26 February 2014

Drawing circles on Windows Phone Here Maps and Windows Store Bing Maps

One of the areas where the mapping systems for Windows Phone and Windows 8 are lacking, is the ability to draw circles. In particular in Windows Store apps, where you have the ability to use geofences, it would come in pretty handy to be able to draw the outline of a geofence (typically a circle, as this is the only supported type right now) on the map – if only for testing purposes.

To this end I have created a set of extension methods, both for Windows Phone 8 and for Windows Store apps. In the first case, they cannot be used to display the location of a geofence as there are no geofences in Windows Phone 8, but well – drawing circles may come in handy anyway.

The results look something like this

imageScreenshot (16)

These are not circles – they look like circles. Basically they are just normal polygons, but their points are drawn in a form to resemble a circle. Would you zoom in very far, you would actually be able to see this. Would you calculate it’s surface area, you would actually find it  fraction smaller than a real circle area. But what the heck – it serves the purpose.

I have created a few extension methods to get this done. I will start with Windows Phone code - hey, I am not a Windows Phone MVP for nothing, right? ;-) -which starts off with this piece of math:

using System;
using System.Collections.Generic;
using System.Device.Location;

namespace WpWinNl.Utilities
{
  public static class GeoCoordinateExtensions
  {
    public static GeoCoordinate GetAtDistanceBearing(this GeoCoordinate point, 
                                                     double distance, double bearing)
    {
      const double degreesToRadian = Math.PI / 180.0;
      const double radianToDegrees = 180.0 / Math.PI;
      const double earthRadius = 6378137.0;

      var latA = point.Latitude * degreesToRadian;
      var lonA = point.Longitude * degreesToRadian;
      var angularDistance = distance / earthRadius;
      var trueCourse = bearing * degreesToRadian;

      var lat = Math.Asin(
          Math.Sin(latA) * Math.Cos(angularDistance) +
          Math.Cos(latA) * Math.Sin(angularDistance) * Math.Cos(trueCourse));

      var dlon = Math.Atan2(
          Math.Sin(trueCourse) * Math.Sin(angularDistance) * Math.Cos(latA),
          Math.Cos(angularDistance) - Math.Sin(latA) * Math.Sin(lat));

      var lon = ((lonA + dlon + Math.PI) % (Math.PI * 2)) - Math.PI;

      var result = new GeoCoordinate(lat * radianToDegrees, lon * radianToDegrees);

      return result;
    }
  }
}

This is a method that, given a coordinate, a distance in meters, and a bearing (in degrees) gives you another point. So a entering 50 for distance and 180 for bearing would give you a point 50 meters south of your original point. An impressive piece of math, if I may say so. Which I totally stole from here - as I am into maps, not so much into math. Having this, it’s pretty easy to add a second extension method:

public static IList<GeoCoordinate> GetCirclePoints(this GeoCoordinate center, 
                                   double radius, int nrOfPoints = 50)
{
  var angle = 360.0 / nrOfPoints;
  var locations = new List<GeoCoordinate>();
  for (var i = 0; i <= nrOfPoints; i++)
  {
    locations.Add(center.GetAtDistanceBearing(radius, angle * i));
  }
  return locations;
}

It divides the circle of 360 degrees in the number of points you want, and then simply adds points to the shape at the same distance but at every 360/points degrees. The higher the number of points, the more the shape will look like a real circle. Drawing the circle on a Windows Phone map is child’s play now:

void MainPageLoaded(object sender, RoutedEventArgs e)
{
  var location = new GeoCoordinate(52.181427, 5.399780);
  MyMap.Center = location;
  MyMap.ZoomLevel = 16;

  var fill = Colors.Purple;
  var stroke = Colors.Red;
  fill.A = 80;
  stroke.A = 80;
  var circle = new MapPolygon
  {
    StrokeThickness = 2,
    FillColor = fill,
    StrokeColor = stroke,
    StrokeDashed = false,
  };

  foreach( var p in location.GetCirclePoints(150))
  {
    circle.Path.Add(p);
  }

  MyMap.MapElements.Add(circle);
}

This draws a circle of 150 meters around my house. 

