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author | Sarah Maddox <sarahmaddox@google.com> | 2015-01-26 20:35:06 +0000 |
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committer | Android Git Automerger <android-git-automerger@android.com> | 2015-01-26 20:35:06 +0000 |
commit | f31eb13b8ef5dbdf82955ca52eb74cd6fc5cff47 (patch) | |
tree | e3c5749efb09a4d5651d9134e06e81da5a624ddc /docs | |
parent | 8995e140ad557c9f3f4667becbaaf0ba4c667638 (diff) | |
parent | 83f40802148e922d78222ffc56377534b8ee92be (diff) | |
download | frameworks_base-f31eb13b8ef5dbdf82955ca52eb74cd6fc5cff47.zip frameworks_base-f31eb13b8ef5dbdf82955ca52eb74cd6fc5cff47.tar.gz frameworks_base-f31eb13b8ef5dbdf82955ca52eb74cd6fc5cff47.tar.bz2 |
am 83f40802: am 95226c98: am 912cacde: Merge "docs: Adds new geocoding sample to Location API training. Uses GoogleApiClient to connect to Play services. Uses the latest Fused Location Provider API." into lmp-docs
* commit '83f40802148e922d78222ffc56377534b8ee92be':
docs: Adds new geocoding sample to Location API training. Uses GoogleApiClient to connect to Play services. Uses the latest Fused Location Provider API.
Diffstat (limited to 'docs')
-rw-r--r-- | docs/html/training/location/display-address.jd | 680 |
1 files changed, 434 insertions, 246 deletions
diff --git a/docs/html/training/location/display-address.jd b/docs/html/training/location/display-address.jd index 621b082..516f14f 100644 --- a/docs/html/training/location/display-address.jd +++ b/docs/html/training/location/display-address.jd @@ -1,280 +1,468 @@ page.title=Displaying a Location Address - trainingnavtop=true - @jd:body - - <div id="tb-wrapper"> -<div id="tb"> + <div id="tb"> -<h2>This lesson teaches you to</h2> -<ol> - <li><a href="#DefineTask">Define the Address Lookup Task</a></li> - <li><a href="#DisplayResults">Define a Method to Display the Results</a></li> - <li><a href="#RunTask">Run the Lookup Task</a></li> -</ol> + <h2>This lesson teaches you how to</h2> + <ol> + <li><a href="#connect">Get a Geographic Location</a></li> + <li><a href="#fetch-address">Define an Intent Service to Fetch the + Address</a></li> + <li><a href="#start-intent">Start the Intent Service</a></li> + <li><a href="#result-receiver">Receive the Geocoding Results</a></li> + </ol> -<h2>You should also read</h2> -<ul> - <li> - <a href="{@docRoot}google/play-services/setup.html">Setup Google Play Services SDK</a> - </li> - <li> - <a href="retrieve-current.html">Retrieving the Current Location</a> - </li> - <li> - <a href="receive-location-updates.html">Receiving Location Updates</a> - </li> -</ul> -<h2>Try it out</h2> + <h2>You should also read</h2> + <ul> + <li> + <a href="{@docRoot}google/play-services/setup.html">Setting up Google + Play Services</a> + </li> + <li> + <a href="retrieve-current.html">Getting the Last Known Location</a> + </li> + <li> + <a href="receive-location-updates.html">Receiving Location Updates</a> + </li> + </ul> + <h2>Try it out</h2> -<div class="download-box"> -<a href="http://developer.android.com/shareables/training/LocationUpdates.zip" class="button">Download - the sample app</a> -<p class="filename">LocationUpdates.zip</p> + <ul> + <li> + <a href="https://github.com/googlesamples/android-play-location/tree/master/LocationAddress" class="external-link">LocationAddress</a> + </li> + </ul> + </div> </div> -</div> -</div> +<p>The lessons <a href="retrieve-current.html">Getting the Last Known + Location</a> and <a href="receive-location-updates.html">Receiving Location + Updates</a> describe how to get the user's location in the form of a + {@link android.location.Location} object that contains latitude and longitude + coordinates. Although latitude and longitude are useful for calculating + distance or displaying a map position, in many cases the address of the + location is more useful. For example, if you want to let your users know where + they are or what is close by, a street address is more meaningful than the + geographic coordinates (latitude/longitude) of the location.</p> + +<p>Using the {@link android.location.Geocoder} class in the Android framework + location APIs, you can convert an address to the corresponding geographic + coordinates. This process is called <em>geocoding</em>. Alternatively, you can + convert a geographic location to an address. The address lookup feature is + also known as <em>reverse geocoding</em>.