Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
A RoomDatabase ties together Entities and Daos to create one cohesive database. In this video we'll create the RoomDatabase for our app!
Related Links
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
Now that we've created our dows and
0:00
our entities it's time to create a room
database to help organize all of it.
0:02
As per usual this will
involve using annotations.
0:07
And it'll even involve
using an abstract class.
0:11
But don't worry,
0:14
you don't need to understand how it works
under the hood to be able to use it.
0:15
The first thing we'll need to
do is create an abstract class
0:19
that extends from room database.
0:22
Inside the data package, let's create
a new class, And name it pizza database.
0:25
Then let's make this an abstract class
by adding abstract to the front and
0:34
make it extend from room database.
0:39
And use Alt+Enter to add
the call to the constructor.
0:44
Next, above the class,
we need to add the @Database annotation.
0:47
Inside this annotation is
where it'll specify which
0:52
entities are in our database,
as well as the version number.
0:54
We'll start the version number at 1, and
0:58
increase it every time we change
something structural about our database.
1:00
Like adding a new table or
renaming a column.
1:04
Inside the parenthesis,
1:07
let's set the entities parameter equal to
an array containing our entity classes.
1:09
We've got Pizza::class,
1:14
PizzaTopping class and
1:19
Topping::class.
1:24
Then let's add a comma, and
set version equal to 1.
1:28
Awesome, now that we've connected
the entities to our database,
1:33
it's time to give access to our DAOs.
1:38
For each DAO,
1:40
we'll need to add an abstract function
that returns an instance of that DAO.
1:41
Let's start by creating
an abstract function PizzaDao and
1:46
make it return a PizzaDao.
1:51
>> Then let's make another abstract
function called PizzaToppingDao.
1:56
>> And make it return a PizzaToppingDao.
2:03
>> And finishing up,
let's create an abstract function
2:07
called toppingDao which
returns toppingDao.
2:12
All right, that does it for
our room database.
2:15
Let's see how to use it.
2:20
Let's open up main activity.
2:21
And right below the call to set content
view, let's create a new val named db and
2:24
set it equal to room inner to
import it database builder.
2:31
And then we need to pass in a context,
2:38
the Java class of our room database and
what we would like to call the database.
2:40
So let's pass in this for the context.
2:47
PizzaDatabase::class.java for the class.
2:49
And let's call it PizzaDatabase.
2:56
And then give us a little
more room as well.
3:04
And now we've got our
database builder object.
3:08
From here we can set some
properties of our database or
3:11
use the build a function to return
an instance of our specific database.
3:15
Which in our case, is a pizza database.
3:19
Let's add a call to .build which we
can see returns a pizza database.
3:22
And on the next line, if we type db.,
we've got access to each
3:27
of our DAOs and
can call in to any of our queries.
3:32
Okay, it's time to start
implementing this in the app and
3:39
finally make the UI do something, right?
3:43
Not quite, we've done a lot of work here.
3:46
But to make sure we've done it correctly,
we'll need to test it.
3:49
Sure, we could just test it in the app,
but then we'd have to go through and
3:52
test everything manually.
3:57
And that might be hard to tell the
difference between a bug in the database
3:58
and a bug in the UI.
4:02
Instead, let's write some tests
to make sure everything's working
4:03
before we start putting it in the app.
4:07
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up