For Windows Store, the story is nearly the same. The differences are:

  1. You will need to install the Bing Maps SDK for Windows 8.1 Store apps
  2. The Bing Maps SDK does not understand System.Device.Location.GeoCoordinate you will need to make the extension method on Bing.Maps.Location

It’s very unfortunate that the mapping APIs for Windows Phone and Windows Store lack convergence even at the point of something as basic the naming of location types. I hope this will get more attention in the future, as mapping is something that I really care about - in case you had not noticed that from this blog ;-).

However, clever use of C# aliasing brings this convergence a bit closer. I changed the top of this file to

using System;
using System.Collections.Generic;
#if WINDOWS_PHONE
using GeoCoordinate = System.Device.Location.GeoCoordinate;
#else
using GeoCoordinate=Bing.Maps.Location;
#endif

et voil√°, this file compiles under both Windows Phone and Windows Store (provided you have the Map SDK installed). You can forget about PCLs, but sharing code is definitely a possibility now as far as this little method goes.

Drawing a shape in the Windows Store app is now nearly the same:

void MainPageLoaded(object sender, RoutedEventArgs e)
{
  var location = new Location(52.181427, 5.399780);
  MyMap.Center = location;
  MyMap.ZoomLevel = 18;
  var fill = Colors.Purple;
  fill.A = 80;
  var circle = new MapPolygon
  {
   FillColor = fill,
  };

  foreach (var p in location.GetCirclePoints(150))
  {
    circle.Locations.Add(p);
  }

  var layer = new MapShapeLayer();
  layer.Shapes.Add(circle);

  MyMap.ShapeLayers.Add(layer);
}

Although attentive readers might notice there is no stroke color defined (as MapPolygon in Windows Store does not feature a separate outer shape border) and adding shapes to a map regrettably also works a bit differently. The API of both mapping systems definitely could benefit from some attention here. But anyway – it get’s the job done now at this point.

Full demo solution is downloadable here. One more time – to be able to compile this you will need to install the Bing Maps SDK for Windows 8.1 Store apps first!

23 February 2014

A behavior to replace LayoutAwarePage in Windows Store and Windows Phone apps

Sometimes I think up things all by myself, sometimes I have to read something first to let the ole’ light bulb in my brain go ‘ping’. This post is of the 2nd category, and was inspired by this brilliant piece by C# MVP Iris Classon who is – apart from a very smart and respected coder – also a living and shining (not to mention colorful) axe at the root of the unfortunate gender bigotry that is still widespread in the IT world – a lot of people still think seem convinced “women can’t code, if they do they do it badly, and those who do are socially inept, boring and ugly”. Which is demonstrably untrue – coding requires just a brain and determination - but I am convinced it still shies a lot of brain power out of IT.

Anyway – what I basically did was take Iris’ idea an turn it into – you guessed it – a behavior, to make it more reusable.

To demonstrate how it works, I created the following Store app with a very compelling UI:

image

There is only one text of 75pt there. And then I created three Visual States:

  • Default, which does basically nothing
  • Medium, which changes the font size to 50pt
  • Small, which changes the font size to 25pt

How this is done is amply explained by Iris’ post so I don’t feel very compelled to repeat that here. After creating the states I brought in my WpWinNl nuget package, and added my new SizeVisualStateChangeBehavior to the page. Then I added three entries to “SizeMappings” to the behavior by clicking on the indicated ellipses on the right:

image

  • “Default” with width 801
  • “Medium” with width 800
  • “Small” with width 500

From 801 up to infinity the the Default state will be used (showing the text in it’s default size), between 800 and 501 the Medium state will be used (50pt), and from 500 and lower, the Small state (25pt). And voil√°, automatic sizing of items done by filling in some boxes in Blend – or typing in some XAML in Visual Studio if that’s more of your thing. Notice you can add any number of Visual States for any range of widths, just as long as there is one “Default” state that has a width that’s one higher than the largest none-default width. Notice SizeVisualStateMappings can have any name you like as well, as long as they correspond with names of Visual States.

For extra credit, by the way, I made this behavior attachable to Control objects rather than Page, so it can be used inside (user) controls as well. And with some #ifdef directives it also works for Windows Phone, which might come in handy with more and more of resolutions entering the Windows Phone arena.