</p> + +<p>This lesson shows you how to use the + {@link android.location.Geocoder#getFromLocation getFromLocation()} method to + convert a geographic location to an address. The method returns an estimated + street address corresponding to a given latitude and longitude.</p> + +<h2 id="connect">Get a Geographic Location</h2> + +<p>The last known location of the device is a useful starting point for the + address lookup feature. The lesson on + <a href="retrieve-current.html">Getting the Last Known Location</a> shows you + how to use the + <a href="{@docRoot}reference/com/google/android/gms/location/FusedLocationProviderApi.html#getLastLocation(com.google.android.gms.common.api.GoogleApiClient)">{@code getLastLocation()}</a> + method provided by the + <a href="{@docRoot}reference/com/google/android/gms/location/FusedLocationProviderApi.html">fused + location provider</a> to find the latest location of the device.</p> + +<p>To access the fused location provider, you need to create an instance of the + Google Play services API client. To learn how to connect your client, see + <a href="{@docRoot}training/location/retrieve-current.html#play-services">Connect + to Google Play Services</a>.</p> + +<p>In order for the fused location provider to retrieve a precise street + address, set the location permission in your app manifest to + {@code ACCESS_FINE_LOCATION}, as shown in the following example:</p> -<p> - The lessons <a href="retrieve-current.html">Retrieving the Current Location</a> and - <a href="receive-location-updates.html">Receiving Location Updates</a> describe how to get the - user's current location in the form of a {@link android.location.Location} object that - contains latitude and longitude coordinates. Although latitude and longitude are useful for - calculating distance or displaying a map position, in many cases the address of the location is - more useful. -</p> -<p> - The Android platform API provides a feature that returns an estimated street addresses for - latitude and longitude values. This lesson shows you how to use this address lookup feature. -</p> -<p class="note"> - <strong>Note:</strong> Address lookup requires a backend service that is not included in the - core Android framework. If this backend service is not available, - {@link android.location.Geocoder#getFromLocation Geocoder.getFromLocation()} returns an empty - list. The helper method {@link android.location.Geocoder#isPresent isPresent()}, available - in API level 9 and later, checks to see if the backend service is available. -</p> -<p> - The snippets in the following sections assume that your app has already retrieved the - current location and stored it as a {@link android.location.Location} object in the global - variable {@code mLocation}. -</p> -<!-- - Define the address lookup task ---> -<h2 id="DefineTask">Define the Address Lookup Task</h2> -<p> -To get an address for a given latitude and longitude, call -{@link android.location.Geocoder#getFromLocation Geocoder.getFromLocation()}, which returns a -list of addresses. The method is synchronous, and may take a long time to do its work, so you -should call the method from the {@link android.os.AsyncTask#doInBackground -doInBackground()} method of an {@link android.os.AsyncTask}. -</p> -<p> -While your app is getting the address, display an indeterminate activity -indicator to show that your app is working in the background. Set the indicator's initial state -to {@code android:visibility="gone"}, to make it invisible and remove it from the layout -hierarchy. When you start the address lookup, you set its visibility to "visible". -</p> -<p> -The following snippet shows how to add an indeterminate {@link android.widget.ProgressBar} to -your layout file: -</p> <pre> -<ProgressBar -android:id="@+id/address_progress" -android:layout_width="wrap_content" -android:layout_height="wrap_content" -android:layout_centerHorizontal="true" -android:indeterminate="true" -android:visibility="gone" /> +<manifest xmlns:android="http://schemas.android.com/apk/res/android" + package="com.google.android.gms.location.sample.locationupdates" > + + <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> +</manifest> </pre> -<p> -To create the background task, define a subclass of {@link android.os.AsyncTask} that calls -{@link android.location.Geocoder#getFromLocation