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Tuesday, 29 September 2015

Android 5.0 APIs

Android 5.0 APIs

API Level: 21
Android 5.0 (LOLLIPOP) offers new features for users and app developers. This document provides an introduction to the most notable new APIs.
If you have a published app, make sure to check out the Android 5.0 Behavior Changes that you should account for in your app. These behavior changes may affect your app on Android 5.0 devices, even if you are not using new APIs or targeting new functionality.
For a high-level look at the new platform features, instead see the Android Lollipop highlights.

Start developing

To start building apps for Android 5.0, you must first get the Android SDK. Then use the SDK Manager to download the Android 5.0 SDK Platform and System Images.

Update your target API level

To better optimize your app for devices running Android 5.0, set yourtargetSdkVersion to "21", install your app on an Android 5.0 system image, test it, then publish the updated app with this change.
You can use Android 5.0 APIs while also supporting older versions by adding conditions to your code that check for the system API level before executing APIs not supported by your minSdkVersion. To learn more about maintaining backward compatibility, read Supporting Different Platform Versions.
For more information about how API levels work, read What is API Level?

Important behavior changes

If you have previously published an app for Android, be aware that your app might be affected by changes in Android 5.0.
Please see Android 5.0 Changes for complete information.

User Interface

Material design support

Android 5.0 adds support for Android's new material design style. You can create apps with material design that are visually dynamic and have UI element transitions that feel natural to users. This support includes:
  • The material theme
  • View shadows
  • The RecyclerView widget
  • Drawable animation and styling effects
  • Material design animation and activity transition effects
  • Animators for view properties based on the state of the view
  • Customizable UI widgets and app bars with color palettes that you control
  • Animated and non-animated drawables based on XML vector graphics
To learn more about adding material design functionality to your app, see Material Design.

Concurrent documents and activities in the recents screen

In previous releases, the recents screen could only display only one task for each app that the user interacted with most recently. Now your app can open more tasks as needed for additional concurrent activities for documents. This feature facilitates multitasking by letting users quickly switch between individual activities and documents from the recents screen, with a consistent switching experience across all apps. Examples of such concurrent tasks might include open tabs in a web browser app, documents in a productivity app, concurrent matches in a game, or chats in a messaging app. Your app can manage its tasks through the ActivityManager.AppTask class.
To insert a logical break so that the system treats your activity as a new task, use FLAG_ACTIVITY_NEW_DOCUMENT when launching the activity with startActivity(). You can also get this behavior by setting the <activity> element'sdocumentLaunchMode attribute to "intoExisting" or "always" in your manifest.
To avoid cluttering the recents screen, you can set the maximum number of tasks from your app that can appear in that screen. To do this, set the <application> attribute android:maxRecents. The current maximum that can be specified is 50 tasks per user (25 for low RAM devices).
Tasks in the recents screen can be set to persist across reboots. To control the persistence behavior, use theandroid:persistableMode attribute. You can also change the visual properties of an activity in the recents screen, such as the activity’s color, label, and icon, by calling the setTaskDescription() method.

WebView updates

Android 5.0 updates the WebView implementation to Chromium M37, bringing security and stability enhancements, as well as bug fixes. The default user-agent string for a WebView running on Android 5.0 has been updated to incorporate as the version number.
This release introduces the PermissionRequest class, which allows your app to grant the WebView permission to access protected resources like the camera and microphone, through web APIs such as getUserMedia(). Your app must have the appropriate Android permissions for these resources in order to grant the permissions to the WebView.
With the new onShowFileChooser() method, you can now use an input form field in the WebView, and launch a file chooser to select images and files from the Android device.
Additionally, this release brings support for the WebAudioWebGL, and WebRTC open standards. To learn more about the new features included in this release, see WebView for Android.

