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We've got a pizza object and
a topping object.

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And when the app is created
we use the toppings list

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to generate our topping bitmaps.

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With that out of the way let's
move on to the activities.

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We've got main activity,
which was the list of pizzas.

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And creator activity,
which let's us customize the pizzas.

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Let's start with main activity.

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At the top of the file,
we've got a pizza ID constant.

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Other than that,
we just find the recyclerview.

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Give it a layout manager, and
set it up with an adapter.

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If you've not seen something
like this before, don't worry.

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It's just an anonymous
function stored in a variable.

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So launch creator activity is
a function that takes in an integer

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which might be null and when this
function runs, it will create an intent,

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add the pizza ID to the intent and
then start creator activity.

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So, let's jump into Main Adapter and
start from the top.

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You can use Cmd or
CTRL+B to jump to a class from its usage.

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First, we've got our LaunchCreatorActivity
function as the only parameter.

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And as we just saw it takes an integer
that might be null and returns nothing.

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From here, we have a list of pizzas
which will contain the pizzas

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to display on the screen.

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Each row in this RecyclerView
will use the pizza row layout.

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If we take a look at that layout,
under Resources and the Layout directory.

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We can see that it contains a text
view for the name of the pizza,

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a create new pizza button and
a divider line at the bottom.

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So instead of using multiple views for
the pizza rows and

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the create new pizza button, we just used
this one view and we'll hide the elements

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we don't need depending on whether we
wanna show the pizza or the button.

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Getting back to the adapter,
let's move onto the view holder.

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Back in the code we can see that the item
count is one more than the size of

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the list, this is to account for
the new pizza button at the bottom.

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Moving on to the view holder, we show or

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hide the views depending
on which type of row it is.

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So, if it's not the last item in the list,
we'll hide the button and if it is

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the last item in the list, we'll make the
button visible and hide everything else.

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We also set up the on click
listeners to call through to our

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launch creator activity function.

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If it's a pizza row that was clicked,
we'll pass in the ID of the pizza.

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And if the new pizza button was clicked,
we'll just pass in null.

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So regardless of which row we click,
we'll end up launching CreatorActivity.

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Let's hop over to CreatorActivity and
see where we go from here.

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Let me give us just a little
more room here as well.

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Let me just hide it instead.

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At the top of CreatorActivity we
create a pizza ID variable and

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lateinit it another
variable named pizzaView.

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In Cotland, when you create a variable
you have to give it a value.

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But with lateinit, we can get around that.

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We just need to make sure it gets
initialized before we use it.

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Speaking of PizzaView, let's take
a quick detour of the PizzaView class.

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Remember, Cmd or Ctrl+B on the class
name will jump us into the class.

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PizzaView is a custom view, meaning it
extends from View that draws a pizza.

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It starts by drawing a big circle for
the crust.

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Then it draws a smaller circle for
the body of the pizza.

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And finally draws each
of the toppings on top.

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To tell it which toppings to draw,
we pass in a map of toppings to Booleans.

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If a topping is paired with
the value of true, we draw it.

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Otherwise we don't and that's about all we
need to know about the PizzaView class.

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Though, feel free to pause me and

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look through the rest of
this code if you'd like.

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Getting back to CreatorActivity and
the onCreate method,

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we retrieve the Pizza ID
from the intent and

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initialize our PizzaView to an empty
pizza, by passing in an empty map.

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Later on when we have some data,
we'll update this map to not be empty.

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From here we add our PizzaView to the
frameLayout at the top of the screen and

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set up our recyclerView
that lives at the bottom.

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To finish out CreatorActivity,

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we've got a couple methods to set up
the menu at the top of the screen.

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On create options menu,
creates the menu and

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on options item selected is where we
add functionality to the menu items.

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The last class we need to
look at is CreatorAdaptor.

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This class manages the recyclerView
at the bottom of CreatorActivity.

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And as a parameter,
it takes in a pizza view.

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With this pizza view at the bottom,
when a switch is checked,

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we update the toppings mapping
with the state of the switch and

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tell the pizza view to update by
calling the invalidate method.

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Awesome we've now got a good
understanding of the app, and

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are ready to implement that resistance,
I know that was a lot to cover.

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But don't worry, from here on out we'll
be taking things one step at at time.

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And if you want to spend some
more time playing around and

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getting comfortable with the app,
please do.

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I'll be here waiting for
you when you get back.