问题
I am using simple location manager object to get lastKnownLocation() of device but getting null object in return can any one tell me why ?
Code :
public Location getLocation() {
LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
if (locationManager != null) {
Location lastKnownLocationGPS = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (lastKnownLocationGPS != null) {
return lastKnownLocationGPS;
} else {
Location loc = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
System.out.println("1::"+loc);----getting null over here
System.out.println("2::"+loc.getLatitude());
return loc;
}
} else {
return null;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.location);
getLocation();-----calling service
}
permissions given :
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
so is anything missing to set up? I have checked my location service is on in device please give some links for working examples
回答1:
Silly thing as answer to this ...I restarted my device ...and it worked...Please ensure that your service for location are enabled and working properly
回答2:
The thing i use to get Location with Name of the place is
GPSTracker gpsTracker = new GPSTracker(CameraActivity.this);
String stringLatitude = "", stringLongitude = "", nameOfLocation="";
if (gpsTracker.canGetLocation()) {
stringLatitude = String.valueOf(gpsTracker.latitude);
stringLongitude = String.valueOf(gpsTracker.longitude);
nameOfLocation = ConvertPointToLocation(stringLatitude,stringLongitude);
}
public String ConvertPointToLocation(String Latitude, String Longitude) {
String address = "";
Geocoder geoCoder = new Geocoder(getBaseContext(), Locale.getDefault());
try {
List<Address> addresses = geoCoder.getFromLocation(
Float.parseFloat(Latitude), Float.parseFloat(Longitude), 1);
if (addresses.size() > 0) {
for (int index = 0; index < addresses.get(0)
.getMaxAddressLineIndex(); index++)
address += addresses.get(0).getAddressLine(index) + " ";
}
} catch (IOException e) {
e.printStackTrace();
}
return address;
}
GPSTracker.java
package in.appology.lss;
import java.io.IOException;
import java.util.List;
import java.util.Locale;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;
/**
* Create this Class from tutorial :
* http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial
*
* For Geocoder read this :
* http://stackoverflow.com/questions/472313/android-reverse
* -geocoding-getfromlocation
*
*/
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS Status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
boolean canGetLocation = false;
Location location;
double latitude;
double longitude;
// The minimum distance to change updates in metters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10
// metters
// The minimum time beetwen updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
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;
// First get location from Network Provider
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);
updateGPSCoordinates();
}
}
// 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);
updateGPSCoordinates();
}
}
}
}
} catch (Exception e) {
// e.printStackTrace();
Log.e("Error : Location",
"Impossible to connect to LocationManager", e);
}
return location;
}
public void updateGPSCoordinates() {
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
/**
* 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;
}
/**
* Function to get longitude
*/
public double getLongitude() {
if (location != null) {
longitude = location.getLongitude();
}
return longitude;
}
/**
* Function to check GPS/wifi enabled
*/
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
*/
public void showSettingsAlert() {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS");
// Setting Dialog Message
alertDialog
.setMessage("Please enable location in settings for accurate results!");
// On Pressing Setting button
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
@Override
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() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
alertDialog.show();
}
/**
* Get list of address by latitude and longitude
*
* @return null or List<Address>
*/
public List<Address> getGeocoderAddress(Context context) {
if (location != null) {
Geocoder geocoder = new Geocoder(context, Locale.ENGLISH);
try {
List<Address> addresses = geocoder.getFromLocation(latitude,
longitude, 1);
return addresses;
} catch (IOException e) {
// e.printStackTrace();
Log.e("Error : Geocoder", "Impossible to connect to Geocoder",
e);
}
}
return null;
}
/**
* Try to get AddressLine
*
* @return null or addressLine
*/
public String getAddressLine(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String addressLine = address.getAddressLine(0);
return addressLine;
} else {
return null;
}
}
/**
* Try to get Locality
*
* @return null or locality
*/
public String getLocality(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String locality = address.getLocality();
return locality;
} else {
return null;
}
}
/**
* Try to get Postal Code
*
* @return null or postalCode
*/
public String getPostalCode(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String postalCode = address.getPostalCode();
return postalCode;
} else {
return null;
}
}
/**
* Try to get CountryName
*
* @return null or postalCode
*/
public String getCountryName(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String countryName = address.getCountryName();
return countryName;
} else {
return null;
}
}
@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 intent) {
return null;
}
}
回答3:
// Get the location from the given provider
Location location = locationManager
.getLastKnownLocation(provider);
locationManager.requestLocationUpdates(provider, 1000, 1, this);
回答4:
To fetch the last location, you can refer to the above provided answers where you can use Location Manager or FusedLocationClient
But You can also make use of LocationServices which is faster than other approaches.