As to how this behavior works, it’s not quite rocket science. First, we have this hugely complex class :-P that holds one SizeVisualStateMapping:

namespace WpWinNl.Behaviors
{
  public class SizeVisualStateMapping
  {
    public string VisualState { get; set; }
    public int Width { get; set; }
  }
}

The actual behavior’s setup almost immediately shows what I am doing – I simply latch on to the SizeChanged event of the object that the behavior is attached to:

using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
#if WINDOWS_PHONE
using System.Windows;
using System.Windows.Controls;
#else
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
#endif

namespace WpWinNl.Behaviors
{
  public class SizeVisualStateChangeBehavior : SafeBehavior<Control>
  {
    protected override void OnSetup()
    {
      AssociatedObject.SizeChanged += AssociatedObjectSizeChanged;
      base.OnSetup();
      UpdateVisualState();
    }
    
    private void AssociatedObjectSizeChanged(object sender, SizeChangedEventArgs e)
    {
      UpdateVisualState();
    }
  }
}
The core of the behavior’s functionality is the UpdateVisualState method:
private void UpdateVisualState()
{
  if (SizeMappings != null)
  {
    SizeVisualStateMapping wantedMapping = null;
    var wantedMappings = 
SizeMappings.Where(p => p.Width >= AssociatedObject.ActualWidth); if (wantedMappings.Any()) { wantedMapping = wantedMappings.OrderBy(p => p.Width).First(); } else { var orderedMappings = SizeMappings.OrderBy(p => p.Width); if (AssociatedObject.ActualWidth < orderedMappings.First().Width) { wantedMapping = orderedMappings.First(); } else if (AssociatedObject.ActualWidth > orderedMappings.Last().Width) { wantedMapping = orderedMappings.Last(); } } if (wantedMapping != null) { VisualStateManager.GoToState(AssociatedObject, wantedMapping.VisualState,
false); } } }

Which simply tries to find a SizeVisualStateMapping that’s fit for the current width of the associated object. If it finds that, it tells the VisualStateManager to go to that state, which proceeds to do the actual work. And that’s basically all. All that's left are an Dependency Property SizeMapping of type List<SizeVisualStateMapping> SizeMappings that holds the actual mapings, and a Cleanup method that detaches the behavior from the SizeChanged event again.

Full details, and a working solution including this behavior, can be found here. If you run this app in split screen and slowly makes it’s window width smaller, you will notice the text getting smaller. Be aware that the change only fires when you actually let the window divider control go – as long as you keep it active (by touching or dragging it) nothing will happen.

18 February 2014

Commercial break 2 – introducing 2 Tablet Pong aka Play On Both

310x310Regular readers might remember the launch of 2 Phone Pong in August 2013, one of the first – if not the very first – action game that could be played on two Windows Phones, first only over NFC, later over Bluetooth. It’s been a moderate success, particularly popular in Brazil and Turkey.

Today I launch 2 Tablet Pong, essentially the same game, for Windows 8.1.

But this release has a little twist – not only can you play against any Windows 8.1 device (provided it supports Wi-FI direct) but also against a Windows Phone running the newest version of 2 Phone Pong, making it possible the first cross-platform action game in town.

The gameplay on two Windows 8.1 devices is exactly the same as on Windows Phone. Here you see my Surface Pro 1 (right) and my Surface 2 (left) being used in the game

Surface versus Surface Pro

This is actually the instruction movie inside the game. As is the next one, that shows how my Lumia 1020 (right) connects to the Surface Pro – which is called “Blue”* on my network

You will need to pair a phone to a Windows 8.1 over Bluetooth first, and then they will be able to find each other. That is to say, the phone finds the PC (after some time), never the other way around. With a PC-to-PC connection it’s a matter of who starts first – the last one always finds the connection.

There were some interesting challenges to the port, but thanks to the extensive use of MVVMLight and my WpWinNl library I was able to use 90% of my code and I think 75% of XAML. I mostly used shared code, sometimes partial classes. There are also some extra rules in the Windows version – the ball speed adapts to the size of the screen, so if you play the game on half a screen, it will only go half as fast, or else it will become unplayable.

The game is free, but will be ad-supported in a soon-to-be-released update. I hope it will enjoy a just as enthusiastic reception as it’s phone predecessor.

I will soon update WpWinNl with everything I learned from porting this game, and I have a lot to blog about – I hope the community can benefit from that. Enjoy!

