How to send lightning payment request to lnurl from Android app with extra comment data?

Question

I'm looking for a way to include extra description (comment) info in a lightning payment request i.e. LUD-12.

Either with anchor link:

<a href="lightning:[email protected]" comment="[email protected]">send ln payment</a>

Or even better using an Android Intent:

Intent(Intent.ACTION_SEND).apply {

    data = Uri.parse("lightning:[email protected]") 
    //type = "message/rfc822"
    putExtra("comment", "[email protected]")

}

The above anchor link works, but does not send comment data to receiving wallet. And I can't get the Android intent to launch wallet app at all. Anyone know how to get this working?

Answer 1

The fine folks at Alby helped solve this ->

First, add query intent to manifest:

<queries>
    <intent>
        <action android:name="android.intent.action.VIEW" />
        <data android:scheme="lightning" />
    </intent>
</queries>

Second, query getalby.com for encoded lnurl:

val requestUrl = "https://getalby.com/lnurlp/bitanon/callback?amount=1000000&comment=hello" // amount is in millisats
val client = OkHttpClient() 
val request = Request.Builder().url(requestUrl).build() 
val response = client.newCall(request).await()

Third, parse json response for 'pr' which contains encoded lnurl.

Fourth, send Lightning PayRequest Android Intent, which will open with device lightning wallet of your choice:

val intent = Intent(Intent.ACTION_VIEW).apply {
    data = Uri.parse("lightning:$lnurl")
}
if (intent.resolveActivity(packageManager) != null) {
    startActivity(intent)
}

Fifth, parse and handle additional response info, such as transaction verification url etc.