Tag Archives: App quality

Android Developer Story: Music app developer DJIT builds higher quality experiences and a successful businesses on Android

Posted by Lily Sheringham, Google Play team

Paris-based DJiT is the creator of edjing, one of the most downloaded DJ apps in the world, it now has more than 60 million downloads and a presence in 182 countries. Following their launch on Android, the platform became the largest contributor of business growth, with 50 percent of total revenue and more than 70 percent of new downloads coming from their Android users.

Hear from Jean-Baptiste Hironde, CEO & Co-founder, Séverine Payet, Marketing Manager, and Damien Delépine, Android Software Engineer, to learn how DJit improved latency on new Android Marshmallow, as well as leveraged other Android and Google Play features to create higher quality apps.

Find out more about building great audio apps and how to find success on Google Play.

Tablet changes in Google Play

Posted by Ellie Powers, Google Play team

Fueled by the Nexus 7 and other great devices, more than 70 million Android tablets have been activated. Thousands of developers have already designed their apps to look great on tablets, and with the holidays fast approaching, we’re making it even easier for the next wave of tablet owners to discover great apps and games.

Play Store tablet changes coming up on November 21

Last year, Google Play added a “designed for tablets” section, where users could easily discover apps that look great on their 7”- and 10”-tablets. This section includes only apps and games which meet criteria and guidelines we established last year. (Here’s an overview if you missed it.) Developers who invest the time to meet the criteria are seeing great results; take Remember The Milk, which saw an 83% increase in tablet downloads from being in this section. (see the whole story here).

On November 21 2013, the Play Store made a series of changes so it’s even easier for tablet users to find those apps that are best for their devices. First, by default, users browsing Google Play on a tablet will now see apps and games that are designed for tablets on the top lists (Top Paid, Top Free, Top Grossing, Top New Paid, Top New Free, and Trending). Tablet users will still be able to switch the view so they can see all apps or games if they choose. Also starting November 21, apps and games that do not meet the “designed for tablets” criteria will be marked as “designed for phones” for users who browse the Play Store on tablets.

You’ll want to make sure that your app is designed for tablets; read more about how to do this at the end of this blog post.

Make sure your app is ready!

If you want to be sure your app is included in the “Designed for tablets” view, go to the Developer Console to check your tablet optimization tips. If you see any issues listed there, you’ll need to address them in your app and upload a new binary for distribution. If there are no issues listed, your app is eligible to be included in the “Designed for tablets" view in the top lists.

Also, make sure to read the full tablet quality checklist to understand how to build outstanding tablet experiences.

Everyday, thousands of Android developers are taking advantage of the tremendous Android tablet opportunity. The flood of new users coupled with the increased screen size means new user experiences, more engagement and more monetization opportunities. We’re excited to see what you do!

Respecting Audio Focus

Posted by Kristan Uccello, Google Developer Relations

It’s rude to talk during a presentation, it disrespects the speaker and annoys the audience. If your application doesn’t respect the rules of audio focus then it’s disrespecting other applications and annoying the user. If you have never heard of audio focus you should take a look at the Android developer training material.

With multiple apps potentially playing audio it's important to think about how they should interact. To avoid every music app playing at the same time, Android uses audio focus to moderate audio playback—your app should only play audio when it holds audio focus. This post provides some tips on how to handle changes in audio focus properly, to ensure the best possible experience for the user.

Requesting audio focus

Audio focus should not be requested when your application starts (don’t get greedy), instead delay requesting it until your application is about to do something with an audio stream. By requesting audio focus through the AudioManager system service, an application can use one of the AUDIOFOCUS_GAIN* constants (see Table 1) to indicate the desired level of focus.

Listing 1. Requesting audio focus.

