Im new new to xamarin Android....I have an app which shows users current latitude and longitude which seems to be working...
Now, from latitude and longitude, Im trying to get address using API Geocoder. Im passing proper latitude and longitude but its not giving me any address though I cant see any error.
Following is my code :-
async Task<Address> ReverseGeocodeCurrentLocationAsync(double Latitude, double Longitude)
{
Geocoder geocoder = new Geocoder(this);
IList<Address> addressList = await
geocoder.GetFromLocationAsync(Latitude, Longitude, 10); // ???????? its not wrking....Here, Im properly able to pass latitude and longitude still issue getting adress.
IList<Address> testaddresses = await geocoder.GetFromLocationAsync(42.37419, -71.120639, 1); // ???????? i tried both sync and async method but not wrking....
Address address = addressList.FirstOrDefault();
return address;
}
// calling part
Address address = await ReverseGeocodeCurrentLocationAsync(location.Latitude, location.Longitude);
Also, you can find source code at :https://github.com/4pawan/XamarinDroidSample
Please let me know what I'm doing wrong and how to rectify ?
Regards,
Pawan
Always check if a Geocoder is available as this requires a background service to be available and it is possible that it is not available as it not included in the base Android framework:
Geocoder.IsPresent
Register your app in Google's Dev API Console
Add your Google Map API Key your your app's manifest
If you are using Google's fused location provider (via Google Play services) and need Geo-Coding, make sure your app has ACCESS_FINE_LOCATION permission:
Network connectivity is required to receive an address list from the Geocoder service.
Depending upon your device's Geocoder service, it can take more then one request before "Google" or your device's Geocoder service replies with a list of addresses.
Do not spam the service, you will get throttled, use an increasing time delay between requests.
Note: A extremely frequent response is:
`Timed out waiting for response from server`
In this case, wait a short peroid time and retry.
But there are a number of other errors that include, no addresses found, invalid lat/log, geocoder not currently available, etc...
Note: I normally use ReactiveUI to wrap the failures, retries and continuation, but here is a simple example:
Basic Geocode method (much like yours):
async Task<Address> ReverseGeocodeLocationAsync(Location location)
{
try
{
var geocoder = new Geocoder(this);
IList<Address> addressList = await geocoder.GetFromLocationAsync(location.Latitude, location.Longitude, 3);
Address address = addressList.FirstOrDefault();
return address;
}
catch (Exception e)
{
Log.Error(TAG, e.Message);
}
return null;
}
The Retry:
int retry = 0;
Address address = null;
do
{
address = await ReverseGeocodeLocationAsync(_currentLocation);
if (address != null)
{
Log.Info(TAG, $"Address found: {address.ToString()}");
// Do something with the address(es)
break;
}
retry++;
Log.Warn(TAG, $"No addresses returned...., retrying in {retry * 2} secs");
await Task.Delay(retry * 2000);
} while (retry < 10);
This is how you get the full address using Latitude and Longitude in Xmarin android
using Android.App;
using Android.OS;
using Android.Support.V7.App;
using Android.Runtime;
using Android.Widget;
using Xamarin.Essentials;
using System;
using System.Threading.Tasks;
using Android.Content.PM;
using System.Collections.Generic;
using System.Linq;
namespace GeoLocation
{
[Activity(Label = "#string/app_name", Theme = "#style/AppTheme", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
TextView txtnumber;
protected async override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
// Set our view from the "main" layout resource
SetContentView(Resource.Layout.activity_main);
txtnumber = FindViewById<TextView>(Resource.Id.textView1);
double GmapLat = 0;
double GmapLong = 0;
try
{
var request = new GeolocationRequest(GeolocationAccuracy.Medium, TimeSpan.FromSeconds(10));
var location = await Geolocation.GetLocationAsync(request);
txtnumber.Text = "finish get geolocation";
GmapLat = location.Latitude;
GmapLat=location.Longitude;
if (location != null)
{
var placemarks = await Geocoding.GetPlacemarksAsync(location.Latitude, location.Longitude);
var placemark = placemarks?.FirstOrDefault();
if (placemark != null)
{
// Combine those string to built full address... placemark.AdminArea ,placemark.CountryCode , placemark.Locality , placemark.SubAdminArea , placemark.SubLocality , placemark.PostalCode
string GeoCountryName = placemark.CountryName;
}
txtnumber.Text = "GPS: Latitude " + location.Latitude + " Longitude " + location.Longitude;
}
}
catch (FeatureNotSupportedException fnsEx)
{
// Handle not supported on device exception
}
catch (FeatureNotEnabledException fneEx)
{
// Handle not enabled on device exception
}
catch (PermissionException pEx)
{
// Handle permission exception
}
catch (Exception ex)
{
// Unable to get location
txtnumber.Text = ex.Message.ToString();
}
}
}
}
Related
I am trying to get locations from the string which is being searched. But, in some cases addressList is returning size 0(i.e. H.M. education centre, kolkata). I don't have latitude and longitude to search the place. Needed help.
