Location with GPS is not always correct and crashes without connection

Question

I've got a problem when I try to find my current location that I need to display the weather. This is the method I use to find my location:

protected class GetPosition extends AsyncTask<String, Void, String> {
        protected String doInBackground(String... params) {

            List<Address> addresses = null;
            try {
                LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
                Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                double longitude = location.getLongitude();
                double latitude = location.getLatitude();
                Geocoder gcd = new Geocoder(getApplicationContext(), Locale.getDefault());
                addresses = gcd.getFromLocation(latitude, longitude, 1);
                if (addresses.size() > 0) return addresses.get(0).getLocality();
            } catch (Exception e) {
                return "Nessuna posizione disponibile";
            }
            return addresses.get(0).getLocality();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            citylb.setText(s);
            getWeather((String) citylb.getText());


        }
    }

and this is the way I check if there is some connection like data or wifi:

public boolean isOnline() {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null || netInfo.isConnectedOrConnecting()) { //Here crashes
            return true;
        }
        return false;
    }
private void getWeather(String location) {
        if (isOnline()) {
            Log.d("YWeatherGetter4a", "onCreate");
            YahooWeatherUtils yahooWeatherUtils = YahooWeatherUtils.getInstance();
            yahooWeatherUtils.queryYahooWeather(getApplicationContext(), location, this);
        } else
            Toast.makeText(getApplicationContext(), "Sorry, no connection available", Toast.LENGTH_SHORT).show();

    }

I've got two problems:

1) If I am without any connection, the application crashes at the line if (netInfo != null || netInfo.isConnectedOrConnecting()), netInfo seems null.

2) The location isn't always correct. Frequently it returns an "old" location and not current. Example: if two hours ago, I was at Rome and now in Milano, it shows me Rome. I can't understand where I'm wrong.

About first problem I tried also writing: if (netInfo != null && netInfo.isConnectedOrConnecting()) with the && instead ||. Not crashes but it finds the location only in wifi and not in data connection. How can I solve these problems? Thanks

score 2 · Answer 1 · answered Apr 09 '14 at 09:11

2

When you are using the getLastKnowLocation method, you are getting the last location that was returned by the given provider. If that provider hasn't been used for a while by any other application, the location returned will be old. In such a case, you should use one of the requestLocationUpdates (http://developer.android.com/reference/android/location/LocationManager.html) method family, the one that suits your needs.

Regarding the crash, you should include the following permission on your manifest:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

answered Apr 09 '14 at 09:11

akalipetis

938
1
7
14

The mainifest it's ok. There is already that permission.. So i can't understand the problem. About location, so what you exactly suggest? How can i change the code to have the current location in accurately way? – Atlas91 Apr 09 '14 at 09:17
For the location, I would suggest to use the Fused Location Provider, available with the Google Play Services SDK (http://developer.android.com/google/play-services/location.html). You can read more on how to implement it here: http://developer.android.com/training/location/retrieve-current.html . For the crash, a stack trace would definitely help. – akalipetis Apr 09 '14 at 09:21

Roman Black · Accepted Answer · 2014-04-09T09:54:39.700

2

You are using getLastKnownLocation() to get location but You doesn't use

locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 2000, 0, null);

The second parameter is delation between updates in milliseconds. The fourth parameter is listener, you can use it to update locations vithout any async threads, for example:

...
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 2000, 0, this);
...

public void onLocationChanged(Location arg0) {
    if (arg0 != null){
        double longitude = arg0.getLongitude();
        double latitude = arg0.getLatitude();

        ...
    }
}

LocationManager.NETWORK_PROVIDER is no good way to recieve location because it using location recieved by another location services when device was near wifi router. If location was not recieved near some router by another services in some reasons it will not provide you correct location.
There is a bug in some devices (for example Sony) when mobile data turned on and networkInfo == null. Some times it solves getting needed networkInfo directly. For Exmple:

android.net.NetworkInfo wifi = cm.getNetworkInfo(ConnectivityManager.TYPE_WIFI); android.net.NetworkInfo mobile = cm.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

Example:

public class MyActivity extends Activity implements LocationListener
{

    ...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ...

        locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

        ... // do something

        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 2000, // every 2 seconds
                0, this);
    }

    ...

    public void onLocationChanged(Location arg0) {
        if (arg0 != null){
            double longitude = arg0.getLongitude();
            double latitude = arg0.getLatitude();

            ...
        }
    }

}

edited Apr 09 '14 at 09:54

answered Apr 09 '14 at 09:31

Roman Black

3,501
1
22
31

Thank you for the suggest.. i will try also your code. :) – Atlas91 Apr 09 '14 at 09:38
but do you think is possible integrate this part of code with mine? – Atlas91 Apr 09 '14 at 09:39
So, just only insert in my onCreate() method `getLastKnownLocation` and `requestLocationUpdates` and then create the `onLocationChanged` method..mmh.ok.. and then automatically will update the latidute/longitude in the other mine methods? – Atlas91 Apr 09 '14 at 10:00
Yes, location updates will refresh getLastKnownLocation results, also you can store onLocationChanger param in some variable and use it when you need without getLastKnownLocation method. – Roman Black Apr 09 '14 at 10:07
Also you can process variables inside onLocationChanged implementation. – Roman Black Apr 09 '14 at 10:08
@RomanBlack I am following this code and do I need to create `LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);` before calling `locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 2000, // every 2 seconds 0, this);` – Yogesh D Apr 09 '14 at 11:03
1

@y. dixit Yes, you are Right. You can use GPS_PROVIDER to recieve perfect location updates. For example: requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 0, this); – Roman Black Apr 09 '14 at 11:10
1

@y. dixit Also you need to add permissions – Roman Black Apr 09 '14 at 11:11
@RomanBlack i get an error `onLocationChanged()` . Sometime it crahses. Here there is the log http://stackoverflow.com/questions/22975503/crash-onlocationchanged-android/22976524?noredirect=1#22976524 if you can help me please. – Atlas91 Apr 10 '14 at 09:04

score 1 · Answer 3 · edited May 23 '17 at 11:57

1)

Already answered but here is my isOnline() implementation anyways:

public Boolean isOnline() {
    ConnectivityManager cm = (ConnectivityManager) context
            .getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo ni = cm.getActiveNetworkInfo();
    if (ni != null && ni.isConnected())
        return true;

    return false;
}

2)

Also already answered - it is the expected behavior.

However, I have implemented some code that fires the GPS and issues a callback as soon as a valid new position is found (GPS-firstfix). You can find the code in my answer to this question: Location servise GPS Force closed

When the valid position has been obtained you can simply stop the GPS immediately after.

score 0 · Answer 4 · answered Apr 09 '14 at 09:15

The if condition should be

if(netInfo != null && netInfo.isConnectedOrConnecting())

The way || operator works is if the first condition is false, it will test the second condition as well.

getLastKnownLocation will provide you the last updated location, instead of fetching the current location. The location might have been requested by another application, giving you correct results sometimes. If you need updated location, you need to register a LocationListener (refer docs)

Location with GPS is not always correct and crashes without connection

4 Answers4