android_frameworks_base/docs/html/training/location/change-location-settings.jd

page.title=Changing Location Settings
trainingnavtop=true
@jd:body

<div id="tb-wrapper">
  <div id="tb">

  <h2>This lesson teaches you how to</h2>
  <ol>
    <li><a href="#connect">Connect to Location Services</a></li>
    <li><a href="#location-request">Set Up a Location Request</a></li>
    <li><a href="#get-settings">Get Current Location Settings</a></li>
    <li><a href="#prompt">Prompt the User to Change Location Settings</a></li>
  </ol>

  <h2>You should also read</h2>
  <ul>
    <li>
      <a href="https://developers.google.com/android/guides/setup"
      class="external-link">Setting up Google Play Services</a>
    </li>
    <li>
      <a href="retrieve-current.html">Getting the Last Known Location</a>
    </li>
   </ul>
  </div>
</div>

<p>If your app needs to request location or receive permission updates, the
  device needs to enable the appropriate system settings, such as GPS or Wi-Fi
  scanning. Rather than directly enabling services such as the device's GPS,
  your app specifies the required level of accuracy/power consumption and
  desired update interval, and the device automatically makes the appropriate
  changes to system settings. These settings are defined by the
  <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest"
  class="external-link">{@code LocationRequest}</a>
  data object. </p>

<p>This lesson shows you how to use the
  <a href="https://developers.google.com/android/reference/com/google/android/gms/location/SettingsApi">Settings API</a>
  to check which settings are enabled, and present the Location Settings
  dialog for the user to update their settings with a single tap.</p>

<h2 id="connect">Connect to Location Services</h2>

<p>In order to use the location services provided by Google Play Services and
  the fused location provider, connect your app using the
  <a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient">Google API Client</a>,
  then check the current location settings and prompt the user to enable the
  required settings if needed. For details on connecting with the
  Google API client, see <a href="retrieve-current.html">Getting the Last Known Location</a>.</p>

<p>Apps that use location services must request location permissions. For this
  lesson, coarse location detection is sufficient. Request this permission
  with the <code>uses-permission</code> element in your app manifest, as shown
  in the following example:</p>

<pre><code>&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.google.android.gms.location.sample.locationupdates" &gt;

  &lt;uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/&gt;
&lt;/manifest&gt;
</code></pre>

<p>If the device is running Android 6.0 or higher, and your app's target
  SDK is 23 or higher, the app has to list the permissions in the manifest
  <em>and</em> request those permissions at run time. For more information, see
<a href="{@docRoot}training/permissions/requesting.html">Requesting Permissions at Run Time</a>.</p>

<h2 id="location-request">Set Up a Location Request</h2>

<p>To store parameters for requests to the fused location provider, create a
  <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html">{@code LocationRequest}</a>.
  The parameters determine the level of accuracy for location requests. For
  details of all available location request options, see the
  <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html">{@code LocationRequest}</a>
  class reference. This lesson sets the update interval, fastest update
  interval, and priority, as described below:</p>

<dl>
  <dt>
    Update interval
  </dt>
  <dd>
    <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#setInterval(long)">{@code setInterval()}</a>
    - This method sets the rate in milliseconds at which your app prefers to
    receive location updates. Note that the location updates may be faster than
    this rate if another app is receiving updates at a faster rate, or slower
    than this rate, or there may be no updates at all (if the device has no
    connectivity, for example).
  </dd>
  <dt>
    Fastest update interval
  </dt>
  <dd>
    <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#setFastestInterval(long)">{@code setFastestInterval()}</a>
    - This method sets the <strong>fastest</strong> rate in milliseconds at which
    your app can handle location updates. You need to set this rate because
    other apps also affect the rate at which updates are sent. The Google Play
    services location APIs send out updates at the fastest rate that any app
    has requested with
    <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#setInterval(long)">{@code setInterval()}</a>.
    If this rate is faster
    than your app can handle, you may encounter problems with UI flicker or data
    overflow. To prevent this, call
    <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#setFastestInterval(long)">{@code setFastestInterval()}</a>
    to set an upper limit to the update rate.
  </dd>
  <dt>Priority</dt>
  <dd>
    <p>
      <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#setPriority(int)">{@code setPriority()}</a>
      - This method sets the priority of the request, which gives the Google Play
      services location services a strong hint about which location sources to use.
      The following values are supported:</p>
      <ul>
        <li>
          <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#PRIORITY_BALANCED_POWER_ACCURACY">{@code PRIORITY_BALANCED_POWER_ACCURACY}</a>
          - Use this setting to request location precision to within a city
          block, which is an accuracy of approximately 100 meters. This is
          considered a coarse level of accuracy, and is likely to consume less
          power. With this setting, the location services are likely to use WiFi
          and cell tower positioning. Note, however, that the choice of location
          provider depends on many other factors, such as which sources are
          available.</li>
        <li>
          <a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#PRIORITY_HIGH_ACCURACY">{@code PRIORITY_HIGH_ACCURACY}</a>
          - Use this setting to request the most precise location possible. With
          this setting, the location services are more likely to use GPS
          to determine the location.</li>
        <li><a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#PRIORITY_LOW_POWER">{@code PRIORITY_LOW_POWER}</a>
          - Use this setting to request city-level precision, which is
          an accuracy of approximately 10 kilometers. This is considered a
          coarse level of accuracy, and is likely to consume less power.</li>
        <li><a href="https://developers.google.com/android/reference/com/google/android/gms/location/LocationRequest.html#PRIORITY_NO_POWER">{@code PRIORITY_NO_POWER}</a>
          - Use this setting if you need negligible impact on power consumption,
          but want to receive location updates when available. With this
          setting, your app does not trigger any location updates, but
          receives locations triggered by other apps.</li>
      </ul>
  </dd>
</dl>

