android_frameworks_base/docs/html/training/location/geofencing.jd

page.title=Creating and Monitoring Geofences

trainingnavtop=true
@jd:body


<div id="tb-wrapper">
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<h2>This lesson teaches you to</h2>
<ol>
    <li><a href="#RequestGeofences">Set up for Geofence Monitoring</a></li>
    <li><a href="#CreateAdd">Create and Add Geofences</a></li>
    <li><a href="#HandleGeofenceTransitions">Handle Geofence Transitions</a></li>
    <li><a href="#StopGeofenceMonitoring">Stop Geofence Monitoring</a></li>
    <li><a href="#BestPractices">Use Best Practices for Geofencing</a></li>
    <li><a href="#Troubleshooting">Troubleshoot the Geofence Entrance Event</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>
</ul>

<h2>Try it out</h2>

   <ul>
      <li>
        <a href="https://github.com/googlesamples/android-play-location/tree/master/Geofencing"
        class="external-link">Geofencing</a>
      </li>
    </ul>

</div>
</div>
<p>
    Geofencing combines awareness of the user's current location with awareness of the user's
    proximity to locations that may be of interest. To mark a
    location of interest, you specify its latitude and longitude. To adjust the proximity for the
    location, you add a radius. The latitude, longitude, and radius define a geofence, creating a
    circular area, or fence, around the location of interest.
</p>
<p>
    You can have multiple active geofences, with a limit of 100 per device user. For each geofence,
    you can ask Location Services to send you entrance and exit events, or you can specify a
    duration within the geofence area to wait, or <em>dwell</em>, before triggering an event. You
    can limit the duration of any geofence by specifying an expiration duration in milliseconds.
    After the geofence expires, Location Services automatically removes it.
</p>

<img src="{@docRoot}images/training/geofence@2x.png"
srcset="{@docRoot}images/training/geofence.png 1x, {@docRoot}images/training/geofence@2x.png 2x" alt=""
  width="400" height="400"/>
<p>
    This lesson shows you how to add and remove geofences, and then listen for geofence transitions
    using an {@link android.app.IntentService}.</p>

<p>We recommend upgrading existing apps to use the
<a href="{@docRoot}reference/com/google/android/gms/location/LocationServices.html">
LocationServices</a> class, which contains the
<a href="{@docRoot}reference/com/google/android/gms/location/GeofencingApi.html">
GeofencingApi</a> interface. The
<a href="{@docRoot}reference/com/google/android/gms/location/LocationServices.html">
LocationServices</a> class replaces the
<a href="{@docRoot}reference/com/google/android/gms/location/LocationClient.html">
LocationClient</a> (deprecated).</p>

<h2 id="RequestGeofences">Set up for Geofence Monitoring</h2>
<p>
    The first step in requesting geofence monitoring is to request the necessary permission.
    To use geofencing, your app must request
    {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION}. To request this
    permission, add the following element as a child element of the
<code><a href="{@docRoot}guide/topics/manifest/manifest-element.html">&lt;manifest&gt;</a></code>
    element in your app manifest:
</p>
<pre>
&lt;uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/&gt;
</pre>

<p>
    If you want to use an {@link android.app.IntentService} to listen for geofence transitions,
    add an element specifying the service name. This element must be
    a child of the <code><a href="{@docRoot}guide/topics/manifest/application-element.html">
    &lt;application&gt;</a></code> element:
</p>

<pre>
&lt;application
   android:allowBackup=&quot;true&quot;&gt;
   ...
   &lt;service android:name=".GeofenceTransitionsIntentService"/&gt;
&lt;application/&gt;
</pre>

<p>To access the location APIs, 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>

<h2 id="CreateAdd">Create and Add Geofences</h2>

<p>Your app needs to create and add geofences using the location API's builder class for
 creating Geofence objects, and the convenience class for adding them. Also, to handle the
 intents sent from Location Services when geofence transitions occur, you can define a
 {@link android.app.PendingIntent} as shown in this section.
</p>

<p class="note"><strong>Note:</strong> On single-user devices, there is a limit of 100 geofences per app. For multi-user devices, the limit is 100 geofences per app per device user.</p>

<h3>Create geofence objects</h3>

<p>
    First, use <code><a href="{@docRoot}reference/com/google/android/gms/location/Geofence.Builder.html">
    Geofence.Builder</a></code> to create a geofence, setting the desired radius, duration, and
    transition types for the geofence. For example, to populate a list object named
    {@code mGeofenceList}:
    </p>

<pre>
mGeofenceList.add(new Geofence.Builder()
    // Set the request ID of the geofence. This is a string to identify this
    // geofence.
    .setRequestId(entry.getKey())