String addressString = (String) adapterView.getItemAtPosition(position);
String addressString1 = (String) adapterView.getItemAtPosition(position);
List<Address> addressList = null;
Address address = null;
if (!TextUtils.isEmpty(addressString))
{
Geocoder geocoder = new Geocoder(this, Locale.getDefault());
try
{
addressList = geocoder.getFromLocationName(addressString, 1);
}
catch (IOException e)
{
e.printStackTrace();
addressString = addressString1;
}
//noinspection ConstantConditions
if(addressList != null && addressList.size() > 0)
{
address = addressList.get(0);
}
}
As alternative you can use Geocoding API or Places API web services. I checked your address 'H.M. education centre, kolkata' in Geocoding API web service request and figured out that coordinate can be found. Have a look at Geocoder tool with this address:
https://google-developers.appspot.com/maps/documentation/utils/geocoder/#q%3DH.M.%2520education%2520centre%252C%2520kolkata
In your Java code I can suggest using the Java Client for Google Maps Services hosted at Github:
https://github.com/googlemaps/google-maps-services-java
The code snippet to execute web service request with this client library is the following
GeoApiContext context = new GeoApiContext.Builder()
.apiKey("AIza...")
.build();
GeocodingResult[] results = GeocodingApi.geocode(context,
"H.M. education centre, kolkata").await();
The Javadoc for the current version of the library can be found at
https://googlemaps.github.io/google-maps-services-java/v0.2.7/javadoc/
Note also that places like this one can be found via Places API web service. In this case the code snippet will be
GeoApiContext context = new GeoApiContext.Builder()
.apiKey("AIza...")
.build();
TextSearchRequest req = PlacesApi.textSearchQuery(context, "H.M. education centre, kolkata");
try {
PlacesSearchResponse resp = req.await();
if (resp.results != null && resp.results.length > 0) {
//Process your results here
}
} catch(Exception e) {
Log.e(TAG, "Error getting places", e);
}
I hope this helps!
I am new to Android development, following is my code about use Geocoder to get city name of current location, it returns null:
private void updateCurrentLocation(Location location) {
double lat = 0.0, lng = 0.0;
if (location != null) {
lat = location.getLatitude();
lng = location.getLongitude();
Log.i("tag", "Latitute is" + lat + ", Longtitute is" + lng);
} else {
City_Name = "Unavailable";
}
List<Address> list = null;
Geocoder geocoder = new Geocoder(this.getActivity());
try {
list = geocoder.getFromLocation(lat, lng, 1);
} catch (IOException e) {
e.printStackTrace();
}
//may provide multiple locations.
if (list != null && list.size() > 0) {
Address address = list.get(0);
City_Name = address.getLocality();
}
Log.i("Try", "CityName:" + City_Name);
//send empty message
handler.sendEmptyMessage(1);
}
I opened GPS services, add ACCESS_FINE_LOCATION and INTERNET permission in Manifest already. Also, I searched similar questions in Stackoverflow about Geocoder returns null, but haven't found useful solutions. One of them is analyze JSON from Geocoder website, but it doesn't work either.
Can anyone help with this? Thank you!
