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Handling Being Killed
3:13In this video we go over the various return values from onStartCommand and what each of those values means!
Enough of this stopping services stuff.
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Let's get back to the par with
the invincible service refuses today.
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But first a quick recap.
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The return value of onStarCommand
represents what will happen to a service
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if its process is killed after
returning from onStarCommand,
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but before being stopped.
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Put more simply,
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it's what will happen if your service
is killed without finishing its work.
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Earlier I mentioned that there
are three constants we can return from
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onStarCommand.
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Those constants are START_STICKY,
START_NOT_STICKY, and
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START_REDELIVER_INTENT.
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There's actually a fourth value
START_STICKY_COMPATIBILITY.
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But it's not important to learn about,
so we've just got START_STICKY,
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START_NOT_STICKY, and
START_REDELIVER_INTENT.
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Let's kick things off with START_STICKY.
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Returning Service.START_STICKY and
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onStartCommand tells Android to restart
our service using a null intent.
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This is useful for things you might
want to leave running for a long time.
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Like a music player or
an app to track where you went on a run.
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Once these things are started, it's up
to the user to decide when to stop them.
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If I'm out running and Android kills
my run tracking app, I'm going to be
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pretty unhappy if it doesn't come back and
track the rest of my run.
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S is just what you think it would be.
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If we return Service.START_NOT_STICKY
from onStartCommand,
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then our service won't be restarted.
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An example of this would be a service
that checks for new emails in your inbox.
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And let say this service is
started every five minutes.
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So every five minutes,
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this service will run and
update your inbox with any new messages.
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But if Android is so
burdened that it kills your app,
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it's probably not the best idea to throw
rescheduling this service into the mix.
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After all, it'll be started
again in five minutes anyway.
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Last, but not least,
is START_REDELIVER_INTENT.
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If we return
Service.START_REDELIVER_INTENT
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from onStartCommand, our service will be
restarted using the last delivered intent.
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In fact, for every intent,
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if the associated start ID hasn't
been included in a call to stop self
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then our service's onStartCommand
method will be called with the intent.
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Here's an example.
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Let's say we've downloaded the first two
songs and then our process gets killed.
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Since we've only downloaded
two songs we haven't yet
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called stopSelf for songs 3, 4 or 5.
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So the three intense associated with
these songs will be redelivered to
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our service when it's restarted.
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And there we go.
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Those are the three things we can have
happen when our process is killed
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while our service is still working.
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We can restart the service with
a null intent, START_STICKY,
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not restart the service, START_NOT_STICKY,
or restart the service and
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redeliver all unfinished intents,
START_REDELIVER_INTENT.
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