I'm using ios mapkit for my project. Basically, I'm trying to notify the user when he arrives at a given location. What I do here is I get the distance to the destination and if it's somewhere around 20 meters I'm calling a REST API which will send a push notification to another user. This works fine if the app in the foreground. But how can I do this while the app is in the background? I know there are background modes in the ios. But I can't figure out which mode going to fit here
Thanks
Having tested and deployed region monitoring in production code, I can tell you its bad for walking. It relies on cell towers and the alerts are very flakey at fence sizes of less that 150-200 meters, which is a long way to walk. We initially tried 30 meters and the results were disastrous with tons of false negatives and a few false positives. If you really want to detect 20 meters then you need to use GPS mode, which is drains the battery but its the only thing that has that kind of granularity.
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With CLLocationManager
I am defining regions and responding to didEnterRegion and didExitRegion. This works fine in that I get the callbacks for the Enter and Exit as the device moves between regions.
The problem is that I have run the app overnight a few times with the phone device sitting on a table and not moving. The phone device is in the center of an entered region.
During the night, about once an hour, I get a didExitRegion and then within less than 15 seconds I get a didEnterReqion.
My solution to filter these phantom exit/enter pairs was to set up a timer when I get an exit to wait 15 seconds and then if I do not receive an Enter for the same region within that timer window then I process the Exit.
This works if the app is in foreground, BUT in background it fails. In background mode I still get the didExitEvent but I think the App is going back in to background mode before the 15 second window has elapsed do I don't fire that timer until the phone goes back in to foreground mode.
The Radius of my Region is 250M and the accuracy mode is nearest 10 meters. My device, while sitting still, is centered in the Region and yet I still get these phantom Exit/Enter pairs once an hour.
Either I need to find a way to stop the phantom exit/enter pairs, or need a way to keep the timer running the full 15 seconds before the app moves back to background mode.
Does anyone have a good solution for dealing with random exit/enter or enter/exit pairs for stationary devices?
Also what is the max time that a timer can run upon an app waking event in background mode?
Geofencing does not use triangulation (that's why "accuracy mode" you mentioned is totally irrelevant). Geofencing relies on a "digital signature" - set of wifi access points and cell towers your iPhone detected along with strength of signal coming from these sources. Whenever this digital signature changes, the phone might be fooled into triggering a geofence event.
However, before reporting the event, iOS runs triangulation (in most cases without GPS) - and the resulting location is available to you to check if you are really outside the geofence. If location accuracy is too low relative to size of your geofence, you may obtain a better reading - requestLocation() will do the trick, as it will not run for more than 10 seconds.
By the way, that triangulation sequence the iOS runs after detecting a geofence event most likely is why your phone registers didEnter event shortly after didExit.
Arming a timer in background mode makes no sense, as iOS silently suspends background tasks after first 15 to 20 seconds of background execution. This behavior was introduced with iOS 7 and enforced for timers during iOS 10 lifetime.
Is there a way to hook into/run a bg task in an iOS app depending on accelerometer action? I.e. the unit elevates three feet, or goes in a certain direction
No, there's not. You would have to run your app constantly in the background, monitoring the accelerometer constantly. And note that you really can't detect things like "raises 3 feet". The accelerometer is pretty bad at measuring changes in position because it is very subject to drift. What it detects is acceleration, so it detects jerks, bumps, and thrust. If it's moving smoothly in a car at 100 KPH it can't tell, for example.
I am by no means an iOS developer, and am just hacking something basic together for myself. Sorry if this is too beginner of a question.
I'm trying to collect my own location data from my phone to my own back-end service. Looking around, I found a sample project to collect location info: https://github.com/chriseidhof/PostGPS/
From the looks of things, this project uses significant location update, so even though I changed my desired accuracy to 100 meters, the app will still only provide update when enough cell towers have changed.
Instead, I'm thinking of using geofencing (CLCircularRegion) by creating grids of 3x3 geofences with 500 meter radius (with maybe a 50 meter overlap between each region), and each time I exit the central region, a new set of 3x3 geofences gets generated.
My questions are as follows:
Is this (the deleting and re-fencing part) a correct use of geofencing on iOS?
Is this going to be more accurate than what I currently have?
Will this significantly negatively affect my battery life?
The problem with using geofencing is that you can't monitor more than 20 regions at a time(OS limitation). It's better to use significant location changes. It is triggered while you're in foreground or background and the location is updated if the cell tower has changed or you have opened the app while the app was not in memory. But this method will be triggered only in the intervals of 15 mins. So even if the cell tower changes rapidly, this method will be invoked only once in 15 mins.
So if you want to update the location in background keeping in mind the battery usage as well, use significant location api.
I'm creating an activity tracker similar to the "Moves" app that seeks to track steps, distance, calories and active time.
For Iphone5s+ devices, I am using the built in M7 chip to determine Steps, and then making estimates at the rest from that. For M7 devices I never use GPS. There is basically no battery drain and the interpolated numbers are reasonable enough for the need. This gets walking/running data reasonably enough.
However to support Iphone5 and Iphone4 at least, I need to use GPS to get location and then interpolate steps and calories from the distance. I'm running into significant battery drain issues (somewhat expected), and am seeking advice on how to minimize this. I'm also using the accelerometer in addition to speed to help make an educated guess on activity type (walking,running,biking,transport)
Some things I've tried for GPS optimization:
Deferred Updates: The Iphone5 and a minimum version of IOS supports this. The code to do this is straight forward, however whether the device actually uses it is questionable. I've only seen it work on 1 out of 4 devices, where it does regularly. 3 other devices have never deferred updates from the same code. Another user suggested other apps prevent the device from sleeping, including when I had "Moves" also installed. This thus hasn't helped much beyond theory.
