I’m about to implement a feature with geofences and before I get any serious work done, I need to know whether geofences remain active after the first transition.
The core of the feature is:
every time I’m within x meters of point P (call this Area A), I want Action B to occur.
What I need to know is
- Do I just have to add a geofence with
Geofence.NEVER_EXPIREand rest assured that I will get a PendingIntent every time I enter the specified area regardless of elapsed time, reboots, etc
- Do I have to re-register this geofence once I exit Area A in order to get notified the next time I enter Area A?
I’m hoping that the former is the case
The good proposition is the first one. If you create a geofence with the flag NEVER_EXPIRE as expiration time, you won’t have to re-register it when it is triggered (by going in or out). I’m 100% certain of this, I’m right now just finished coding and testing a POC about geofence.
From the doc, the only way for a geofence to be deleted is either expiration time is reached or it is deleted by the device itself.
How long the geofence should remain active. Once the
expiration time is reached, Location Services deletes the geofence.
Most of the time, you should specify an expiration time, but you may
want to keep permanent geofences for the user’s home or place of work.
To stop geofence monitoring, you remove the geofences themselves
Please remember that NEVER_EXPIRE will cause the geofence to be registered even after a user uninstalls the app in case the app doesn’t uninstall them. There is no way to remove these. Ever. So they will keep draining battery. Therefore, setting an expiration time is advisable and to set the geofence again in case they expire before you want them to.
Be advised that “all registered geofences will be removed” in THIS case (i.e. when user disables Location is his phone settings).
BE ADVISED: at the top of that documentation is warning “This class is deprecated. Use LocationServices.”
While you will get pending intent (transition) irrespective of how many times you enter/exit the geofence, the catch is that a device reboot will remove all your geofences. So in case of device reboot you must re-register all your geofences again (which you would have saved via shared preferences) using a broadcast receiver and set intent filter action
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
Also please remember that the system restores geofences even if the Google Play Services is killed+restarted/upgraded but not if you clear its data. The same is also mentioned in the developer docs under the section “Re-register geofences only when required”
Also note, in case user toggles OR switches off the location/gps setting, all the geofences will be removed and an intent is generated by the provided pending intent. In this case, hasError() api will return true and getErrorCode() api will return GEOFENCE_NOT_AVAILABLE.