How does Starbucks show a UI on Android devices when near store?

Question

I am a fairly new Android developer. One thing that I noticed is that when I walk near/inside a Starbucks store, my Android device shows the following:

Question:

1. How does this UI render automatically onto my mobile device when I am near/inside the store?
2. Does this UI appear because I have the Starbucks app installed on my phone? Does the app use a Network Broadcast Listener? Ex: If "Google Starbucks" Wi-Fi is detected in the area, does the app then show the UI as an Activity?
3. Or, does the Starbucks Router broadcast a special Network Packet to Mobile Devices to force the Mobile Device to render this? If so, what is inside this Network Packet? I'd like to do the same.

Answer 1

This isn't the Starbucks app, this is just your device detecting that an open network that you have connected to in the past is available, and requires authentication to access the internet. The Android OS automatically opens this window as it is directed by Starbucks' internet service.