A class for handling geocoding and reverse geocoding. Geocoding is the process of transforming a street address or other description of a location into a (latitude, longitude) coordinate. Reverse geocoding is the process of transforming a (latitude, longitude) coordinate into a (partial) address. The amount of detail in a reverse geocoded location description may vary, for example one might contain the full street address of the closest building, while another might contain only a city name and postal code. The Geocoder class requires a backend service that is not included in the core android framework. The Geocoder query methods will return an empty list if there no backend service in the platform. Use the isPresent() method to determine whether a Geocoder implementation exists.
https://developers.google.com/maps/documentation/geocoding/
http://stackoverflow.com/questions/9272918/service-not-available-in-geocoder
package com.example.android.location;
import java.util.List;
import java.util.Locale;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicResponseHandler;
import org.json.JSONArray;
import org.json.JSONObject;
import android.annotation.SuppressLint;
import android.content.Context;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.net.http.AndroidHttpClient;
import android.os.AsyncTask;
import android.util.Log;
public class GeocoderHelper {
private static final AndroidHttpClient ANDROID_HTTP_CLIENT = AndroidHttpClient.newInstance(GeocoderHelper.class.getName());
private boolean running = false;
@SuppressLint("NewApi")
public void fetchCityName(final Context contex, final Location location) {
if (running)
return;
new AsyncTask<Void, Void, String>() {
protected void onPreExecute() {
running = true;
};
@Override
protected String doInBackground(Void... params) {
String cityName = null;
if (Geocoder.isPresent()) {
try {
Geocoder geocoder = new Geocoder(contex, Locale.getDefault());
List<Address> addresses = geocoder.getFromLocation(location.getLatitude(),
location.getLongitude(), 1);
if (addresses.size() > 0) {
cityName = addresses.get(0).getLocality();
}
} catch (Exception ignored) {
// after a while, Geocoder start to trhow
// "Service not availalbe" exception. really weird since
// it was working before (same device, same Android
// version etc..
}
}
if (cityName != null) // i.e., Geocoder succeed
{
return cityName;
} else // i.e., Geocoder failed
{
return fetchCityNameUsingGoogleMap();
}
}
// Geocoder failed :-(
// Our B Plan : Google Map
private String fetchCityNameUsingGoogleMap() {
String googleMapUrl = "http://maps.googleapis.com/maps/api/geocode/json?latlng="
+ location.getLatitude() + "," + location.getLongitude()
+ "&sensor=false&language=zh-CN";
try {
JSONObject googleMapResponse = new JSONObject(ANDROID_HTTP_CLIENT.execute(new HttpGet(googleMapUrl),
new BasicResponseHandler()));
// many nested loops.. not great -> use expression instead
// loop among all results
JSONArray results = (JSONArray) googleMapResponse.get("results");
for (int i = 0; i < results.length(); i++) {
// loop among all addresses within this result
JSONObject result = results.getJSONObject(i);
if (result.has("address_components")) {
JSONArray addressComponents = result.getJSONArray("address_components");
// loop among all address component to find a
// 'locality' or 'sublocality'
for (int j = 0; j < addressComponents.length(); j++) {
JSONObject addressComponent = addressComponents.getJSONObject(j);
if (result.has("types")) {
JSONArray types = addressComponent.getJSONArray("types");
// search for locality and sublocality
String cityName = null;
for (int k = 0; k < types.length(); k++) {
if ("locality".equals(types.getString(k)) && cityName == null) {
if (addressComponent.has("long_name")) {
cityName = addressComponent.getString("long_name");
} else if (addressComponent.has("short_name")) {
cityName = addressComponent.getString("short_name");
}
}
if ("sublocality".equals(types.getString(k))) {
if (addressComponent.has("long_name")) {
cityName = addressComponent.getString("long_name");
} else if (addressComponent.has("short_name")) {
cityName = addressComponent.getString("short_name");
}
}
}
if (cityName != null) {
return cityName;
}
}
}
}
}
} catch (Exception ignored) {
ignored.printStackTrace();
}
return null;
}
protected void onPostExecute(String cityName) {
running = false;
if (cityName != null) {
// Do something with cityName
Log.i("GeocoderHelper", cityName);
}
};
}.execute();
}
}