Category Archives: Windows Phone 7

Determining Whether you’re in DesignMode in a Windows Phone 7 Project

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Filed under .NET, Windows Phone 7

When you’re building usercontrols in a Windows Phone 7 project, it’s often necessary to know whether the code is running in Design Mode (i.e. being invoked by the Visual Studio IDE or by Expression Blend), or whether you’re actually running in the real program.

It’s a trivial matter, really, but it can be hard to remember exactly how to do it when I need it, so I wrapped it in an IsInDesigner function:

    Public Function IsInDesigner() As Boolean
        Return System.ComponentModel.DesignerProperties.IsInDesignTool
    End Function

Commenting out Blocks of XAML

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Filed under Windows Phone 7

Just happened across a very handy trick for commenting out large blocks of XAML. If you’ve worked very much with XAML, you’ve probably run into the problem of wanting to comment out a large chunk, which might or might not already have XML style comments (<!– comment here –>).

If you’ve tried it, you’ve quickly discovered you can’t nest XML comments, which isn’t so much a XAML thing as it is an XML thing.

However, there is a fairly easy solution that works quite nicely.

First, in the declaration part of your XML file (up at the very top, where all the XMLNS elements are defined), add these lines:

<UserControl
    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:c="comment" <-- NOTICE THIS LINE
    mc:Ignorable="d c"  <-- NOTICE THE "C" in this line
    d:DesignHeight="800" d:DesignWidth="424">

And finally, when you want to add a comment, instead of the <!– –> pair as you might normally, use this instead:

<c:comment>
   I'm commenting out the use of the text block below

   <!-- This text block should be commented -->
   <TextBlock />

    <c:comment>This is a nested comment</c:comment>
</c:comment>

Not only can you continue to use normal XML comments as usual, but, when necessary, you can easily (and obviously) comment out entire blocks, even if they already contain other comment elements, or XML comments.

And, by using the mc:Ignorable attribute, VS and Blend complete ignore the content of the comment elements.

Not perfect, but pretty dang close!

More Fun with Generic XAML Errors

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Filed under Troubleshooting, Windows Phone 7

Here’s another obscure XAML error I hope no one else stumbles onto.

I have several VisualStates defined for a particular UserControl. One example is:

<VisualState x:Name="Waiting">
    <Storyboard>
        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="pnlBeforeWakeup">
            <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="0" />
        </ObjectAnimationUsingKeyFrames>

Now, I’d entered that state by hand and it worked just fine in Visual Studio, compiles and runs (at least, on the phone emulator).

But, when I tried to fire up Expression Blend, the control would load initially, but when I tried to view the States tab, crash!

After a few false starts, I just removed all my VisualStates manually and recreated one via Expression Blend.

Presto! Anyone care to guess the “fault”?

<queue Jeopardy theme>

Ok, here’s the version that works fine in both VS and Blend.

<VisualState x:Name="Waiting">
    <Storyboard>
        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="pnlBeforeWakeup">
            <DiscreteObjectKeyFrame KeyTime="00:00:00">
                <DiscreteObjectKeyFrame.Value>
                    <Visibility>Visible</Visibility>
                </DiscreteObjectKeyFrame.Value>
            </DiscreteObjectKeyFrame>
        </ObjectAnimationUsingKeyFrames>

Notice that instead of Value=”0”, Blend seems to want a specific Value element, with a Visibility sub-element.

And finally, here’s the Expression error that results from using the Value attribute as I did originally.

image

The only clues that helped were the fact that it only happened when I tried clicking on a particular State that made use of the Value=”0” for Visibility, and the mention of “StoryBoard” in the StackTrace above.

“Unspecified Error” in XAML under WP7

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Filed under Troubleshooting, Windows Phone 7

Ran into a very strange error today that took me a bit to figure out.

Essentially, I was templating a standard ol’ Silverlight Button (I wanted it to have a bit of a gradient and a nice rounded border in this instance).

I was mainly messing around with things, so I was defining the control template inside the button control itself, instead of the more general purpose way of defining a Style.

