
    <VisualStateManager.VisualStateGroup>
      <VisualStateGroup>
        <VisualState>
          <VisualState.StateTriggers>
            <AdaptiveTrigger MinWindowWidth="720"/>
          </VisualState.StateTriggers>
          <VisualState.Setters>
            <Setter Target="TitleTextBlock.FontSize" Value="24"/>
          <VisualState.Setters>        
        <VisualState>
      </VisualStateGroup>
    </VisualStateManager.VisualStateGroup>
  </ScrollViewer>
  <Grid>
    ...
    <TextBlock Name="TitleTextBlock" Text="Bill" FontSize="12"/>
    ...
  </Grid>
</Page>

As you can see the amount of XAML that needs to actually be written is fairly minimal. How does the StateTrigger actually work? The AdaptiveTrigger object defined specifies that if the screen size is more than 720 pixels (that is the state condition) then the TextBlock object will have the font size set to 24; however if the screen size is less than 720 pixels the TextBlock object will have the font size set to 12. This can be seen working below (using the exact XAML code above).

My next example will be in a follow up blog post, so stay tuned for another post real soon about Dynamic UI. That one I feel is more important and relevant as it moves UI objects around to ensure an optimal layout for a change in screen size and what it looks like on a mobile device.