Develop Reference

Better way to query GPS regularly

I have a timer that runs every second. Every second I get the GPS location and do other stuffs.
I am wondering which way is better:
1- Request a single location update and then get the last known location
private void timeout(){
String data[] =new String[DATA_LENGTH];
locationManager.requestSingleUpdate(LocationManager.GPS_PROVIDER, this, null);
Location loc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
.
.
.
}
2- Start Location listener and then just get the last known location whenever my timer expire
OnCreate(){
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, mlocListener);
}
private void timeout(){
String data[] =new String[DATA_LENGTH];
Location loc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
.
.
.
}
Thank you
PS: Note that battery is not a concern to me as per the requirement of the product

requestSingleUpdate is meant to be single, if you need to query the GPS frequently you should definitely go with option 2.
Keep a global Location object in memory, use it in you other stuff and update it whenever your listener gets an update from the LocationManager.

You can listen for changes via requestLocationUpdates - the code below is a quick-n-dirty example (untested). Remember, you have to have location services turned on to use this.
LocationListener locGPSListener= new LocationListener() {...}
LocationListener locNetworkListener= new LocationListener() {...}
mgr = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
// listens using GPS for location
mgr .requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locGPSListener);
// uses towers for location
mgr .requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locNetworkListener);
...

What approach is better, depends on
Androids GPS behaviour and
your Application.
ad 1. if explicitly getting a location delivers a more recent fix, than this is an advantage, because:
ad 2. if your application don't want the android filtering behaviour, and you can filter it yourself better, then this would be better for your app.
Example: (is for ios, but may apply here too:) if I drive with my car to a traffic signal, and do a harsh breaking, then ios still shows 5 km/h speed, although I am standing still. This I call unwanted filtering.
This has all nothing to do with battery: if you get the location via message or if you query it is the same from battery point of view. It smore a software design issue: (events vs. polling)
A difference would only be if GPS is disabled, but disabling GPS makes only sense if it can be disabled for long time.

Android: requestLocationUpdates updates location at most every 45 seconds

Background
I am writing an Android app whose main function is tracking the user's location and making an alert when the user gets near some point. Therefore I need to update the user's location at regular intervals, and these intervals should get smaller as the user comes closer to the target. So when the user is within, say, 1 km of the target, I want the location to be updated every 20 seconds and so on, until the user arrives.
Problem
When I test it (provider = LocationManager.NETWORK_PROVIDER), a call to requestLocationUpdates(provider, minTime, minDistance, locationListener) with any minTime < 45000 has the same effect as minTime = 45000, i.e. I get updates with an interval of exactly 45 seconds.
I know the minimum time parameter is only a "hint", but it is not taken as a hint by my app. I get updates with the interval specified until that interval passes below 45 seconds. It seems as though a minimum time of 45 seconds between location updates is hardcoded into Android, but that would be kind of odd. Plus I have never heard of this problem before, and I have not been able to find it addressed here on Stackoverflow.
Because I am not able to get frequent updates, my workaround (for now) is to manually call requestLocationUpdates whenever a new location is needed, and then just use the first available location. To do this at small intervals I use handler.postDelayed(myRunnable, updateInterval) to delay the calls, and myRunnable then takes care of calling requestLocationUpdates. However, this method only works about 50 (apparently random) percent of the time.
Does anybody know of the problem, and is there a way to fix it? Or is my only option to set minTime = 0 and just hope for the best?
Source code
Here is the source code for myRunnable, whose run() method I manually call regularly with handler.postDelayed(myRunnable, updateInterval):
public class MyRunnable implements Runnable {
private LocationManager manager;
private LocationListener listener;
#Override
public void run() {
// This is called everytime a new update is requested
// so that only one request is running at a time.
removeUpdates();
manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
listener = new LocationListener() {
#Override
public void onLocationChanged(Location loc) {
location = loc;
latitude = loc.getLatitude();
longitude = loc.getLongitude();
accuracy = Math.round(loc.getAccuracy());
handler.sendMessage(Message.obtain(handler, KEY_MESSAGE_LOCATION_CHANGED));
checkForArrival();
}
// Other overrides are empty.
};
if(!arrived)
manager.requestLocationUpdates(provider, updateInterval, 0, listener);
}
/**
* Removes location updates from the LocationListener.
*/
public void removeUpdates() {
if(!(manager == null || listener == null))
manager.removeUpdates(listener);
}
// Another method for "cleaning up" when the user has arrived.
}
And here is my handler:
handler = new Handler() {
#Override
public void handleMessage(Message msg) {
switch(msg.what) {
case KEY_MESSAGE_LOCATION_CHANGED:
if(myRunnable != null) {
myRunnable.removeUpdates();
handler.postDelayed(myRunnable, updateInterval);
}
break;
}
}
};
Additional info
The whole location updating thing runs in a service.
I have read the doc several times, Google'd the problem, and tried various other workarounds. Nothing quite does it.
I have logged the damn out of this thing, and the only exciting thing to see is a big fat "ignore" to my frequent location requests. All the right methods are called.
Any help will be very much appreciated!

