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Jerry Nixon is the Microsoft Developer Evangelist in Colorado. He has scary knowledge about Architecture, XAML, and SQL Server. He has terrifying knowledge about Windows Phone, the Kinect, and C#. And, he has simply ridiculous knowledge on Windows Desktop development in Windows 8. Jerry is a DZone MVB and is not an employee of DZone and has posted 104 posts at DZone. You can read more from them at their website. View Full User Profile

Windows Phone Mango Sample: Introducing the Info Hub

01.15.2012
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If I could ask God one question, it would surely be “Where am I going to die?” That way I could avoid it. With my bad luck He would likely say “the bathroom.” D’oh!

Seriously, for Windows Phone developers there’s a lot of information (about the device, OS , sensors, and more) –  it is scattered all over the freaking place!

Developers need an Info Hub!

Introducing the Info Hub


This is awesome!

imageA Windows Phone Hub is where different things come together in a single, digestible location. The Info Hub is where developer info (across classes and namespaces) is brought together.

Yes, I wrote the Info Hub – this is NOT a Microsoft product. Lots of hard lessons, MSDN, Stack Overflow, and so much more get credit for the Info Hub. Today, I am giving Info Hub to you, yes you!

Why the Info Hub?


  • Which OS Version is running?
  • How much RAM your app is using?
  • Which physical Phone are you on?
  • Is the Gyro is supported?
  • Is WIFI connected?
  • Is the theme Light or Dark?


These are all available to developers. Everything. However, knowing them, getting to them, and parsing their result can be tricky.

Wouldn’t it be nice if there was a single place to go for all this information? Now you see why Info Hub is handy.

Usage

Before we get started let me just say: this is not complex. I am going to show you a series of ways to use the Info Hub. It’s up to you how to use it. Don’t stress. It’s a simple class.


The only thing Info Hub needs to work is the Dispatcher. Simply pass it to the constructor.

Why?

Some information, especially network information, can take a long time in certain situations. This blocks your application.

Info Hub queues these in the Thread Pool – the background thread needs dispatcher to avoid a cross-thread exception.

Here’s how (Data Context):

Because the Info Hub is 100% data binding-ready, you can set it as your XAML’s Data Context and its INotifyPropertyChanged implementation(discussed below) takes care of keeping your UI up-to-date.

image

In the code above, we are setting the Data Context  to the Info Hub and calling the non-blocking LoadAsync() method. As the properties are populated, the data context will reflect the changes.

Here’s how (asynchronous):

imageUsing Info Hub in an asynchronous way means your UI is never blocked. But it also means you need to handle the LoadComplete event.

image

In the code above, see that I call LoadAsync()? This is a non-blocking method that raises LoadComplete after it is finished.

Subscribing to LoadComplete also means you can react to any changes in property values. I’ll talk about that more below.

Here how (blocking):

Using Info Hub synchronously means your code is blocked. However, it also means you can reliable use properties after it is finished.

image

In the code above, see that I call Load()? Load is a blocking method. This means it will not return until all properties are set. This means you can reliably read any property after it is complete.

Note: Load is blocking. Some properties, especially network information, can take a long time in certain situations. Be sure you do not block the UI during this operation.


Up-to-Date Happiness

The Info Hub subscribes to the changed events of all its dynamic properties. Doing this, the Info Hub property are always up-to-date.

Property Changed

Info Hub implements INotifyPropertyChanged. So, if you data bind to Info Hub in XAML, your UI will always reflect the current value. Here’s how:

image

In the XAML above, we assume the Info Hub is the Data Context of the outer container. Given that, we can use standard Binding syntax to reference one of its properties.

If you need to respond to the change something based on an individual property’s change, you can subscribe to PropertyChanged like this:

image

In the code above, we’re subscribing to the PowerSource property change. This might change if the user plugs in or unplugs their phone. When this property is raised, we do something.

If I were you

If I were you, I would put the Info Hub as a public, static property in App.xaml.cs. This keeps the logic in one place, and ensures the expensive properties are not over-called as the user navigates from page to page.

image

imageIn the code above, I show a sample implementation. I am setting up a public, static property for the Info Hub in the App.xaml.cs – which is constant, and shared by the whole application.

My Favorite Property

My favorite property is a derived property called PhoneVersion. This property returns a custom enumeration of the Windows Phone version on the phone. Right now there are two possibilities. But that is changing soon. This property will be helpful when you are targeting OS-specific features.

Conclusion

You can get the Info Hub here.

Look, I will continue to keep this up to date. But I welcome any suggestions.

One more thing, remember that some values are just plain crazy in the emulator. On a real phone they are fine. If you see something crazy, try it on your phone. It will be up to you to deal with that craziness. I just give you the raw values!


Best of luck!


Source:  http://blog.jerrynixon.com/2012/01/mango-sample-introducing-info-hub.html

Published at DZone with permission of Jerry Nixon, author and DZone MVB.

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)

Comments

Schlacter Adam replied on Sat, 2012/04/14 - 1:17am

I am getting an Exception being thrown when the Load method is trying to access Application.Current.Resources["PhoneDarkThemeVisibility"] - the initial load is OK, but if (in the emulator) I switch to/from keyboard entry for a textbox the exception gets thrown as it appears to re-invoke the Load method.

Am I doing something wrong, the InfoHub is a static property of the App as per the suggestion above.

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