Nico Vermeir

Nico Vermeir

Hi, My name is Nico, I’m a Windows Development MVP living in Belgium. I’m currently employed as a Technical Consultant at Realdolmen, one of Belgium’s leading IT single source providers.

I'm also founding member and board member of the Belgian Modern App Developer Network, a user group focussed on modern application development. If you're in Belgium feel free to drop by if we're doing an event. http://www.madn.be

grid column behavior–xamarin xaml vs ms xaml

There’s a small detail difference in how rows and columns in a Grid behave in Xamarin Forms vs Microsoft XAML. A small difference but with quite a big impact. Look at the following XAML snippet (Microsoft XAML)

Code Snippet
  1. <Grid Background="Red">
  2.     <Grid.RowDefinitions>
  3.         <RowDefinition Height="50" />
  4.         <RowDefinition Height="*" />
  5.     </Grid.RowDefinitions>
  6.  
  7.     <Grid Grid.Row="1" Background="Blue">
  8.         <Grid.RowDefinitions>
  9.             <RowDefinition Height="Auto" />
  10.             <RowDefinition Height="300" />
  11.         </Grid.RowDefinitions>
  12.     </Grid>
  13. </Grid>

At runtime this looks like:

Exactly what we as seasoned XAML developers would expect.

Converted to Xamarin Forms XAML this turns into:

Code Snippet
  1. <Grid BackgroundColor="Red">
  2.   <Grid.RowDefinitions>
  3.     <RowDefinition Height="50" />
  4.     <RowDefinition Height="*" />
  5.   </Grid.RowDefinitions>
  6.   
  7.   <Grid Grid.Row="1" BackgroundColor="Blue">
  8.     <Grid.RowDefinitions>
  9.       <RowDefinition Height="Auto" />
  10.       <RowDefinition Height="300" />
  11.     </Grid.RowDefinitions>
  12.   </Grid>
  13. </Grid>

Only difference is the property name to set the background color. However, if we look at this at runtime we see a completely different story.

It looks like the inner Grid isn’t rendered at all. But let’s try to add a Label to the inner Grid.

Code Snippet
  1. <Grid BackgroundColor="Red">
  2.   <Grid.RowDefinitions>
  3.     <RowDefinition Height="50" />
  4.     <RowDefinition Height="*" />
  5.   </Grid.RowDefinitions>
  6.   
  7.   <Grid Grid.Row="1" BackgroundColor="Blue">
  8.     <Grid.RowDefinitions>
  9.       <RowDefinition Height="Auto" />
  10.       <RowDefinition Height="300" />
  11.     </Grid.RowDefinitions>
  12.     <Label Text="Hello Xamarin!" />
  13.   </Grid>
  14. </Grid>

So what exactly is going on here? The inner Grid (the blue one) doesn’t specify any columns, that means that by default there’s only one column available. In Microsoft XAML the width of that default column is set to “*” so it takes up all available space. In Xamarin Forms that width is set to “Auto” so it only takes up the space it needs. A subtle difference with a big impact.

To fix this, add a column with “*” as width

Code Snippet
  1. <Grid BackgroundColor="Red">
  2.   <Grid.RowDefinitions>
  3.     <RowDefinition Height="50" />
  4.     <RowDefinition Height="*" />
  5.   </Grid.RowDefinitions>
  6.   <Grid.ColumnDefinitions>
  7.     <ColumnDefinition Width="*" />
  8.   </Grid.ColumnDefinitions>
  9.   
  10.   <Grid Grid.Row="1" BackgroundColor="Blue">
  11.     <Grid.RowDefinitions>
  12.       <RowDefinition Height="Auto" />
  13.       <RowDefinition Height="300" />
  14.     </Grid.RowDefinitions>
  15.  
  16.   </Grid>
  17. </Grid>

result:

Conclusion

In this post I’ve shown a difference in implementation between Xamarin Forms XAML and Microsoft XAML and how to fix it.

Note that this sample is based on Xamarin Forms 1.2. Xamarin has stated that they will change the implementation in Forms 1.3 to reflect the Microsoft implementation.

This is an imported post. It was imported from my old blog using an automated tool and may contain formatting errors and/or broken images.

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