Using intents, Apps can be used like a library or API. This can be a powerful way to drive downloads for some applications.

1. Sean Owen
Co-author “Barcode Scanner”
Droidcon 2010
29 October 2010

4.  Google NYC 20% project,
2 people, from early 2007
 Born as part of PrintAds
 Released as ZXing
open source project
 Just a demo app for
cameraAPI in Android 1.0

5.  CameraAPI
 Preview, SurfaceView
 Focus, zoom, etc.
 Fast image processing
 Read/write contacts, bookmarks
 Wi-fi configuration …
 Intents
 Web – App integration

6.  < 1 person project
 10.3M installs, 6M active
 Growing ~33K per day
 #8 Android Market app
 Powers (directly or indirectly) most
barcode apps for iPhone, Android and RIM
…
1 rating :
~100 installs

7.  Makes Barcode Scanner a dependency
 Dependency drives downloads!

8. (Developers only!)

9. Intent
(ARG1, ARG2,
…)
Intent
(RES1, RES2, …)
setResult()
startActivityForResult()

10. <activity ...>
...
<intent-filter>
<action android:name=“com.myapp.DO_IT”/>
<category android:name=“
android.intent.category.DEFAULT”/>
</intent-filter>
...
</activity>

11. static final int DO_IT_RESULT = 0xDEADBEEF;
Intent doIt =
new Intent(“com.myapp.DO_IT”);
doIt.addCategory(Intent.CATEGORY_DEFAULT);
doIt.putExtra(“ARG1”, arg1);
startActivityForResult(doIt, DO_IT_RESULT);

12. public void onResume() {
Intent intent = getIntent();
String action = intent.getAction();
if (“com.myapp.DO_IT”.equals(action))) {
String arg1 =
intent.getStringExtra(“ARG1”);
// Do that something
...
}
...
}

13. Intent reply = new Intent(action);
// Put result values as Intent “extras”
reply.putExtra(“RES1”, res1);
reply.putExtra(“RES2”, res2);
setResult(RESULT_OK, reply);
finish();

14. public void onActivityResult(
int request, int result, Intent reply) {
if (request == DO_IT_REQUEST &&
result == RESULT_OK) {
String res1 = reply.getExtra(“RES1”);
String res2 = reply.getExtra(“RES2”);
// Process result
...
}
}

15.  ActivityNotFoundException
on startActivityForResult()
if app is not installed
 Caller sends user to Market to
download instead
 Provide code and examples
so caller gets it right
(see android-integration/)

16. startActivityForResult(...);
} catch (ActivityNotFoundException anfe) {
// Prompt user with AlertDialog
// If user clicks “Yes”:
Uri uri = Uri.parse(
"market://search?q=pname:com.myapp");
Intent intent =
new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}

18. <activity ...>
...
<intent-filter>
<action android:name=“android.intent.action.VIEW”/>
<category android:name=“
android.intent.category.DEFAULT”/>
<category android:name=“
android.intent.category.BROWSABLE”/>
<data android:scheme="http”
android:host=”myapp.com”
android:path="/doIt"/>
</intent-filter>
...
</activity>

19. <a href=“http://myapp.com/doIt?ARG1=arg”>
Do it</a>
Return informational page at
http://myapp.com/doIt ;
automatically shows when app
not yet installed!
MyApp!

20. public void onResume() {
Intent intent = getIntent();
String ds = intent.getDataString();
if (ds.startsWith(
“http://myapp.com/doIt”) {
Uri uri = Uri.parse(ds);
String arg1 =
uri.getQueryParameter(“ARG1”);
// Do that something
}
...
}

21. Uri uri = Uri.parse(
“http://myapp.com/doneIt?RES1=res”);
Intent reply = new Intent(
Intent.ACTION_VIEW, Uri.parse(uri));
startActivity(reply);
finish();

22. http://myapp.com/doneIt?RES1=res1&RES2=res2
RESULTS
res1
res2

23.  Exposing an API can “leak” permissions
 Example: App which retrieves contacts via Intent
 Then any app can read contacts
(without Android permission)!
 Think about abuses
 Is API consistent with users’
permission expectations?

25.  Can’t open source? Open an API
 API doesn’t have to mean free
 “Open” looks good and is good
 If you don’t, someone will
1

26.  Think platform, not just app
 Platforms get preinstalled
 Platforms are hard to uninstall
 Foothold for other services
2

27.  Drive downloads – and hence users
 Download is most of the battle
 Users try what’s on the phone
 Users stick with what they know
3

28.  code.google.com/p/zxing
 groups.google.com/group/zxing
 Barcode Scanner
in Android Market