title: what is the purpose of `setInitialTrigger` on GeofencingRequest?
body: <p>I really don't understand the function <code>setInitialTrigger</code> on <code>GeofencingRequest</code> class.</p>
  
  <p>I know that we can create some <code>Geofence</code> object whith different transition:</p>
  
  <ol>
  <li>Enter</li>
  <li>Exit</li>
  <li>Dwell</li>
  </ol>
  
  <p>Which is fine for me and acceptable.</p>
  
  <p>Now, my problem is relatively to the class <code>GeofencingRequest</code> and more precisely the method <code>setInitialTrigger</code>.
  I really don't understand the value that we should put there...
  Android documentation (<a href="https://developer.android.com/training/location/geofencing.html" rel="nofollow noreferrer">here</a>) isn't really helpful regarding to the meaning of that method.</p>
  
  <p>Imagine that I have this piece of code:</p>
  
  <pre><code>private GeofencingRequest getGeofencingRequest() {
          GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
          builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER);
          builder.addGeofences(mGeofenceList);
          return builder.build();
      }
  </code></pre>
  
  <p>What is the meaning of <code>GeofencingRequest.INITIAL_TRIGGER_ENTER</code> ?</p>
  
  <p>For me it means, that <code>GeofencingRequest</code> should trigger any <code>Geofence</code> object which have an <strong>ENTER</strong> transition.</p>
  
  <p>But imagine that I have multiple Geofence with different behaviour ENTER or EXIT transition.</p>
  
  <p>How should I handle/implement with GeofencingRequest Builder?</p>