 

* disclaimer: those who think the name “Blue” has any significance or hints at something – I have a total lack of fantasy as far as device names are concerned, so I have a long standing tradition of naming my PCs after my wife’s pet hamsters. “Blue” is a 26 month old Russian dwarf hamster – she is called that way because that’s the name of the color variety. Go Bing it if you don’t believe me. My next PC will be called Smokey ;)

Build for both–an instruction video pivot page for Windows Phone apps

For Windows Phone apps, the same goes a for Windows 8 store apps – a picture tells more than a thousand words and a video even more. So as promised earlier, I am going to show you how to make a video instruction pivot for Windows Phone, that works as showed here below.

Windows Phone video instruction demo

The Pivot part is easy, as this is already built-in – controlling the MediaElements proved to be substantially harder.

A recap of the objectives:

  • Start the video on the current visible pivot item automatically – and start the first video on the first pivot as soon as the user access the page.
  • Repeat that movie automatically when it ends
  • Stop it as soon as the user selects a different pivot item

Setting the stage

  • Create a blank Windows Phone app
  • Bring in my WpWinNl library from Nuget
  • Add an empty page “Help.xaml”
  • Open WMAppManifest.xml, look for the box “Navigation Page” and change this from “MainPage.xaml” to “Help.xaml”. This will make your app start the Help page on startup. That’s not a smart move for production code but it will make a demo app a lot easier.

The XAML basics

Basically the page (expect for the header) is filled by a StackPanel containing a PivotItem and some styling for (mostly) the MediaElementand the PivotItem. That gives every MediaElement a specific alignment and size that will make it fit just in a portrait-oriented page.

<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,30,0,0">
  <TextBlock x:Name="ApplicationTitle" Text="MY APP" 
             Style="{StaticResource PhoneTextNormalStyle}" Margin="0,0,30,0"/>
  <phone:Pivot x:Name="VideoPivot" Title="How to do stuff" 
               HeaderTemplate="{StaticResource HeaderTemplate}" Margin="-25,0,0,0">
    <phone:Pivot.Resources>
      <Style TargetType="MediaElement">
        <Setter Property="Margin" Value="12,0,0,0"></Setter>
        <Setter Property="VerticalAlignment" Value="Top"></Setter>
        <Setter Property="HorizontalAlignment" Value="Left"></Setter>
        <Setter Property="Width" Value="478"></Setter>
        <Setter Property="Height" Value="268"></Setter>
      </Style>
      <Style TargetType="phone:PivotItem">
        <Setter Property="CacheMode" Value="{x:Null}"></Setter>
      </Style>
    </phone:Pivot.Resources>
    <phone:PivotItem Header="connect via tap+send">
      <MediaElement Source="Video/2PhonePongConnect.mp4" />
    </phone:PivotItem>
  <!-- More PivotItems with video -->
  </phone:Pivot>
</StackPanel>

Also note that the styling turns off CacheMode for the Pivot items. That seems to be necessary. The MediaElements themselves contain, apart from the url to the video, nothing else. The rest is set from code behind.

You might also notice that the Pivot used a HeaderTemplate: that’s fairly simple and just exists to limit the header text size a little:

<DataTemplate x:Key="HeaderTemplate">
   <TextBlock Text="{Binding}" FontSize="35"/>
</DataTemplate>

And again some code to make it work

There is an important difference between the FlipView and the Pivot – in what I think is an effort to conserve memory, not all the pivot panes are loaded into memory at startup: only the selected one (i.e. the first), and the ones left en right of that. So we have no way of retrieving all the MediaElements up front. So we have to gather and attach to those elements as we go along.

There is also an important issue with MediaElement on Windows Phone – it does not like to have multiple initialized MediaElements on one page. So I designed all kind of trickery to make this work. For starters, in order to make this work, we need a dictionary of all the video elements and their sources:

using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using WpWinNl;
using WpWinNl.Utilities;

namespace TwoPhonePong
{
  public partial class Help
  {
    private readonly Dictionary<MediaElement, Uri> sources = 
new Dictionary<MediaElement, Uri>(); } }
The constructor, of course, kicks off the whole process
public Help()
{
  InitializeComponent();
  VideoPivot.Loaded += VideoPivotLoaded;
  VideoPivot.LoadedPivotItem += VideoPivotLoadedPivotItem;
}
Then comes the funky stuff:
private void VideoPivotLoaded(object sender, RoutedEventArgs e)
{
  VideoPivot.GetVisualDescendents().OfType<MediaElement>().
ForEach(StoreMediaElementReference); PlayMovieOnPivotItem((PivotItem)VideoPivot.SelectedItem); } private void StoreMediaElementReference(MediaElement mediaElement) { sources.Add(mediaElement, mediaElement.Source); mediaElement.Source = null; mediaElement.AutoPlay = false;

mediaElement.MediaEnded += MovieMediaElementMediaEnded; mediaElement.MediaOpened += MovieMediaElementMediaEnded; }