You are completely right, the minimum time 45 seconds is harcoded in Android.
This seems to be a NetworkLocationProvider class source code, when it was still in Android core:
http://www.netmite.com/android/mydroid/frameworks/base/location/java/com/android/internal/location/NetworkLocationProvider.java
Look at the variable:
private static final long MIN_TIME_BETWEEN_WIFI_REPORTS = 45 * 1000; // 45 seconds
And the method:
#Override
public void setMinTime(long minTime) {
if (minTime < MIN_TIME_BETWEEN_WIFI_REPORTS) {
mWifiScanFrequency = MIN_TIME_BETWEEN_WIFI_REPORTS;
} else {
mWifiScanFrequency = minTime;
}
super.setMinTime(minTime);
}
Now NetworkLocationProvider is out of the Android core, you can find it in NetworkLocation.apk in /system/app
You can find an explanation of why is out of the core here:
https://groups.google.com/forum/?fromgroups=#!topic/android-platform/10Yr0r2myGA
But 45 seconds min time seems to still be there.
Look at this NetworkProvider decompilation:
http://android.fjfalcon.com/xt720/miui-trans/apk-decompiled/NetworkLocation/smali/com/google/android/location/NetworkLocationProvider.smali
.line 149
const-wide/32 v4, 0xafc8
iput-wide v4, p0, Lcom/google/android/location/NetworkLocationProvider;->mWifiScanFrequency:J
As you might guess if you convert 0xafc8 to decimal you get 45000 milliseconds
I haven't found an explanation of why 45 seconds. I suppose there will be reasons like avoiding service overloading or other uses they don't want.
In fact, there is a 100 request courtesy limit to Geolocation API:
https://developers.google.com/maps/documentation/business/geolocation/#usage_limits
But they don't seem to respect this rule in Google Maps app. If you open it and you only active network location you can notice that yout location is updated much more frequently than 45 seconds.
I noticed this line suspiciously frequent (33 times a second) in logcat when Google Maps is open:
02-20 17:12:08.204: V/LocationManagerService(1733): getAllProviders
I guess Google Maps is also calling removeUpdates() and requestLocationUpdates() again to obtain a new position.
So I think there is no fix and this is the best you can do if you want to get network locations over one in 45 seconds.

You can set the minTime to any value. However, you will only get an update once a new location is available. The network only updates every 45 sec or so on every phone I own. This seems to be a limitation of the Network Provider. If you want more frequent updates use the GPS provider. Depending on the GPS hardware you should get a maximum update rate around 4Hz.

I was having a similar issue. I put a call to locationManager.requestSingleUpdate() at the end of onLocationChanged() and it forced back to back updates. You could set a delay command then execute requestSingleUpdate, making sure to register the containing locationListener.
I was trying to create a GPS clock but the updates were inconsistent updating anywhere from 1-5 seconds or so. but it might work for another application.

Android requestLocationUpdates when phone idle

I'd like to track my Location every minute. For that I use a locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 60000, 0, pll);
Here is the log when my phone is idle.
Date Latitude Longitude Accuracy
07:45:35 51.362402459999996 - 6.2174867399999995 (75.0)
07:46:35 51.362402459999996 - 6.2174867399999995 (75.0)
07:47:35 51.362402459999996 - 6.2174867399999995 (75.0)
...
07:50:35 51.362402459999996 - 6.2174867399999995 (75.0) # I'm further than 75m away from my home at that time
I've indeed a new location every minute but it is exactly the same. Just the time is updated. The position is not updated (maybe normal when I don't move enough) but I find it strange that the coordinates are exactly the same. Also as I don't have wireless activated, it should locate me accordingly to the CellId (with an accuracy of ~1000m), here I still have an accuracy of 75.0. It seems, it is the last location recorded using wireless networks.
Any idea how can I record the real last location (even with low accuracy) ?
public void onLocationChanged(Location location) {
System.out.println(new Date(location.getTime())+" "
+location.getLatitude()+" - "+location.getLongitude()+" ("+location.getAccuracy()+")");
callback.addEntry(location);
}

Hey use GPS_PROVIDER instead of NETWORK_PROVIDER as per below code
locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 60000, 0, pll);
NETWORK_PROVIDER will give you only fix tower location and gps will give you exact changing location

You have got nearest GSM tower coordinates.