1. AudioManager am = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);
3.  int result = am.requestAudioFocus(mOnAudioFocusChangeListener,
4.    // Hint: the music stream.
5.    AudioManager.STREAM_MUSIC,
6.    // Request permanent focus.
7.    AudioManager.AUDIOFOCUS_GAIN);
8.  if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
9.    mState.audioFocusGranted = true;
10. } else if (result == AudioManager.AUDIOFOCUS_REQUEST_FAILED) {
11.   mState.audioFocusGranted = false;
12. }

In line 7 above, you can see that we have requested permanent audio focus. An application could instead request transient focus using AUDIOFOCUS_GAIN_TRANSIENT which is appropriate when using the audio system for less than 45 seconds.

Alternatively, the app could use AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK, which is appropriate when the use of the audio system may be shared with another application that is currently playing audio (e.g. for playing a "keep it up" prompt in a fitness application and expecting background music to duck during the prompt). The app requesting AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK should not use the audio system for more than 15 seconds before releasing focus.

Handling audio focus changes

In order to handle audio focus change events, an application should create an instance of OnAudioFocusChangeListener. In the listener, the application will need to handle theAUDIOFOCUS_GAIN* event and AUDIOFOCUS_LOSS* events (see Table 1). It should be noted that AUDIOFOCUS_GAIN has some nuances which are highlighted in Listing 2, below.

Listing 2. Handling audio focus changes.

1. mOnAudioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {  
3. @Override
4. public void onAudioFocusChange(int focusChange) {
5.   switch (focusChange) {
6.   case AudioManager.AUDIOFOCUS_GAIN:
7.     mState.audioFocusGranted = true;
9.     if(mState.released) {
10.   initializeMediaPlayer();
11.    }
13. switch(mState.lastKnownAudioFocusState) { 14. case UNKNOWN: 15. if(mState.state == PlayState.PLAY && !mPlayer.isPlaying()) { 16. mPlayer.start(); 17. } 18. break; 19. case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT: 20. if(mState.wasPlayingWhenTransientLoss) { 21. mPlayer.start(); 22. } 23. break; 24. case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK: 25. restoreVolume(); 26. break; 27. } 28.
29. break; 30. case AudioManager.AUDIOFOCUS_LOSS: 31. mState.userInitiatedState = false; 32. mState.audioFocusGranted = false; 33. teardown(); 34. break; 35. case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT: 36. mState.userInitiatedState = false; 37. mState.audioFocusGranted = false; 38. mState.wasPlayingWhenTransientLoss = mPlayer.isPlaying(); 39. mPlayer.pause(); 40. break; 41. case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK: 42. mState.userInitiatedState = false; 43. mState.audioFocusGranted = false; 44. lowerVolume(); 45. break; 46. } 47. mState.lastKnownAudioFocusState = focusChange; 48. } 49.};

AUDIOFOCUS_GAIN is used in two distinct scopes of an applications code. First, it can be used when registering for audio focus as shown in Listing 1. This does NOT translate to an event for the registered OnAudioFocusChangeListener, meaning that on a successful audio focus request the listener will NOT receive an AUDIOFOCUS_GAIN event for the registration.

AUDIOFOCUS_GAIN is also used in the implementation of an OnAudioFocusChangeListener as an event condition. As stated above, the AUDIOFOCUS_GAIN event will not be triggered on audio focus requests. Instead the AUDIOFOCUS_GAIN event will occur only after an AUDIOFOCUS_LOSS* event has occurred. This is the only constant in the set shown Table 1 that is used in both scopes.

There are four cases that need to be handled by the focus change listener. When the application receives an AUDIOFOCUS_LOSS this usually means it will not be getting its focus back. In this case the app should release assets associated with the audio system and stop playback. As an example, imagine a user is playing music using an app and then launches a game which takes audio focus away from the music app. There is no predictable time for when the user will exit the game. More likely, the user will navigate to the home launcher (leaving the game in the background) and launch yet another application or return to the music app causing a resume which would then request audio focus again.