I case you are wondering about your sanity (or mine) – don’t worry, what you seems to be reading is correct: VideoPivotLoaded finds all the active MediaElements on the Pivot, an the calls StoreMediaElementReference – which stores the URL of their source in the sources directory and then clears the MediaElement’s Source (basically un-initializing it) and sets AutoPlay to false. And then it add the MovieMediaElementMediaEnded method to both the MediaEnded and MediaOpened events of the MediaElement. It does this – of course – only for the PivotItems that are actually loaded.

In case you think thinks can’t get any weirder than this, wait till you see the PlayMovieOnPivotItem method

private void PlayMovieOnPivotItem(PivotItem e)
{
  var mediaElement = e.GetVisualDescendents().
OfType<MediaElement>().FirstOrDefault(); VideoPivot.GetVisualDescendents().OfType<MediaElement>(). Where(p => p != mediaElement).ForEach( p => { p.Stop(); p.Source = null; }); if (mediaElement != null) { mediaElement.Position = new TimeSpan(0); if (!sources.ContainsKey(mediaElement)) { StoreMediaElementReference(mediaElement); } mediaElement.Source = sources[mediaElement]; }

So, first it tries to find the MediaElement on the current PivotItem. Then it stops all the MediaElements that are not on this Pivot, and clears their source – effectively as I said, uninitializing them. For the MediaElement on the current PivotItem – if it’s not in the sources dictionary (so it was on the fourth or higher PivotItem) it is added to the sources using StoreMediaElementReference. However – the source of the MediaElement – that at this point is null, whether it was in the sources dictionary or not – is now set from that sources dictionary.

If the movie has finished loading the MediaOpened event is fired, and calls the MovieMediaElementMediaEnded method – remember that is was wired up in StoreMediaElementReference?

private void MovieMediaElementMediaEnded(object sender, RoutedEventArgs e)
{
  var mediaElement = sender as MediaElement;
  if (mediaElement != null)
  {
    mediaElement.Position = new TimeSpan(0);
    mediaElement.Play();
  }
}

This method starts video playback it – so as soon as the video loaded, it starts playing. And since this same method is wired up to the MediaEnded event too – this will enable the repeated playback of this video as well. Until it is not by code.

Of course – when a user changes the selected PivotItem by swiping left or right – a new video needs to be started and the other ones stopped. This is pretty easily done now:

private void VideoPivotLoadedPivotItem(object sender, PivotItemEventArgs e)
{
  PlayMovieOnPivotItem(e.Item);
}

This method was wired up to the Pivot’s LoadedPivotItem way up in the constructor of this page.

Your video instruction page now works. Now to prevent memory leaks and especially prevent blocking other MediaElements elsewhere in the application, this method clears all even wiring and the MediaElement’s Source properties

protected override void OnNavigatedFrom(NavigationEventArgs e)
{
  sources.Keys.ForEach(p =>
                       {
                         p.Source = null;
                         p.MediaEnded -= MovieMediaElementMediaEnded;
                         p.MediaOpened -= MovieMediaElementMediaEnded;
                       });
  VideoPivot.Loaded -= VideoPivotLoaded;
  VideoPivot.LoadedPivotItem -= VideoPivotLoadedPivotItem;
  base.OnNavigatedFrom(e);
}

And thus you have created a video instruction page that works on Windows Phone under all circumstances (at least under all circumstances I have encountered).

Enjoy – and find the demo solution here

14 February 2014

Build for both–an instruction video pivot page for Windows store apps

For my game 2 Phone Pong – and its Windows 8.1 counterpart 2 Tablet Pong, that at the time of this writing is going through some interesting certification challenges  – I created a page with video instructions. I did not feel much like writing a lot of text on how to connect the apps and play the game – a short video usually tells so much more. That proved to be less straightforward than I had hoped, so I thought it a good idea to share how I got it to work.