<Button Name="btnTest" Content="Caption" Click="btnTest_Click" HorizontalAlignment="Stretch" >
    <Button.Template>
        <ControlTemplate>
                <Border BorderBrush="White" BorderThickness="3" CornerRadius="10" Margin="{StaticResource PhoneMargin}" >
                    <Border.Background>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FFCDCDE5" Offset="0" />
                        <GradientStop Color="#FF389940" Offset="0.25" />
                        <GradientStop Color="#FF008d00" Offset="0.314" />
                        <GradientStop Color="#FF002200" Offset="1" />
                    </LinearGradientBrush>
                </Border.Background>
                <TextBlock Text="{TemplateBinding Content}" HorizontalAlignment="Stretch" TextAlignment="Center" FontFamily="Segoe WP" FontSize="{StaticResource PhoneFontSizeExtraLarge}" Margin="0,6,0,18"/>
            </Border>
        </ControlTemplate>
    </Button.Template>
</Button>

Nothing special, but when I ran the program and navigated onto the page containing this button….

image

Ugh, Just about the most general error message possible.

Fortunately, I’d checked things in just a little earlier so I had a record of what had changed, the main thing being that I’d added the use of the TemplateBinding Content feature.

The idea there is to be able to customize exactly what UI element is used to display the “Content” property of the Button control itself. As you can see, I set the button’s Content to “Caption” and then bind to that in a TextBlock.

Simple stuff.

But it crashed.

If I took out the TemplateBinding reference, everything worked just fine.

After a lot of headscratching, I eventually realized that in this case, I did NOT provide a TargetType argument to ControlTemplate. I guess I was thinking that sense the ControlTemplate was being defined within an actual control instance, it wasn’t necessary. Lo, I was but mistaken!

Once I’d specified the TargetType for the ControlTemplate element, everything was back on track.

<Button.Template>
    <ControlTemplate TargetType="Button">

It truly is the tiny things in XAML that’ll get you!

Determining Whether You’re Running on the Windows Phone Emulator or Not

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Filed under .NET, Windows Phone 7

This is a tiny little quick-tip for Windows Phone 7

I came up with a tiny little function to make it easy to check whether you’re running under the Windows Phone Emulator this afternoon.

    Public Function IsEmulator() As Boolean
        Select Case Microsoft.Devices.Environment.DeviceType
            Case Microsoft.Devices.DeviceType.Device
                Return False
            Case Microsoft.Devices.DeviceType.Emulator
                Return True
            Case Else
                '---- just a fall back case
                Return True
        End Select
    End Function

It’s trivial really, I know, but I often wrap these kinds of utility functions in an easy-to-remember function name, because remembering “Microsoft.Devices.Environment.DeviceType” is a lot more difficult than “IsEmulator” <g>.

Showing a Bing Map in Windows Phone 7.1 With Directions

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Filed under .NET, Windows Phone 7

image

For a Windows Phone 7 app I’ve been playing with, one last element I wanted to include was a “directions” function. Basically, I just wanted to pop up a Bing Map with a start and end point and directions, much like you’d get if you went directly to the maps application on the phone and manually entered the start and end point.

The API for this is pretty straightforward, at least for WP7.1 (Mango).

Essentially, you create a BingMapsDirectionsTask, supply a start and end point and invoke Show.

Dim bmt = New BingMapsDirectionsTask()
bmt.Start = New LabeledMapLocation(StartName, New GeoCoordinate)
bmt.End = New LabeledMapLocation(EndName, New GeoCoordinate)
bmt.Show()

The problem was that New GeoCoordinate element. For the BingMapsDirectionsTask, you have to supply two LabeledMapLocation objects, one for the start and one for the end point.

No big deal, but according to the docs, you need to supply a Name for the labeled location, and a coordinate (essentially, just a Lat/Lon). This means that if all you have is an address, supplying the lat/lon becomes an issue of geocoding, and as far as I can tell, there’s no built-in service on the phone to geocode addresses.

I was able to turn up several good examples of using the BingMapGeoCodeService online, and they all worked fine (once you go through the requisite step of obtaining an AppID from www.bingmapsportal.com).

But, in the process of making that work, I discovered something interesting.

When creating the LabeledMapLocation objects for the start and end points, if you supply an address for the name, and nothing  for the GeoCoordinate, the BingMapsDirectionsTask will automatically geocode the address!

The Disclaimer

I’m not sure whether this is intentional behavior, as the available docs for BingMapsDirectionsTask are pretty sparse, and it could be that this won’t make it into the final 7.1 release.

But, it sure makes interacting with BingMaps for simple direction functionality ridiculously easy.

The final code, then, would look like this:

Dim bmt = New BingMapsDirectionsTask()
bmt.Start = New LabeledMapLocation("12 Main St, Dallas, Tx 76011", Nothing)
bmt.End = New LabeledMapLocation("500 Oak Lawn Ave, Dallas, Tx, 76011", Nothing)
bmt.Show()

Granted, using the BingMapGeoCodeService, you’ll have a lot more flexibility, including the ability to specify the level of confidence at which to filter geocoding hits, and you can actually retrieve multiple hit values and present them to the user in whatever fashion you want.

