Grid doesn't fill parent grid in xamarin forms - xaml

Question

In my xamarin forms project
I need that the White Grid fill the aqua Grid. without relativeLayout it doesn't happens, so, I tried to use relative layout for it but it stills not working....
I have no ideas now...Why does it happen?
how it is now:
this is My xaml code for this page grid:
<RelativeLayout VerticalOptions="FillAndExpand">
<!--Picker Grid-->
<Grid BackgroundColor="Aqua" x:Name="lojas_grid_picker" VerticalOptions="FillAndExpand"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}">
<Image Source="pickers.png"
Opacity="0.5"
Aspect="Fill"
VerticalOptions="FillAndExpand"
Grid.Row="0"
Grid.Column="0"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}"/>
<!--left, top, right, bottom-->
<!--<StackLayout
x:Name="lojas_stack_pickers"
Grid.Row="0"
Grid.Column="0"
VerticalOptions="CenterAndExpand">
<StackLayout.Padding>
<OnPlatform x:TypeArguments="Thickness"
Android="10, 5, 30, 30"
iOS="10, 10, 30, 30"/>
</StackLayout.Padding>
<StackLayout.Spacing>
<OnPlatform x:TypeArguments="x:Double"
Android="10"
iOS="50"/>
</StackLayout.Spacing>-->
<Grid BackgroundColor="White" Grid.Row="0" Grid.Column="0" x:Name="lojas_stack_pickers" VerticalOptions="FillAndExpand"
RelativeLayout.XConstraint =
"{ConstraintExpression Type=RelativeToParent,
Property=X,
Factor=1,
Constant=0}"
RelativeLayout.YConstraint =
"{ConstraintExpression Type=RelativeToParent,
Property=Y,
Factor=1,
Constant=0}"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}"
RelativeLayout.HeightConstraint="{ConstraintExpression
Type=RelativeToView,
ElementName=lojas_grid_picker,
Property=Height,
Factor=1,
Constant=0}">
<Grid.RowDefinitions>
<RowDefinition Height="3*"/>
<RowDefinition Height="3*"/>
<RowDefinition Height="4*"/>
</Grid.RowDefinitions>
<Picker Grid.Row="0" x:Name="estadopicker" TextColor="{StaticResource MarromEscuro}" Title="Estado" SelectedIndexChanged="PickerEstado_SelectedindexChanged" VerticalOptions="FillAndExpand"/>
<Picker Grid.Row="1" x:Name="cidadepicker" TextColor="{StaticResource MarromEscuro}" VerticalOptions="FillAndExpand" ItemsSource="{Binding cidadeItems}" Title="Cidade" SelectedIndexChanged="PickerCidade_SelectedindexChanged"/>
<Picker Grid.Row="2" Margin="0,0,0,20" x:Name="lojapicker" VerticalOptions="FillAndExpand" TextColor="{StaticResource MarromEscuro}" Title="Loja" SelectedIndexChanged="PickerLoja_SelectedindexChanged"/>
</Grid>
<!--</StackLayout>-->
</Grid>
<!--Picker Grid-->
</RelativeLayout>
Complete Code:
<?xaml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="neoFly_Montana.Views.ProcuraLojasView"
xmlns:local="clr-namespace:neoFly_Montana.LayoutScripts"
Title="Nossas Lojas">
<ContentPage.Content>
<Grid VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" >
<Image Source="backgroundlojas.jpg" Grid.Row="0" Grid.Column="0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" Aspect="Fill"/>
<StackLayout Grid.Row="0" Grid.Column="0" HorizontalOptions="Fill" VerticalOptions="FillAndExpand">
<StackLayout VerticalOptions="CenterAndExpand" Padding="60">
<Label Text="Escolha uma loja" Style="{StaticResource labelsfont}" Margin="0,0,30,0" FontSize="Large" TextColor="White"/>
<StackLayout Spacing="0">
<RelativeLayout
VerticalOptions="FillAndExpand">
<!--Picker Grid-->
<Grid BackgroundColor="Aqua" x:Name="lojas_grid_picker" VerticalOptions="FillAndExpand"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}">
<Image Source="pickers.png"
Opacity="0.5"
Aspect="Fill"
VerticalOptions="FillAndExpand"
Grid.Row="0"
Grid.Column="0"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}"/>
<!--left, top, right, bottom-->
<!--<StackLayout
x:Name="lojas_stack_pickers"
Grid.Row="0"
Grid.Column="0"
VerticalOptions="CenterAndExpand">
<StackLayout.Padding>
<OnPlatform x:TypeArguments="Thickness"
Android="10, 5, 30, 30"
iOS="10, 10, 30, 30"/>
