Windows Phone 8 - Map and Clusters

This code example demonstrates how to dynamically group pushpins in the map control.
There is a lot of code for Windows Phone 7, then I merged all what I need to create a project for WP8.

First of all you need some namespace declaration: for map control and for pushpins from WP Toolkit.

xmlns:map="clr-namespace:Microsoft.Phone.Maps.Controls;assembly=Microsoft.Phone.Maps"
xmlns:maptk="clr-namespace:Microsoft.Phone.Maps.Toolkit;assembly=Microsoft.Phone.Controls.Toolkit"

You need also two templates: one for a standard pushpin and the other for the cluster.

<phone:PhoneApplicationPage.Resources>
 <DataTemplate x:Key="PushpinTemplate">
  <maptk:Pushpin GeoCoordinate="{Binding GeoCoordinate}" Content="{Binding}" />
 </DataTemplate>
 <DataTemplate x:Key="ClusterTemplate">
  <maptk:Pushpin GeoCoordinate="{Binding GeoCoordinate}" Content="{Binding Count}"/>
 </DataTemplate>
</phone:PhoneApplicationPage.Resources>

ClustersGenerator is the core of the project. It's a static class that accepts in input

• Map control
• Pushpins collection
• Cluster DataTemplate.

public ClustersGenerator(Map map, List<Pushpin> pushpins, DataTemplate clusterTemplate)
{
 _map = map;
 _pushpins = pushpins;
 this.ClusterTemplate = clusterTemplate;

 // maps event
 _map.ViewChanged += (s, e) => GeneratePushpins();
 _map.ZoomLevelChanged += (s, e) => GeneratePushpins();
 _map.CenterChanged += (s, e) => GeneratePushpins();

 // first generate
 GeneratePushpins();
}

Every map event launches the pushpins elaboration, but first to explain GeneratePushpins method, let's introduce another class: PushpinGroup.
PushpinGroup represents a standard pushpin or a cluster, and exposes a GetElement method to return them. If the group is a cluster, it needs to get only the first pushpin GeoCoordinate and the content is a group of all pushpins.

public class PushpinsGroup
{
 private List<Pushpin> _pushpins = new List<Pushpin>();
 public Point MapLocation { get; set; }

 public PushpinsGroup(Pushpin pushpin, Point location)
 {
  _pushpins.Add(pushpin);
  MapLocation = location;
 }

 public FrameworkElement GetElement(DataTemplate clusterTemplate)
 {
  if (_pushpins.Count == 1)
   return _pushpins[0];

  // more pushpins
  return new Pushpin()
  {
   // just need the first coordinate
   GeoCoordinate = _pushpins.First().GeoCoordinate,
   Content = _pushpins.Select(p => p.DataContext).ToList(),
   ContentTemplate = clusterTemplate,
  };
 }

 public void IncludeGroup(PushpinsGroup group)
 {
  foreach (var pin in group._pushpins)
   _pushpins.Add(pin);
 }
}

The GeneratePushipins function creates clusters based on map ViewPort and a constant named MAXDISTANCE. An extension method convert pushpin GeoCoordinate to a ViewPort Point. That is used to get the distance from other points. If this distance is less then the MAXDISTANCE, the pushpin become a part of cluster.

private void GeneratePushpins()
{
 List<PushpinsGroup> pushpinsToAdd = new List<PushpinsGroup>();
 foreach (var pushpin in _pushpins)
 {
  bool addGroup = true;
  var newGroup = new PushpinsGroup(pushpin, _map.ConvertGeoCoordinateToViewportPoint(pushpin.GeoCoordinate));

  foreach (var pushpinToAdd in pushpinsToAdd)
  {
   double distance = pushpinToAdd.MapLocation.GetDistanceTo(newGroup.MapLocation);

   if (distance < MAXDISTANCE)
   {
    pushpinToAdd.IncludeGroup(newGroup);
    addGroup = false;
    break;
   }
  }

  if (addGroup)
   pushpinsToAdd.Add(newGroup);
 }

 _map.Dispatcher.BeginInvoke(() =>
 {
  _map.Layers.Clear();
  MapLayer layer = new MapLayer();
  foreach (var visibleGroup in pushpinsToAdd.Where(p => _map.IsVisiblePoint(p.MapLocation)))
  {
   var cluster = visibleGroup.GetElement(this.ClusterTemplate) as Pushpin;
   if (cluster != null)
   {
    layer.Add(new MapOverlay() { GeoCoordinate = cluster.GeoCoordinate, Content = cluster.Content, ContentTemplate = cluster.ContentTemplate});
   }
  }
  if (layer.Count > 0)
   _map.Layers.Add(layer);
 });
}

The extension method GetDistanceTo is the algorithm to calculate the distance between two points:

public static double GetDistanceTo(this Point p1, Point p2)
{
 return Math.Sqrt((p1.X - p2.X) * (p1.X - p2.X) + (p1.Y - p2.Y) * (p1.Y - p2.Y));
}

Instead IsPointVisible returns true if the point is visible in the map, otherwise false:

public static bool IsVisiblePoint(this Map map, Point point)
{
 return point.X > 0 && point.X < map.ActualWidth && point.Y > 0 && point.Y < map.ActualHeight;
}

Now in your MainPage.xaml, you only need to pass all pushpins to the ClusterGenerator and it will do all work for you.

var clusterer = new ClustersGenerator(map, pushpins, this.Resources["ClusterTemplate"] as DataTemplate);

You can download all code here.

