Announcing the Winners of ADC 2

Back in May at Google I/O, we announced ADC 2 -- the second Android Developer Challenge -- to encourage the development of cool apps that delight mobile users. We received many interesting and high-quality applications -- everything from exciting arcade games to nifty productivity utilities. We also saw apps that took advantage of openness of Android to enhance system behavior at a deep level to provide users with a greater degree of customization and utility. We were particularly pleased to see submissions from many smaller and independent developers.

Over the last couple of months, tens of thousands of Android users around the world reviewed and scored these applications. There were many great apps and the scores were very close. Together with our official panel of judges, these users have spoken and selected our winners!

I am pleased to present the ADC 2 winners gallery, which includes not only the top winners overall and in each category, but also all of the applications that made it to the top 200. There are a lot of great applications in addition to the top winners.

Thanks to everyone who submitted applications or helped us judge the entrants. We encourage all developers to submit their applications to Android Market where their app can be downloaded and enjoyed by Android users around the world.

ADC 2 Public Judging is now closed

Thanks to tens of thousands of Android users around the world who participated in the review of ADC 2 finalist applications, we have now collected sufficient scores to complete Round 2 of public judging.

We are reviewing the final results and will announce the top winners this coming Monday, November 30. Thanks to all who've participated in ADC 2 and good luck to all the finalists.

Integrating Application with Intents

Written in collaboration with Michael Burton,; Ivan Mitrovic, uLocate; and Josh Garnier, OpenTable.

OpenTable, uLocate, and worked together to create a great user experience on Android. We saw an opportunity to enable WHERE and GoodFood users to make reservations on OpenTable easily and seamlessly. This is a situation where everyone wins — OpenTable gets more traffic, WHERE and GoodFood gain functionality to make their applications stickier, and users benefit because they can make reservations with only a few taps of a finger. We were able to achieve this deep integration between our applications by using Android's Intent mechanism. Intents are perhaps one of Android's coolest, most unique, and under-appreciated features. Here's how we exploited them to compose a new user experience from parts each of us have.


One of the first steps is to design your Intent interface, or API. The main public Intent that OpenTable exposes is the RESERVE Intent, which lets you make a reservation at a specific restaurant and optionally specify the date, time, and party size.

Hereʼs an example of how to make a reservation using the RESERVE Intent:

startActivity(new Intent("com.opentable.action.RESERVE",

Our objective was to make it simple and clear to the developer using the Intent. So how did we decide what it would look like?

First, we needed an Action. We considered using Intent.ACTION_VIEW, but decided this didn't map well to making a reservation, so we made up a new action. Following the conventions of the Android platform (roughly <package-name>.action.<action-name>), we chose "com.opentable.action.RESERVE". Actions really are just strings, so it's important to namespace them. Not all applications will need to define their own actions. In fact, common actions such as Intent.ACTION_VIEW (aka "android.intent.action.VIEW") are often a better choice if youʼre not doing something unusual.

Next we needed to determine how data would be sent in our Intent. We decided to have the data encoded in a URI, although you might choose to receive your data as a collection of items in the Intent's data Bundle. We used a scheme of "reserve:" to be consistent with our action. We then put our domain authority and the restaurant ID into the URI path since it was required, and we shunted off all of the other, optional inputs to URI query parameters.


Once we knew what we wanted the Intent to look like, we needed to register the Intent with the system so Android would know to start up the OpenTable application. This is done by inserting an Intent filter into the appropriate Activity declaration in AndroidManifest.xml:

<activity android:name=".activity.Splash" ... >
<action android:name="com.opentable.action.RESERVE"/>
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="reserve" android:host=""/>

In our case, we wanted users to see a brief OpenTable splash screen as we loaded up details about their restaurant selection, so we put the Intent Filter in the splash Activity definition. We set our category to be DEFAULT. This will ensure our application is launched without asking the user what application to use, as long as no other Activities also list themselves as default for this action.

Notice that things like the URI query parameter ("partySize" in our example) are not specified by the Intent filter. This is why documentation is key when defining your Intents, which weʼll talk about a bit later.


