How to prevent reloading xamarin map when I change control template? - xamarin

Question

I am using Xamarin.Forms.Maps as a ContentPresenter of ControlTemplate.
When the control template is changed and move map to some area, the map has been reloaded with own initial position.
The buttons below my example code can change the control template.
Can it be resolved?
What do I do? please figure out.
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
ControlTemplate = (ControlTemplate)Resources["main"];
}
void OpenSubTemplate_Clicked(object sender, EventArgs e)
{
ControlTemplate = (ControlTemplate)Resources["sub"];
}
void OpenMainTemplate_Clicked(object sender, EventArgs e)
{
ControlTemplate = (ControlTemplate)Resources["main"];
}
}
<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:maps="clr-namespace:Xamarin.Forms.Maps;assembly=Xamarin.Forms.Maps"
mc:Ignorable="d"
x:Class="MapTest.MainPage">
<ContentPage.Resources>
<ResourceDictionary>
<ControlTemplate x:Key="main">
<Grid>
<BoxView HeightRequest="50" Color="Blue" VerticalOptions="Start" />
<ContentPresenter />
</Grid>
</ControlTemplate>
<ControlTemplate x:Key="sub">
<Grid>
<BoxView HeightRequest="50" Color="Red" VerticalOptions="Start" />
<ContentPresenter />
</Grid>
</ControlTemplate>
</ResourceDictionary>
</ContentPage.Resources>
<Grid>
<maps:Map x:Name="myMap">
<x:Arguments>
<maps:MapSpan>
<x:Arguments>
<maps:Position>
<x:Arguments>
<x:Double>36.9628066</x:Double>
<x:Double>-122.0194722</x:Double>
</x:Arguments>
</maps:Position>
<x:Double>0.01</x:Double>
<x:Double>0.01</x:Double>
</x:Arguments>
</maps:MapSpan>
</x:Arguments>
</maps:Map>
<StackLayout Orientation="Horizontal" VerticalOptions="End">
<Button Text="Sub" BackgroundColor="Red" Clicked="OpenSubTemplate_Clicked" HorizontalOptions="FillAndExpand" />
<Button Text="Main" BackgroundColor="Blue" Clicked="OpenMainTemplate_Clicked" HorizontalOptions="FillAndExpand" />
</StackLayout>
</Grid>
</ContentPage>

Answer 1

I test it. I found this issue just happened in the Map controls. If we used Button Entry or Image, all of them will not reload, when change the control template. Here are two running GIF.
used Button Entry or Image
used map
If you still want to achieve this result, my workaround is not use this ControlTemplate. Just use Gird to put control. Updating the location by map API.
Here is running gif.
Here is my layout.
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="0.1*" />
<RowDefinition Height="0.8*" />
<RowDefinition Height="0.1*" />
</Grid.RowDefinitions>
<BoxView x:Name="MyBoxView" HeightRequest="50" Color="Red" VerticalOptions="Start" Grid.Row="0"/>
<!--<ContentPresenter Grid.Row="1" />-->
<maps:Map x:Name="myMap" Grid.Row="1" >
<x:Arguments>
<maps:MapSpan>
<x:Arguments>
<maps:Position>
<x:Arguments>
<x:Double>36.9628066</x:Double>
<x:Double>-122.0194722</x:Double>
</x:Arguments>
</maps:Position>
<x:Double>0.01</x:Double>
<x:Double>0.01</x:Double>
</x:Arguments>
</maps:MapSpan>
</x:Arguments>
</maps:Map>
<StackLayout Orientation="Horizontal" VerticalOptions="End" Grid.Row="2">
<Button Text="Sub" BackgroundColor="Red" Clicked="OpenSubTemplate_Clicked" HorizontalOptions="FillAndExpand" />
<Button Text="Main" BackgroundColor="Blue" Clicked="OpenMainTemplate_Clicked" HorizontalOptions="FillAndExpand" />
</StackLayout>
</Grid>
Here is my background code.
void OpenSubTemplate_Clicked(object sender, System.EventArgs e)
{
MyBoxView.Color=Color.Red;
myMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(47.6368678, -122.137305), Distance.FromMiles(1.0)));
}
void OpenMainTemplate_Clicked(object sender, System.EventArgs e)
{
MyBoxView.Color = Color.Blue;
myMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(36.9628066, -122.0194722), Distance.FromMiles(1.0)));
}