Application Visibility Issues

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Recently we became aware that some Android applications were not visible on the Android Market. While we were internally troubleshooting and qualifying the fix and communicating with our hardware partners, developers were trying hard to get our help through various technical support sites. Regrettably, we fell short of our own standard for customer support by not communicating the issue to our developers and how we were working to resolve it.

We’re pleased to say that the issue looks to be resolved with a patch, and to our best knowledge, all apps that were previously impacted are up and visible again. Again, apologies for the delay and inconvenience this created.

Apps on SD Card: The Details

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[This post is by Suchi Amalapurapu, an engineer who worked on this feature. — Tim Bray]

Android 2.2 supports application installation on external storage devices like the SD card. This should give users room for many more apps, and will also benefit certain categories, like games, that need huge assets.

(Note that not all of the contents of an “SD-card-resident” APK are actually on the card; the dex files, private data directories, and native shared libraries remain in internal storage.)

The “Manage Applications” screen in the Settings app now has an “On SD Card” tab. The sizes listed in Manage Applications only include the space taken by the application on internal storage.

The Application Info screen now has either a “move to SD card” or “move to phone” button, but this is often disabled. Copy-protected apps and updates to system apps can’t be moved to the SD card, nor can those which are don’t specify that they work on the SD card.

Controlling Installation Preference

SD-card installation is an optional feature on Android 2.2, is under the control of the developer not the user, and will not affect any applications built prior to Android 2.2.

Application developers can set the field android:installLocation in the root manifest element to one of these values:

• internalOnly: Install the application on internal storage only. This will result in storage errors if the device runs low on internal storage.

• preferExternal: The android system tries to install the application on external storage. If that is full, the application is installed on internal storage.

• auto: Let the Android system decide the best install location for the application. The default system policy is to install the application on internal storage first. If the system is running low on storage, the application is then installed on external storage.

If the installLocation is not specified (as is the case for all applications prior to Android 2.2), the application is installed on internal storage. Application updates will by default try to retain their install location, but application developers may change the installLocation field in an update. Installing an application with this new attribute on older devices will not break compatibility and these applications will be installed on internal storage only.

Application developers can also explicitly install under-development code on external storage via adb install flags, which override the installLocation field: -f for internal storage, and -s for external storage. They can also override the default install location to verify and test application installation on SD card with an adb shell pm command:

adb shell pm setInstallLocation option

Where option is one of:

• 0 [auto] Let the system decide.

• 1 [internal only]

• 2 [external]

The current install location can be retrieved via
adb shell pm getInstallLocation
Note that changing this default can cause applications to misbehave if they’re not prepared to live on the SD card.

USB Mass Storage interactions

The Android system stores the SD-card-resident applications’ APKs in a secure application-specific container. A new flag FLAG_EXTERNAL_STORAGE in ApplicationInfo object indicates that an application is currently installed on the SD card. This storage is removed when an SD-card-resident app is uninstalled.

When an Android device’s SD card is unmounted, applications installed on it are no longer available. Their internal storage is still there and such apps can be uninstalled without replacing the SD card.

The Android framework provides several broadcast intents to support the (small) class of applications, such as launchers, that access other applications’ resources:

• When the SD card is unmounted, ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE with a list of the disabled applications and a list of corresponding application uid’s via extra attributes in the broadcast intent.

• When the SD card is mounted, ACTION_EXTERNAL_APPLICATIONS_AVAILABLE with a list of enabled applications and a list of corresponding application uid’s via extra attributes in the broadcast intent.

Applications that handle broadcast intents like ACTION_PACKAGE_ADDED, ACTION_PACKAGE_REMOVED may also want to handle these additional notifications.

When an application gets moved between internal to external storage and vice versa, the application is disabled first (which includes broadcasting intent ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE), the asset resources are copied, and then the application is enabled (which includes broadcasting intent ACTION_EXTERNAL_APPLICATIONS_AVAILABLE).

Security and Performance Implications

Applications on SD card are mounted via Linux’s loopback interface and encrypted via a device-specific key, so they cannot be decrypted on any other device. Note that this is security measure and does not provide copy protection; the apps are world readable just like the resources of normal applications installed on the device’s internal storage. Copy-protected applications cannot be installed on external media. In the interests of stability, updates to system applications also cannot be installed on the external media. The application resources stored on external storage are read-only and hence there are no performance issues with loading or launching applications on SD card.

Swapping or Transferring SD Card Contents

It has always been the case that when you swap SD cards on an Android device, if you physically copy the contents of the old card to the new one, the system will use the data on the new card as if nothing had changed. This is also true of apps which have been installed on the SD card.

