1
00:00:00,000 --> 00:00:00,869
[MUSIC]

2
00:00:00,869 --> 00:00:07,110
We've just finishing
building our database.

3
00:00:07,110 --> 00:00:10,070
Now, to finish up the app,
we just need to connect it to the UI.

4
00:00:10,070 --> 00:00:14,960
We'll start by updating the save
button and creator activity.

5
00:00:14,960 --> 00:00:19,460
And by the end, we'll have the UI updating
itself whenever anything changes.

6
00:00:21,050 --> 00:00:25,000
The first step to using our database
is to retrieve an instance of it.

7
00:00:25,000 --> 00:00:28,130
Rather than retrieving our
database all over the place,

8
00:00:28,130 --> 00:00:32,140
let's just get it done once in our
application's onCreate method, and

9
00:00:32,140 --> 00:00:34,620
then make it available to
the rest of our project

10
00:00:34,620 --> 00:00:40,120
by declaring that variable outside of the
class to scope it to the entire project.

11
00:00:40,120 --> 00:00:42,150
Let's go ahead and
close the files we have open.

12
00:00:44,090 --> 00:00:46,160
And then head over to the app file.

13
00:00:48,360 --> 00:00:52,550
And below our toppings array
let's create a new lateinit var

14
00:00:53,660 --> 00:00:57,380
named db and
give it a type of pizza database.

15
00:00:59,780 --> 00:01:04,110
Then down in onCreate let's
add a line at the top and

16
00:01:04,110 --> 00:01:09,400
set db equal to a new instance
of our pizza database.

17
00:01:09,400 --> 00:01:14,400
So Room.databaseBuilder,

18
00:01:14,400 --> 00:01:18,300
we'll pass in the context,
which is just applicationContext.

19
00:01:19,890 --> 00:01:24,530
Then the database class
PizzaDatabaseclass.java.

20
00:01:24,530 --> 00:01:28,846
The name of the database which is

21
00:01:28,846 --> 00:01:34,471
"PizzaDatabase").build().

22
00:01:34,471 --> 00:01:35,480
Great.

23
00:01:35,480 --> 00:01:39,310
Now whenever we want to access
our database we'll just type, db,

24
00:01:39,310 --> 00:01:41,480
and be done with it.

25
00:01:41,480 --> 00:01:44,220
Now another thing we'll want
to do in this onCreate method

26
00:01:44,220 --> 00:01:46,870
is add our toppings to the database.

27
00:01:46,870 --> 00:01:49,580
Since we've already got a loop
going over the toppings list,

28
00:01:51,150 --> 00:01:54,280
let's just insert each of these
toppings to the database.

29
00:01:57,070 --> 00:02:03,220
So let's just add db.toppingDao.insert.

30
00:02:03,220 --> 00:02:04,260
And pass in the topping.

31
00:02:06,160 --> 00:02:09,550
Then, just to double check things,
let's try running the app.

32
00:02:09,550 --> 00:02:13,880
Don't forget to select app from the drop
down at the top before running it.

33
00:02:18,097 --> 00:02:20,880
Once it runs,
it looks like we got an error.

34
00:02:22,980 --> 00:02:28,991
And if we look in the logcat, And

35
00:02:28,991 --> 00:02:36,180
filter by errors, We can find the error.

36
00:02:36,180 --> 00:02:41,400
Cannot access database on the main thread
since it may potentially lock the UI for

37
00:02:41,400 --> 00:02:43,470
a long period of time.

38
00:02:43,470 --> 00:02:48,380
To fix this, every time we access our
database we need to do it on a new thread.

39
00:02:50,010 --> 00:02:56,400
Let's add a line above our foreach loop
and then wrap it inside a thread block.

40
00:03:01,930 --> 00:03:06,521
If you've not used Kotlin before this
is just a nice shortcut to let us

41
00:03:06,521 --> 00:03:09,460
quickly create new threads.

42
00:03:09,460 --> 00:03:11,050
Now let's try running the app again.

43
00:03:16,503 --> 00:03:18,419
Okay?

44
00:03:23,832 --> 00:03:29,840
Looks like we're getting a UNIQUE
constraint failed on our Topping.id.

45
00:03:29,840 --> 00:03:34,160
And if we look back at the app class we
can see that each time we run the app

46
00:03:34,160 --> 00:03:38,320
we're inserting the same
toppings each time.

47
00:03:38,320 --> 00:03:41,140
Or rather we're trying to insert them.

48
00:03:41,140 --> 00:03:45,920
But it's not letting us because these
toppings are already in the database.

49
00:03:45,920 --> 00:03:48,450
To fix this let's head
over to topping dow.

50
00:03:54,812 --> 00:03:58,502
And after the Insert annotation,
let's add () and

51
00:03:58,502 --> 00:04:01,213
then specify an on conflict strategy.

52
00:04:01,213 --> 00:04:05,694
onConflict = and let's set it =

53
00:04:05,694 --> 00:04:10,340
OnConflictStrategy.replace.

54
00:04:11,750 --> 00:04:17,110
Now if we try to insert the same topping
twice instead of throwing an error

55
00:04:17,110 --> 00:04:19,990
it will just replace
that row in the database.

56
00:04:19,990 --> 00:04:20,830
Perfect.

57
00:04:20,830 --> 00:04:22,220
Let's try running the app again.

58
00:04:29,130 --> 00:04:30,368
And there we go.

59
00:04:30,368 --> 00:04:32,590
The app ran successfully.

60
00:04:32,590 --> 00:04:35,340
Now that we've got our database
ready with our toppings,

61
00:04:35,340 --> 00:04:37,880
we can handle saving
pizzas in the next video.