    .setCircularRegion(
            entry.getValue().latitude,
            entry.getValue().longitude,
            Constants.GEOFENCE_RADIUS_IN_METERS
    )
    .setExpirationDuration(Constants.GEOFENCE_EXPIRATION_IN_MILLISECONDS)
    .setTransitionTypes(Geofence.GEOFENCE_TRANSITION_ENTER |
            Geofence.GEOFENCE_TRANSITION_EXIT)
    .build());
</pre>

<p>This example pulls data from a constants file. In actual practice, apps might
    dynamically create geofences based on the user's location.</p>

<h3>Specify geofences and initial triggers</h3>

<p>
    The following snippet uses the <code><a href="{@docRoot}reference/com/google/android/gms/location/GeofencingRequest.html">
    GeofencingRequest</a></code> class
    and its nested <code><a href="{@docRoot}reference/com/google/android/gms/location/GeofencingRequest.Builder.html">
    GeofencingRequestBuilder</a></code> class to
    specify the geofences to monitor and to set how related geofence events are triggered:
</p>
<pre>
private GeofencingRequest getGeofencingRequest() {
    GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
    builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER);
    builder.addGeofences(mGeofenceList);
    return builder.build();
}
</pre>

<p>
    This example shows the use of two geofence triggers. The <code>
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_ENTER">
    GEOFENCE_TRANSITION_ENTER</a></code>
    transition triggers when a device enters a geofence, and the <code>
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_EXIT">
    GEOFENCE_TRANSITION_EXIT</a></code>
    transition triggers when a device exits a geofence. Specifying
    <code>
<a href="{@docRoot}reference/com/google/android/gms/location/GeofencingRequest.html#INITIAL_TRIGGER_ENTER">
        INITIAL_TRIGGER_ENTER</a></code> tells Location services that
    <code>
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_ENTER">
        GEOFENCE_TRANSITION_ENTER</a></code>
    should be triggered if the the device is already inside the geofence.</p>
</p>

<p>In many cases, it may be preferable to use instead <code>
<a href="{@docRoot}reference/com/google/android/gms/location/GeofencingRequest.html#INITIAL_TRIGGER_DWELL">
    INITIAL_TRIGGER_DWELL</a></code>,
    which triggers events only when the user stops for a defined duration within a geofence.
    This approach can help reduce "alert spam" resulting from large numbers notifications when a
    device briefly enters and exits geofences. Another strategy for getting best results from your
    geofences is to set a minimum radius of 100 meters. This helps account for the location accuracy
    of typical Wi-Fi networks, and also helps reduce device power consumption.
</p>

<h3>Define an Intent for geofence transitions</h3>
<p>
    The {@link android.content.Intent} sent from Location Services can trigger various actions in
    your app, but you should <i>not</i> have it start an activity or fragment, because components
    should only become visible in response to a user action. In many cases, an
    {@link android.app.IntentService} is a good way to handle the intent. An
    {@link android.app.IntentService} can post a notification, do long-running background work,
    send intents to other services, or send a broadcast intent. The following snippet shows how
    to define a {@link android.app.PendingIntent} that starts an {@link android.app.IntentService}:
</p>
<pre>
public class MainActivity extends FragmentActivity {
    ...
    private PendingIntent getGeofencePendingIntent() {
        // Reuse the PendingIntent if we already have it.
        if (mGeofencePendingIntent != null) {
            return mGeofencePendingIntent;
        }
        Intent intent = new Intent(this, GeofenceTransitionsIntentService.class);
        // We use FLAG_UPDATE_CURRENT so that we get the same pending intent back when
        // calling addGeofences() and removeGeofences().
        return PendingIntent.getService(this, 0, intent, PendingIntent.
                FLAG_UPDATE_CURRENT);
    }
</pre>

<h3>Add geofences</h3>

<p>
    To add geofences, use the <code>
<a href="{@docRoot}reference/com/google/android/gms/location/GeofencingApi.html#addGeofences(com.google.android.gms.common.api.GoogleApiClient, com.google.android.gms.location.GeofencingRequest, android.app.PendingIntent)">{@code GeoencingApi.addGeofences()}</a></code> method.
    Provide the Google API client, the <code>
<a href="{@docRoot}reference/com/google/android/gms/location/GeofencingRequest">
    GeofencingRequest</a></code> object, and the {@link android.app.PendingIntent}.
    The following snippet, which processes the results in <code>
<a href="{@docRoot}reference/com/google/android/gms/common/api/ResultCallback.html#onResult(R)">
    onResult()</a></code>, assumes that the main activity implements <code>
<a href="{@docRoot}reference/com/google/android/gms/common/api/ResultCallback.html">
    ResultCallback</a></code>:
</p>
<pre>
public class MainActivity extends FragmentActivity {
    ...
    LocationServices.GeofencingApi.addGeofences(
                mGoogleApiClient,
                getGeofencingRequest(),
                getGeofencePendingIntent()
        ).setResultCallback(this);
</pre>


