Staying awake with WakeLocks

Earlier in this chapter we learned that we can use a BroadcastReceiver to handle alarms, and even do work in the background for up to 10 seconds, though only on devices running API level 11 or greater.

In the previous section, we saw that handling alarms directly with services is not a reliable solution for scheduling long-running work, since there is no guarantee that our Service will start up before the device returns to sleep.

We have a problem! If we want to perform long-running work in response to alarms, we need a solution that overcomes these limitations.

What we really want is to start a Service to handle the work in the background, and to keep the device awake until the Service has finished its work. Fortunately, we can do that by combining the wakefulness guarantees of BroadcastReceiver to get the Service started, then keep the device awake with explicit power management using PowerManager and WakeLock.

As you might guess, WakeLock is a way to force the...