getFromLocation()} and returns an address. -Define a {@link android.widget.TextView} object {@code mAddress} to contain the returned -address, and a {@link android.widget.ProgressBar} object that allows you to control the -indeterminate activity indicator. For example: -</p> + +<h2 id="fetch-address">Define an Intent Service to Fetch the Address</h2> + +<p>The {@link android.location.Geocoder#getFromLocation getFromLocation()} + method provided by the {@link android.location.Geocoder} class accepts a + latitude and longitude, and returns a list of addresses. The method is + synchronous, and may take a long time to do its work, so you should not call + it from the main, user interface (UI) thread of your app.</p> + +<p>The {@link android.app.IntentService IntentService} class provides a + structure for running a task on a background thread. Using this class, you can + handle a long-running operation without affecting your UI's responsiveness. + Note that the {@link android.os.AsyncTask AsyncTask} class also allows you to + perform background operations, but it's designed for short operations. An + {@link android.os.AsyncTask AsyncTask} shouldn't keep a reference to the UI if + the activity is recreated, for example when the device is rotated. In + contrast, an {@link android.app.IntentService IntentService} doesn't need to + be cancelled when the activity is rebuilt.</p> + +<p>Define a {@code FetchAddressIntentService} class that extends + {@link android.app.IntentService}. This class is your address lookup service. + The intent service handles an intent asynchronously on a worker thread, and + stops itself when it runs out of work. The intent extras provide the data + needed by the service, including a {@link android.location.Location} object + for conversion to an address, and a {@link android.os.ResultReceiver} object + to handle the results of the address lookup. The service uses a {@link + android.location.Geocoder} to fetch the address for the location, and sends + the results to the {@link android.os.ResultReceiver}.</p> + +<h3>Define the Intent Service in your App Manifest</h3> + +<p>Add an entry to your app manifest defining the intent service:</p> + <pre> -public class MainActivity extends FragmentActivity { +<manifest xmlns:android="http://schemas.android.com/apk/res/android" + package="com.google.android.gms.location.sample.locationaddress" > + <application + ... + <service + android:name=".FetchAddressIntentService" + android:exported="false"/> + </application> ... - private TextView mAddress; - private ProgressBar mActivityIndicator; +</manifest> +</pre> + +<p class="note"><strong>Note:</strong> The {@code <service>} element in + the manifest doesn't need to include an intent filter, because your main + activity creates an explicit intent by specifying the name of the class to use + for the intent.</p> + +<h3>Create a Geocoder</h3> + +<p>The process of converting a geographic location to an address is called + <em>reverse geocoding</em>. To perform the main work of the intent service, + that is, your reverse geocoding request, implement + {@link android.app.IntentService#onHandleIntent onHandleIntent()} within the + {@code FetchAddressIntentService} class. Create a + {@link android.location.Geocoder} object to handle the reverse geocoding.</p> + +<p>A locale represents a specific geographical or linguistic region. Locale + objects are used to adjust the presentation of information, such as numbers or + dates, to suit the conventions in the region represented by the locale. Pass a + <a href="{@docRoot}reference/java/util/Locale.html">{@code Locale}</a> object + to the {@link android.location.Geocoder} object, to ensure that the resulting + address is localized to the user's geographic region.