Screen capturing and sharing

Android 5.0 lets you add screen capturing and screen sharing capabilities to your app with the newandroid.media.projection APIs. This functionality is useful, for example, if you want to enable screen sharing in a video conferencing app.
The new createVirtualDisplay() method allows your app to capture the contents of the main screen (the default display) into a Surface object, which your app can then send across the network. The API only allows capturing non-secure screen content, and not system audio. To begin screen capturing, your app must first request the user’s permission by launching a screen capture dialog using an Intent obtained through the createScreenCaptureIntent() method.
For an example of how to use the new APIs, see the MediaProjectionDemo class in the sample project.


Lock screen notifications

Lock screens in Android 5.0 have the ability to present notifications. Users can choose via Settings whether to allow sensitive notification content to be shown over a secure lock screen.
Your app can control the level of detail visible when its notifications are displayed over the secure lock screen. To control the visibility level, call setVisibility() and specify one of these values:
  • VISIBILITY_PRIVATE: Shows basic information, such as the notification’s icon, but hides the notification’s full content.
  • VISIBILITY_PUBLIC: Shows the notification’s full content.
  • VISIBILITY_SECRET: Shows nothing, excluding even the notification’s icon.
When the visibility level is VISIBILITY_PRIVATE, you can also provide a redacted version of the notification content that hides personal details. For example, an SMS app might display a notification that shows "You have 3 new text messages" but hides the message content and senders. To provide this alternative notification, first create the replacement notification using Notification.Builder. When you create the private notification object, attach the replacement notification to it through the setPublicVersion() method.

Notifications metadata

Android 5.0 uses metadata associated with your app notifications to sort the notifications more intelligently. To set the metadata, call the following methods in Notification.Builder when you construct the notification:
  • setCategory(): Tells the system how to handle your app notifications when the device is in priority mode (for example, if a notification represents an incoming call, instant message, or alarm).
  • setPriority(): Marks the notification as more or less important than normal notifications. Notifications with the priority field set to PRIORITY_MAX or PRIORITY_HIGH appear in a small floating window if the notification also has sound or vibration.
  • addPerson(): Enables you to add one or more people who are relevant to a notification. Your app can use this to signal to the system that it should group together notifications from the specified people, or rank notifications from these people as being more important.


Support for OpenGL ES 3.1

Android 5.0 adds Java interfaces and native support for OpenGL ES 3.1. Key new functionality provided in OpenGL ES 3.1 includes:
  • Compute shaders
  • Separate shader objects
  • Indirect draw commands
  • Multisample and stencil textures
  • Shading language improvements
  • Extensions for advanced blend modes and debugging
  • Backward compatibility with OpenGL ES 2.0 and 3.0
The Java interface for OpenGL ES 3.1 on Android is provided with GLES31. When using OpenGL ES 3.1, be sure that you declare it in your manifest file with the <uses-feature> tag and the android:glEsVersion attribute. For example:
    <uses-feature android:glEsVersion="0x00030001" />
For more information about using OpenGL ES, including how to check the device’s supported OpenGL ES version at runtime, see the OpenGL ES API guide.

Android Extension Pack

In addition to OpenGL ES 3.1, this release provides an extension pack with Java interfaces and native support for advanced graphics functionality. These extensions are treated as a single package by Android. (If theANDROID_extension_pack_es31a extension is present, your app can assume all extensions in the package are present and enable the shading language features with a single #extension statement.)
The extension pack supports:
  • Guaranteed fragment shader support for shader storage buffers, images, and atomics (Fragment shader support is optional in OpenGL ES 3.1.)
  • Tessellation and geometry shaders
  • ASTC (LDR) texture compression format
  • Per-sample interpolation and shading
  • Different blend modes for each color attachment in a frame buffer
The Java interface for the extension pack is provided with GLES31Ext. In your app manifest, you can declare that your app must be installed only on devices that support the extension pack. For example:
    <uses-feature android:name=“android.hardware.opengles.aep”
        android:required="true" />


