If you're developing an Android application, Android 3.0 introduces several features that allow +you to enhance your user's experience on tablets and similar devices. Any application you've already +published is compatible with devices running Android 3.0, by default, because Android applications +are forward-compatible. However, there are some simple changes you should make to optimize your +application for tablet-type devices.
+ +This document shows how you can optimize your existing application for Android 3.0 and +maintain compatibility with older versions or upgrade your application completely with new APIs.
+ + +To get started:
+ +When you have an existing application and want to maintain compatibility with +older versions of Android.
+When you want to upgrade your application to use APIs introduced in Android 3.0 or + create a new application targeted to tablets and similar devices.
To start testing and developing your application on Android 3.0, set up your existing Android +SDK with the new platform:
+ +(If you don't have an existing Android SDK, download the +SDK starter package now.)
+ +Set the target to "Android 3.0" and the skin to "WXGA" (the default skin).
Because the Android emulator must simulate the ARM instruction set on your computer +and the WXGA screen is significantly larger than a typical virtual device, emulator performance is +much slower than a real device.
+ +In particular, initializing the emulator can be slow and can take several minutes, depending on +your hardware. When the emulator is booting, there is limited user feedback, so please be patient +and wait until you see the home screen (or lock screen) appear.
+ +However, you don't need to boot the emulator each time you rebuild your +application—typically you only need to boot at the start of a session and keep it running. +Also see the tip below for information about using a snapshot to drastically reduce startup time +after the first initialization.
+ +We're working hard to resolve the performance issues and it will improve in future tools +releases. For the time being, the emulator is still best way to evaluate your application's +appearance and functionality on Android 3.0 without a real device.
+ +Tip: To improve the startup time for the emulator, enable snapshots +for the AVD when you create it with the SDK and AVD Manager (there's a checkbox in the AVD creator +to Enable snapshots). Then, start the AVD from the AVD manager and check Launch +from snapshot and Save to snapshot. This way, when you close the emulator, a snapshot of +the AVD state is saved and used to quickly relaunch the AVD next time. However, when you choose to +save a snapshot, the emulator will be slow to close, so you might want to disable Save to +snapshot after you've acquired an initial snapshot (after you close the AVD for the first +time).
+ + + +If you've already developed an application for an earlier version of Android, there are a few +things you can do to optimize it for a tablet-style experience on Android 3.0 without changing the +minimum version required (you don't need to change your manifest's {@code +android:minSdkVersion}).
+ +Note: All Android applications are forward-compatible, so +there's nothing you have to do—if your application is a good citizen of the Android +APIs, your app should work fine on devices running Android 3.0. However, in order to provide users +a better experience when using your app on an Android 3.0 tablet or similar-size device, you +should update your application to inherit the new system theme and provide some optimizations for +larger screens.
+ +Here are a few things you can do to optimize your application for devices running Android +3.0:
+ ++<manifest ... > + <uses-sdk android:minSdkVersion="4" + android:targetSdkVersion="11" /> + <application ... > + ... + <application> +</manifest> ++
By targeting the Android 3.0 platform, the system automatically applies the holographic theme +to each activity when your application runs on an Android 3.0 device. The holographic theme +provides a new design for widgets, such as buttons and text boxes, and restyles other +visual elements. This is the standard theme in applications built for Android 3.0, so your +application will look more at home by enabling the theme.
+Additionally, the holographic theme enables the Action Bar in your activities when running on an +Android 3.0 device. The Action Bar replaces the traditional title bar at the top of the activity +window and provides the user access to the activity's Options Menu.
+Note: If you have applied other themes directly to your +activities, they will override the inherited holographic theme. To resolve this, you can use +the system +version qualifier to provide an alternative theme for Android 3.0 devices that's based on the +holographic theme. For more information, read how to select a theme based on platform +version.
+By providing alternative
+resources when running on extra large screens (using the xlarge resource
+qualifier), you can improve the user experience of your application on tablet-type devices without
+using new APIs.
