Android app running as homescreen launcher + OAuth flow launches second instance

[mattdsteele]

Hi folks! 👋

Has anyone built an app that run as a homescreen launcher (e.g. it has the android.intent.category.HOME category), and which also can be launched via a custom URL scheme (e.g. com.foo.bar://)? I am having a hard time getting the two to play with each other.

For context, I'm trying to build a secured launcher that authenticates a user via an OAuth server, using Chrome Custom Tabs. Its redirect URI is a custom scheme which points back to the app. I can authenticate fine, but when it redirects, a second instance of my app gets started, and my original "launcher" instance moves to the background.

I've tried all sorts of combinations setting taskMode to singleInstance, singleTop, and lots of other combinations, and tried settings flags on the CustomTabsIntent but I've made no progress, an am beginning to think that I can't square that circle.

As a workaround, my current plan is to authenticate by launching a second app, which will perform the OAuth flow, and then immediately exit, returning the user back to the launcher. It's ugly, but I know I can retain only one instance of the app running this way. I'm really hoping there's a better way though!