It seems there is no way to force to compute the position using the LocationManager with the celltower only when there is no wireless connexion.
Maybe another way would be to use the method mentioned in the thread Poor Man GPS : manually compute the position knowing the CellId.
Pseudo code :
onLocationChanged(new_location)
if isConnected()
record(new_location)
else
cell_location = poorManGPS()
record(cell_location)
end
The problem is of course that I cannot query the cell-id database with no internet connection. I see several solutions :
Store the current (and previous) cell id when I have internet and hope I'll stay in this one when I won't have internet
Use the cell id database on the phone (but I think root privileges needed)
Store the cell id for further localization

locationListener is only called once when requested in a Service

I have written a small app, that has a Activity to control and display
data, and a Service that Gets data from the GPS and send it to the
Activity.
Reason for this is that I like this to run even after the Activity is
exited..
I did a work around where I in the end of my Location Listener remove
the listener and redefined it..
lm.removeUpdates(locationListener);
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, iGPSMovement, locationListener);
But It is not nice and now it fails on my HTC desire Z..
Has someoen encountered this?
What is the work around?
I have written a small App (One activity) that do not uses a Service and that
works fine with the requestLocationChange only called at onCreate..
Please help
Kim

Not sure this matters anymore, but the reason you had to set your distance to 0 was that this is the MINIMUM distance the unit must move in order for the thread to fire. So if the phone was sitting on your desk and was not moved at least X distance from the spot it occupied when the program began, you would not get an update. By setting it to 0 you are forcing the program to update at your minimum time interval regardless of distance moved. I'm pretty sure it works only as long as both minimum conditions are satisfied. I.e. it's been more than 5 seconds and you've moved more the 10 meters.

OK so I tried to rewrite a super simple Service and Activity and using a broatcast reciever and that worked like a charme..
So I converts my app and it is still not working... But I then found that the Meters movement HAS to be 0 for the request to work on my Desire.. Is that odd or what? Anyway that solved my issue..
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0, locationListener);
Is what I ended up with and that seams to fix everything regardless of how I communicate to between service and Activity..

requestLocationUpdates interval in Android

I try to get the correct speed in updates for the function onLocationChanged, this is my class:
public class LocationService extends Service implements LocationListener {
Putting the minTime on 6000 does not help, it wil keep updating constantly, what am i doing wrong?
public void requestLocationUpdates (String provider, long minTime, float minDistance, LocationListener listener, Looper looper) {
Greetings

The minTime is just a hint for the LocationProvider, and it doesn't mean that your location listener will be called once every 6 seconds. You will receive more location updates, and its up to your code to pick the most accurate one.
Monitor the GPS icon on your phone. A call to requestLocationUpdates will trigger the GPS to pinpoint your location, and it will send one or more location updates to the locationlistener if it's able to get a fix. (At this point, your GPS icon should be animated as it searches for a location).
During that time, your locationlistener may receive several location updates. Your code can go and pick the most accurate location, and process only that one.
After the GPS has sent the location update(s) to your listener, there should be a period of inactivity. (your GPS icon should disappear for a couple of seconds). This period of inactivity should correspond with your minTime. The status of the GPS will also change, as it will be put into TEMPORARILY_UNAVAILABLE.
After that, the same process is repeated. (The GPS becomes AVAILABLE, and you'll again receive one or more location updates).
Also take into account, if the GPS is unable to get a location fix, the GPS icon will remain active for more then 6 seconds, but you won't be receiving location updates.
You can also monitor the status of your GPS provider through your listener, via the following method :
public void onStatusChanged(String provider, int status, Bundle extras) {}
The status is one of the following constants defined on android.location.LocationProvider
public static final int OUT_OF_SERVICE = 0;
public static final int TEMPORARILY_UNAVAILABLE = 1;
public static final int AVAILABLE = 2;
Have a look at Understanding the LocationListener in Android for an example on the minTime behavior, and a scenario (including some logging) to help you understand what's going on.
Keep in mind that tweaking the minTime and minDistance parameters on the LocationManager, and acting upon GPS status updates will allow you to fine-tune your user location development.

6000 in milliseconds equals 6 seconds, and it may seems like continiously updating.
From Android dev guide "minTime under 60000ms are not recommended"
Maybe it is worth to increase it to 60000ms