Camera API for advanced camera capabilities

Android 5.0 introduces the new android.hardware.camera2 API to facilitate fine-grain photo capture and image processing. You can now programmatically access the camera devices available to the system with getCameraIdList()and connect to a specific device with openCamera(). To start capturing images, create a CameraCaptureSession and specify the Surface objects to send captured images. The CameraCaptureSession can be configured to take single shots or multiple images in a burst.
To be notified when new images are captured, implement the CameraCaptureSession.CaptureCallback listener and set it in your capture request. Now when the system completes the image capture request, yourCameraCaptureSession.CaptureCallback listener receives a call to onCaptureCompleted(), providing you with the image capture metadata in a CaptureResult.
The CameraCharacteristics class lets your app detect what camera features are available on a device. The object'sINFO_SUPPORTED_HARDWARE_LEVEL property represents the camera's level of functionality.
To see how to use the updated Camera API, refer to the Camera2Basic and Camera2Video implementation samples in this release.

Audio playback

This release includes the following changes to AudioTrack:
  • Your app can now supply audio data in floating-point format (ENCODING_PCM_FLOAT). This permits greater dynamic range, more consistent precision, and greater headroom. Floating-point arithmetic is especially useful during intermediate calculations. Playback endpoints use integer format for audio data, and with lower bit depth. (In Android 5.0, portions of the internal pipeline are not yet floating point.)
  • Your app can now supply audio data as a ByteBuffer, in the same format as provided by MediaCodec.
  • The WRITE_NON_BLOCKING option can simplify buffering and multithreading for some apps.

Media playback control

Use the new notification and media APIs to ensure that the system UI knows about your media playback and can extract and show album art. Controlling media playback across a UI and a service is now easier with the new MediaSession andMediaController classes.
The new MediaSession class replaces the deprecated RemoteControlClient class and provides a single set of callback methods for handling transport controls and media buttons. If your app provides media playback and runs on the AndroidTV or Wear platform, use the MediaSession class to handle your transport controls using the same callback methods.
You can now build your own media controller app with the new MediaController class. This class provides a thread-safe way to monitor and control media playback from your app's UI process. When creating a controller, specify aMediaSession.Token object so that your app can interact with the given MediaSession. By using theMediaController.TransportControls methods, you can send commands such as play()stop()skipToNext(), and setRating() to control media playback on that session. With the controller, you can also register aMediaController.Callback object to listen for metadata and state changes on the session.
In addition, you can create rich notifications that allow playback control tied to a media session with the newNotification.MediaStyle class.

Media browsing

Android 5.0 introduces the ability for apps to browse the media content library of another app, through the newandroid.media.browse API. To expose the media content in your app, extend the MediaBrowserService class. Your implementation of MediaBrowserService should provide access to a MediaSession.Token so that apps can play media content provided through your service.
To interact with a media browser service, use the MediaBrowser class. Specify the component name for a MediaSessionwhen you create an MediaBrowser instance. Using that browser instance, your app can then connect to the associated service and obtain a MediaSession.Token object to play content exposed through that service.


Directory selection

Android 5.0 extends the Storage Access Framework to let users select an entire directory subtree, giving apps read/write access to all contained documents without requiring user confirmation for each item.
To select a directory subtree, build and send an OPEN_DOCUMENT_TREE intent. The system displays allDocumentsProvider instances that support subtree selection, letting the user browse and select a directory. The returned URI represents access to the selected subtree. You can then use buildChildDocumentsUriUsingTree() andbuildDocumentUriUsingTree() along with query() to explore the subtree.
The new createDocument() method lets you create new documents or directories anywhere under the subtree. To manage existing documents, use renameDocument() and deleteDocument(). Check COLUMN_FLAGS to verify provider support for these calls before issuing them.
If you're implementing a DocumentsProvider and want to support subtree selection, implement isChildDocument() and include FLAG_SUPPORTS_IS_CHILD in your COLUMN_FLAGS.
Android 5.0 also introduces new package-specific directories on shared storage where your app can place media files for inclusion in MediaStore. The new getExternalMediaDirs() returns paths to these directories on all shared storage devices. Similarly to getExternalFilesDir(), no additional permissions are needed by your app to access the returned paths. The platform periodically scans for new media in these directories, but you can also use MediaScannerConnectionto explicitly scan for new content.

