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 LocationClient.getLastLocation() returns old and inaccurate location with a new timestamp

I've been using the fused location provider since its release and I am pretty happy with it (way better than the old system). But I ran into a peculiar problem when using geofencing in combination with LocationClient.lastKnownLocation(). The setup is as follows:
I drop several geofences around some home location (with increasing ranges). When I get the intent that a fence is crossed I retrieve the last known location from LocationClient and work with it. Apart from than I also registered for regular location updates with update mode PRIORITY_BALANCED_POWER_ACCURACY.
Most of the times this works perfectly fine, but sometimes this happens:
Time 000 s - (Lat,Lon,Accuracy) = (48.127316,11.5855167,683.0)
Time 120 s - (Lat,Lon,Accuracy) = (48.1260497,11.5731745,31.823)
Time 300 s - (Lat,Lon,Accuracy) = (48.1217455,11.5641666,143.81)
Time 420 s - (Lat,Lon,Accuracy) = (48.1189942,11.559061,36.0)
Time 600s - (Lat,Lon,Accuracy) = (48.127316,11.5855167,683.0)
Notice that all these locations are retrieved by getLastKnownLocation(). What seems fishy here is that the first and the last location are identical (even in the other attributes), to be more specific:
* intent at time 0: *
component: ComponentInfo{package.Class}
key [location]: Location[mProvider=fused,mTime=1373524391934,mLatitude=48.127316,mLongitude=11.5855167,mHasAltitude=false,mAltitude=0.0,mHasSpeed=false,mSpeed=0.0,mHasBearing=false,mBearing=0.0,mHasAccuracy=true,mAccuracy=683.0,mExtras=Bundle[mParcelledData.dataSize=352]]
* intent at time 600: *
component: ComponentInfo{package.Class}
key [location]: Location[mProvider=fused,mTime=1373524994871,mLatitude=48.127316,mLongitude=11.5855167,mHasAltitude=false,mAltitude=0.0,mHasSpeed=false,mSpeed=0.0,mHasBearing=false,mBearing=0.0,mHasAccuracy=true,mAccuracy=683.0,mExtras=Bundle[mParcelledData.dataSize=352]]
* note the ~600 s difference in the timestamp *
I do not understand how this can happen, as there have been locations in between that were both more recent and more accurate. Also the new timestamp on an old location makes me curious... apparently similar things happened when using the old API, but this new location provider is just called fused, so I can not distinguish GPS from WPS from sensors... If it is the cell tower switching problem (outlined in the linked question concerning the old API) then why would the phone connect to a "far away" tower if it has seen closer towers?
Why is this happening?

The first and last points were gotten using cell triangulation. The error/accuracy is typical of cell-based location, and it looks like the Google power saving logic decided that switching to cell would be OK, even as you say its recent history included points much closer.

Aw, SHUCKS! I got this too today... And I moved to the new Google Play Services location precisely to AVOID this... And I was so thrilled up until just now when I got it too. You may or may not know that the old one had these kind of problems, and it was a pain.
There are lots of threads regarding this, including one of my own :(
Why is locationmanager returning old location fixes with new gettime-timestamp?
I guess the only thing to do is avoid using cached location...

Instead of polling, one can work around one or more sources of inaccuracy using this subscription mechanism.
LocationListener locListener = new LocationListener() {
#Override
public void onLocationChanged(Location location) {
if (location == null)
return;
// process these:
// location.getLatitude();
// location.getLongitude();
// location.getAccuracy();
...
}
...
}
((LocationManager) getSystemService(Context.LOCATION_SERVICE)
.requestLocationUpdates(LocationManager.GPS_PROVIDER,
minTimeMilliSec,
minDistanceMeters,
locListener));

How do I stop the user waiting for a long time to get a location fix?

I am building a GPS Android application which gets the nearest places based on the user's current location.
This is what my application does:
Check if GPS or Network is available
If neither is available then don't do anything. Else, we first check for GPS if it's there, if not then we check for Network.
After using one of them, we get the current location and then send it off to the server.
Once we retrieve data from the server and update the UI, we stop listening for further location updates. Once is enough, until they press the refresh button which starts this again.
What I hope to do:
If GPS or network fails to retrieve a location, for example, 2 minutes, then we switch providers. We don't want the user to wait too long.
It would also be nice to be able to use both providers and then get the most accurate from that. I've taken a look at http://developer.android.com/guide/topics/location/strategies.html and I saw the isBetterLocation method. How would I integrate this method in my application? I'm having trouble understand how, where and when it should be called. I assume that the isBetterLocation() requires me to call both Network and GPS at the same time. It would be nice for my application to listen to both for accuracy. How do I do this? What if one of them isn't available?
Here's parts of my code:
if(!GPSEnabled && !networkEnabled)
{
Toast.makeText(this, "Error: This application requires a GPS or network connection",
Toast.LENGTH_SHORT).show();
}
else
{
if(GPSEnabled)
{
locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}
else if(networkEnabled)
{
System.out.println("Getting updates from network provider");
locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
}
}
This is the onLocationChanged method. I get the lat/lng values and then send them off to my server and then do appropriate stuff with it.
public void onLocationChanged(Location location)
{
//Get coordinates
double lat = (location.getLatitude());
double lng = (location.getLongitude());
Log.d("MainActivity", "got location: " + lat + ": " + lng);
//get nearest locations
new GetLocations().execute(SharedVariables.root + SharedVariables.locationsController + SharedVariables.getNearestMethod + lat + "/" + lng);
// Zoom in, animating the camera after the markers have been placed
map.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(lat, lng), 10));
System.out.println("lat = " + lat + ", lng = " + lng);
//Stop listening for updates. We only want to do this once.
locManager.removeUpdates(this);
}

Either using GPS or the network, you can't drastically reduce the eventual waiting time to get your location.
Both of these location methods have their disadvantages and advantages:
GPS usually takes a longer time to know your location, because finding and calibrating GPS satellites is a tremendous task (finding at least 3 correctly-aligned satellites is required). On top of that, add the eventual obstructing objects/environment blocking the signals. Unless you enable GPS before/when your app starts, wait is mandatory. On the other side, you get a fine-grained location.
If you only need a rough location, using the network is a solution: it returns data in a few seconds. However the precision of the location varies depending on the available/used networks; I don't have any practical examples, but I guess the precision can greatly vary. GPS will ALWAYS have a better-grained location than network.
Understand there is no predefined choice. Anything depends on what your app does with this data.
Use GPS if available, while making the location request to the network, and fall back to network if there is no GPS device. Then take either:
the first-coming result if you just need a location
the preferred result if you want the most precise data
If GPS or network fails to retrieve a location, for example, 2 minutes, then we switch providers. We don't want the user to wait too long.
In both cases, do not make a fallback timer: you'll just lengthen the waiting time in the case where the first provider fails; so do both request at the same time, unless the android API does not permit asynchronous location requests.

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