When not to install on SD card?

The advantage of installing on SD card is easy to understand: contention for storage space is reduced. There are costs, the most obvious being that your app is disabled when the SD card is either removed or in USB Mass Storage mode; this includes running Services, not just interactive Activities. Aside from this, device removal disables an application’s Widgets, Input methods, Account Managers, Device administrators, Live wallpapers, and Live folders, and may require explicit user action to re-enable them.

Application Stats on Android Market

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[This post is by Eric Chu, Android Developer Ecosystem. —Dirk Dougherty]

On the Android Market team, it’s been our goal to bring you improved ways of seeing and understanding the installation performance of your published applications. We know that this information is critical in helping you tune your development and marketing efforts. Today I’m pleased to let you know about an important new feature that we’ve added to Android Market called Application Statistics.

Application Statistics is a new type of dashboard in the Market Developer Console that gives you an overview of the installation performance of your apps. It provides charts and tables that summarize each app’s active installation trend over time, as well as its distribution across key dimensions such as Android platform versions, devices, user countries, and user languages. For additional context, the dashboard also shows the comparable aggregate distribution for all app installs from Android Market (numbering in the billions). You could use this data to observe how your app performs relative to the rest of Market or decide what to develop next.

To start with, we’ve seeded the application Statistics dashboards with data going back to December 22, 2010. Going forward, we’ll be updating the data daily.

We encourage you to check out these new dashboards and we hope they’ll give you new and useful insights into your apps’ installation performance. You can access the Statistics dashboards from the main Listings page in the Developer Console.

Watch for more announcements soon. We are continuing to work hard to deliver more reporting features to help you manage your products successfully on Android Market.

Announcing: Apps for Android

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We are pleased to announce that a new open source project has been created on Google code hosting called apps-for-android. Our goal is to share some sample applications that demonstrate different aspects of the Android platform.

The first application to be included in the new project is called WikiNotes for Android.

For anyone not familiar with the concept of a wiki, it is a simple way to link up pages of information using WikiWords (words that use CamelCase). For example, in the previous sentence, both WikiWords and CamelCase would become live links in a Wiki, and would take you to pages of information.

WikiNotes for Android is a form of wiki known as a personal wiki. These run on desktops or (in this case) mobile computing devices, and many people like them. They bring a bit more structure to your notes than just a list of subjects. You can choose to link notes or pages up in any manner you like.

This particular implementation uses a regular expression to match WikiWords and turn them into links that fire Intents to go to other notes. Because of the way the links are implemented, the application will also create links out of telephone numbers that take you to the dialer and URLs that start up the browser.

Search by title and content is also implemented, so even if you forget the structure, you can still find that all-important note about where you left your car in the airport car park.

This wiki has a view mode and an edit mode. In view mode, the links become active and allow you to navigate to other notes, or to other activities like dialer and web browser. In edit mode, you see a plain text view that you can edit, and when you confirm the changes it goes back to view mode. There is both a menu entry and keyboard shortcut to switch to edit view, so that you can very quickly make changes. And, if you get lost in the note structure, there is also an option to take you back to the start page.

WikiNotes for Android was written to demonstrate a number of core concepts in Android, including:

• Multiple Activities in an Application (View, Edit, Search, etc.)
• Default intent filters for View/Edit/Search based on MIME types
• Life cycle of Activities
• Message passing via Bundles in Intents
• Use of Linkify to add Intent-firing links to text data
• Using Intents within an application
• Using Intents to use an Activity within another application
• Writing a custom ContentProvider that implements search by note title
• Registration of ReST-like URIs to match titles, and do contents searches
• SQLite implementations for insert, retrieve, update, delete and search
• UI layout and creation for multiple activities
• Menus and keyboard shortcuts

The application remains small in size and features to make it easy to understand. In time, more features will be added to the application to make it more useful, but a sample version with the minimal functionality will always be available for developers new to the Android platform.

If you believe that firing an Intent for every link that is clicked is sub-optimal and will waste resources, please take a look at the running application using DDMS. You will see how efficiently Android re-uses the running Activities and indeed, this is one of the main reasons WikiNotes for Android was written. It demonstrates that using the Android Activities and Intents infrastructure not only makes construction of component-based applications easy, but efficient as well.

There will also be a series of technical articles about the application right here on the Android Developer blog.

And please, keep an eye on the apps-for-android project, as more sample applications will be added to it soon.

Happy wiki-ing.