</StackLayout.Padding>
<StackLayout.Spacing>
<OnPlatform x:TypeArguments="x:Double"
Android="10"
iOS="50"/>
</StackLayout.Spacing>-->
<Grid BackgroundColor="White" Grid.Row="0" Grid.Column="0" x:Name="lojas_stack_pickers" VerticalOptions="FillAndExpand"
RelativeLayout.XConstraint =
"{ConstraintExpression Type=RelativeToParent,
Property=X,
Factor=1,
Constant=0}"
RelativeLayout.YConstraint =
"{ConstraintExpression Type=RelativeToParent,
Property=Y,
Factor=1,
Constant=0}"
RelativeLayout.WidthConstraint="{ConstraintExpression
Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}"
RelativeLayout.HeightConstraint="{ConstraintExpression
Type=RelativeToView,
ElementName=lojas_grid_picker,
Property=Height,
Factor=1,
Constant=0}">
<Grid.RowDefinitions>
<RowDefinition Height="3*"/>
<RowDefinition Height="3*"/>
<RowDefinition Height="4*"/>
</Grid.RowDefinitions>
<Picker Grid.Row="0" x:Name="estadopicker" TextColor="{StaticResource MarromEscuro}" Title="Estado" SelectedIndexChanged="PickerEstado_SelectedindexChanged" VerticalOptions="FillAndExpand"/>
<Picker Grid.Row="1" x:Name="cidadepicker" TextColor="{StaticResource MarromEscuro}" VerticalOptions="FillAndExpand" ItemsSource="{Binding cidadeItems}" Title="Cidade" SelectedIndexChanged="PickerCidade_SelectedindexChanged"/>
<Picker Grid.Row="2" Margin="0,0,0,20" x:Name="lojapicker" VerticalOptions="FillAndExpand" TextColor="{StaticResource MarromEscuro}" Title="Loja" SelectedIndexChanged="PickerLoja_SelectedindexChanged"/>
</Grid>
<!--</StackLayout>-->
</Grid>
<!--Picker Grid-->
</RelativeLayout>
<Label x:Name="lbl_ou" Text="ou" Style="{StaticResource labelsfont}" TextColor="White" FontSize="Large"/>
<!--Loja mais próxima Grid-->
<Grid x:Name="loja_prox_btn" VerticalOptions="EndAndExpand">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Image Source="lojamaisproximabtn.png"
Aspect="Fill"
Grid.Row="0"
Grid.Column="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="BtnOnTapGestureRecognizerTapped"/>
</Image.GestureRecognizers>
</Image>
<StackLayout
Orientation="Horizontal"
VerticalOptions="Center"
HorizontalOptions="Center"
Margin="0,30,0,15"
Grid.Row="0"
Grid.Column="0">
<Image Source="reloadicon.png" VerticalOptions="Center"/>
<Label Text="Vá para a loja mais próxima" VerticalOptions="Center" FontAttributes="Bold" FontSize="Micro" FontFamily="Arial" TextColor="{StaticResource MarromEscuro}"/>
</StackLayout>
</Grid>
<!--Loja mais próxima Grid-->
</StackLayout>
</StackLayout>
<!--Rodapé Grid-->
<RelativeLayout HorizontalOptions="FillAndExpand" VerticalOptions="EndAndExpand">
<Grid
RelativeLayout.WidthConstraint =
"{ConstraintExpression Type=RelativeToParent,
Property=Width,
Factor=1,
Constant=0}">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Image Source="rodape.png"
Margin="0,20,0,0"
Aspect="Fill"
HorizontalOptions="FillAndExpand"
Grid.Row="0"
Grid.Column="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="FranqueadoOnTapGestureRecognizerTapped"/>
</Image.GestureRecognizers>
</Image>
<!--Escrito Rodapé-->
<StackLayout Orientation="Vertical"
VerticalOptions="EndAndExpand"
HorizontalOptions="FillAndExpand"
Grid.Row="0"
Spacing="0"
Grid.Column="0">
<Image Source="franqButton.png">
<Image.Scale>
<OnPlatform x:TypeArguments="x:Double"
iOS="0.75"
Android="0.75"/>
</Image.Scale>
</Image>
<StackLayout Spacing="0" Orientation="Horizontal" HorizontalOptions="Center"
Margin="0,0,0,10">
<local:MyLabel NamedFontSize="Medium"
FontSizeFactor="0.7"
Text="SEJA UM FRANQUEADO: "
TextColor="White"
FontAttributes="Bold"
Style="{StaticResource labelsfont}"/>
<local:MyLabel NamedFontSize="Medium"
FontSizeFactor="0.7" Text="montanaexpress.com"
Style="{StaticResource labelsfont}"
TextColor="{StaticResource laranjacolor}"/>
</StackLayout>
</StackLayout>
</Grid>
</RelativeLayout>
</StackLayout>
</Grid>
</ContentPage.Content>
What is the problem?