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diff --git a/docs/html/training/basics/location/geocoding.jd b/docs/html/training/basics/location/geocoding.jd new file mode 100644 index 0000000..6364976 --- /dev/null +++ b/docs/html/training/basics/location/geocoding.jd @@ -0,0 +1,98 @@ +page.title=Displaying the Location Address +parent.title=Making Your App Location Aware +parent.link=index.html + +trainingnavtop=true +previous.title=Obtaining the Current Location +previous.link=currentlocation.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="geocoding.html#TaskReverseGeocoding">Perform Reverse Geocoding</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/topics/location/index.html">Location and Maps</a></li> +</ul> + +<h2>Try it out</h2> + +<div class="download-box"> +<a href="http://developer.android.com/shareables/training/LocationAware.zip" class="button">Download + the sample app</a> +<p class="filename">LocationAware.zip</p> +</div> + +</div> +</div> + +<p>As shown in previous lessons, location updates are received in the form of latitude and longitude coordinates. While this format is useful for calculating distance or displaying a pushpin on a map, the decimal numbers make no sense to most end users. If you need to display a location to user, it is much more preferable to display the address instead.</p> + +<h2 id="TaskReverseGeocoding">Perform Reverse Geocoding</h2> + +<p>Reverse-geocoding is the process of translating latitude longitude coordinates to a human-readable address. The {@link android.location.Geocoder} API is available for this purpose. Note that behind the scene, the API is dependent on a web service. If such service is unavailable on the device, the API will throw a "Service not Available exception" or return an empty list of addresses. A helper method called {@link android.location.Geocoder#isPresent()} was added in Android 2.3 (API level 9) to check for the existence of the service.</p> + +<p>The following code snippet demonstrates the use of the {@link android.location.Geocoder} API to perform reverse-geocoding. Since the {@link android.location.Geocoder#getFromLocation(double, double, int) getFromLocation()} method is synchronous, you should not invoke it from the UI thread, hence an {@link android.os.AsyncTask} is used in the snippet.</p> + +<pre> +private final LocationListener listener = new LocationListener() { + + public void onLocationChanged(Location location) { + // Bypass reverse-geocoding if the Geocoder service is not available on the + // device. The isPresent() convenient method is only available on Gingerbread or above. + if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD && Geocoder.isPresent()) { + // Since the geocoding API is synchronous and may take a while. You don't want to lock + // up the UI thread. Invoking reverse geocoding in an AsyncTask. + (new ReverseGeocodingTask(this)).execute(new Location[] {location}); + } + } + ... +}; + +// AsyncTask encapsulating the reverse-geocoding API. Since the geocoder API is blocked, +// we do not want to invoke it from the UI thread. +private class ReverseGeocodingTask extends AsyncTask<Location, Void, Void> { + Context mContext; + + public ReverseGeocodingTask(Context context) { + super(); + mContext = context; + } + + @Override + protected Void doInBackground(Location... params) { + Geocoder geocoder = new Geocoder(mContext, Locale.getDefault()); + + Location loc = params[0]; + List<Address> addresses = null; + try { + // Call the synchronous getFromLocation() method by passing in the lat/long values. + addresses = geocoder.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1); + } catch (IOException e) { + e.printStackTrace(); + // Update UI field with the exception. + Message.obtain(mHandler, UPDATE_ADDRESS, e.toString()).sendToTarget(); + } + if (addresses != null &s;&s; addresses.size() > 0) { + Address address = addresses.get(0); + // Format the first line of address (if available), city, and country name. + String addressText = String.format("%s, %s, %s", + address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "", + address.getLocality(), + address.getCountryName()); + // Update the UI via a message handler. + Message.obtain(mHandler, UPDATE_ADDRESS, addressText).sendToTarget(); + } + return null; + } +} +</pre>
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