So let me provide a brief working :
1) Add these two dependencies in your gradle app file
implementation 'com.google.android.gms:play-services-maps:17.0.0'
implementation 'com.google.android.gms:play-services-location:17.0.0'
2) Add these permissions in the manifest file outside applicationtag
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
3) Declare variable outside onCreate
private FusedLocationProviderClient fusedLocationClient;
4) Now inside onCreate :
fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
fetchLastLocation();
5) No define fetchLastLocation method
private void fetchLastLocation() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// Activity#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for Activity#requestPermissions for more details.
// Toast.makeText(MainActivity.this, "Permission not granted, Kindly allow permission", Toast.LENGTH_LONG).show();
showPermissionAlert();
return;
}
}
fusedLocationClient.getLastLocation()
.addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location location) {
// Got last known location. In some rare situations this can be null.
if (location != null) {
// Logic to handle location object
Log.e("LAST LOCATION: ", location.toString());
}
}
});
}
6) Now define other two method for permission request
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
switch (requestCode) {
case 123: {
// If request is cancelled, the result arrays are empty.
if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
// permission was denied, show alert to explain permission
showPermissionAlert();
}else{
//permission is granted now start a background service
if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
fetchLastLocation();
}
}
}
}
}
private void showPermissionAlert(){
if (ActivityCompat.checkSelfPermission(MainHomeActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(MainHomeActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainHomeActivity.this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 123);
}
}
Note : Replace context with your class context
You will get your location in Logcat.
Hope this will hope you or somebody else
回答5:
Below is the way I am trying to get last location.
private void setUpMap(){
//Location location = mMap.getMyLocation();
mMap.setMyLocationEnabled(true);
//mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
@Override
public void onMyLocationChange(Location location) {
mMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude(), location.getLongitude())).title("My Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(location.getLatitude(),location.getLongitude()),10));
mMap.setOnMyLocationChangeListener(null);
}
});
}
回答6:
before get last location, maybe you want get current location, check if null or have. if not set last loccation if you want use FusedLocationProviderClient and before use it adding this:
implementation 'com.google.android.gms:play-services-location:16.0.0'
on your build.gradle(Module: app), and call method zoomMyCuurentLocation() whean activity create.
private void zoomMyCuurentLocation() {
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION);
}
Location location = locationManager.getLastKnownLocation(locationManager.getBestProvider(criteria, false));
if (location != null) {
double lat = location.getLatitude();
double longi = location.getLongitude();
LatLng latLng = new LatLng(lat,longi);
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 14.f));
Log.d(TAG, "zoomMyCuurentLocation: location not null");
} else {
setMyLastLocation();
}
}
private void setMyLastLocation() {
Log.d(TAG, "setMyLastLocation: excecute, and get last location");
FusedLocationProviderClient fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return;
}
fusedLocationClient.getLastLocation().addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location location) {
if (location != null){
double lat = location.getLatitude();
double longi = location.getLongitude();
LatLng latLng = new LatLng(lat,longi);
Log.d(TAG, "MyLastLocation coordinat :"+latLng);
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 14.f));
}
}
});
}
来源：https://stackoverflow.com/questions/25483352/how-to-get-last-known-location-for-location-manager-in-android