</p> + +<pre> +@Override +protected void onHandleIntent(Intent intent) { + Geocoder geocoder = new Geocoder(this, Locale.getDefault()); ... - @Override - protected void onCreate(Bundle savedInstanceState) { - super.onCreate(savedInstanceState); +} +</pre> + +<h3 id="retrieve-street-address">Retrieve the street address data</h3> + +<p>The next step is to retrieve the street address from the geocoder, handle + any errors that may occur, and send the results back to the activity that + requested the address. To report the results of the geocoding + process, you need two numeric constants that indicate success or failure. + Define a {@code Constants} class to contain the values, as shown in this code + snippet:</p> + +<pre> +public final class Constants { + public static final int SUCCESS_RESULT = 0; + public static final int FAILURE_RESULT = 1; + public static final String PACKAGE_NAME = + "com.google.android.gms.location.sample.locationaddress"; + public static final String RECEIVER = PACKAGE_NAME + ".RECEIVER"; + public static final String RESULT_DATA_KEY = PACKAGE_NAME + + ".RESULT_DATA_KEY"; + public static final String LOCATION_DATA_EXTRA = PACKAGE_NAME + + ".LOCATION_DATA_EXTRA"; +} +</pre> + +<p>To get a street address corresponding to a geographical location, call + {@link android.location.Geocoder#getFromLocation getFromLocation()}, + passing it the latitude and longitude from the location object, and the + maximum number of addresses you want returned. In this case, you want just one + address. The geocoder returns an array of addresses. If no addresses were + found to match the given location, it returns an empty list. If there is no + backend geocoding service available, the geocoder returns null.</p> + +<p>Check for the following errors as shown in the code sample below. If an error + occurs, place the corresponding error message in the {@code errorMessage} + variable, so you can send it back to the requesting activity:</p> + +<ul> + <li><strong>No location data provided</strong> - The intent extras do not + include the {@link android.location.Location} object required for reverse + geocoding.</li> + <li><strong>Invalid latitude or longitude used</strong> - The latitude + and/or longitude values provided in the {@link android.location.Location} + object are invalid.</li> + <li><strong>No geocoder available</strong> - The background geocoding service + is not available, due to a network error or IO exception.</li> + <li><strong>Sorry, no address found</strong> - The geocoder could not find an + address for the given latitude/longitude.</li> +</ul> + +<p>To get the individual lines of an address object, use the + {@link android.location.Address#getAddressLine getAddressLine()} + method provided by the {@link android.location.Address} class. Then join the + lines into a list of address fragments ready to return to the activity that + requested the address.</p> + +<p>To send the results back to the requesting activity, call the + {@code deliverResultToReceiver()} method (defined in + <a href="#return-address">Return the address to the requestor</a>). The + results consist of the previously-mentioned numeric success/failure code and + a string. In the case of a successful reverse geocoding, the string contains + the address. In the case of a failure, the string contains the error message, + as shown in the code sample below:</p> + +<pre> +@Override +protected void onHandleIntent(Intent intent) { + String errorMessage = ""; + + // Get the location passed to this service through an extra. + Location location = intent.getParcelableExtra( + Constants.LOCATION_DATA_EXTRA); + ... - mAddress = (TextView) findViewById(R.id.address); - mActivityIndicator = - (ProgressBar) findViewById(R.id.address_progress); + + List<Address> addresses = null; + + try { + addresses = geocoder.getFromLocation( + location.getLatitude(), + location.getLongitude(), + // In this sample, get just a single address. + 1); + } catch (IOException ioException) { + // Catch network or other I/O problems. + errorMessage = getString(R.string.service_not_available); + Log.e(TAG, errorMessage, ioException); + } catch (IllegalArgumentException illegalArgumentException) { + // Catch invalid latitude or longitude values. + errorMessage = getString(R.string.invalid_lat_long_used); + Log.e(TAG, errorMessage + ". " + + "Latitude = " + location.getLatitude() + + ", Longitude = " + + location.getLongitude(), illegalArgumentException); } - ... - /** - * A subclass of AsyncTask that calls getFromLocation() in the - * background. The class definition has these generic types: - * Location - A {@link android.location.Location} object containing - * the current location. - * Void - indicates that progress units are not used - * String - An address passed to onPostExecute() - */ - private class GetAddressTask extends - AsyncTask<Location, Void, String> { - Context mContext; - public GetAddressTask(Context context) { - super(); - mContext = context; + + // Handle