BTW, is there any better solution to receive a city name? Thank you!
If the "getFromLocation" method gives you an empty set then it's because the server that is being looked up doesn't have the address information for the coordinates you're passing it. This is also noted in the docs. So I think that you should let it go and use another service like the Google Maps geocoding service or another one like Nominatim from the OpenStreetMap project.
Assume the following situation:
The User chooses a country from a list. After clicking on a country, the map should zoom to the selected country.
How can I achieve the zoomToCountry in OSMDroid if I only know the country name from the list?
In the PHP API "GoogleMaps v3" there is a solution like
function findAddress(address) {
var geocoder = null;
geocoder = new google.maps.Geocoder();
if (!address)
var address=document.getElementById("countryselect").value;
if ((address != '') && geocoder) {
geocoder.geocode( { 'address': address}, function(results, status) {
if (status == google.maps.GeocoderStatus.OK) {
if (status != google.maps.GeocoderStatus.ZERO_RESULTS) {
if (results && results[0] && results[0].geometry && results[0].geometry.viewport)
map.fitBounds(results[0].geometry.viewport);
} else {
alert("No results found");
}
} else {
alert("Geocode was not successful for the following reason: " + status);
}
});
}
}
Is there any similar in OSMDroid or the OSMBonuspack?
The PHP solution is a call to geocoding service with the country name, to get country bounding box.
You can do something similar using Nominatim service. So OSMBonusPack GeocoderNominatim should be usable.
Roughly that (without error handling, AsyncTask and so on):
GeocoderNominatim coder = new GeocoderNominatim(ctx);
List<Address> results = coder.getFromLocationName(countryName, 1);
Address address = results.get(0);
Bundle extras = address.getExtras();
BoundingBoxE6 bb = extras.getParcelable("boundingbox");
Then:
mapView.zoomToBoundingBox(bb);
As simple as PHP/GoogleMaps solution, isn't it?
An android application which takes city name as input and return longitude and latitude of the city.
Which method i should used to do it?
What changes will be needed in android manifest file?
You can try using Forward GeoCoding like this:
if(Geocoder.isPresent()){
try {
String location = "MyLocation";
Geocoder gcoder = new Geocoder(this);
List<Address> addresses= gcoder.getFromLocationName(location, 5); // get the found Address Objects
List<LatLng> ll = new ArrayList<LatLng>(addresses.size()); // A list to save the coordinates if they are available
for(Address addr : addresses){
if(addr.hasLatitude() && addr.hasLongitude()){
ll.add(new LatLng(addr.getLatitude(), addr.getLongitude();
}
}
} catch (IOException e) {
// handle the exception
}
}
You will require permission for Internet in manifest file.
<uses-permission android:name="android.permission.INTERNET"/>
Here is a blog that can help you.
Hope this helps.
i want to get the latitude and longitude using the zipcode for android application
This is a much simpler solution, assuming the geocoder services are present:
final Geocoder geocoder = new Geocoder(this);
final String zip = "90210";
try {
List<Address> addresses = geocoder.getFromLocationName(zipCode, 1);
if (addresses != null && !addresses.isEmpty()) {
Address address = addresses.get(0);
// Use the address as needed
String message = String.format("Latitude: %f, Longitude: %f",
address.getLatitude(), address.getLongitude());
Toast.makeText(this, message, Toast.LENGTH_LONG).show();
} else {
// Display appropriate message when Geocoder services are not available
Toast.makeToast(this, "Unable to geocode zipcode", Toast.LENGTH_LONG).show();
}
} catch (IOException e) {
// handle exception
}
There is no rival of Google in GeoCoding :)
You have to just make an http Get request for the following link.
Here's a link
Just change the postal code Element According to your requirements. And Enjoy.
For further reference follow the link.Maps Geocoding Reference
You could use YQL like so: select centroid from geo.places where text="ZIPCODE_HERE"
You will have to use a Geocoding Service, like the ones provided by Google or the freely available Nominatim. Note that since you will be just providing a ZIP code, you might not get the results you want due to the inaccuracy of the address itself.