1page.title=Determining and Monitoring the Docking State and Type
2parent.title=Optimizing Battery Life
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6previous.title= Monitoring the Battery Level and Charging State
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11@jd:body
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13<div id="tb-wrapper">
14<div id="tb">
15
16<h2>This lesson teaches you to</h2>
17<ol>
18  <li><a href="#CurrentDockState">Determine the Current Docking State</a></li>
19  <li><a href="#DockType">Determine the Current Dock Type</a></li>
20  <li><a href="#MonitorDockState">Monitor for Changes in the Dock State or Type</a></li>
21</ol>
22
23
24<h2>You should also read</h2>
25<ul>
26  <li><a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filters</a>
27</ul>
28
29</div>
30</div>
31
32<p>Android devices can be docked into several different kinds of docks. These include car or home
33docks and digital versus analog docks. The dock-state is typically closely linked to the charging
34state as many docks provide power to docked devices.</p>
35
36<p>How the dock-state of the phone affects your update rate depends on your app. You may choose
37to increase the update frequency of a sports center app when it's in the desktop dock, or disable
38your updates completely if the device is car docked. Conversely, you may choose to maximize your
39updates while car docked if your background service is updating traffic conditions.</p>
40
41<p>The dock state is also broadcast as a sticky {@link android.content.Intent}, allowing you to
42query if the device is docked or not, and if so, in which kind of dock.</p>
43
44
45<h2 id="CurrentDockState">Determine the Current Docking State</h2>
46
47<p>The dock-state details are included as an extra in a sticky broadcast of the {@link
48android.content.Intent#ACTION_DOCK_EVENT} action. Because it's sticky, you don't need to register a
49{@link android.content.BroadcastReceiver}. You can simply call {@link
50android.content.Context#registerReceiver registerReceiver()} passing in {@code null} as the
51broadcast receiver as shown in the next snippet.</p>
52
53<pre>IntentFilter ifilter = new IntentFilter(Intent.ACTION_DOCK_EVENT);
54Intent dockStatus = context.registerReceiver(null, ifilter);</pre>
55
56<p>You can extract the current docking status from the {@code EXTRA_DOCK_STATE} extra:<p>
57
58<pre>int dockState = battery.getIntExtra(EXTRA_DOCK_STATE, -1);
59boolean isDocked = dockState != Intent.EXTRA_DOCK_STATE_UNDOCKED;</pre>
60
61
62<h2 id="DockType">Determine the Current Dock Type</h2>
63
64<p>If a device is docked, it can be docked in any one of four different type of dock:
65<ul><li>Car</li>
66<li>Desk</li>
67<li>Low-End (Analog) Desk</li>
68<li>High-End (Digital) Desk</li></ul></p>
69
70<p>Note that the latter two options were only introduced to Android in API level 11, so it's good
71practice to check for all three where you are only interested in the type of dock rather than it
72being digital or analog specifically:</p>
73
74<pre>boolean isCar = dockState == EXTRA_DOCK_STATE_CAR;
75boolean isDesk = dockState == EXTRA_DOCK_STATE_DESK ||
76                 dockState == EXTRA_DOCK_STATE_LE_DESK ||
77                 dockState == EXTRA_DOCK_STATE_HE_DESK;</pre>
78
79
80<h2 id="MonitorDockState">Monitor for Changes in the Dock State or Type</h2>
81
82<p>Whenever the device is docked or undocked, the {@link
83android.content.Intent#ACTION_DOCK_EVENT} action is broadcast. To monitor changes in the
84device's dock-state, simply register a broadcast receiver in your application manifest as shown in
85the snippet below:</p>
86
87<pre>&lt;action android:name="android.intent.action.ACTION_DOCK_EVENT"/></pre>
88
89<p>You can extract the dock type and state within the receiver implementation using the same
90techniques described in the previous step.</p>
91