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[MUSIC]

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Hi, I'm Ben.

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In this course, we're going to
learn about the Activity Lifecycle.

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In the Android operating system, almost
all apps start and end with an activity.

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Activities get created,
paused, stopped and eventually,

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destroyed and
it's our responsibility as developers

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to make sure that we handle each of
these lifecycle changes gracefully.

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There's a bunch of different lifecycle
methods but before we get into that,

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let's see why it's so important that
we manage the activity lifecycle.

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Here's the fun facts project
from the very first course.

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Let's see what happens when we get
a new fun fact and then rotate the app.

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Instead of showing the new fact,
it's showing the first fact.

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It turns out, activities are entirely
recreated when the orientation changes.

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At first glance, this probably seems
a little weird but since different

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orientations require different layouts,
and those layouts require

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different resources, activities are always
recreated on an orientation change.

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Since Android handles
recreating the activity,

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all we have to handle is saving and
restoring our activity state.

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For example,
if a user is halfway down a giant list and

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they rotate the app, normally,
the activity will be restarted, and

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they'll be looking at the top of the list.

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But if we hook into
the right lifecycle events,

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we can save off their position in
the list when the activity stops and

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restore that position
when it gets recreated.

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That way, the user will be totally unaware
of what just happened behind the scenes.

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In the rest of this course,
we'll see how we can use a bundle to

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handle these kinds of changes, how we can
save data using shared preferences and

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we'll finish with a project that will you
a chance to show off what you've learned.

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It's a lot to cover.

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Let's get started.