case where no address was found. + if (addresses == null || addresses.size() == 0) { + if (errorMessage.isEmpty()) { + errorMessage = getString(R.string.no_address_found); + Log.e(TAG, errorMessage); } - ... - /** - * Get a Geocoder instance, get the latitude and longitude - * look up the address, and return it - * - * @params params One or more Location objects - * @return A string containing the address of the current - * location, or an empty string if no address can be found, - * or an error message - */ - @Override - protected String doInBackground(Location... params) { - Geocoder geocoder = - new Geocoder(mContext, Locale.getDefault()); - // Get the current location from the input parameter list - Location loc = params[0]; - // Create a list to contain the result address - List<Address> addresses = null; - try { - /* - * Return 1 address. - */ - addresses = geocoder.getFromLocation(loc.getLatitude(), - loc.getLongitude(), 1); - } catch (IOException e1) { - Log.e("LocationSampleActivity", - "IO Exception in getFromLocation()"); - e1.printStackTrace(); - return ("IO Exception trying to get address"); - } catch (IllegalArgumentException e2) { - // Error message to post in the log - String errorString = "Illegal arguments " + - Double.toString(loc.getLatitude()) + - " , " + - Double.toString(loc.getLongitude()) + - " passed to address service"; - Log.e("LocationSampleActivity", errorString); - e2.printStackTrace(); - return errorString; - } - // If the reverse geocode returned an address - if (addresses != null && addresses.size() > 0) { - // Get the first address - Address address = addresses.get(0); - /* - * Format the first line of address (if available), - * city, and country name. - */ - String addressText = String.format( - "%s, %s, %s", - // If there's a street address, add it - address.getMaxAddressLineIndex() > 0 ? - address.getAddressLine(0) : "", - // Locality is usually a city - address.getLocality(), - // The country of the address - address.getCountryName()); - // Return the text - return addressText; - } else { - return "No address found"; - } + deliverResultToReceiver(Constants.FAILURE_RESULT, errorMessage); + } else { + Address address = addresses.get(0); + ArrayList<String> addressFragments = new ArrayList<String>(); + + // Fetch the address lines using {@code getAddressLine}, + // join them, and send them to the thread. + for(int i = 0; i < address.getMaxAddressLineIndex(); i++) { + addressFragments.add(address.getAddressLine(i)); } - ... + Log.i(TAG, getString(R.string.address_found)); + deliverResultToReceiver(Constants.SUCCESS_RESULT, + TextUtils.join(System.getProperty("line.separator"), + addressFragments)); } - ... } </pre> -<p> -The next section shows you how to display the address in the user interface. -</p> -<!-- Define a method to display the address --> -<h2 id="DisplayResults">Define a Method to Display the Results</h2> -<p> - {@link android.os.AsyncTask#doInBackground doInBackground()} returns the result of the address - lookup as a {@link java.lang.String}. This value is passed to - {@link android.os.AsyncTask#onPostExecute onPostExecute()}, where you do further processing - on the results. Since {@link android.os.AsyncTask#onPostExecute onPostExecute()} - runs on the UI thread, it can update the user interface; for example, it can turn off the - activity indicator and display the results to the user: + +<h3 id="return-address">Return the address to the requestor</h3> + +<p>The final thing the intent service must do is send the address back to a + {@link android.os.ResultReceiver} in the activity that started the service. + The {@link android.os.ResultReceiver} class allows you to send a + numeric result code as well as a message containing the result data. The + numeric code is useful for reporting the success or failure of the geocoding + request. In the case of a successful reverse geocoding, the message contains + the address. In the case of a failure, the message contains some text + describing the reason for failure.</p> + +<p>You have already retrieved the address from the geocoder, trapped any errors + that may occur, and called the {@code deliverResultToReceiver()} method. Now + you need to define the {@code deliverResultToReceiver()} method that sends + a result code and message bundle to the result receiver.