ActivityResultLauncher<Intent> vpnLauncher = registerForActivityResult(
        new ActivityResultContracts.StartActivityForResult(),
        new ActivityResultCallback<ActivityResult>() {
            @Override
            public void onActivityResult(ActivityResult result) {
                if (result.getResultCode() != Activity.RESULT_OK) {
                    app.startProxyService();
                }
            }
        });

You can see how ugly this api is: redundant, repetitive, vague to understand. Obviously It can be simplified like this: Launcher<Intent> vpnLaucher = new Launcher().onResult((Result result) { .... })

The split between the unconditional registration and the

launch

is intentional and necessary: https://kotlinlang.slack.com/archives/C0B8M7BUY/p1694440647301139?thread_ts=1694438126.574999&amp;cid=C0B8M7BUY

The only problem is that Android is not good designed, components' parents are not recorded, and return data can not be send back to their parents by default.