Bug 45266 - RelativeLayout: setting a height constraint relative to another item does not work
Summary: RelativeLayout: setting a height constraint relative to another item does not...
Status: CONFIRMED
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: 2.3.2
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Paul DiPietro [MSFT]
URL:
Depends on:
Blocks:
 
Reported: 2016-10-11 06:12 UTC by softlion
Modified: 2017-06-21 13:38 UTC (History)
4 users (show)

Tags: ac
Is this bug a regression?: ---
Last known good build:


Attachments
Reproduction project (343.59 KB, application/x-zip-compressed)
2017-03-27 01:27 UTC, Paul DiPietro [MSFT]
Details


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Status:
CONFIRMED

Description softlion 2016-10-11 06:12:07 UTC
A repro layout looks like this:
    <Grid>
        <RelativeLayout>

          <BoxView x:Name="TopLayout"
            RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"
            HeightRequest="200"
            />
          
          <Grid x:Name="TheGrid" BackgroundColor="Yellow" VerticalOptions="End" HorizontalOptions="Fill" 
            RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"
            RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToView, ElementName=TopLayout, Property=Height, Factor=1}"
                />
        
         </RelativeLayout>
    </Grid>

The height constraint in TheGrid is ignored.
The only workaround found after 6 hours is to override LayoutChildren in the page and force TheGrid's height:

       protected override void LayoutChildren(double x, double y, double width, double height)
        {
            base.LayoutChildren(x, y, width, height);

            //Force TheGridto have the same height as TopLayout
            //This does not work in Xaml as of 2016-10-11
            if (TheGrid.HeightRequest != TopLayout.Height)
                TheGrid.HeightRequest = TopLayout.Height;
        }
Comment 1 Paul DiPietro [MSFT] 2017-03-27 01:27:10 UTC
Attaching a proper reproduction project until I can get some feedback on this behavior.
Comment 2 Paul DiPietro [MSFT] 2017-03-27 01:27:30 UTC
Created attachment 20851 [details]
Reproduction project