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Revision as of 21:10, 11 June 2013 by influencer (Talk | contribs)

URI associations for Windows Phone

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This article explains how to associate your application with an URI scheme in order to launch it when interaction with such URI is detected.

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Article Metadata
Code ExampleCompatibility
Platform(s): Windows Phone 8
Windows Phone 8
Article
Keywords: Custom URI
Created: MaMi (28 Nov 2012)
Last edited: influencer (11 Jun 2013)

Contents

Introduction

Windows Phone 8 introduces the possibility for your app to register to a predefined kind of URI scheme. This will allow you to launch your application from various sources and with various optional parameters. The URI will have to be formatted as follows:

<Custom Protocol Name>:<The landing page>?[First parameter name]=[First parameter value]&[Second parameter name]=[Second parameter value]

For example:

myappuri:MainPage?Category=5&Subcategory=3

Note that its not mandatory to put the landing page after the semi colon, but it is a good practice. You can use an ID like this:

myappuri:45645645645

How to register for an URI association

To register an URI scheme for your app you will have to manually edit the app manifest. In the Solution Explorer open the Properties folder, right click on the WMAppManifest.xml file and select View Code. Scroll down to the end of the Tokens element and add an Extensions element with a Protocol children like this:

<Extensions>
<Protocol Name="myappuri" NavUriFragment="encodedLaunchUri=%s" TaskID="_default" />
</Extensions>

Just replace myappuri value with the URI you want to use. The other parameters are mandatory and must stay like this.

What URI scheme should I use?

To ensure you don't accidentally re-use a URI reserved by the operating system or default applications or a URI registered to another third party app, we recommend you include your company and app name in your URI as shown (see Designing URI scheme handlers for more detail):

<companyName>-<nameOfApp>

Tip.pngTip: Don't forget to document your app URI scheme and include it in our URI Association Schemes List.

Developers can also create and use protocols that are intended for general "classes" of apps. For example, developers of Calendar apps might agree a common protocol, and allow end-users to determine what app they choose to download or use as the handler. Note that there is nothing to stop developers using any protocol that isn't reserved for the default apps/operating system.

How to detect that your user launched the app from the URI association

You will have to implement a custom UriMapper that will parse the Uri at the launch of your application and try to detect the source. Following the sample provided above, the UriMapper would look like this in our case:

    class AssociationUriMapper : UriMapperBase
{
private string tempUri;
public override Uri MapUri(Uri uri)
{
tempUri = System.Net.HttpUtility.UrlDecode(uri.ToString());
// URI association launch for my app detected
if (tempUri.Contains("myappuri:MainPage?Category="))
{
// Get the category (after "Category=").
int categoryIndex = tempUri.IndexOf("Category=") + 9;
string category = tempUri.Substring(categoryIndex);
// Redirect to the MainPage.xaml with the proper category to be displayed
return new Uri("/MainPage.xaml?Category=" + category, UriKind.Relative);
}
// Otherwise perform normal launch.
return uri;
}
}

One more step to ensure that your application will use your new UriMapper, go to App.xamls.cs file in the InitializePhoneApplication() method and add this line:

RootFrame.UriMapper = new AssociationUriMapper();

Your app will now try to detect if it was launched from the normal way or from the URI association, and in this case it will parse the parameters provided and redirect to the proper page.

How to retrieve the parameters once you have been redirected

Like for any page navigation in Windows Phone you'll have to check the QueryString in NavigationContext once you've reached your target page to retrieve your parameters:

protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (NavigationContext.QueryString.ContainsKey("Category"))
{
Category = int.Parse(NavigationContext.QueryString["Category"]);
}
base.OnNavigatedTo(e);
}

What will and will not work

Note.pngNote: This article is based on personal experimentation. I do not say that all of this will never work but from what I was able to test it is currently not working.

What will trigger your URI association and launch your app:

  • Get the URI from NFC tag.
  • Get the URI by mail.
  • Click on a HTML link containing the URI.
  • Webpage redirection with a custom protocol.
  • Get the URI from NFC device sharing an URI (e.g. PublishUriMessage(Uri) from ProximityDevice).

What will NOT trigger your URI association and launch your app

  • Enter directly the URI in the Web Browser.
  • Scan a QR code from Bing search.

What MAY trigger your URI association and launch your app

  • Get the URI by SMS. It seems to depend on the uri your registered and could be connected to its length

What if many applications registered the same name

In this case the user will be prompted to select which application he want to launch

Two-way communication

It is also possible to send data back and forth by using URI associations between two apps, App1 and App2. Both apps register for URI associations. App2 shows a text. App1 then launches App2 and sends its own text, that is then displayed in App2. In App2 there is a textbox into which a text can be entered. Upon pressing a button the entered text is sent back to App1 and displayed there. The launching process and the request to install the other app can be seen - if the other app is not yet installed. For this to work correctly it is necessary that the apps know each other. App1 needs to know App2's URI protocol and vice versa. To get around this is it is feasible that the URI protocol accepts the protocol definition for the calling app as parameter. That way an app might send back data to arbitrary apps.

Document your custom URI protocol

Your application can now be started by, and can receive data from, other applications. But in order for this to work, you must document your protocol. You add the scheme to the URI Association Schemes List to advertise it to other developers.

Code sample

Media:UriAssociation.zip

Media:appcommunication.zip Code sample for section 'Two-way communication'

Reference

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