Now the only thing left to do was write the code to handle the intent.

    protected void onCreate(Bundle savedInstanceState) {
final Uri uri;
final int restaurantId;
try {
uri = getIntent().getData();
restaurantId = Integer.parseInt( uri.getPathSegments().get(0));
} catch(Exception e) {
// Restaurant ID is required
startActivity( FindTable.start(FindTablePublic.this));
final String partySize = uri.getQueryParameter("partySize");

Although this is not quite all the code, you get the idea. The hardest part here was the error handling. OpenTable wanted to be able to gracefully handle erroneous Intents that might be sent by partner applications, so if we have any problem parsing the restaurant ID, we pass the user off to another Activity where they can find the restaurant manually. It's important to verify the input just as you would in a desktop or web application to protect against injection attacks that might harm your app or your users.

Calling and Handling Uncertainty with Grace

Actually invoking the target application from within the requester is quite straight-forward, but there are a few cases we need to handle. What if OpenTable isn't installed? What if WHERE or GoodFood doesn't know the restaurant ID?

Restaurant ID knownRestaurant ID unknown
User has OpenTableCall OpenTable IntentDon't show reserve button
User doesn't have OpenTableCall Market IntentDon't show reserve button

You'll probably wish to work with your partner to decide exactly what to do if the user doesn't have the target application installed. In this case, we decided we would take the user to Android Market to download OpenTable if s/he wished to do so.

    public void showReserveButton() {

// setup the Intent to call OpenTable
Uri reserveUri = Uri.parse(String.format( "reserve://",
Intent opentableIntent = new Intent("com.opentable.action.RESERVE", reserveUri);

// setup the Intent to deep link into Android Market
Uri marketUri = Uri.parse("market://search?q=pname:com.opentable");
Intent marketIntent = new Intent(Intent.ACTION_VIEW).setData(marketUri);

opentableButton.setVisibility(opentableId > 0 ? View.VISIBLE : View.GONE);
opentableButton.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
PackageManager pm = getPackageManager();
startActivity(pm.queryIntentActivities(opentableIntent, 0).size() == 0 ?
opentableIntent : marketIntent);

In the case where the ID for the restaurant is unavailable, whether because they don't take reservations or they aren't part of the OpenTable network, we simply hide the reserve button.

Publishing the Intent Specification

Now that all the technical work is done, how can you get other developers to use your Intent-based API besides 1:1 outreach? The answer is simple: publish documentation on your website. This makes it more likely that other applications will link to your functionality and also makes your application available to a wider community than you might otherwise reach.

If there's an application that you'd like to tap into that doesn't have any published information, try contacting the developer. It's often in their best interest to encourage third parties to use their APIs, and if they already have an API sitting around, it might be simple to get you the documentation for it.


It's really just this simple. Now when any of us is in a new city or just around the neighborhood its easy to check which place is the new hot spot and immediately grab an available table. Its great to not need to find a restaurant in one application, launch OpenTable to see if there's a table, find out there isn't, launch the first application again, and on and on. We hope you'll find this write-up useful as you develop your own public intents and that you'll consider sharing them with the greater Android community.

ADC 2 Round 2 Voting Open

The results from ADC 2 Round 1 are now tabulated and verified. With the top 200 applications identified, it's time to begin the final round judging. Be sure to download the ADC 2 judging application, or update your existing application, and help us select the final winners!

For the final round, both users and a Google-selected panel of industry judges will provide votes to determine the final winners. Prizes will be distributed to the top 3 entrants in each of the 10 categories, and the top 3 overall entrants will receive additional prizes. Please see our reference page for full challenge information.

Your vote is critical! We will keep voting open until we have received sufficient votes for all of the applications. We encourage you to download the ADC 2 judging application and evaluate entrants for yourself.

Download Android Developer Challenge 2:

Bring Your Lab Coats

With the recent release of Android 2.0 and the growing number of available devices, we want to give developers a convenient way to test drive their apps on these new devices. We also want to make our Android advocates available to answer any questions you may have.

We are pleased to announce that we will host a series of all day Android developer labs over the next month in the following cities (dates in local time):

  • Mountain View, CA - Nov 9
  • New York, NY - Nov 16
  • London, UK - Nov 17
  • Tokyo, JP - Nov 18
  • Taipei, TW - Nov 20

Due to limited space, developers who have already published an application in Android Market will be given priority. You can request a spot on a first-come, first-serve basis by going to this page. We will send a follow-up email with venue information and other registration details to those who have secured a spot.

Thank you for your continued excitement in Android. We look forward to meeting many of you in the coming weeks!