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Notifications are another type of communication in Android that is similar in spirit to Broadcast Intents and Receivers. Local notifications show up in the notification drawer and display some information to the user, and optionally trigger some actions, too.
We first covered Notifications here at Treehouse in the Threads and Services course. To familiarize yourself with the initial setup, check out the Foreground Services video, where Ben Deitch sets up a local notification for a foreground service.
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[MUSIC]
0:00
[SOUND] Let's change
gears a little bit and
0:04
talk about a different
kind of communication.
0:06
Notifications, you probably know a little
bit about using Notifications from earlier
0:08
work here at Treehouse.
0:13
As usual check the teacher's notes for
links but
0:14
will cover it pretty well
in this last section.
0:17
Let's take another look at the table
we've been using in this course.
0:20
This last row shows an example of
when we might want a notification.
0:23
When a service needs to
send an update to the user.
0:27
In this example we'll extend an existing
notification that shows in the drawer
0:30
when the user is playing a song.
0:35
Note in this list that we don't
talk about using notifications
0:38
from an activity to the system.
0:41
We don't need a notification in that
scenario because the activity's
0:42
already visible to the user and
we can use a stacked bar or
0:45
some other in app mechanism for
alerting the user to something.
0:49
Let's start here by taking a look at
the documentation about notifications.
0:53
First part of a notification
is the icon that appears
0:57
in the notification bar at the top.
1:00
Then when the user pulls the drawer down,
the notification has its own
1:02
row in the drawer and
we can even add actions to them like this.
1:06
This app is currently using
a notification in the player service.
1:10
So let's check it out.
1:14
So here in the onStartCommand method
we are using the builder pattern from
1:16
the notification class to
build a simple notification.
1:21
All it does is display our app's
icon when a song is playing and
1:24
then it goes away when
the service stops playing music.
1:27
I think it would be nice to show
the title of the song playing.
1:29
So let's see how to do that.
1:32
First the notification builder
has a fluent interface.
1:34
So let's delete this semi-colon and
chain some of these things together.
1:38
I'm gonna get rid of notification builder,
tab over and
1:43
now at the end of this I can append
another line .setContentTitle.
1:47
Okay how do we get the song title in here.
1:54
We need to pass in a song
when this service is started.
1:57
Let's go back to Main Activity.
2:01
We're starting this service
when the play button is tapped.
2:03
So let's look at the On Click listener
we're going to scroll all the way up
2:06
to on create, and
here we have mplay button and
2:10
in this listener is where we
are starting the service.
2:14
All we need to do is add the song
as an extra to this intent.
2:17
So we say, intent.putExtra.
2:22
We can use the EXTRA key word SONG, and
2:24
now for the song itself, we can just
pass in the first song in our playlist.
2:29
Our playlist itself
isn't fully functional.
2:34
Though that would be an interesting
exercise if you'd like to extend this and
2:36
make it play everything in a given list.
2:39
Anyhow, let's type Playlist.songs, and
2:41
get the first one at index zero.
2:45
Now a challenge for you.
2:49
Pause me and see if you can set the song
and artist back in the service.
2:51
Use autocomplete to help you figure
out the additional text field
2:54
you might use for the artist name.
2:57
Okay did you get it?
3:01
I'm going to go back and
3:01
let's start with some place holders
here before we build our notification.
3:03
We have a string called title and
we'll initialize it to a blank string.
3:08
And then a string called artist
also initialized to a blank value.
3:13
I'm setting these to blank strings
because I'm going to do a null check and
3:18
I'll only update them
if a song is passed in.
3:22
I don't want the app to crash
if song data is missing.
3:24
So for the null check,
if (intent.getParcelableExtra) and
3:27
then we can use MainActivity.EXTRA_SONG.
3:32
If that's not equal to null, then we can
get a song and set title and artist.
3:37
So first, we have Song song
= intent.getParcelableExtra
3:43
MainActivity EXTRA_SONG.
3:50
Now we can set title equal
to song.getTitle and
3:53
artist equal to song.getArtist.
3:57
Now we can use these in
our notification builder.
4:01
So for ContentTitle let's pass in title.
4:04
And then I'm going to chain the artist
with .setContentText, and pass in artist.
4:07
And one more thing,
4:16
our regular app icon doesn't look
very good as a notification icon.
4:17
So I downloaded another one.
4:20
Let's call
R.Drawable.ic_queue_music_white.
4:23
Okay, let's try it out.
4:27
Okay, so we want to play some music.
4:32
There we go.
4:36
And look, there's our notification
showing up, and if we pull it down.
4:37
Hey it's showing the icon,
the title, and the artist.
4:40
Cool.
4:44
It would be really nice to open our
app directly from this notification.
4:45
Let's try to do that in the next video.
4:49
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