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
Add some final polish by saving state across rotation and displaying loading and error states.
Now we need to actually
perform our API call.
0:00
You don't have a method to actually do
that from our Etsy class yet so let's go
0:03
ahead and add in a new method to Etsy
class so we can perform a call to our API.
0:07
This method needs to be public so that
the activity class has access to it and
0:13
can call it.
0:17
Now the important thing
is that this is void.
0:20
We're just going to be
passing in the call back.
0:22
So the call back is going to get
called back when the network request
0:25
completes and
is parsed into the active listings.
0:29
I'm gonna call this getActiveListings.
0:34
And it's going to take in
the callback of type active listings.
0:37
And what we're going to do is,
oh, import callback type,
0:42
what we're going to do is just call API,
and the API has our active listings.
0:47
And to call that we need
to include images and shop.
0:54
And it's asking for
the call back itself, which is here, so
0:58
now that, since this is public,
we can call it from our main activity.
1:02
First what we need to do is
set up our recycler view.
1:08
To do this we need to set a layout
manager on our recycler view, and
1:14
in this case, I'm just going to use
a staggered grid layout manager.
1:18
And it's going to take number
of spans that we want.
1:23
For now, I'll just say one.
1:26
And it wants an orientation, which just
going to say vertical to start out with.
1:27
You might want to change the span
count to be based on a dimension or
1:35
integer, based on the number columns
that might fit on the screen.
1:39
You can choose whatever you want.
1:43
I'm just going to go ahead and
go with one for now.
1:45
And our list is going to be scrolling hor,
vertically up and down.
1:47
So we've chosen vertical.
1:51
Next, we need to go ahead and
set an adapter on here.
1:54
I'm going to say new listing adapter.
1:56
We need a pass and a context,
which is this referring to the activity.
2:02
And we need, actually,
2:07
to use this adapter because remember
this adapter is our call back.
2:08
So, let's go ahead and
take this adapter object, and
2:12
get that reference before we assign it.
2:16
And then what we're going to do
is first time we're running,
2:23
saved instance state will be null.
2:28
We can go ahead and
just fire off the API call.
2:29
We're going to pass in the adapter.
2:34
Okay.
This looks pretty great.
2:37
We need to go ahead and
save state as well.
2:39
So let's override the on
save instance state method,
2:42
and in on save instance state,
2:48
we need to save the data
that came back from the API,
2:51
so I'm going to keep the key for
the save instance state.
2:56
If savedInstanceState was null, it was the
first time, we're going to go ahead, and
3:10
again, and show loading.
3:14
If it wasn't null, we need to go ahead and
pull out from savedInstanceState.
3:18
The parsable object,
which is our active listings and
3:25
on our adapter,
we need to call success with that data.
3:32
The data is the parsable object.
3:44
Which is in fact active listings, object.
3:45
And the second value of success
is the response itself.
3:51
Which we can just pass in null.
3:59
So now, if it's the first time running,
we're going to go ahead and show loading,
4:03
we're going to make the call to
the network, otherwise when we come back,
4:07
if we have that active listings there,
we're going to just go ahead and
4:10
set it on the adapter and
display our lists.
4:15
But it might be the case that we don't
have any data yet, so we need to make sure
4:20
we check if there's any data to begin
with in the saved instance state.
4:24
So we're gonna only do this if the saved
instance state contains the key.
4:27
So if it contains that key
that means it had some data.
4:35
And it, on saving some state, we're gonna
go ahead and check by getting that data.
4:39
Now we need to add a method to our
adapter to get the current data, so
4:45
let's go ahead and add that in here.
4:49
Public, it's gonna return back
that active listings object,
4:53
getActiveListings, and we're just gonna
return our active listings object.
4:58
It may or may not be null,
it could be null.
5:03
So, we need to check that.
5:06
Now we have to have access to our
adapter here so, let's go ahead and
5:08
move the scope of this to be just
within our activity class itself.
5:13
So, if the active listings are not null,
we're gonna to go ahead and
5:31
put them in our outState window.
5:34
Put parsable, going to give it the key,
and the actual active listings object.
5:38
So if we have that data, it'll be
passed into the bundle, the outstate.
5:44
Then come back to on create.
5:49
We're going to check if there's data.
5:52
Go ahead and display it.
5:54
If not, kick off a call to the API.
5:55
So in this case, again there was an eta,
it wasn't stored in the save instance
5:59
state bundle, so again we need to show
loading, and do another call to the API.
6:04
One last thing we want to do is in
our adapter, we want to go ahead and
6:15
if failure does happen,
we want to call back to our activity and
6:19
say we should display that error text.
6:22
So, since that's the case,
we need access to that activity.
6:25
So, instead of passing in
a generic context here,
6:28
let's just pass in our
main activity itself.
6:31
And we'll just call this activity instead.
6:35
And we'll keep a reference
to it here in the class.
6:40
And then down on success.
6:53
We're gonna go ahead and show the list by
calling to our activity show the list.
6:58
Otherwise, you wanna show that failure.
7:05
So it's gonna show the error message here.
7:11
And error message we can actually
retrieve from our object here.
7:14
Okay, let's go ahead and run this to
see if everything is working okay,
7:18
we should get a call to the network, get
a response back, display some listings.
7:21
Our app now displays listings from an API.
7:30
We use the Retrofit library to
make it easy to call the API and
7:34
parse the response to the type we need.
7:37
After that, we displayed
the list using Recycler view and
7:40
the staggered grid layout manager.
7:43
Finally, in our adapter, we used
the Picasso library to display the images.
7:46
You need to sign up for Treehouse in order to download course files.
Sign up