1page.title=Manipulating Broadcast Receivers On Demand 2parent.title=Optimizing Battery Life 3parent.link=index.html 4 5trainingnavtop=true 6 7previous.title=Determining and Monitoring the Connectivity Status 8previous.link=connectivity-monitoring.html 9 10@jd:body 11 12<div id="tb-wrapper"> 13<div id="tb"> 14 15<h2>This lesson teaches you to</h2> 16<ol> 17 <li><a href="#ToggleReceivers">Toggle and Cascade State Change Receivers to Improve 18Efficiency</a></li> 19</ol> 20 21 22<h2>You should also read</h2> 23<ul> 24 <li><a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filters</a> 25</ul> 26 27</div> 28</div> 29 30<p>The simplest way to monitor device state changes is to create a {@link 31android.content.BroadcastReceiver} for each state you're monitoring and register each of them in 32your application manifest. Then within each of these receivers you simply reschedule your recurring 33alarms based on the current device state.</p> 34 35<p>A side-effect of this approach is that your app will wake the device each time any of these 36receivers is triggered—potentially much more frequently than required.</p> 37 38<p>A better approach is to disable or enable the broadcast receivers at runtime. That way you can 39use the receivers you declared in the manifest as passive alarms that are triggered by system events 40only when necessary.</p> 41 42 43<h2 id="ToggleReceivers">Toggle and Cascade State Change Receivers to Improve Efficiency </h2> 44 45<p>You can use the {@link android.content.pm.PackageManager} to toggle the enabled state on any 46component defined in the manifest, including whichever broadcast receivers you wish to enable or 47disable as shown in the snippet below:</p> 48 49<pre>ComponentName receiver = new ComponentName(context, myReceiver.class); 50 51PackageManager pm = context.getPackageManager(); 52 53pm.setComponentEnabledSetting(receiver, 54 PackageManager.COMPONENT_ENABLED_STATE_ENABLED, 55 PackageManager.DONT_KILL_APP)</pre> 56 57<p>Using this technique, if you determine that connectivity has been lost, you can disable all of 58your receivers except the connectivity-change receiver. Conversely, once you are connected you can 59stop listening for connectivity changes and simply check to see if you're online immediately before 60performing an update and rescheduling a recurring update alarm.</p> 61 62<p>You can use the same technique to delay a download that requires higher bandwidth to complete. 63Simply enable a broadcast receiver that listens for connectivity changes and initiates the 64download only after you are connected to Wi-Fi.</p> 65