With this article I won TechNet Guru Contribution June 2013 - Windows Phone.

Read More

Windows Phone - Caliburn Micro and App.xaml error

When I add Caliburn Micro to a new project, I have always some error in App.xaml.
With Caliburn 1.5.1 I found a new problem: "Object Reference not set to an instance of an object".

This error don't prevent the project build, but it seems related to the xaml.
That's why the RootFrame into designer is null.

The fix is easy! Just open your Bootstrapper and change

container.RegisterPhoneServices(RootFrame);

with..

if (!Execute.InDesignMode)
 container.RegisterPhoneServices(RootFrame);

Read More

Windows Phone - Caliburn Micro and Telerik

When you use Caliburn Micro you always have a file Bootstrapper like this:

public class Bootstrapper : PhoneBootstrapper
{
 PhoneContainer container;

 protected override void Configure()
 {
  container = new PhoneContainer();
  
  container.RegisterPhoneServices(RootFrame);

  container.PerRequest<MainPageViewModel>();
  
  AddCustomConventions();
 }

 static void AddCustomConventions()
 {
 }

 protected override object GetInstance(Type service, string key)
 {
  return container.GetInstance(service, key);
 }

 protected override IEnumerable<object> GetAllInstances(Type service)
 {
  return container.GetAllInstances(service);
 }

 protected override void BuildUp(object instance)
 {
  container.BuildUp(instance);
 }
}

I love to use Windows Phone controls from Telerik and I always add RadPhoneApplicationFrame in my applications, but how to add it in the Bootstrapper?

You need only some lines of code.

private PhoneApplicationFrame rootFrame;
private new PhoneApplicationFrame RootFrame
{
 get
 {
  if (this.rootFrame == null)
   this.rootFrame = new RadPhoneApplicationFrame();

  return this.rootFrame;
 }
 set
 {
  this.rootFrame = value;
 }
}

protected override PhoneApplicationFrame CreatePhoneApplicationFrame()
{
 return this.RootFrame;
}
  

I created a public property to instantiate the RadPhoneApplicationFrame and overrided the CreatePhoneApplicationFrame to return the custom frame.

Here the new Bootstrapper:

public class Bootstrapper : PhoneBootstrapper
{
 PhoneContainer container;

 private PhoneApplicationFrame rootFrame;

 private new PhoneApplicationFrame RootFrame
 {
  get
  {
   if (this.rootFrame == null)
    this.rootFrame = new RadPhoneApplicationFrame();

   return this.rootFrame;
  }
  set
  {
   this.rootFrame = value;
  }
 }

 protected override void Configure()
 {
  container = new PhoneContainer();
  
  container.RegisterPhoneServices(RootFrame);

  container.PerRequest<MainPageViewModel>();
  
  AddCustomConventions();
 }

 protected override PhoneApplicationFrame CreatePhoneApplicationFrame()
 {
  return this.RootFrame;
 }

 static void AddCustomConventions()
 {
 }

 protected override object GetInstance(Type service, string key)
 {
  return container.GetInstance(service, key);
 }

 protected override IEnumerable<object> GetAllInstances(Type service)
 {
  return container.GetAllInstances(service);
 }

 protected override void BuildUp(object instance)
 {
  container.BuildUp(instance);
 }
}

Read More

Coding4Fun - ThemedImageConverter

When you publish an application, you need to meet the requirement 5.5.2 from Dev Center:
"App content, such as text and visual elements, must be visible and legible regardless of the phone theme without panning horizontally or zooming.."

The example is when you have an image with the same color of background theme.

What you can do?

- select a different color for image.

- manage the image source swap from code behind.

- the best practice is to use the ThemedImageConverter from Coding4Fun Toolkit.

Let's go:
Download the Coding4Fun Toolkit from NuGet or Codeplex.

Add the static resource in your page:

<c4fun:themedimageconverter x:key="ThemedImageConverter"></c4fun:themedimageconverter>

Use this simple converter in your image:

<Image Source="{Binding Converter={StaticResource ThemedImageConverter}, ConverterParameter={StaticResource PhoneBackgroundColor}}" DataContext="/Assets/{0}/img.png" />

You can check also the InverseThemedImageConverter to swap from light and dark themes.

Read More