Wireless & Connectivity

Multiple network connections

Android 5.0 provides new multi-networking APIs that let your app dynamically scan for available networks with specific capabilities, and establish a connection to them. This functionality is useful when your app requires a specialized network, such as an SUPL, MMS, or carrier-billing network, or if you want to send data using a particular type of transport protocol.
To select and connect to a network dynamically from your app, follow these steps:
  1. Create a ConnectivityManager.
  2. Use the NetworkRequest.Builder class to create an NetworkRequest object and specify the network features and transport type your app is interested in.
  3. To scan for suitable networks, call requestNetwork() or registerNetworkCallback(), and pass in theNetworkRequest object and an implementation of ConnectivityManager.NetworkCallback. Use therequestNetwork() method if you want to actively switch to a suitable network once it’s detected; to receive only notifications for scanned networks without actively switching, use the registerNetworkCallback() method instead.
When the system detects a suitable network, it connects to the network and invokes the onAvailable() callback. You can use the Network object from the callback to get additional information about the network, or to direct traffic to use the selected network.

Bluetooth Low Energy

Android 4.3 introduced platform support for Bluetooth Low Energy (Bluetooth LE) in the central role. In Android 5.0, an Android device can now act as a Bluetooth LE peripheral device. Apps can use this capability to make their presence known to nearby devices. For instance, you can build apps that allow a device to function as a pedometer or health monitor and communicate its data with another Bluetooth LE device.
The new android.bluetooth.le APIs enable your apps to broadcast advertisements, scan for responses, and form connections with nearby Bluetooth LE devices. To use the new advertising and scanning features, add theBLUETOOTH_ADMIN permission in your manifest. When users update or download your app from the Play Store, they are asked to grant the following permission to your app: "Bluetooth connection information: Allows the app to control Bluetooth, including broadcasting to or getting information about nearby Bluetooth devices."
To begin Bluetooth LE advertising so that other devices can discover your app, call startAdvertising() and pass in an implementation of the AdvertiseCallback class. The callback object receives a report of the success or failure of the advertising operation.
Android 5.0 introduces the ScanFilter class so that your app can scan for only the specific types of devices it is interested in. To begin scanning for Bluetooth LE devices, call startScan() and pass in a list of filters. In the method call, you must also provide an implementation of ScanCallback to report when a Bluetooth LE advertisement is found.

NFC enhancements

Android 5.0 adds these enhancements to enable wider and more flexible use of NFC:
  • Android Beam is now available in the share menu.
  • Your app can invoke the Android Beam on the user’s device to share data by calling invokeBeam(). This avoids the need for the user to manually tap the device against another NFC-capable device to complete the data transfer.
  • You can use the new createTextRecord() method to create an NDEF record containing UTF-8 text data.
  • If you are developing a payment app, you now have the ability to register an NFC application ID (AID) dynamically by calling registerAidsForService(). You can also use setPreferredService() to set the preferred card emulation service that should be used when a specific activity is in the foreground.

Project Volta

In addition to new features, Android 5.0 emphasizes improvements in battery life. Use the new APIs and tool to understand and optimize your app’s power consumption.

Scheduling jobs

Android 5.0 provides a new JobScheduler API that lets you optimize battery life by defining jobs for the system to run asynchronously at a later time or under specified conditions (such as when the device is charging). Job scheduling is useful in such situations as:
  • The app has non-user-facing work that you can defer.
  • The app has work you'd prefer to do when the unit is plugged in.
  • The app has a task that requires network access or a Wi-Fi connection.
  • The app has a number of tasks that you want to run as a batch on a regular schedule.
A unit of work is encapsulated by a JobInfo object. This object specifies the scheduling criteria.
Use the JobInfo.Builder class to configure how the scheduled task should run. You can schedule the task to run under specific conditions, such as:
  • Start when the device is charging
  • Start when the device is connected to an unmetered network
  • Start when the device is idle
  • Finish before a certain deadline or with a minimum delay
For example, you can add code like this to run your task on an unmetered network:
JobInfo uploadTask = new JobInfo.Builder(mJobId,
                                         mServiceComponent /* JobService component */)
JobScheduler jobScheduler =
        (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE);
If the device has stable power (that is, it has been plugged in for more than 2 minutes and the battery is at a healthy level), the system will run any scheduled job that is ready to run, even if the job’s deadline has not expired.
To see an example of how to use the JobScheduler API, refer to the JobSchedulerSample implementation sample in this release.

