Develop Reference

How can I cat latitude and longitude of Android device?

So I'm making this app which finds restaurants near you, fetching information from a food-delivery app, using JSoup library.
The only problem with it is that sometimes the latitude and the longitude are getting null value.
Situations in which my application is working:
-turning on GPS and the waiting at least 1-2 minutes;
-opening google maps, closing it, and then returning to the application;
So the main problem: I can't fetch the location right after I enable it and hit the 'Find restaurants' button, I need to wait 1-2 minutes after enabling location, then it's working.
private TextView result;
private FusedLocationProviderClient client;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
requestPermission();
client = LocationServices.getFusedLocationProviderClient(this);
getBtn = findViewById(R.id.getRestaurants);
result = findViewById(R.id.restaurantsList);
getBtn.setOnClickListener(this);
}
private void requestPermission(){
ActivityCompat.requestPermissions(this, new String[]{ACCESS_FINE_LOCATION}, 1 );
}
public void onClick(View v) {
if (ActivityCompat.checkSelfPermission(MainActivity.this, ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}
client.getLastLocation().addOnSuccessListener(MainActivity.this, new OnSuccessListener<Location>() {
#Override
public void onSuccess(Location location) {
result.setText("Getting location...");
if(location != null){
double latitude = getLat(location);
double longitude = getLng(location);
result.setText("Finding restaurants near you...");
getWebsite(latitude, longitude);
}else{
result.setText("Couldn't fetch location!");
}
}
});

Here is a good way to implement the FusedLocationProvider in Kotlin (you might adapt to Java or use Java and Kotlin side by side) :
private fun startLoc() {
fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
try {
fusedLocationClient.lastLocation
.addOnSuccessListener { location: Location? ->
//showDialog(this#MapsActivity, TAG, "last know loc = ${location?.latitude} + ${location?.longitude}")
if (location != null){
lastKnowLoc = LatLng(location.latitude, location.longitude)
addMarkerToLocation(lastKnowLoc)
}
}
val locationRequest = LocationRequest()
locationRequest.interval = 10000
locationRequest.fastestInterval = 10000
locationRequest.priority = LocationRequest.PRIORITY_HIGH_ACCURACY
locationCallback = object : LocationCallback() {
override fun onLocationResult(locationResult: LocationResult?) {
locationResult ?: return
for (location in locationResult.locations){
//showDialog(this#MapsActivity, "locationResult", "location=${location.latitude};${location.longitude}")
addMarkerToLocation(LatLng(location.latitude, location.longitude))
val speed = location.speed
updateCamera(location.bearing)
}
}
}
fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null)
btnStartLoc.isEnabled = false
btnStopLoc.isEnabled = true
}catch (e:SecurityException){}
}

you must use requestLocationUpdates()
you are using getLastLocation() and when the GPS is off and turned on after the last known location becomes null so you must call requestLocationUpdates()
you can find more information in the below link
https://developer.android.com/training/location/receive-location-updates

android LocationManager last position

i have this code:
if (item.getItemId() == R.id.tempMap) {
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Location location = null;
if(locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)||locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)){
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
provider = locationManager.getBestProvider(criteria, true);
location = locationManager.getLastKnownLocation(provider);
locationManager.requestLocationUpdates(provider, 20000, 1, this);
if (location != null) {
Log.e("PROVIDER SCELTO", provider);
onLocationChanged(location);
Log.e("LATITUDE", String.valueOf(latitude));
Log.e("LONGITUDE", String.valueOf(longitude));
and:
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
latitude = location.getLatitude();
longitude = location.getLongitude();
}
but the last gps point that it return is the last point after i use the "google maps navigator". So, if i not use gm navigator, the latitude and longitude is not updated.
WHY???
Thank you

location fix requires time wait till a good fix is recived this checks the time of the fix and sets location only if the fix is within a time period if you dont check the time of the fix it will provide the last fix recived irespective of when
public void onLocationChanged(Location location) {
Date dd=new Date(location.getTime());
Date ddd=new Date(System.currentTimeMillis()-(1000*60*15));
Log.e("", String.valueOf(location.getTime()+":"+System.currentTimeMillis()+":"+dd+":"+ddd));
if (dd.compareTo(ddd)==1?true:false) {
got=true;
latitude=String.valueOf(location.getLatitude());
longitude=String.valueOf(location.getLongitude());}
}

GPS Tracking Comparison (Android)

I am developing an indoor map app for my college. I have stored the longitude and latitude for each place in the map in the database. The next step is getting the user's location from the GPS and comparing with the database to be able to give the user the name of their location. My problem is with the comparing step - how could I do it? The GPS tracking works perfectly.
The class for the GPS tracking:
public class GPSTracker {
public GPSTracker(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
/**
* Stop using GPS listener
* Calling this function will stop using GPS in your app
* */
public void stopUsingGPS(){
if(locationManager != null){
locationManager.removeUpdates(GPSTracker.this);
}
}
/**
* Function to get latitude
* */
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
* #return boolean
* */
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
#Override
public void onLocationChanged(Location location) {
}
#Override
public void onProviderDisabled(String provider) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
#Override
public IBinder onBind(Intent arg0) {
return null;
}
}
The code to display tracking in MainActivity::
// check if GPS enabled
if(gps.canGetLocation()){
double latitude = gps.getLatitude();
double longitude = gps.getLongitude();
// \n is for new line
Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
} else {
// can't get location
// GPS or Network is not enabled
// Ask user to enable GPS/network in settings
gps.showSettingsAlert();
}