For example, here are some things to consider when creating a new layout for extra large +screens:
+You can specify landscape resources with the land resource
+qualifier, but if you want alternative resources for an extra large landscape screen, you
+should use both xlarge and land qualifiers. For example, {@code
+res/layout-xlarge-land/}. The order of the qualifier names is important; see
+Providing Alternative Resources for more information.
xlarge configurations.In general, always be sure that your application follows the Best Practices +for Screen Independence.
+If you want to develop an application that's fully enhanced for tablet-type devices running +Android 3.0, then you need to use new APIs in Android 3.0. This section introduces some of +the new features you should use.
+ + +The first thing to do when you create a project for Android 3.0 is set your manifest's {@code android:minSdkVersion} +to {@code "11"}. For example:
+ ++<manifest ... > + <uses-sdk android:minSdkVersion="11" /> + <application ... > + ... + <application> +</manifest> ++ +
By targeting the Android 3.0 platform, the system automatically applies the new holographic theme +to each of your activities.
+ +Additionally, the holographic theme enables the Action Bar for each activity.
+ + +The Action Bar is a widget for activities that replaces the traditional title bar at the top of +the screen. By default, the Action Bar includes the application logo on the left side, followed by +the activity title, and any available items from the Options Menu on the right side.
+ +You can enable items from your activity's Options Menu to appear directly in the Action Bar as +"action items" by adding {@code showAsAction="ifRoom"} to specific items in your menu resource. You can also add +navigation features to the Action Bar, such as tabs, and use the application icon to navigate to +your application's "home" activity or "up" the activity hierarchy.
+ +For more information, read Using the +Action Bar.
+ + + +A fragment represents a behavior or a portion of user interface in an activity. You can combine +multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple +activities. You can think of a fragment as a modular section of an activity, which has its own +lifecycle, receives its own input events, and which you can add or remove while the activity is +running.
+ +For example, a news application can use one fragment to show a list of articles on the left and +another fragment to display an article on the right—both fragments appear in one activity, +side by side, and each fragment has its own set of lifecycle callback methods and handles its own +input events. Thus, instead of using one activity to select an article and another activity to +read the article, the user can select an article and read it all within the same activity.
+ +For more information, read the Fragments document.
+ + +An all new flexible animation framework allows you to animate arbitrary properties of any object +(View, Drawable, Fragment, Object, or anything else). You can define several animation aspects +(such as duration, repeat, interpolation, and more) for an object's int, float, and hexadecimal +color values, by default. That is, when an object has a property field for one of these types, you +can change its value over time to affect an animation.
+ +The {@link android.view.View} class also provides new APIs that leverage the new animation +framework, allowing you to easily apply 2D and 3D transformations to views in your activity layout. +New transformations are made possible with a set of object properties that define the view's layout +position, orientation, transparency and more.
+ +For more information, read the Property Animation document.
+ + +You can now enable the OpenGL renderer for your application by setting {@code +android:hardwareAccelerated="true"} in your manifest's {@code <application>} +element or for individual {@code +<activity>} elements. Hardware acceleration results in smoother animations, smoother +scrolling, and overall better performance and response to user interaction. When enabled, be sure +that you thoroughly test your application on a device that supports hardware acceleration.
+ + +App widgets allow users to access information from your application directly from the Home +screen and interact with ongoing services (such as preview their email and control music playback). +Android 3.0 enhances these capabilities by enabling collections, created with widgets such as +{@link android.widget.ListView}, {@link android.widget.GridView}, and the new {@link +android.widget.StackView}. These widgets allow you to create more interactive app +widgets, such as one with a scrolling list, and can automatically update their data through a {@link +android.widget.RemoteViewsService}.
+ +Additionally, you should create a preview image of your app widget using the Widget Preview +application (pre-installed in an Android 3.0 AVD) and reference it with the {@link +android.appwidget.AppWidgetProviderInfo#previewImage android:previewImage} attribute, so that users +can see what the app widget looks like before adding it to their Home screen.