Both platforms have their own limitations and idiosyncrasies. Windows 8 does not have a Pivot, and Windows Phone makes life pretty difficult when it comes to playing multiple videos on one page. I have solved the first problems by creating FlipViewPanoramaBehavior and I was successfully able to reuse that behavior, although it’s now running on top of the official Windows RT Behavior SDK, no longer using my stopgap project WinRtBehaviors.

In this post I will show you how to build a video page for Windows Store apps – the next one will show you how to do the same for Windows Phone. The Windows version is actually the most simple

When I set out to create the video instruction page I wanted it to do the following:

  • Start the video on the current visible pivot item automatically – and start the first video on the first pivot as soon as the user access the page.
  • Repeat that movie automatically when it ends
  • Stop it as soon as the user selects a different pivot item

This gives the following effect:

Store video instruction page demo

How I got to this, is explained below

Setting the stage

The beginning is pretty simple - it usually is ;-)

  • Created an Blank XAML store app
  • Bring in my WpWinNl library from Nuget
  • Add an empty page “Help.xaml”
  • Go to App.xaml.cs and change rootFrame.Navigate(typeof(MainPage), e.Arguments); to rootFrame.Navigate(typeof(Help), e.Arguments);
  • Bring in a couple of video’s you want to use. I took three of my actual instruction videos from 2 Tablet Pong.

The XAML basics

The page contains the usual stuff for a nice page header, but as far as the video instruction part is concerned, it only contains the following things:

  • A FlipView with some (very minor) styling for the header text
  • My FlipViewPanoramaBehavior attached to it
  • A few FlipViewItems, each containing a grid with a header and a MediaElement with the Video in it

That looks more or less like this:

<FlipView x:Name="VideoFlipView"  >
  <FlipView.Resources>
    <Style TargetType="TextBlock">
      <Setter Property="FontSize" Value="30"></Setter>
    </Style>
  </FlipView.Resources>
  <interactivity:Interaction.Behaviors>
    <behaviors:FlipViewPanoramaBehavior/>
  </interactivity:Interaction.Behaviors>
  <FlipViewItem >
    <Grid>
      <Grid.RowDefinitions>
        <RowDefinition Height="40"></RowDefinition>
        <RowDefinition Height="Auto"></RowDefinition>
      </Grid.RowDefinitions>
      <TextBlock Text="Connect via WiFi" ></TextBlock>
      <MediaElement x:Name="FirstMovieMediaElement" 
        Source="Video/ConnectWiFi.mp4" Grid.Row="1" >
       </MediaElement >
    </Grid>
  </FlipViewItem>
  <!-- More FlipViewItems with video -->
</FlipView>

Important to see is that both the FlipView and the first FlipViewItem have a name, this is because we need to reference it form the page code.

Some code to make it work

First order or business is getting this thing on the road, so we need to define some starter events in the constructor:

using System.Linq;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using WpWinNl;
using WpWinNl.Utilities;

namespace Win8VideoPivot
{
  public sealed partial class Help : Page
  {
    public Help()
    {
      InitializeComponent();
      VideoFlipView.SelectionChanged += SelectedIndexChanged;
      FirstMovieMediaElement.MediaOpened += 
        FirstMovieMediaElementMediaOpened;
    }
  }
}

Next up is a little helper property that give us a short cut to all the MediaElements on the page, using a helper method from WpWinNl:

private IEnumerable<MediaElement> AllMediaElements
{
  get
  {
    return VideoFlipView.GetVisualDescendents().OfType<MediaElement>();
  }
}
The main method of this page is StartMovieOnSelectedFlipViewItem - that finds the MediaElement on the current selected FlipViewItem, stops MediaElements on all the other FlipViewItems, and kicks off the current one to play it's movie:
private void StartMovieOnSelectedFlipViewItem()
{
  var pivotItem = (FlipViewItem)VideoFlipView.SelectedItem;
  var mediaItem = pivotItem.GetVisualDescendents().OfType<MediaElement>().FirstOrDefault();
  AllMediaElements.Where(p => p != mediaItem).ForEach(p => p.Stop());

  if (mediaItem != null)
  {
    mediaItem.Play();
  }
}

In the constructor we wired up FirstMovieMediaElementMediaOpened, to be fired when the first MediaElement has opened it's media file. It does, as you would expect, start the first movie file by simply calling StartMovieOnSelectedFlipViewItem  What it also does is setting all the MediaElement’s AutoPlay properties to false, and attach a method to their MediaEnded property, so that a movie is automatically restarted again when it ends.

private void FirstMovieMediaElementMediaOpened(object sender, RoutedEventArgs e)
{
  AllMediaElements.ForEach(p =>
  {
    p.MediaEnded += MovieMediaElementMediaEnded;
    p.AutoPlay = false;
  });
  StartMovieOnSelectedFlipViewItem();
}

private void MovieMediaElementMediaEnded(object sender, RoutedEventArgs e)
{
  ((MediaElement)sender).Play();
}

This might seem a mighty odd place to do it here, and not in the constructor – but I have found that it simply does not have the desired effect when I placed this code in a constructor. A typical ‘yeah whatever’ thing.