However another case exists that warrants some discussion. There is a difference between losing audio focus permanently (as described above) and temporarily. When an application receives an AUDIOFOCUS_LOSS_TRANSIENT, the behavior of the app should be that it suspends its use of the audio system until it receives an AUDIOFOCUS_GAIN event. When the AUDIOFOCUS_LOSS_TRANSIENT occurs, the application should make a note that the loss is temporary, that way on audio focus gain it can reason about what the correct behavior should be (see lines 13-27 of Listing 2).

Sometimes an app loses audio focus (receives an AUDIOFOCUS_LOSS) and the interrupting application terminates or otherwise abandons audio focus. In this case the last application that had audio focus may receive an AUDIOFOCUS_GAIN event. On the subsequent AUDIOFOCUS_GAIN event the app should check and see if it is receiving the gain after a temporary loss and can thus resume use of the audio system or if recovering from an permanent loss, setup for playback.

If an application will only be using the audio capabilities for a short time (less than 45 seconds), it should use an AUDIOFOCUS_GAIN_TRANSIENT focus request and abandon focus after it has completed its playback or capture. Audio focus is handled as a stack on the system — as such the last process to request audio focus wins.

When audio focus has been gained this is the appropriate time to create a MediaPlayer or MediaRecorder instance and allocate resources. Likewise when an app receives AUDIOFOCUS_LOSS it is good practice to clean up any resources allocated. Gaining audio focus has three possibilities that also correspond to the three audio focus loss cases in Table 1. It is a good practice to always explicitly handle all the loss cases in the OnAudioFocusChangeListener.

Table 1. Audio focus gain and loss implication.


Note: AUDIOFOCUS_GAIN is used in two places. When requesting audio focus it is passed in as a hint to the AudioManager and it is used as an event case in the OnAudioFocusChangeListener. The gain events highlighted in green are only used when requesting audio focus. The loss events are only used in the OnAudioFocusChangeListener.

Table 2. Audio stream types.

Stream Type Description
STREAM_ALARM The audio stream for alarms
STREAM_DTMF The audio stream for DTMF Tones
STREAM_MUSIC The audio stream for "media" (music, podcast, videos) playback
STREAM_NOTIFICATION The audio stream for notifications
STREAM_RING The audio stream for the phone ring
STREAM_SYSTEM The audio stream for system sounds

An app will request audio focus (see an example in the sample source code linked below) from the AudioManager (Listing 1, line 1). The three arguments it provides are an audio focus change listener object (optional), a hint as to what audio channel to use (Table 2, most apps should use STREAM_MUSIC) and the type of audio focus from Table 1, column 1. If audio focus is granted by the system (AUDIOFOCUS_REQUEST_GRANTED), only then handle any initialization (see Listing 1, line 9).

Note: The system will not grant audio focus (AUDIOFOCUS_REQUEST_FAILED) if there is a phone call currently in process and the application will not receive AUDIOFOCUS_GAIN after the call ends.

Within an implementation of OnAudioFocusChange(), understanding what to do when an application receives an onAudioFocusChange() event is summarized in Table 3.

In the cases of losing audio focus be sure to check that the loss is in fact final. If the app receives an AUDIOFOCUS_LOSS_TRANSIENT or AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK it can hold onto the media resources it has created (don’t call release()) as there will likely be another audio focus change event very soon thereafter. The app should take note that it has received a transient loss using some sort of state flag or simple state machine.

If an application were to request permanent audio focus with AUDIOFOCUS_GAIN and then receive an AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK an appropriate action for the application would be to lower its stream volume (make sure to store the original volume state somewhere) and then raise the volume upon receiving an AUDIOFOCUS_GAIN event (see Figure 1, below).

Table 3. Appropriate actions by focus change type.

Focus Change Type Appropriate Action
AUDIOFOCUS_GAIN Gain event after loss event: Resume playback of media unless other state flags set by the application indicate otherwise. For example, the user paused the media prior to loss event.
AUDIOFOCUS_LOSS Stop playback. Release assets.
AUDIOFOCUS_LOSS_TRANSIENT Pause playback and keep a state flag that the loss is transient so that when the AUDIOFOCUS_GAIN event occurs you can resume playback if appropriate. Do not release assets.
AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK Lower volume or pause playback keeping track of state as with AUDIOFOCUS_LOSS_TRANSIENT. Do not release assets.