</p> + +<p>For the result code, use the value that you've passed to the + {@code deliverResultToReceiver()} method in the {@code resultCode} parameter. + To construct the message bundle, concatenate the {@code RESULT_DATA_KEY} + constant from your {@code Constants} class (defined in + <a href="#retrieve-street-address">Retrieve the street address data</a>) and + the value in the {@code message} parameter passed to the + {@code deliverResultToReceiver()} method, as shown in the following sample: </p> + <pre> - private class GetAddressTask extends - AsyncTask<Location, Void, String> { - ... - /** - * A method that's called once doInBackground() completes. Turn - * off the indeterminate activity indicator and set - * the text of the UI element that shows the address. If the - * lookup failed, display the error message. - */ - @Override - protected void onPostExecute(String address) { - // Set activity indicator visibility to "gone" - mActivityIndicator.setVisibility(View.GONE); - // Display the results of the lookup. - mAddress.setText(address); - } - ... +public class FetchAddressIntentService extends IntentService { + protected ResultReceiver mReceiver; + ... + private void deliverResultToReceiver(int resultCode, String message) { + Bundle bundle = new Bundle(); + bundle.putString(Constants.RESULT_DATA_KEY, message); + mReceiver.send(resultCode, bundle); } +} </pre> -<p> - The final step is to run the address lookup. -</p> -<!-- Get and display the address --> -<h2 id="RunTask">Run the Lookup Task</h2> -<p> - To get the address, call {@link android.os.AsyncTask#execute execute()}. For example, the - following snippet starts the address lookup when the user clicks the "Get Address" button: -</p> + +<h2 id="start-intent">Start the Intent Service</h2> + +<p>The intent service, as defined in the previous section, runs in the + background and is responsible for fetching the address corresponding to a + given geographic location. When you start the service, the Android framework + instantiates and starts the service if it isn't already running, and creates a + process if needed. If the service is already running then it remains running. + Because the service extends {@link android.app.IntentService IntentService}, + it shuts down automatically when all intents have been processed.</p> + +<p>Start the service from your app's main activity, + and create an {@link android.content.Intent} to pass data to the service. You + need an <em>explicit</em> intent, because you want only your service + to respond to the intent. For more information, see + <a href="{@docRoot}guide/components/intents-filters.html#Types">Intent + Types</a>.</p> + +<p>To create an explicit intent, specify the name of the + class to use for the service: {@code FetchAddressIntentService.class}. + Pass two pieces of information in the intent extras:</p> + +<ul> + <li>A {@link android.os.ResultReceiver} to handle the results of the address + lookup.</li> + <li>A {@link android.location.Location} object containing the latitude and + longitude that you want to convert to an address.</li> +</ul> + +<p>The following code sample shows you how to start the intent service:</p> + <pre> -public class MainActivity extends FragmentActivity { +public class MainActivity extends ActionBarActivity implements + ConnectionCallbacks, OnConnectionFailedListener { + + protected Location mLastLocation; + private AddressResultReceiver mResultReceiver; ... - /** - * The "Get Address" button in the UI is defined with - * android:onClick="getAddress". The method is invoked whenever the - * user clicks the button. - * - * @param v The view object associated with this method, - * in this case a Button. - */ - public void getAddress(View v) { - // Ensure that a Geocoder services is available - if (Build.VERSION.SDK_INT >= - Build.VERSION_CODES.GINGERBREAD - && - Geocoder.isPresent()) { - // Show the activity indicator - mActivityIndicator.setVisibility(View.VISIBLE); - /* - * Reverse geocoding is long-running and synchronous. - * Run it on a background thread. - * Pass the current location to the background task. - * When the task finishes, - * onPostExecute() displays the address. - */ - (new GetAddressTask(this)).execute(mLocation); + + protected void startIntentService() { + Intent intent = new Intent(this, FetchAddressIntentService.class); + intent.putExtra(Constants.RECEIVER, mResultReceiver); + intent.putExtra(Constants.LOCATION_DATA_EXTRA, mLastLocation); + startService(intent); + } +} +</pre> + +<p>Call