How to launch my app via NFC tag?

Question

I\'m currently working on porting an app to UWP. The app has a page with a \"Write to NFC\" button. After the user taps it, it waits for an NFC tag and writes a Launch

Answer 1

Windows 10 Mobile UWP

If you are only targeting Windows 10 Mobile, the 8.1 way still works, given that you get the right App ID. It can be retrieved through:

Windows.ApplicationModel.Store.CurrentApp.AppId

However, that only works when the app is installed through the store, as the ID is assigned during store association / publishing. In developer deployed builds, the API will crash through with "Exception from HRESULT: 0x803F6107".

The resulting LaunchApp record then needs the platform "WindowsPhone" and that app ID. The following code creates a LaunchApp tag through the open source NFC / NDEF library (https://github.com/andijakl/ndef-nfc) and works on Windows 10 Mobile - both for writing the tag and for launching the app. Again - given it has been published & installed through the store:

var record = new NdefLaunchAppRecord { Arguments = "Hello World" };
var appId = Windows.ApplicationModel.Store.CurrentApp.AppId;    // Note: crashes when app is not installed through app store!
record.AddPlatformAppId("WindowsPhone", appId);
var message = new NdefMessage { record };
proximityDevice.PublishBinaryMessage("NDEF:WriteTag", msgArray.AsBuffer(), MessageWrittenHandler);

Windows 10 PC

Unfortunately, things are different for PCs. The method above does not work there, neither does the documented method for Windows 8.1.

The closest I could get so far is to get Windows 10 to recognize the LaunchApp tag and to open the store on the correct page. But Windows / the store does not realize that the app is already installed and therefore does not open it.

This is the code, again using the NFC / NDEF library:

var record = new NdefLaunchAppRecord { Arguments = "Hello World" };
var familyName = Windows.ApplicationModel.Package.Current.Id.FamilyName;
var appId = Windows.ApplicationModel.Store.CurrentApp.AppId;    // Note: crashes when app is not installed through app store!
record.AddPlatformAppId("Windows", "{" + familyName + "!" + appId + "}");
var message = new NdefMessage { record };
proximityDevice.PublishBinaryMessage("NDEF:WriteTag", msgArray.AsBuffer(), MessageWrittenHandler);

Of course, you can also combine the two platform IDs to a single NFC tag, given that you have enough writable memory, as those app IDs are huge.