- What is Model-View-Presenter (MVP)? 4:45
- Why Do We Use MVP? 3:28
- Review: Model-View-Presenter 8 questions
- Defining the Data Model 2:53
- Implementing the Data Model 6:26
- Creating a Data Model 4 objectives
- Adding Story Resources 2:57
- Creating the Story 3:54
- Adding Custom Constructors 4:05
- Adding a Custom Constructor 2 objectives
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Adding Custom Constructors
4:05Finally, we will make our model code even easier to work with by adding some custom constructors to our Page and Choice classes.
We now want to add some custom
constructors to our model objects.
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Let's open up our page class first.
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Now, we could just type out
a constructor here, but once again,
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there's a really helpful
shortcut from Android Studio.
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If we click on Code, and then Generate,
we can pick a Constructor.
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And we want to use all four of these as
parameters, so I'll hold down Shift and
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click on the last item.
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Click OK and there we go, we have a nice
tidy constructor that will populate a new
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page object with all four settings.
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Let's do the same thing for
our Choice class.
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So again, I'm gonna put my cursor where
I want the new constructor to go,
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then click on Code > Generate >
Constructor, select both and click OK.
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All right, so
let's use these back in our story class.
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Let's get rid of this code here, and
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we'll do it a little bit differently
with our fancy new constructors.
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So, this time the page at
index 0 will equal a new Page,
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and we can pass in those parameters we
were all ready using, R.drawable.page0.
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For the text ID, R.string.page0.
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And for the choices, we can create
new choice objects right in line.
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But just to make this
a little easier to read,
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I'm going to put each
parameter on a new line.
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So next, we have choice one,
so I'll say newChoice.
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And the text will be
R.string.page0_choice1.
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The second primer is the next page,
but I'm gonna leave that blank for
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just a second.
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Add a comma and do it again,
new Choice R.string.page0_choice2.
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With another blank.
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I will add this semicolon though.
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Right now we're working on Page 0, here.
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The first choice takes us to page 1, and
the second choice takes us to page 2, so
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we can plug in the page
numbers in our constructor.
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Okay, so here's the first choice,
and it goes to page 1, and
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the second choice goes to page 2.
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Cool, we have our first page.
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The rest will follow this same format,
so I'm just going to copy and
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paste the remaining page details.
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This code is once again available for
you to copy and
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paste from the teacher's notes.
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Now, I have some errors down here
at the bottom, but that's okay.
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Take a look at pages 5 and
6 in our story map.
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These are the two final
pages of the story,
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which means that we don't have
any choices at this point.
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How should we handle this scenario?
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Once again,
we could solve this a few different ways.
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But since we don't need any choices, let's
add a second custom constructor in our
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page class that simply doesn't
have any choice parameters.
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So back here I'm gonna add a new one
up here and I'm going to generate it.
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Code > Generate a constructor, and
this time I only want image and text.
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So, without setting any choice parameters,
those will now be null by default.
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Now, for
this scenario where it is a final page,
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I want to add one more
variable that tells us so.
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So, here at the top,
lets add private boolean isFinalPage.
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IsFinalPage will be false by default, but
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I'd like to make that explicitly clear
by adding = false just to make sure.
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Now, inside of our new constructor,
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we can add another line to
set final page to true.
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So this.isFinalPage in this case is true.
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We'll use this when we're crafting
our story in just a little bit.
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We should add getters and setters for
this new variable too, so
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I'm going to add a new line down here.
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Then click on Code and Generate >
Getter and Setter for the new variable.
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Click OK and there we go.
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Our data model is complete and
we have a story to read.
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In the past few videos, we explored how
to turn the abstract data of this app
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into a set of concrete Java
objects that we could use.
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The way we structured our
objects allows us to store and
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manage the data separately from the view
and controller parts of our app.
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Which is a core component
of the MVC pattern.
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Now, I don't know about you but
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I am really excited to finally
display our story in the app.
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So, why don't you take a break for
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a co-challenge, and then we will
finish it up in the next section.
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