+ + +Android 3.0 introduces many more APIs that you might find valuable for your +application, such as drag and drop APIs, new Bluetooth APIs, a system-wide clipboard framework, a +new graphics engine called Renderscript, and more.
+ +To learn more about the APIs mentioned above and more, see the Android 3.0 Platform document.
+ + +You should also decide whether your application is only for +tablet-type devices (specifically, xlarge devices) or for all types of screen sizes.
+ +If you want your application to be available to all screen sizes (for example, for all +phones and tablets), there's nothing you need to do. By default, an application with {@code +android:minSdkVersion} set to {@code "4"} or higher will resize to fit any screen size.
+ +If your application is only for xlarge screens, include the {@code +<supports-screens>} element in your manifest and declare that the application supports +only xlarge screens, by declaring all other sizes {@code "false"}. For example:
+ ++<manifest ... > + ... + <supports-screens android:smallScreens="false" + android:normalScreens="false" + android:largeScreens="false" + android:xlargeScreens="true" /> + <application ... > + ... + <application> +</manifest> ++ +
With this declaration, you indicate that your application does not support any screen size except +extra large. External services such as Android Market may then use this information to filter your +application from devices that do not have an extra large screen.
+ + + +Many of the new features and APIs that are described in the Android 3.0 Platform Preview also have accompanying
+samples that can help you understand how to use them. To get the samples, download them from the SDK
+repository using the Android SDK Manager. After downloading the samples ("Samples for SDK API 11"),
+you can find them in <sdk_root>/samples/android-11/. The links below can help you
+find samples for the features you are interested in:
Also see the Optimizing Apps for Android +3.0 document for information about how to optimize your existing applications for Android 3.0 +devices, even if you want to remain compatible with previous versions.
+Welcome to Android 3.0!
- -Android 3.0 is the next major release of the Android platform and is optimized for larger screen -devices, particularly tablets. We're offering a preview SDK so you can get a head-start developing -applications for it or simply test and optimize your existing application for upcoming devices.
- -Be aware that:
-When you have an existing application and you want to maintain compatibility with -older versions of Android.
-When you want to upgrade your application to use APIs introduced in Android 3.0 or - create a new application targeted to tablets and similar devices.
Many of the new features and APIs that are described in the
-Android 3.0 Platform Preview also have accompanying samples that help you understand how to use them.
-To get the samples, download them from the SDK repository using the Android SDK Manager. After download
-the samples are located in <sdk_root>/samples/android-Honeycomb. The list of links
-below helps you find samples for the features you are interested in:
To start using the Android 3.0 preview SDK, set up your existing Android SDK with the new -platform:
-(If you don't have an existing SDK, download it -now.)
-Because the Android emulator must simulate the ARM instruction set architecture on your -computer and the WXGA screen is significantly larger than what the emulator -normally handles, emulator performance is much slower than usual.
- -In particular, initializing the emulator can be slow and can take several -minutes, depending on your hardware. When the emulator is booting there is -limited user feedback, so please be patient and continue waiting until you see -the home screen appear.
- -Note that you do not need to do a full boot of your emulator each time you -rebuild your application — typically you only need to boot at the start of -a session. See the Tips section below for information about using Snapshots to -cut startup time after first initialization.
- -We're working hard to resolve the performance issues and it will improve in future releases. -Unfortunately, the emulator will perform slowly during your trial with the preview SDK. For the time -being, the emulator is still best way to evaluate your application's appearance and functionality on -Android 3.0.
- -Tip: To improve the startup time for the emulator, enable -snapshots for the AVD when you create it with the SDK and AVD Manager (there's a checkbox in -the GUI). Then, start the AVD from the manager and check Launch from snapshot and Save to -snapshot. This way, when you close the emulator, a snapshot of the AVD state is saved and -used to quickly relaunch the AVD next time. However, when you choose to save a snapshot, the -emulator will be slow to close, so you might want to enable Save to -snapshot only for the first time you launch the AVD.