<h2 id="HandleGeofenceTransitions">Handle Geofence Transitions</h2>
<p>
    When Location Services detects that the user has entered or exited a geofence, it
    sends out the {@link android.content.Intent} contained in the {@link android.app.PendingIntent}
    you included in the request to add geofences. This {@link android.content.Intent} is received
    by a service like <code>GeofenceTransitionsIntentService</code>,
    which obtains the geofencing event from the intent, determines the type of Geofence transition(s),
    and determines which of the defined geofences was triggered. It then sends a notification as
    the output.
</p>
<p>
    The following snippet shows how to define an {@link android.app.IntentService} that posts a
    notification when a geofence transition occurs. When the user clicks the notification, the
    app's main activity appears:
</p>
<pre>
public class GeofenceTransitionsIntentService extends IntentService {
   ...
    protected void onHandleIntent(Intent intent) {
        GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
        if (geofencingEvent.hasError()) {
            String errorMessage = GeofenceErrorMessages.getErrorString(this,
                    geofencingEvent.getErrorCode());
            Log.e(TAG, errorMessage);
            return;
        }

        // Get the transition type.
        int geofenceTransition = geofencingEvent.getGeofenceTransition();

        // Test that the reported transition was of interest.
        if (geofenceTransition == Geofence.GEOFENCE_TRANSITION_ENTER ||
                geofenceTransition == Geofence.GEOFENCE_TRANSITION_EXIT) {

            // Get the geofences that were triggered. A single event can trigger
            // multiple geofences.
            List<Geofence> triggeringGeofences = geofencingEvent.getTriggeringGeofences();

            // Get the transition details as a String.
            String geofenceTransitionDetails = getGeofenceTransitionDetails(
                    this,
                    geofenceTransition,
                    triggeringGeofences
            );

            // Send notification and log the transition details.
            sendNotification(geofenceTransitionDetails);
            Log.i(TAG, geofenceTransitionDetails);
        } else {
            // Log the error.
            Log.e(TAG, getString(R.string.geofence_transition_invalid_type,
                    geofenceTransition));
        }
    }
</pre>

<p>After detecting the transition event via the {@link android.app.PendingIntent},
    this {@link android.app.IntentService} gets the geofence transition type and tests whether
    it is one of the events the app uses to trigger notifications -- either
    <code><a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_ENTER">GEOFENCE_TRANSITION_ENTER</a></code>
     or <code><a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_EXIT">GEOFENCE_TRANSITION_EXIT</a></code>
    in this case. The service then sends a notification and logs the transition details.</p>
<!--
    Remove Geofences
 -->
<h2 id="StopGeofenceMonitoring">Stop Geofence Monitoring</h2>

<p>Stopping geofence monitoring when it is no longer needed or desired can help save battery
    power and CPU cycles on the device. You can stop geofence monitoring
    in the main activity used to add and remove geofences; removing a geofence stops it
    immediately. The API provides methods to
    remove geofences either by request IDs, or by removing geofences associated with a given
    {@link android.app.PendingIntent}.
</p>
<p>
    The following snippet removes geofences by {@link android.app.PendingIntent}, stopping all
    further notification when the device enters or exits previously added geofences:
</p>
<pre>
LocationServices.GeofencingApi.removeGeofences(
            mGoogleApiClient,
            // This is the same pending intent that was used in addGeofences().
            getGeofencePendingIntent()
    ).setResultCallback(this); // Result processed in onResult().
}
</pre>

<p>
    You can combine geofencing with other location-aware features, such as periodic location updates.
    For more information, see the other lessons in this class.
</p>

<h2 id="BestPractices">Use Best Practices for Geofencing</h2>

<p>This section outlines recommendations for using geofencing with the location
APIs for Android.</p>

<h3>Reduce power consumption</h3>

<p>You can use the following techniques to optimize power consumption in your apps that use geofencing:</p>

<ul>
<li><p>Set the <a href="{@docRoot}android/reference/com/google/android/gms/location/Geofence.Builder.html#setNotificationResponsiveness(int)">
notification responsiveness</a> to a higher value. Doing so improves power consumption by
increasing the latency of geofence alerts. For example, if you set a responsiveness value of five
minutes your app only checks for an entrance or exit alert once every five minutes.
Setting lower values does not necessarily mean that users will be notified within that time period
(for example, if you set a value of 5 seconds it may take a bit longer than that to receive the
alert).</p></li>
<li><p>Use a larger geofence radius for locations where a user spends a significant amount of time,
such as home or work. While a larger radius doesn't directly reduce power consumption, it reduces
the frequency at which the app checks for entrance or exit, effectively lowering overall power
consumption.</p></li>
</ul>

