How to design a button from bottom of my Grid in Xamarin.forms - xaml

Question

I have a grid view and I want to add a button in bottom of my screen
I have used following code:
[![enter image description here][1]][1]
<Grid>[![enter image description here][2]][2]
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*" />
<ColumnDefinition Width="2*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="88*"/>
<RowDefinition Height="12*"/>
</Grid.RowDefinitions>
<Grid Grid.Column="0" Grid.Row="0" BackgroundColor="White">
<Grid Grid.Column="1" Grid.Row="0" BackgroundColor="White">
<Grid Grid.Row="1" BackgroundColor="#f24245" HorizontalOptions="FillAndExpand">
<Button Text="Lookupjshgkdfjghkdjfghdkjfhgdlfkjghfk" HorizontalOptions="FillAndExpand" TextColor="White" FontSize="Large" BackgroundColor="#f24245"/>
</Grid>
</Grid>
[1]: https://i.stack.imgur.com/vsEn9.png
[2]: https://i.stack.imgur.com/TazCg.png

Answer 1

Please Add Grid.ColumnSpan="2" Like,
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*" />
<ColumnDefinition Width="2*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="88*"/>
<RowDefinition Height="12*"/>
</Grid.RowDefinitions>
<Grid Grid.Column="0" Grid.Row="0" BackgroundColor="White">
<!--Place you code Here-->
</Grid>
<Grid Grid.Column="1" Grid.Row="0" BackgroundColor="White">
<!--Place you code Here-->
</Grid>
<Grid Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" BackgroundColor="#f24245" HorizontalOptions="FillAndExpand">
<Button Text="Lookupjshgkdfjghkdjfghdkjfhgdlfkjghfk" HorizontalOptions="FillAndExpand" TextColor="White" FontSize="Large" BackgroundColor="#f24245"/>
</Grid>
</Grid>

Answer 2

Use VerticalOptions="End"
Example:
<Grid Padding="20" RowSpacing="0">
<Grid.RowDefinitions>
<RowDefinition Height="0.7*" />
<RowDefinition Height="0.3*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<!-- row 0 -->
<Image Grid.Row="0" Source="icon-76.png" WidthRequest="150" HeightRequest="150" />
<!-- row 1 -->
<StackLayout Grid.Row="2" VerticalOptions="End">
<Button Margin="0,5,0,5" Text="Button at the bottom" BackgroundColor="#4a4acd" TextColor="White" FontAttributes="Bold" />
</StackLayout>
</Grid>
This will give you the following view: