Great questions! Let's break these down clearly:

Android's Geofence API is built to trigger events locally on a single device based on that device's own location changes. So out of the box, you can't directly set up a fence and get notified when another user's device enters it—since the fence is tied to your device's location monitoring, not other users'.

But you absolutely can build this functionality with a combination of Geofences and backend infrastructure:

• When you create your geofence, save its details (latitude, longitude, radius) to a backend server.
• Have other users' apps either:
  • Check their location against the stored geofences locally (using the Geofence API) and send an event to the server when they enter your fence, or
  • Periodically report their location to the server, which then checks if they're inside your fence.
• Once the server detects a user has entered your fence, it can send a push notification (like via Firebase Cloud Messaging) directly to your device.

So the Geofence API handles the local location detection for the entering user, but you need a server to connect the dots between users.

The 100-geofence limit applies per individual app installation on a single device. That means:

• If your app is installed on 10 different phones, each phone can have up to 100 active geofences at the same time.
• It's not a global limit tied to your app's package name across all devices.

This makes sense because each device manages its own geofence monitoring independently through Google Play Services—there's no shared quota across devices for the same app.

内容的提问来源于stack exchange，提问作者Sergio76