As you told you have already made collection of database in which all the places of you collage Lat and Long. Now any user who is near to canteen of your collage open your app now
app should find the nearest place where user standing right now.
I assuming above requirement of your collage.
For the above requirement the best way is Haversine formula. check this wiki link : Link
and make some R&D on it. Now by using this formula technical flow is like below :
1 : Get user's lat and long using GPS.
2 : Send this GSP Co-ordinates to your php web service where you have implemented Haversin formula. By using this formula you will find the nearest place from you current place from your database.
3 : Now you have nearest place from your existing place.
For use Haversin Formula in php web service please refer this links : Link
Hope you get what you want to do. Please do some R&D on it and I am sure that you will solve it.

You compare two Lat Lon coordinates, where at least one is not perfect because measured by e.g GPS, by calculating the distance in meters inbetween them.
If the distance is lower than a specific threshold, you can consider them as matching.
Android has a method for that distance calculation.

Location returns NULL

I am writing an Android app that returns longitude and latitude, however location holds a Null value.
Please see if you can see why, Its been bugging me all day. Code below:
public class example extends Activity {
public static double latitude;
public static double longitude;
LocationManager lm;
LocationListener ll;
Location location;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.questions);
lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
ll = new MyLocationListener();
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, ll);
//location = lm.getLastKnownLocation(lm.getBestProvider(criteria, true));
Button b = (Button) findViewById(R.id.button2);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
String provider = Settings.Secure.getString(getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
int index1 = provider.indexOf("gps");
if(index1 < 0)
// gps not enabled, call msgbox
showMsgBox("GPS is off", "GPS is off. Turn it on?", "Turn on");
else
areWeThereYet(); }});
}
private void areWeThereYet()
{
if(weAreThere())
{
toastMsg("in correct place");
}
else if(location!=null)
toastMsg("not there yet");
}
private boolean weAreThere() {
location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location!=null)
{
longitude = location.getLongitude();
latitude = location.getLatitude();
toastMsg(latitude + " " + longitude);
return inCorrectPlace(question);
}
else
{
toastMsg("Location not ready yet");
return false;
}
}
private void toastMsg(String msg) {
Toast toast = Toast.makeText(this, msg, 2000);
toast.setGravity(Gravity.BOTTOM, 0, 0);
toast.show();
}
}

If the GPS has not ever gotten a location since the device was booted, the location object will be null. One thing you can do is attempt to get a GPS location and a network location, and check to two to see if either of them are good (or which one is better) and use that location.

If you're using the emulator, then see here for advice on setting up the emulator to provide a location. If you're testing it on your device, it may be because you've never had a gps location on it. Try using the Google maps application before testing your app.

Android requestLocationUpdates without minDistance

I have a need to get the gps location every 20 seconds or so, but ignoring the need to have the user move a certain number of meters, I tried setting the minDistance to zero but still no luck, its only when I manually send the location using the location control from DDMS that this gets activated and the location gets updated.
Note - This is run and tested from the emulator and not a real device, for now at least
private final static Long INTERVAL_TIME = new Long(20);
private final static Float METERS_MOVED_VALUE = 0f;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.journey);
Bundle dataBundle = this.getIntent().getExtras();
try {
driverData = new JSONObject(dataBundle.getString("driverData"));
} catch (JSONException e) {
e.printStackTrace();
}
//Set the UI elements into variables
journeyDescription = (TextView)findViewById(R.id.journeyDescription);
journeyText = (TextView)findViewById(R.id.journeyText);
confirmButton = (Button)findViewById(R.id.btnCheck);
//Acquire a reference to the system Location Manager
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
try{
//Until requests are found keep broadcasting the drivers location and checking for requests
if(!foundRequest){
updateDriverLocationAndCheckForNewDriverRequests(location);
}
//Always keep updating the drivers location
Double latitude = location.getLatitude()*1E6;
Double longitude = location.getLongitude()*1E6;
geoPoint = new GeoPoint(latitude.intValue(), longitude.intValue());
}catch(JSONException e){
Toast.makeText(JourneyActivity.this, "An unexpected error occurred", Toast.LENGTH_LONG).show();
e.printStackTrace();
}
}
public void onStatusChanged(String provider, int status, Bundle extras) {}
public void onProviderEnabled(String provider) {}
public void onProviderDisabled(String provider) {}
};
//Register the listener with the Location Manager to receive location updates can be either gps provider
if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, INTERVAL_TIME, METERS_MOVED_VALUE, locationListener);
}
else {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, INTERVAL_TIME, METERS_MOVED_VALUE, locationListener);
}
}
Here is the related code fragment, any ideas on how to trigger the listener without having the user move or me having to send information from the DDMS Location Controls woild be greatly appreciated
Regards,
Milinda

requestLocationUpdates takes milliseconds, not seconds.
You should change:
private final static Long INTERVAL_TIME = new Long(20);
private final static Float METERS_MOVED_VALUE = 0f;
to:
private final static int INTERVAL_TIME_SECONDS = 20 * 1000; // 20 seconds
private final static float INTERVAL_DISTANCE_METERS = 0f; // 0 meters

As far as testing on the emulator goes. I think your limited to manually pushing GPS locations or creating a few automated simulators:
Testing GPS in Android