Xamarin.Forms XAML RelativeLayout: define one height, have the rest filled dynamically

Question

Using Xamarin.Forms and XAML, I need to define a layout for screen sizes of various heights.

Here's the results I'm getting, and the code below it:

(Just for convenience the example code uses Boxes where an Image and StackLayout should go)

   <Grid  
        BackgroundColor="Blue"
        Padding="10">
        <Grid.RowDefinitions>
            <RowDefinition
                Height="1*" />
            <RowDefinition
                Height="8*" />
            <RowDefinition
                Height="1*" />
        </Grid.RowDefinitions>
        <RelativeLayout
            Grid.Row="1"
            BackgroundColor="Yellow">
            <BoxView
                x:Name="whereImageGoes"
                RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                BackgroundColor="Orange" />

            <BoxView
                x:Name="whereStackLayoutGoesButShouldFillAllYellowAreaUnderIt"
                VerticalOptions="FillAndExpand"
                RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width}"
                RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                BackgroundColor="Green" />
        </RelativeLayout>
    </Grid>

Here's what's going on, and the problem I'm having:

The blue area is the Grid, the bottommost element.
The yellow area is the RelativeLayout, filling the Grid Row it's in.
The orange area is where an image has to be placed, and the size it has to be--a square that's exactly half the width of the layout it's in.
The green area is where a StackLayout should go, except it should extend downward to cover all the yellow area below it, and this is the key thing: that height will be different on different devices, so it can't be defined using a Factor. [btw I don't know why it has any height at all in this example, but it does]

So... how do I dynamically stretch the StackLayout to fill that lower yellow area while still making sure the image has a consistent ratio of size to the layout's width?

cahyo cahyo · Accepted Answer · 2021-01-31T04:37:37

Try this code

    <Grid
        BackgroundColor="Blue"
        Padding="10">
        <Grid.RowDefinitions>
            <RowDefinition
                Height="1*" />
            <RowDefinition
                Height="8*" />
            <RowDefinition
                Height="1*" />
        </Grid.RowDefinitions>

        <StackLayout Spacing="0" Padding="0" Margin="0" Grid.Row="1">
            <RelativeLayout Margin="0" Padding="0" VerticalOptions="Start"
                BackgroundColor="Yellow">
                <BoxView
                    x:Name="whereImageGoes"
                    RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                    RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                    BackgroundColor="Orange" />
            </RelativeLayout>

            <BoxView
                    x:Name="whereStackLayoutGoesButShouldFillAllYellowAreaUnderIt"
                    VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand"
                    BackgroundColor="Green" />
        </StackLayout>

    </Grid>

Xamarin.Forms XAML RelativeLayout: define one height, have the rest filled dynamically

1 Answers