<p>Create the location request and set the parameters as shown in this
  code sample:</p>

<pre>
protected void createLocationRequest() {
    LocationRequest mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10000);
    mLocationRequest.setFastestInterval(5000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}
</pre>

<p>The priority of
  <a href="{@docRoot}reference/com/google/android/gms/location/LocationRequest.html#PRIORITY_HIGH_ACCURACY">{@code PRIORITY_HIGH_ACCURACY}</a>,
  combined with the
  {@link android.Manifest.permission#ACCESS_FINE_LOCATION ACCESS_FINE_LOCATION}
  permission setting that you've defined in the app manifest, and a fast update
  interval of 5000 milliseconds (5 seconds), causes the fused location
  provider to return location updates that are accurate to within a few feet.
  This approach is appropriate for mapping apps that display the location in
  real time.</p>

<p class="note"><strong>Performance hint:</strong> If your app accesses the
  network or does other long-running work after receiving a location update,
  adjust the fastest interval to a slower value. This adjustment prevents your
  app from receiving updates it can't use. Once the long-running work is done,
  set the fastest interval back to a fast value.</p>

<h2 id="get-settings">Get Current Location Settings</h2>

<p>Once you have connected to Google Play services and the location services
    API, you can get the current location settings of a user's device. To do
    this, create a
    <a href="{@docRoot}reference/com/google/android/gms/location/LocationSettingsRequest.Builder"><code>LocationSettingsRequest.Builder</code></a>,
    and add one or more location requests. The following code snippet shows how
    to add the location request that was created in the previous step:</p>

<pre>LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
     .addLocationRequest(mLocationRequest);
</pre>

<p>Next check whether the current location settings are satisfied:</p>

<pre>PendingResult&lt;LocationSettingsResult&gt; result =
         LocationServices.SettingsApi.checkLocationSettings(mGoogleClient,
                 builder.build());</pre>

<p>When the <a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult"><code>PendingResult</code></a>
  returns, your app can check the location settings by looking at the status
  code from the <a href="{@docRoot}reference/com/google/android/gms/location/LocationSettingsResult"><code>LocationSettingsResult</code></a>
  object. To get even more details about the the current state of the relevant
  location settings, your app can call the
  <a href="{@docRoot}reference/com/google/android/gms/location/LocationSettingsResult">{@code LocationSettingsResult}</a>
  object's
  <a href="{@docRoot}reference/com/google/android/gms/location/LocationSettingsResult#getLocationSettingsStates"><code>getLocationSettingsStates()</code></a>
  method.</p>

<h2 id="prompt">Prompt the User to Change Location Settings</h2>

<p>To determine whether the location settings are appropriate for the location
  request, check the status code from the
  <a href="{@docRoot}reference/com/google/android/gms/location/LocationSettingsResult">{@code LocationSettingsResult}</a>
  object. A status code of <code>RESOLUTION_REQUIRED</code> indicates that the
  settings must be changed. To prompt the user for permission to modify the
  location settings, call
  <a href="{@docRoot}reference/com/google/android/gms/common/api/Status#startResolutionForResult(android.app.Activity, int)">
            {@code startResolutionForResult(Activity, int)}</a>.
  This method brings up a dialog asking for the user's permission to modify
  location settings. The following code snippet shows how to check the location
  settings, and how to call {@code startResolutionForResult(Activity, int)}.
</p>

<pre>result.setResultCallback(new ResultCallback&lt;LocationSettingsResult&gt;()) {
     &#64;Override
     public void onResult(LocationSettingsResult result) {
         final Status status = result.getStatus();
         final LocationSettingsStates = result.getLocationSettingsStates();
         switch (status.getStatusCode()) {
             case LocationSettingsStatusCodes.SUCCESS:
                 // All location settings are satisfied. The client can
                 // initialize location requests here.
                 ...
                 break;
             case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
                 // Location settings are not satisfied, but this can be fixed
                 // by showing the user a dialog.
                 try {
                     // Show the dialog by calling startResolutionForResult(),
                     // and check the result in onActivityResult().
                     status.startResolutionForResult(
                         OuterClass.this,
                         REQUEST_CHECK_SETTINGS);
                 } catch (SendIntentException e) {
                     // Ignore the error.
                 }
                 break;
             case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
                 // Location settings are not satisfied. However, we have no way
                 // to fix the settings so we won't show the dialog.
                 ...
                 break;
         }
     }
 });</pre>

  <p>The next lesson,
    <a href="receive-location-updates.html">Receiving Location Updates</a>, shows
    you how to receive periodic location updates.</p>