Let me know how it works for you!

Simple No-Code Navigation in Windows Phone 7 Apps

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Filed under Windows Phone 7

imageIn working with Windows Phone 7, one element that struck me as odd early on, is that the ApplicationBarIconButton (those “soft” buttons at the bottom of a normal WinPhone 7 page, highlighted in red in the screenshot) requires code in order to navigate. In other words, you MUST supply a CLICK event handler and in code behind, make use of the page’s NavigationService to perform the navigation.

Further, the URI to navigate to ends up in code behind as well.

Not ideal.

But there is a simple solution.

URIMapping

First, to make things really simple, you need to setup URI mapping. This allows your xaml to reference, say /Settings, and actually navigate to the URI /ui/SettingsPage.xaml?pvt=Main.

To do this, open up your App.xaml file and add something like this:

    <Application.Resources>
        <!-- URIs for navigation purposes -->
        <nav:UriMapper x:Key="UriMapper">
            <nav:UriMapping MappedUri="/ui/SettingsPage.xaml?pvt=Main" Uri="/Settings" />
        </nav:UriMapper>
    </Application.Resources>

Obviously, the MappedUri property is what you would normally use in conjunction with NavigationService.Navigate to actually perform the navigation. The Uri property is the new “simplified” Uri that you can use throughout your app to refer to the same page.

If you don’t already have it in your App.xaml file, be sure and add the namespace line for nav:

    xmlns:nav="clr-namespace:System.Windows.Navigation;assembly=Microsoft.Phone"

Create the New ApplicationBarIconNavigator control

Create a new class, call it ApplicationBarIconNavigator, and use the following code:

''' <summary>
''' Provides a handy extension to the ApplicationBarIconButton to facilitate direct navigation
''' </summary>
''' <remarks></remarks>
Public Class ApplicationBarIconNavigator
    Inherits ApplicationBarIconButton

    Public Property URI As Uri
        Get
            Return _Uri
        End Get
        Set(value As Uri)
            _Uri = value
        End Set
    End Property
    Private _Uri As Uri

    Private Sub ApplicationBarIconNavigator_Click(sender As Object, e As System.EventArgs) Handles MyBase.Click
        DirectCast(App.Current.RootVisual, PhoneApplicationFrame).Navigate(Me.URI)
    End Sub
End Class

This Class inherits from the normal ApplicationBarIconButton, but makes two critical changes.

First, it exposes a URI property, to allow us to specify what URI we want to navigate to.

Second, it automatically handles the Click event, and navigates to that URI.

This combination allows us to specify the URI to navigate to and handle the navigation event, all from XAML with no code on the page’s code behind at all.

The ApplicationBarDefinition

Now, in your page’s xaml, usually toward the end of the file is the definition of the ApplicationBar.

    <phone:PhoneApplicationPage.ApplicationBar>
        <shell:ApplicationBar IsVisible="True" IsMenuEnabled="False">
            <shell:ApplicationBarIconButton IconUri="/Images/Settings.png" Text="Settings" Click="Settings_Click"/>
        </shell:ApplicationBar>
    </phone:PhoneApplicationPage.ApplicationBar>

Note that I’ve got only one button defined, and its Click event is set to About_Click, so normally, I’d have to navigate to the event handler, and add code there to perform the actual navigation:

    Private Sub Settings_Click(ByVal sender As Object, ByVal e As EventArgs)
        Me.NavigationService.Navigate(New Uri("/ui/SettingsPage.xaml?pvt=Main", UriKind.Relative))
    End Sub

Not a huge issue, but it does mean you’ve got code behind where there really doesn’t need to be any, which means more code to maintain, etc.

But, with the new control in place (you may have to perform a Build before you can add a reference on the page to it without error), and with the URIMappings set up, you can now do something like this:

    <phone:PhoneApplicationPage.ApplicationBar>
        <shell:ApplicationBar IsVisible="True" IsMenuEnabled="False">
            <local:ApplicationBarIconNavigator                 IconUri="/Images/Settings.png"                 Text="Settings"                 Uri="/Settings" />
        </shell:ApplicationBar>
    </phone:PhoneApplicationPage.ApplicationBar>

At this point, you’re done! You no longer need the event handler logic because the ApplicationBarIconNavigator button will automatically handle it. And your URI complexity is isolated to just the App.xaml resources. Sweet!