<h3>Choose the optimal radius for your geofence</h3>
<p>For best results, the minimium radius of the geofence should be set between 100 - 150 meters.
When Wi-Fi is available location accuracy is usually between 20 - 50 meters. When indoor
location is available, the accuracy range can be as small as 5 meters. Unless you know indoor
location is available inside the geofence, assume that Wi-Fi location accuracy is about
50 meters.</p>

<p>When Wi-Fi location is not available (for example, when you are driving in rural areas) the
location accuracy degrades. The accuracy range can be as large as several hundred meters to
several kilometers. In cases like this, you should create geofences using a larger radius.</p>

<h3>Use the dwell transition type to reduce alert spam</h3>

<p>If you receive a large number of alerts when driving briefly past a geofence, the best way to
reduce the alerts is to use a transition type of <code>
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_DWELL">
GEOFENCE_TRANSITION_DWELL</a></code> instead of <code>
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_ENTER">
GEOFENCE_TRANSITION_ENTER</a></code>. This way, the dwelling alert is sent only when the user stops
inside a geofence for a given period of time. You can choose the duration by setting a 
<a href="{@docRoot}reference/com/google/android/gms/location/Geofence.Builder.html#setLoiteringDelay(int)">
loitering delay</a>.</p>

<h3>Re-register geofences only when required</h3>

<p>Registered geofences are kept in the <code>com.google.process.location</code> process owned by
the <code>com.google.android.gms</code> package.
The app doesn’t need to do anything to handle the following events, because the system
restores geofences after these events:</p>
<ul>
<li>Google Play services is upgraded.</li>
<li>Google Play services is killed and restarted by the system due resource restriction.</li>
<li>The location process crashes.</li>
</ul>
<p>The app must re-register geofences if they're still needed after the following events, since
the system cannot recover the geofences in the following cases:</p>

<ul>
<li>The device is rebooted. The app should listen for the device's boot complete action, and then re-
register the geofences required.</li>
<li>The app is uninstalled and re-installed.</li>
<li>The app's data is cleared.</li>
<li>Google Play services data is cleared.</li>
<li>The app has received a <code><a href="{@docRoot}reference/com/google/android/gms/location/LocationStatusCodes.html#GEOFENCE_NOT_AVAILABLE">GEOFENCE_NOT_AVAILABLE</a></code>
alert. This typically happens
after NLP (Android's Network Location Provider) is disabled.</li>
</ul>

<h2 id="Troubleshooting">Troubleshoot the Geofence Entrance Event</h2>

<p>If geofences are not being triggered when the device enters a geofence
(the <code><a href="{@docRoot}reference/com/google/android/gms/location/Geofence.html#GEOFENCE_TRANSITION_ENTER">
GEOFENCE_TRANSITION_ENTER</a></code> alert isn’t triggered), first ensure that your geofences are
registered properly as described in this guide.</p>

<p>Here are some possible reasons for alerts not working as expected:</p>

<ul>
<li><strong>Accurate location is not available inside your geofence or your geofence is too
small.</strong> On most devices, the geofence service uses only network location for geofence
triggering. The service uses this approach because network location consumes much less
power, it takes less time to get discrete locations, and most importantly it’s available indoors.
Starting with Google Play services 3.2, the geofence service calculates the overlapping ratio of
the location circle and the geofence circle and only generates the entrance alert when the ratio
is at least 85% for a bigger geofence or 75% for a smaller geofence. For an exit alert, the ratio
threshold used is 15% or 25%. Any ratio between these thresholds makes the geofence service mark
the geofence state as <code>INSIDE_LOW_CONFIDENCE</code> or <code>OUTSIDE_LOW_CONFIDENCE</code> and
no alert is sent.</li>
<li><strong>Wi-Fi is turned off on the device.</strong> Having Wi-Fi on can significantly improve
the location accuracy, so if Wi-Fi is turned off, your application might never get geofence alerts
depending on several settings including the radius of the geofence, the device model, or the
Android version. Starting from Android 4.3 (API level 18), we added the capability of “Wi-Fi scan
only mode” which allows users to disable Wi-Fi but still get good network location. It’s good
practice to prompt the user and provide a shortcut for the user to enable Wi-Fi or Wi-Fi scan only
mode if both of them are disabled. Use <a href="{@docRoot}reference/com/google/android/gms/location/SettingsApi">
SettingsApi</a> to ensure that the device's system settings are properly configured for optimal
location detection.</li>
<li><strong>There is no reliable network connectivity inside your geofence.</strong> If there is
no reliable data connection, alerts might not be generated. This is because the geofence service
depends on the network location provider which in turn requires a data connection.</li>
<li><strong>Alerts can be late.</strong> The geofence service does not continuously query for
location, so expect some latency when receiving alerts. Usually the latency is less than 2
minutes, even less when the device has been moving. If the device has been stationary for a
significant period of time, the latency may increase (up to 6 minutes).</li>
</ul>