the above {@code startIntentService()} method when the + user takes an action that requires a geocoding address lookup. For example, + the user may press a <em>Fetch address</em> button on your app's UI. Before + starting the intent service, you need to check that the connection to Google + Play services is present. The following code snippet shows the call to the + {@code startIntentService()} method in the button handler:</p> + +<pre> +public void fetchAddressButtonHandler(View view) { + // Only start the service to fetch the address if GoogleApiClient is + // connected. + if (mGoogleApiClient.isConnected() && mLastLocation != null) { + startIntentService(); + } + // If GoogleApiClient isn't connected, process the user's request by + // setting mAddressRequested to true. Later, when GoogleApiClient connects, + // launch the service to fetch the address. As far as the user is + // concerned, pressing the Fetch Address button + // immediately kicks off the process of getting the address. + mAddressRequested = true; + updateUIWidgets(); +} +</pre> + +<p>You must also start the intent service when the connection to Google Play + services is established, if the user has already clicked the button on your + app's UI. The following code snippet shows the call to the + {@code startIntentService()} method in the + <a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.ConnectionCallbacks.html#onConnected(android.os.Bundle)">{@code onConnected()}</a> + callback provided by the Google API Client:</p> + +<pre> +public class MainActivity extends ActionBarActivity implements + ConnectionCallbacks, OnConnectionFailedListener { + ... + @Override + public void onConnected(Bundle connectionHint) { + // Gets the best and most recent location currently available, + // which may be null in rare cases when a location is not available. + mLastLocation = LocationServices.FusedLocationApi.getLastLocation( + mGoogleApiClient); + + if (mLastLocation != null) { + // Determine whether a Geocoder is available. + if (!Geocoder.isPresent()) { + Toast.makeText(this, R.string.no_geocoder_available, + Toast.LENGTH_LONG).show(); + return; + } + + if (mAddressRequested) { + startIntentService(); + } } - ... } +} +</pre> + +<h2 id="result-receiver">Receive the Geocoding Results</h2> + +<p>The intent service has handled the geocoding request, and uses a + {@link android.os.ResultReceiver} to return the results to the activity that + made the request. In the activity that makes the request, define an + {@code AddressResultReceiver} that extends {@link android.os.ResultReceiver} + to handle the response from {@code FetchAddressIntentService}.</p> + +<p>The result includes a numeric result code (<code>resultCode</code>) as well + as a message containing the result data (<code>resultData</code>). If the + reverse geocoding process was successful, the <code>resultData</code> contains + the address. In the case of a failure, the <code>resultData</code> contains + text describing the reason for failure. For details of the possible errors, + see <a href="#return-address">Return the address to the requestor</a>.</p> + +<p>Override the + {@link android.os.ResultReceiver#onReceiveResult onReceiveResult()} method + to handle the results delivered to the result receiver, as shown in the + following code sample:</p> + +<pre> +public class MainActivity extends ActionBarActivity implements + ConnectionCallbacks, OnConnectionFailedListener { ... + class AddressResultReceiver extends ResultReceiver { + public AddressResultReceiver(Handler handler) { + super(handler); + } + + @Override + protected void onReceiveResult(int resultCode, Bundle resultData) { + + // Display the address string + // or an error message sent from the intent service. + mAddressOutput = resultData.getString(Constants.RESULT_DATA_KEY); + displayAddressOutput(); + + // Show a toast message if an address was found. + if (resultCode == Constants.SUCCESS_RESULT) { + showToast(getString(R.string.address_found)); + } + + } + } } </pre> -<p> - The next lesson, <a href="geofencing.html">Creating and Monitoring Geofences</a>, demonstrates - how to define locations of interest called <b>geofences</b> and how to use geofence monitoring - to detect the user's proximity to a location of interest. -</p> |