Developer tools for battery usage

The new dumpsys batterystats command generates interesting statistical data about battery usage on a device, organized by unique user ID (UID). The statistics include:
  • History of battery related events
  • Global statistics for the device
  • Approximate power use per UID and system component
  • Per-app mobile ms per packet
  • System UID aggregated statistics
  • App UID aggregated statistics
Use the --help option to learn about the various options for tailoring the output. For example, to print battery usage statistics for a given app package since the device was last charged, run this command:
$ adb shell dumpsys batterystats --charged <package-name>
You can use the Battery Historian tool on the output of the dumpsys command to generate an HTML visualization of power-related events from the logs. This information makes it easier for you to understand and diagnose any battery related issues.

Android in the Workplace and in Education

Managed provisioning

Android 5.0 provides new functionality for running apps within an enterprise environment. A device administrator can initiate a managed provisioning process to add a copresent but separate managed profile to a device, if the user has an existing personal account. Apps that are associated with managed profiles appear alongside non-managed apps in the user’s Launcher, recents screen, and notifications.
To start the managed provisioning process, send ACTION_PROVISION_MANAGED_PROFILE in an Intent. If the call is successful, the system triggers the onProfileProvisioningComplete() callback. You can then callsetProfileEnabled() to enable this managed profile.
By default, only a small subset of apps are enabled in the managed profile. You can install additional apps in the managed profile by calling enableSystemApp().
If you are developing a Launcher app, you can use the new LauncherApps class to get a list of launchable activities for the current user and any associated managed profiles. Your Launcher can make the managed apps visually prominent by appending a work badge to the icon drawable. To retrieve the badged icon, call getUserBadgedIcon().
To see how to use the new functionality, refer to the BasicManagedProfile implementation sample in this release.

Device owner

Android 5.0 introduces the ability to deploy a device owner app. A device owner is a specialized type of device administrator that has the additional ability to create and remove secondary users and to configure global settings on the device. Your device owner app can use the methods in the DevicePolicyManager class to take fine-grain control of the configuration, security, and apps on managed devices. A device can have only one active device owner at a time.
To deploy and activate a device owner, you must perform an NFC data transfer from a programming app to the device while the device is in its unprovisioned state. This data transfer sends the same information as in the provisioning intent described in Managed provisioning.

Screen pinning

Android 5.0 introduces a new screen pinning API that lets you temporarily restrict users from leaving your task or being interrupted by notifications. This could be used, for example, if you are developing an education app to support high stakes assessment requirements on Android, or a single-purpose or kiosk application. Once your app activates screen pinning, users cannot see notifications, access other apps, or return to the home screen, until your app exits the mode.
There are two ways to activate screen pinning:
  • Manually: Users can enable screen pinning in Settings > Security > Screen Pinning, and select the tasks they want to pin by touching the green pin icon in the recents screen.
  • Programmatically: To activate screen pinning programmatically, call startLockTask() from your app. If the requesting app is not a device owner, the user is prompted for confirmation. A device owner app can call thesetLockTaskPackages() method to enable apps to be pinnable without the user confirmation step.
When task locking is active, the following behavior happens:
  • The status bar is blank, and user notifications and status information are hidden.
  • The Home and Recent Apps buttons are hidden.
  • Other apps cannot launch new activities.
  • The current app can start new activities, as long as doing so does not create new tasks.
  • When screen pinning is invoked by a device owner, the user remains locked to your app until the app callsstopLockTask().
  • If screen pinning is activity by another app that is not a device owner or by the user directly, the user can exit by holding both the Back and Recent buttons.