One final note, if you haven’t already included one, you’ll need to add a “local” namespace declaration in your page’s xaml so that local:ApplicationBarIconNavigator will resolve.

    xmlns:local="clr-namespace:{your project name}" 

Wrapup

With MVVM frameworks like Prism, I believe this kind of functionality is baked in to some degree. But in my case, just starting out with WP7, I believe it’s important to understand the underpinnings of the system first, then progress to a higher level framework.

Expression Blend Finally Does VB!

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Filed under Expression Blend, Windows Phone 7

imageI started playing with the VB.net functionality associated with Windows Phone 7 months ago. As it was, it worked pretty well and I’ve definitely been able to move forward with a few side projects.

But, one thing that always bothered me was Expression Blend’s lack of support for VB projects. If I wanted to open a XAML file in Blend, I had to construct this complex project arrangement where I shared the XAML file between a VB and C# project and then opened it through the C# project. It worked, but it wasn’t particularly pretty.

My how things have changed!

First, be sure and grab the Visual Studio 2010 Service Pack 1.

Then, download and install the Windows Phone SDK 7.1 Beta 2.

Note that the Beta 2 install takes forever to install. I swear, I think they copy your entire harddrive to the cloud, reformat your drive and then copy it all back down.

But, once it’s done, open up a VB.net phone project, right click on a XAML file in the solution explorer and select “Open with Blend”.

Life is good!

Now if we could just get the ListPicker fixed.

Sizing a Variable Entry Size ListBox under Windows Phone 7

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Filed under Windows Phone 7

imageI’ve been working a little with the latest Windows Phone 7 development options in Visual Studio 2010. Fun stuff!

One widget I was recently working on was a modified ListBox.

Essentially, the idea was to have a normal ListBox, where each Item (the ListBoxItem ControlTemplate) was actually a TextBlock (to show the actual item name), and a custom control (for editing addresses in this case). For the user, clicking an item “opened” the listbox to reveal the address associated with that item. Clicking again closed the item and the ListBox once again looked like a plain ol’ ListBox.

This is also sometimes called an Accordion Box.

The problem (actually, there were several problems, this was just one <g>) was that when the custom control was “revealed”, the ListBox would no longer scroll quite right. If the user was at the very end of the list, invariably, the last bit of the ListBox contents was cut off.

Here’s a picture of the bare ListBox with two items.

image

The red box is my own highlight (not part of the phone’s UI). When the user clicks on “New York” for instance, they should see this.

image

Note the highlighted area at the bottom. Even though I could press and drag the list box contents “up”, it would spring right back to this look when I let go. As a result, that last textbox would never be fully visible on-screen.

Not good.

The Solution

Turns out, the solution is simple, but I never was able to find it online (though I did find this exact question asked on StackOverflow, no solution there either).

The ListBox will automatically size itself to fit its contents under normal circumstances.  If the list is small, that’s fine, but if the list is bigger than a screen, and the listbox isn’t positioned at the VERY TOP of the screen, that can cause problems, the kind of which I was seeing.

To fix it, you can simply set the HEIGHT property of the ListBox to something other than Auto. While this DOES WORK, it’s not terribly elegant. What if the page needs to handle being switched to landscape mode?

In this case, the ListBox itself was a child (the only child) of a StackPanel, that itself was the only child of the PivotItem you see above, which was a child (among several) of a Pivot control.

The StackPanel was being sized properly (I could tell by setting it’s border to red and running the app), so the problem was with the ListBox only.

Then it hit me.

Databind the ListBox HEIGHT property to the StackPanel ActualHeight property (you can’t use the StackPanel’s HEIGHT property because, most likely, it’s set to Auto as well).

Here’s the XAML…

<controls:PivotItem Header="Destinations" Margin="0,0,12,0" Name="pvtItemDestinations">
    <StackPanel Name="stkDestinations">
        <ListBox Name="lstDestinations" HorizontalContentAlignment="Stretch" Height="{Binding ElementName=stkDestinations, Path=ActualHeight, Mode=OneWay}">
            <ListBox.ItemTemplate>
                <DataTemplate>

                ...
                Data template here
                ...

                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </StackPanel>
</controls:PivotItem>

You can see the PivotItem, with the contained StackPanel, and within it, the ListBox.

The key is the Height="{Binding ElementName=stkDestinations, Path=ActualHeight, Mode=OneWay}".

This binds the height of the ListBox to the ActualHeight of its container. Once the Height of the Listbox is set to something other than “Auto”, its internal scrolling logic automatically kicks in and handles scrolling of variable item height items properly.

Simple, sweet, and all XAML!