1
00:00:00,700 --> 00:00:03,800
At this point, you might be wondering
how the heck does the Google Maps

2
00:00:03,800 --> 00:00:06,080
app know that we want to show a location.

3
00:00:06,080 --> 00:00:09,110
And how does the Android system
know if any app can show a location

4
00:00:09,110 --> 00:00:10,650
on a map or not?

5
00:00:10,650 --> 00:00:13,780
Well, Android uses something
called intent filters to track and

6
00:00:13,780 --> 00:00:17,020
register apps that can handle
certain kinds of intents.

7
00:00:17,020 --> 00:00:18,100
The idea is pretty simple.

8
00:00:18,100 --> 00:00:20,709
If you want your app to handle
a certain kind of intent,

9
00:00:20,709 --> 00:00:23,604
either one of the system ones
like this location example, or

10
00:00:23,604 --> 00:00:26,136
a custom one that you or
another developer creates.

11
00:00:26,136 --> 00:00:28,910
Then you need to say so
in your apps manifest.

12
00:00:28,910 --> 00:00:32,860
The Android manifest file contains
all that juicy metadata about

13
00:00:32,860 --> 00:00:35,157
your app that the operating system and

14
00:00:35,157 --> 00:00:39,127
Google Play can use to keep track
of which apps do certain things.

15
00:00:39,127 --> 00:00:42,320
You've actually already seen
intent filters in a manifest.

16
00:00:42,320 --> 00:00:44,230
We just haven't really
talked in detail about them.

17
00:00:45,350 --> 00:00:47,630
Let's open up AndroidManifest.xml.

18
00:00:47,630 --> 00:00:49,260
So it's up here in the manifest folder.

19
00:00:49,260 --> 00:00:50,650
Double click on it.

20
00:00:50,650 --> 00:00:53,600
And check out the registration for
MainActivity here.

21
00:00:54,760 --> 00:00:57,920
It has an element called intent-filter.

22
00:00:57,920 --> 00:01:01,300
And inside are two children,
action and category.

23
00:01:02,390 --> 00:01:05,550
This is the standard mean
launcher intent filter

24
00:01:05,550 --> 00:01:09,260
that specifies which activity
is used to start an app.

25
00:01:09,260 --> 00:01:10,230
Wait a minute.

26
00:01:10,230 --> 00:01:12,980
That means that apps
are started by intents.

27
00:01:12,980 --> 00:01:16,170
Yeah, these things are really
used all over the place.

28
00:01:16,170 --> 00:01:18,550
Since we don't have a map
viewer in this app,

29
00:01:18,550 --> 00:01:21,520
let's learn about intent filters
with a different example.

30
00:01:21,520 --> 00:01:24,080
One of the most common things
to share is simple text data.

31
00:01:24,080 --> 00:01:29,000
Many apps allow you to share data like,
select text, names, URLs or whatever.

32
00:01:29,000 --> 00:01:32,300
And many other apps use intent
filters to accept that data and

33
00:01:32,300 --> 00:01:34,510
do something with it,
like save it or post online.

34
00:01:35,640 --> 00:01:36,680
For demonstration purposes,

35
00:01:36,680 --> 00:01:40,590
let's just display the text in
the detail activity somewhere.

36
00:01:40,590 --> 00:01:42,990
So detail activity is listed
down here at the bottom.

37
00:01:44,230 --> 00:01:47,050
And inside,
we can add an intent filter element.

38
00:01:47,050 --> 00:01:52,026
So first, I'm gonna split this into a real
tag with a start and end activity tag.

39
00:01:54,624 --> 00:01:56,568
Make this line up.

40
00:01:56,568 --> 00:01:58,510
I'm also gonna add a little
bit of space at the bottom so

41
00:01:58,510 --> 00:02:00,590
that this bumps up on my screen.

42
00:02:00,590 --> 00:02:02,340
And we wanna add an intent filter.

43
00:02:04,400 --> 00:02:06,160
Now, how should we set this?

44
00:02:07,650 --> 00:02:11,390
Let's take a look at the documentation for
intents and intent filters.

45
00:02:11,390 --> 00:02:12,910
In the navigation here on the right,

46
00:02:12,910 --> 00:02:15,820
we see a section called
receiving an implicit intent.

47
00:02:15,820 --> 00:02:16,760
That's just what we're looking for.

48
00:02:17,770 --> 00:02:19,210
If we scroll down a little bit,

49
00:02:19,210 --> 00:02:23,460
we come to a section that lists the three
things we may need for an intent-filter.

50
00:02:23,460 --> 00:02:27,300
To be specific, we need one or
more of action, data and

51
00:02:27,300 --> 00:02:29,210
category, depending on
what we're trying to do.

52
00:02:30,580 --> 00:02:33,400
Pay attention to this
important note right here.

53
00:02:33,400 --> 00:02:35,650
In order to receive implicit intents,

54
00:02:35,650 --> 00:02:40,590
you must include the category default
category in the intent-filter.

55
00:02:40,590 --> 00:02:43,930
We are trying to receive an implicit
intent, so we need to add that.

56
00:02:43,930 --> 00:02:47,260
We also need an action and
hey, [LAUGH] look at that.

57
00:02:47,260 --> 00:02:49,850
Down here is an example
of sharing text data.

58
00:02:51,000 --> 00:02:54,970
It says we need to use
the ACTION_SEND as the action, and

59
00:02:54,970 --> 00:03:00,340
we can also specify the mime type
of the data with text/plain.

60
00:03:00,340 --> 00:03:04,804
Mime types can specify text,
images and other types of data.

61
00:03:04,804 --> 00:03:06,152
So let's add the action.

62
00:03:06,152 --> 00:03:11,247
Action and
then we say android:name equals,

63
00:03:11,247 --> 00:03:15,302
android.intent.action.SEND.

64
00:03:15,302 --> 00:03:18,560
And close this tag and
next we need the default category.

65
00:03:18,560 --> 00:03:21,980
So we say category,
then we add android:name, and

66
00:03:21,980 --> 00:03:25,010
this time I will pick from the list,
we want the default category.

67
00:03:26,598 --> 00:03:32,530
Close this tag and finally for
text, we can add the data, element.

68
00:03:32,530 --> 00:03:40,060
Then we wanna use android:mimeType and
type text/plain.

69
00:03:40,060 --> 00:03:40,630
All right.

70
00:03:40,630 --> 00:03:41,860
Our intent-filter is set.

71
00:03:41,860 --> 00:03:42,830
At this point,

72
00:03:42,830 --> 00:03:46,690
if a user wants to share text, our app
will show up as an option for sharing.

73
00:03:46,690 --> 00:03:48,750
It will launch the DetailActivity but

74
00:03:48,750 --> 00:03:51,990
nothing would happen because we haven't
actually handled the intent yet.

75
00:03:51,990 --> 00:03:54,190
All we've done is enable
the routing essentially.

76
00:03:54,190 --> 00:03:57,030
Let's take a short break and then we'll
add the code to handle the intent.