Conclusion and further reading

Understanding how to be a good audio citizen application on an Android device means respecting the system's audio focus rules and handling each case appropriately. Try to make your application behave in a consistent manner and not negatively surprise the user. There is a lot more that can be talked about within the audio system on Android and in the material below you will find some additional discussions.

Example source code is available here:


Unlocking More Users, with Tablets and Games

Posted by Purnima Kochikar, Director of Business Development, Games & Applications

Last week, we unveiled a number of new things in the world of Android. And while we already showcased the new tools available at your disposal in Android 4.3, we also unveiled a new Nexus 7 tablet, as well as the Google Play Games app, both of which represent opportunities to take advantage of a growing number of users.

Nexus 7 and the Android tablet revolution

If you’re a developer optimizing your app for Android tablets, no doubt you’re familiar with the original Nexus 7. It was Google’s statement on what a great Android tablet experience should look like, and since then, the Android tablet ecosystem has come a long way. There have already been more than 70 million activations of Android tablets, with more than 1 in 2 tablets sold today running Android. We’re starting to see with Android tablets what could be the hockey stick growth all of us experienced a couple of years ago with Android smartphones, and we hope that the new Nexus 7 continues to fuel this growth even further.

Most top developers on Android have already prepared their applications for this wave of new Android tablet users, including many of the essentials, like the New York Times, Zappos, Evernote, Flipboard, Pinterest and more. To help users find your tablet-designed apps more easily on Google Play, you can now choose to only see apps designed for tablets in the top lists. There are also over 50 new collections, which highlight outstanding tablet apps.

To take advantage of the Android tablet revolution, check out our Tablet App Quality Checklist, which has tips and techniques on how to deliver a great app experience for tablet users. It details all of the key things you need to do to optimize your app for tablets, like taking advantage of the extra screen real estate and adjusting font sizes and touch targets, to things you can do on the distribution side, like declaring support for tablet screens and showcasing your tablet UI on Google Play by uploading tablet-specific screenshots. Optimizing your app for Android tablets will unlock a whole new group of users, like those who are about to receive their new Nexus 7 tablets.

Taking your game to the next level

The Android games category on Google Play is on fire; in fact, the vast majority of top mobile game developers are building Android tablet games, and most new titles launch immediately on Android. To help game developers take advantage of the next generation of games, at Google I/O in May, we introduced Google Play game services, our gaming platform for Android, iOS, and the web. By building on Google’s strengths in mobile and cloud services, Google Play game services allows game developers to focus on what they’re good at: creating great gaming experiences for their users.

Turbocharging that growth even more, on Wednesday we introduced the Google Play Games app, which brings your friends together with the games you love, where you can invite a friend and start challenging gamers around the world, compete for top achievements, and race to the top of the leaderboard.

Since the launch at Google I/O, just over two months ago, over one thousand games have added Google Play game services, with millions of users enjoying features like leaderboards and multiplayer inside of the games they love. Some of those early developers using Google Play game services are reporting incredible upticks in vital engagement metrics; for instance, Concrete Software is seeing session length up 15%, and Glu is reporting a 40% increase in 7-day user retention.

Here are a few things you can do to take your game to the next level with Google Play:

  • Integrate with Play Games using achievements and leaderboards to activate your players.
  • Add real-time multiplayer to competitive and cooperative games and increase engagement.
  • Use Play Games branding guidelines and create rich visuals that bolster your presence in the Google Play Games app.

Whether it be getting your app ready for the wave of new Android tablets that are lighting up each day, or opening up a whole new set of features for your users with Google Play game services, a great Android experience starts with a great app or game. That’s why we’re working hard to help provide you with the tools and features needed to create those great experiences for your users, and to help you reach as many of them as possible in the process, with Google Play.