The only thing that is now missing is SelectedIndexChanged, that we also wired up in the constructor to be executed when a new FlipViewItem is selected:

private void SelectedIndexChanged(object sender, SelectionChangedEventArgs e)
{
  StartMovieOnSelectedFlipViewItem();
}

It simply restarts a movie that ends all by itself. Note – this is not fired when a movie is stopped by code.

And for good measure, to make sure we don’t introduce all kinds of memory leaks, we detach all the events again in the OnNavigatedTo

protected override void OnNavigatedFrom(NavigationEventArgs e)
{
  base.OnNavigatedFrom(e);
  AllMediaElements.ForEach(p =>
  {
    p.MediaEnded -= MovieMediaElementMediaEnded;
  });
  VideoFlipView.SelectionChanged -= SelectedIndexChanged;
  FirstMovieMediaElement.MediaOpened -= FirstMovieMediaElementMediaOpened;
}

That’s all there is to it – you will find that most of the work will actually go into making videos that are good enough to convey the minimal message without enormously blowing up the size of your app. The code itself, as you see, is pretty easy.

Full demo solution can be found here.

Oh by the way – I did not suddenly do a 180 of MVVM versus code behind – this is just pure view stuff, no business logic needed to drive it, so it’s OK to use code behind in this case.

11 February 2014

Drawing translucent shapes and lines on a Windows Phone 8 Map

Shapes1For those who think the MVP title comes with divine wisdom, I have a disappointing announcement to make: it does not. Recently I discovered (or actually was told) something pretty elementary that I missed all that time: how to draw more or less translucent lines or shapes on a Windows Phone 8 map.

To the right you see a few shapes that I draw on the screen during my 3rd WpDevFusion Mapping session demo. The basic piece for such a shape is very simple:

var line = new MapPolygon
{
  StrokeThickness = 2,
  FillColor=Colors.Purple,
  StrokeColor = Colors.Red,
  StrokeDashed = false
};

Shapes2But what we want is more or less translucent shapes. That turns out to be insanely easy:

var fill = Colors.Purple;
var stroke = Colors.Red;
fill.A = 80;
stroke.A = 80;
var line = new MapPolygon
{
  StrokeThickness = 2,
  FillColor = fill,
  StrokeColor = stroke,
  StrokeDashed = false
};

A Color has four elements : R(ed), G(reen), B(lue) and A(lpha). The last ones determines the opacity of XAML elements, but apparently also that of map shapes. Both fill and stroke are now about 80/255th (or 31%) opaque – or 69% translucent.

And that’s all there is to it. If you don’t mind, I will leave the demo solution for as exercise for the reader this time ;)

01 February 2014

Build for both–a very simple wp8 style app bar hint control for Windows Store apps

Windows Phone users are very familiar with the concept of an app bar at the bottom that, in collapsed state, gives a kind of indication that it’s available. In Windows Store apps app bars are just invisible, unless you specifically activate them by swiping in from the top or the bottom. There have been earlier attempts to solve this UI difference by my fellow Dutch MVP Fons Sonnemans who created the Peeking App Bar. Microsoft itself has apparently become aware of the fact default invisible app bars may not always be ideal, and has created a kind of a hint of an app bar that very much looks like they had some inspiration from Windows Phone – which is now used in the Windows Mail app:

image

Now there are already solutions out there, most notably this one by recently appointed MVP Dave Smits. They work indeed. But I like to make things simple, so I made a very simple. So in a typical programmer fashion, I rolled my own :-)

So I created my HintBar control, which is actually laughably simple. The XAML is only this, and most of it is declaration too:

<UserControl
    x:Class="WpWinNl.Controls.HintBar"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="14"
    d:DesignWidth="400" x:Name="ControlRoot">

