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G'day everyone, welcome back. As SettingsDialog
isn't doing much at the moment, one thing

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it should certainly do, is save the
values of the user changes. We'll do that

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using the default shared preferences, and
we've seen that before, in the flickr

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browser app. We've got two values to save;
the day that a week starts on, and the

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number of seconds for timings that we
won't bother saving. Because the shared

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preferences uses key value pairs to
store the values, just like a bundle,

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I'll declare some constants for the two
keys. I'll also use the constants for the

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default values - the values that will be
used if the user hasn't chosen a

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different value.

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We can use those default constants to
initialize the fields or store the

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values. We also need a default day that
the week starts on.

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When we create a new gregorian calendar
instance and provide it with a locale,

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it'll automatically start the week on the
usual day for that locale. Well, it'll do

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that most of the time. I'll talk more
about that later.

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Alright, now we can write the functions
to save the settings, and read them back

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in again. I'll start with, say, values,
which I'll put after the onViewCreated

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function.

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There's nothing too complicated in there.
The spinner widget has a selected item

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position property, that returns a
zero-based value, corresponding to the

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position of the item in the list. Sunday
will be 0, Monday will be 1, and so forth.

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I've added 1 to the value to save time
later. When we come to work with dates,

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you'll see that the calendar class
uses 1 for Sunday, 2 for Monday, etc.

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The important thing is, that we won't end up
adding an incorrect value. The seek bar

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widget returns its value in the get
Progress method, but because we're using

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Kotlin, we can access it as a property.
We'll get back a value from 0, to the

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maximum value that we set, and we set
that at 24 in the layout. It's still not

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clear why I chose the value 24, but don't
worry, we'll be coming to that. Before

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saving the preferences, we check that
they have changed. That saves the user's

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battery, because we're not writing values
unnecessarily. There's another important

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reason for doing that. Our app will be
listening to the preferences, and will do

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things like re-querying the data, if the
starting date changes. That's quite

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costly, and we really don't want to do
that if the setting hasn't been changed.

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Alright, our SettingsDialog will need
to read in the current settings, so the

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widgets correctly reflect the stored
values. We'll need a readValues function

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to do that, and I'll put it before the
saveValues.

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That's just the reverse of saveValues.
We specify a default value for each call

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to getInt, so that we've got the correct
defaults, if no settings have been saved

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yet. Alright, the last step is to make
sure the two widgets reflect the values

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that we've just read in. The place to do
that is in the onViewStateRestored

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function. I mentioned that back in the
videos about the fragment life cycle.

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If we try to set the widgets in onView
Created, they'll be reset when onRestore

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InstanceState gets called. onViewState
Restored is called after Android's

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restored the state of all the widgets in
the view, and that's where I need to set

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them. I used the example of a checkbox in
the life cycle videos, but it applies to

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any widget that Android will save and
restore for us. I'll get Android studio

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to generate the stub after onViewCreated,

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then add the code.

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We can test the settings are working
after uncommenting that call to save

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Values, in the okButton's onClick
handler, onViewCreated.

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Okay, run the app and let's see how the settings behave.

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I'll change the start date to Monday, and
drag the slider to about halfway.

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When I tap OK, the settings should be saved. That
means they'll show Monday, and a seek

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bar value of about halfway, when I
go back in. And that's looking good.

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I'll choose Thursday and drag the slider all
the way to the right, then tap OK and go

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back into settings. That's working. For
the final test,

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I'll choose Friday and drag the slider
back to halfway. This time, I'll tap

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cancel. When I go back into settings, it
still shows Thursday with the slider

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over on the right. Cancelling doesn't save
the settings, so that's working as well.

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The text above the slider doesn't look
very good. In the next video, we'll see

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how we can replace that with the seek
bar's value. See you then.