Printing Framework

Render PDF as bitmap

You can now render PDF document pages into bitmap images for printing by using the new PdfRenderer class. You must specify a ParcelFileDescriptor that is seekable (that is, the content can be randomly accessed) on which the system writes the the printable content. Your app can obtain a page for rendering with openPage(), then call render() to turn the opened PdfRenderer.Page into a bitmap. You can also set additional parameters if you only want to convert a portion of the document into a bitmap image (for example, to implement tiled rendering to zoom in on the document).
For an example of how to use the new APIs, see the PdfRendererBasic sample.


App usage statistics

You can now access app usage history on an Android device with the new android.app.usage API. This API provides more detailed usage information than the deprecated getRecentTasks() method. To use this API, you must first declare the "android.permission.PACKAGE_USAGE_STATS" permission in your manifest. The user must also enable access for this app through Settings > Security > Apps with usage access.
The system collects the usage data on a per-app basis, aggregating the data over daily, weekly, monthly, and yearly intervals. The maximum duration that the system keeps this data is as follows:
  • Daily data: 7 days
  • Weekly data: 4 weeks
  • Monthly data: 6 months
  • Yearly data: 2 years
For each app, the system records the following data:
  • The last time the app was used
  • The total length of time the app was in the foreground for that time interval (by day, week, month, or year)
  • Timestamp capturing when a component (identified by a package and activity name) moved to the foreground or background during a day
  • Timestamp capturing when a device configuration changed (such as when the device orientation changed because of rotation)

Testing & Accessibility

Testing and accessibility improvements

Android 5.0 adds the following support for testing and accessibility:
  • The new getWindowAnimationFrameStats() and getWindowContentFrameStats() methods capture frame statistics for window animations and content. These methods let you write instrumentation tests to evaluate whether an app is rendering frames at a sufficient refresh frequency to provide a smooth user experience.
  • The new executeShellCommand() method lets you execute shell commands from your instrumentation test. The command execution is similar to running adb shell from a host connected to the device, allowing you to use shell-based tools such as dumpsysamcontent, and pm.
  • Accessibility services and test tools that use the accessibility APIs (such as UiAutomator) can now retrieve detailed information about the properties of windows on the screen that sighted users can interact with. To retrieve a list ofAccessibilityWindowInfo objects, call the new getWindows() method.
  • The new AccessibilityNodeInfo.AccessibilityAction class lets you define standard or customized actions to perform on an AccessibilityNodeInfo. The new AccessibilityNodeInfo.AccessibilityAction class replaces the actions-related APIs previously found in AccessibilityNodeInfo.
  • Android 5.0 provides finer-grain control over text-to-speech synthesis in your app. The new Voice class allows your app to use voice profiles associated with specific locales, quality and latency rating, and text-to-speech engine-specific parameters.


Easier switching between input languages

Beginning in Android 5.0, users can more easily switch between all input method editors (IME) supported by the platform. Performing the designated switching action (usually touching a Globe icon on the soft keyboard) cycles through all such IMEs. This change in behavior is implemented by the shouldOfferSwitchingToNextInputMethod() method.
In addition, the framework now checks whether the next IME includes a switching mechanism at all (and, thus, whether that IME supports switching to the IME after it). An IME with a switching mechanism will not cycle to an IME without one. This change in behavior is implemented by the switchToNextInputMethod() method.
To see an example of how to use the updated IME-switching APIs, refer to the updated soft-keyboard implementation sample in this release. To learn more about how to implement switching between IMEs, see Creating an Input Method.

Manifest Declarations

Declarable required features

The following values are now supported in the <uses-feature> element, so you can ensure that your app is installed only on devices that provide the features your app needs.

User permissions

The following permission is now supported in the <uses-permission> element to declare the permissions your app requires to access certain APIs.
  • BIND_DREAM_SERVICE: When targeting API level 21 and higher, this permission is required by a Daydream service, to ensure that only the system can bind to it.

Portions of this page are reproduced from work created and shared by the Android Open Source Project and used according to terms described in theCreative Commons 2.5 Attribution License.

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