  <Grid x:Name="HintBarGrid" 
        Background="{Binding Background, ElementName=ControlRoot}" 
        Tapped="HintBarGridTapped">
    <TextBlock  x:Name="HintBarText" Text="&#xE10C" 
                FontFamily="Segoe UI Symbol" FontSize="21.333" 
                HorizontalAlignment="Right"  RenderTransformOrigin="0.5,0.5" 
                VerticalAlignment="Center" Margin="0,0,50,0"/>
  </Grid>
</UserControl>

So it’s basically a simple grid that does something when the user taps on it. In the grid there’s only a TextBlock with one ‘glyph’ in it – using the special Segoe UI Symbol character set that Microsoft uses to store all kinds of symbols in. &#xE10C is simply the code for a symbol containing three dots.

The code is not very complex either. It’s basically two attached dependency properties:

  • AssociatedCommandBar, to which you can bind the CommandBar to open when the hint bar is tapped
  • ForeGround, which you can use to change the color of the three dots

If you don’t understand what attached dependency properties are: they are basically the property equivalent of extension methods, and what’s more important – you can data bind to them.

So the AssociatedCommandBar looks like this. It does nothing special

#region Attached Dependency Property AssociatedCommandBar
public static readonly DependencyProperty AssociatedCommandBarProperty =
	 DependencyProperty.RegisterAttached("AssociatedCommandBar",
	 typeof(CommandBar),
	 typeof(HintBar),
	 new PropertyMetadata(default(CommandBar)));

// Called when Property is retrieved
public static CommandBar GetAssociatedCommandBar(DependencyObject obj)
{
  return obj.GetValue(AssociatedCommandBarProperty) as CommandBar;
}

// Called when Property is set
public static void SetAssociatedCommandBar(
   DependencyObject obj,
   CommandBar value)
{
  obj.SetValue(AssociatedCommandBarProperty, value);
}
#endregion

The other property is only a brush defining the text color, and the only thing it does is transferring its value to the text:

#region Attached Dependency Property ForeGround
public static readonly DependencyProperty ForeGroundProperty =
	 DependencyProperty.RegisterAttached("ForeGround",
	 typeof(Brush),
	 typeof(HintBar),
	 new PropertyMetadata(default(Brush), ForeGroundChanged));

// Called when Property is retrieved
public static Brush GetForeGround(DependencyObject obj)
{
  return obj.GetValue(ForeGroundProperty) as Brush;
}

// Called when Property is set
public static void SetForeGround(
   DependencyObject obj,
   Brush value)
{
  obj.SetValue(ForeGroundProperty, value);
}

// Called when property is changed
private static void ForeGroundChanged(
 object sender,
 DependencyPropertyChangedEventArgs args)
{
  var thisObject = sender as HintBar;
  if (thisObject != null)
  {
    thisObject.HintBarText.Foreground = args.NewValue as Brush;
  }
}
#endregion

And the rest of the ‘real code’ of the control is just this:

using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;

namespace WpWinNl.Controls
{
  public sealed partial class HintBar : UserControl
  {
    public HintBar()
    {
      InitializeComponent();
    }

    private void HintBarGridTapped(object sender, 
	                           TappedRoutedEventArgs e)
    {
      var commandBar = GetAssociatedCommandBar(this);
      if (commandBar != null)
      {
        commandBar.IsOpen = true;
      }
    }
  }
}

Not exactly rocket science, right? You tap the grid, the command bar opens. :-)

Using it is pretty simple too. You have a page with a command bar:

<Page
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:controls="using:WpWinNl.Controls"
    x:Class="HintBarDemo.MainPage"
    mc:Ignorable="d" VerticalAlignment="Bottom">

  <Page.BottomAppBar >
    <CommandBar x:Name="BottomBar"  Background="Blue">
    <!-- Content omitted -->
    </CommandBar>
  </Page.BottomAppBar>

  <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <controls:HintBar Background ="Blue" Height="14" VerticalAlignment="Bottom"
     	   AssociatedCommandBar="{Binding ElementName=BottomBar}"/>

  </Grid>
</Page>

Give the command bar a name and bind it to AssociatedCommandBar property of the control. Then it’s just a matter of setting it to the bottom of the page, setting it to the desired height, and choosing a color for your bar. That is all. Life is sometimes very easy.

As always, the demo solution can be found here.