- - -The following known issues occur for Android 3.0 AVDs that are loaded in the emulator:
-If you've already developed an application for Android, there are a few things you can do -to optimize it for a tablet-style experience, without changing the minimum platform version required -(you don't need to change the manifest {@code minSdkVersion}).
- -Note: All Android applications are forward-compatible, so -there's nothing you have to do—if your application is a good citizen of the Android -APIs, your app should work fine on devices running Android 3.0. However, in order to provide users -a better experience when running your app on an Android 3.0 tablet or similar-size device, we -recommend that you update your application to adapt to the new system theme and optimize your -application for larger screens.
- -Here's what you can do to optimize your application for tablets running Android -3.0:
- --<manifest ... > - <uses-sdk android:minSdkVersion="4" - android:targetSdkVersion="Honeycomb" /> - <application ... > - ... - <application> -</manifest> --
Note: The API Level value "Honeycomb" is a provisional API -Level that is valid only while testing against the preview SDK. You -should not publish your application using this API Level. When the final version of -the Android 3.0 SDK is made available, you must change this value to the real API Level that will be -specified for Android 3.0. For more information, read about Android API Levels.
-By targeting the Android 3.0 platform, the system automatically applies the Holographic theme -to each of your activities, when running on an Android 3.0 device.
-Note: If you've applied themes to your activities already, -they will override the Holographic theme that the system applies when you set the {@code -android:targetSdkVersion} to {@code "Honeycomb"}. -Once the Android 3.0 APIs are finalized and an official API Level is assigned, you can use -the system -version qualifier to provide an alternative theme that's based on the Holographic theme when -your application is running on Android 3.0.
-As discussed in the guide to Supporting Multiple Screens, Android
-2.3 and above support the xlarge resource qualifier, which you should use to supply
-alternative layouts for extra large screens.
By providing alternative layouts for some of your activities when running on extra large -screens, you can improve the user experience of your application on a tablet without using any -new APIs.
-For example, here are some things to consider when creating a new layout for tables:
-In general, always be sure that your application follows the Best Practices -for Screen Independence.
- - -If you want to develop something truly for tablet-type devices running Android 3.0, then you need -to use new APIs available in Android 3.0. This section introduces some of the new features that you -should use.
- -The first thing to do when you create a project with the Android 3.0 preview is set the {@code <uses-sdk>} element to -use {@code "Honeycomb"} for the {@code android:minSdkVersion}. For example:
- --<manifest ... > - <uses-sdk android:minSdkVersion="Honeycomb" /> - <application ... > - ... - <application> -</manifest> -- -
Note: The API Level value "Honeycomb" is a provisional API -Level that is valid only while building and testing against the preview SDK. You -cannot publish your application using this API Level. When the final version of the -Android 3.0 SDK is made available, you must change this value to the real API Level that is -specified for Android 3.0. For more information, read about Android API Levels.
- -Be sure that the {@code -<uses-sdk>} element appears before the {@code <application>} -element.
- -By targeting the Android 3.0 platform (and declaring it before {@code <application>}), -the system automatically applies the new Holographic theme to each of your -activities.
- - - -Additionally, you should decide whether your application is for only tablet devices -(specifically, xlarge devices) or for devices of all sizes that may run Android 3.0.
- -If your application is only for tablets (xlarge screens; not for mobile -devices/phones), then you should include the {@code -<supports-screens>} element in your manifest with all sizes except for xlarge declared -false. For example:
- --<manifest ... > - <uses-sdk android:minSdkVersion="Honeycomb" /> - <supports-screens android:smallScreens="false" - android:normalScreens="false" - android:largeScreens="false" - android:xlargeScreens="true" /> - <application ... > - ... - <application> -</manifest> -- -
With this declaration, you indicate that your application does not support any screen size except -extra large. External services such as Android Market may use this to filter your application -from devices that do not have an extra large screen.
- -Otherwise, if you want your application to be available to both small devices (phones) and large -devices (tablets), do not include the {@code -<supports-screens>} element.
- -To learn more about some of the new APIs, -see the Android 3.0 Platform Preview document.
-