Reduce Accuracy: reduce the accuracy of continuous location polling. I started at High, but reduced to 10m, then hundreds of meters, etc. This doesn't seem to help and polling still seems to occur at a regular interval anyway.
startMonitoringSignificantLocationChanges: In order to reduce endless gps polling when the user may not be moving for hours at a time (especially at night), I switched from continuous polling to significant changes only after the device stopped moving for an arbitrary 2 minutes. I then re enable continuous tracking after any significant location update. This works pretty much as expected-- if it stops tracking then battery drain slows, and when it resumes continuously, battery drain resumes. Further, if a user starts walking, there is no guarantee of a significant motion event for some time. This is very poor for accuracy. Sometimes it doesn't seem to resume at all.
I've been relatively impressed that the "Moves" app, among others is able to track location so well with respectable battery drain. It can go most of a day until needing a charge. With my code, users have reported full battery drain in a couple of hours.
What kind of optimizations could be used to improve this but still maintain a reasonable accuracy in tracking movement?
PROGRESS UPDATE:
startMonitoringSignificantLocationChanges. I set this up with a timer that switches to significant monitoring after 2 minutes of inactivity (not moving). Normal location tracking is then resumed again on any significant change, or when the app becomes active from reopening. This seems to work well. My phone still goes from 100% to 10% in 8 hours overnight of sitting around. It is an old iphone with some battery troubles, but normally it might just lose 30-40% uncharged overnight with no apps running. I need to test more, but startMonitoringSignificantLocationChanges still seems to use some battery.
Further, startMonitoringSignificantLocationChanges has some expected accuracy issues in terms of when it restarts the app. In rural setting, it can go several kilometers before restarting. This could be okay for a long drive, but if I want to catch a 30 minute walk, it may miss that entirely. In urban setting it seems to kick in within 2-3 blocks of movement, which is reasonable.
Even if I used continuous location tracking that stopped+started on a timer to check for movement, I'd still likely have worst case of a minute of lag between restarts before resuming continuous logging.
PROGRESS UPDATE 2:
Significant change updates described above have a fatal flaw for me: they don't always start fast enough. Sometimes it takes 1-2 miles it seems!
As an a better approach, I've tried keeping continuous location updates on, but toggling the "desiredAccuracy" property from high to low accuracy when the device is not moving. This should essentially turn the GPS receiver off during inactivity. I've been experimenting between 100meter and 1km accuracy for inactivity with promising results. It does seem to use slightly more batter than only using significant change monitoring, but it seems more responsive as well.
Nothing of your above proposed solutions works.
You need GPS, and that is enabled if you speficiy full precision (CLLocationAcuracyBest).
if I remeber correctly there is a difference betwween CLLocationAcuracyBest and CLLocationAcuracyBestForNavigation that way that the latter uses additonaly the acceleration sensor, which in sum uses more battery.
There is no half battery GPS mode!
A GPS chip is enabled or not.
For distance counting you need GPS, cell Tower and Wlan locations will not work.
And only the cell tower an Wlan locationg can save battery.
On Iphone4 such an full precision GPS App (e.g my) lasts about 8 hours untill the battery is low.
8 hours are enough, if the user has a benefit of the app.
I'm trying to understand how you are supposed to detect proximity changes in the background.
The only window I get to range is when I enter a region, but this might be pretty far away.
I would like to present something when the user enters "near" or "immidiate", but if you get "didEnterRegion" at far, than stand around, then approach the beacon, you don't get any more ranging time, because you are still in the same region.
Is there a way to either extend the "ranging" time to let the user get near the beacon, or can you make "enterRegion" happen at a different proximity than "far"?
Background ranging time is limited to a few seconds as Charles says in his answer.
If you need to delay action until you are in the immediate region, then you must use iBeacons that allow you to reduce the transmit power so the transmission radius is smaller. The RadBeacon product from RadiusNetworks has this configurability for this exact purpose.
If you configure a RadBeacon for minimum transmit power, your phone will not detect it until it is a few feet away, sending you the entry event and starting your limited ranging window at that time.
Full disclosure: I am Chief Engineer for Radius Networks.
This walkthrough shows how to do what you're asking. I'm in the process of adapting and testing it for iOS 8, but the resulting app works well on iOS 7, pushing local notifications whenever the proximity changes.
In the best practices section in Apple's Getting Started with iBeacon guide it mentions that ranging API should not be used in the background.
• Ranging API are not expected to be used in the background. For best results, ranging should
be used when your app is frontmost and the user is interacting with your app.
Could be a shortcut to app rejection, so take caution.
Given this, you shouldn't really be expected to determine proximity when in the background. I'm also employing the low signal technique, but it becomes a little trickier to differentiate between beacons when you only use one monitored region for multiple beacons...
What's possible with iBeacons in background is pretty limited.
What you can do is monitor regions in the background (which gives you the didEnter / didExitRegion events).
You can also switch on ranging for the beacon and, for the 10 or so seconds after you get a beacon enter / exit event from region monitoring you will also get ranging info (i.e. the immediate / near / far data).
Perhaps you could trigger a local notification at that point to try to get the user to bring your app into foreground - then you'd be able to get the ranging data. If not then, based on my tests, you're only going to get the 10 seconds of ranging data.
To your question about adjusting the ranging time or adjusting the enterRegion proximity - no, these aren't possible in the current version of iOS.