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Tuesday, 29 September 2015

Jelly Bean

Jelly Bean
Android 4.3 on phone and tablet
Welcome to Android 4.3, a sweeter version of Jelly Bean!
Android 4.3 includes performance optimizations and great new features for users and developers. This document provides a glimpse of what's new for developers.
See the Android 4.3 APIs document for a detailed look at the new developer APIs.
Find out more about the new Jelly Bean features for users at www.android.com.

Faster, Smoother, More Responsive

Android 4.3 builds on the performance improvements already included in Jelly Bean — vsync timingtriple buffering,reduced touch latencyCPU input boost, and hardware-accelerated 2D rendering — and adds new optimizations that make Android even faster.
For a graphics performance boost, the hardware-accelerated 2D renderer now optimizes the stream of drawing commands, transforming it into a more efficient GPU format by rearranging and merging draw operations. For multithreaded processing, the renderer can also now use multithreading across multiple CPU cores to perform certain tasks.
Android 4.3 also improves rendering for shapes and text. Shapes such as circles and rounded rectangles are now rendered at higher quality in a more efficient manner. Optimizations for text include increased performance when using multiple fonts or complex glyph sets (CJK), higher rendering quality when scaling text, and faster rendering of drop shadows.
Improved window buffer allocation results in a faster image buffer allocation for your apps, reducing the time taken to start rendering when you create a window.
For highest-performance graphics, Android 4.3 introduces support for OpenGL ES 3.0 and makes it accessible to apps through both framework and native APIs. On supported devices, the hardware accelerated 2D rendering engine takes advantage of OpenGL ES 3.0 to optimize texture management and increase gradient rendering fidelity.

OpenGL ES 3.0 for High-Performance Graphics

Android 4.3 introduces platform support for Khronos OpenGL ES 3.0, providing games and other apps with highest-performance 2D and 3D graphics capabilities on supported devices. You can take advantage of OpenGL ES 3.0 and related EGL extensions using either framework APIs or native API bindings through the Android Native Development Kit (NDK).
Key new functionality provided in OpenGL ES 3.0 includes acceleration of advanced visual effects, high quality ETC2/EAC texture compression as a standard feature, a new version of the GLSL ES shading language with integer and 32-bit floating point support, advanced texture rendering, and standardized texture size and render-buffer formats.
You can use the OpenGL ES 3.0 APIs to create highly complex, highly efficient graphics that run across a range of compatible Android devices, and you can support a single, standard texture-compression format across those devices.
OpenGL ES 3.0 is an optional feature that depends on underlying graphics hardware. Support is already available on Nexus 7 (2013), Nexus 4, and Nexus 10 devices.

Enhanced Bluetooth Connectivity

Connectivity with Bluetooth Smart devices and sensors

Now you can design and build apps that interact with the latest generation of small, low-power devices and sensors that use Bluetooth Smart technology.
Android 4.3 gives you a single, standard API for interacting with Bluetooth Smart devices.
Android 4.3 introduces built-in platform support for Bluetooth Smart Ready in the central role and provides a standard set of APIs that apps can use to discover nearby devices, query for GATT services, and read/write characteristics.
With the new APIs, your apps can efficiently scan for devices and services of interest. For each device, you can check for supported GATT services by UUID and manage connections by device ID and signal strength. You can connect to a GATT server hosted on the device and read or write characteristics, or register a listener to receive notifications whenever those characteristics change.
You can implement support for any GATT profile. You can read or write standard characteristics or add support for custom characteristics as needed. Your app can function as either client or server and can transmit and receive data in either mode. The APIs are generic, so you’ll be able to support interactions with a variety of devices such as proximity tags, watches, fitness meters, game controllers, remote controls, health devices, and more.
Support for Bluetooth Smart Ready is already available on Nexus 7 (2013) and Nexus 4 devices and will be supported in a growing number of Android-compatible devices in the months ahead.

AVRCP 1.3 Profile

Android 4.3 adds built-in support for Bluetooth AVRCP 1.3, so your apps can support richer interactions with remote streaming media devices. Apps such as media players can take advantage of AVRCP 1.3 through the remote control client APIs introduced in Android 4.0. In addition to exposing playback controls on the remote devices connected over Bluetooth, apps can now transmit metadata such as track name, composer, and other types of media metadata.
Platform support for AVRCP 1.3 is built on the Bluedroid Bluetooth stack introduced by Google and Broadcom in Android 4.2. Support is available right away on Nexus devices and other Android-compatible devices that offer A2DP/AVRCP capability.

Support for Restricted Profiles

Setting up a Restricted Profile
A tablet owner can set up one or more restricted profiles in Settings and manage them independently.
Setting Restrictions in a Profile
Your app can offer restrictions to let owners manage your app content when it's running in a profile.
Android 4.3 extends the multiuser feature for tablets withrestricted profiles, a new way to manage users and their capabilities on a single device. With restricted profiles, tablet owners can quickly set up separate environments for each user, with the ability to manage finer-grained restrictions in the apps that are available in those environments. Restricted profiles are ideal for friends and family, guest users, kiosks, point-of-sale devices, and more.
Each restricted profile offers an isolated and secure space with its own local storage, home screens, widgets, and settings. Unlike with users, profiles are created from the tablet owner’s environment, based on the owner’s installed apps and system accounts. The owner controls which installed apps are enabled in the new profile, and access to the owner’s accounts is disabled by default.
Apps that need to access the owner’s accounts — for sign-in, preferences, or other uses — can opt-in by declaring a manifest attribute, and the owner can review and manage those apps from the profile configuration settings.
For developers, restricted profiles offer a new way to deliver more value and control to your users. You can implement app restrictions — content or capabilities controls that are supported by your app — and advertise them to tablet owners in the profile configuration settings.
You can add app restrictions directly to the profile configuration settings using predefined boolean, select, and multi-select types. If you want more flexibility, you can even launch your own UI from profile configuration settings to offer any type of restriction you want.
When your app runs in a profile, it can check for any restrictions configured by the owner and enforce them appropriately. For example, a media app might offer a restriction to let the owner set a maturity level for the profile. At run time, the app could check for the maturity setting and then manage content according to the preferred maturity level.
If your app is not designed for use in restricted profiles, you can opt out altogether, so that your app can't be enabled in any restricted profile.

Optimized Location and Sensor Capabilities

Google Play services offers advanced location APIs that you can use in your apps. Android 4.3 optimizes these APIs on supported devices with new hardware and software capabilities that minimize use of the battery.
Hardware geofencing optimizes for power efficiency by performing location computation in the device hardware, rather than in software. On devices that support hardware geofencing, Google Play services geofence APIs will be able to take advantage of this optimization to save battery while the device is moving.
Wi-Fi scan-only mode is a new platform optimization that lets users keep Wi-Fi scan on without connecting to a Wi-Fi network, to improve location accuracy while conserving battery. Apps that depend on Wi-Fi for location services can now ask users to enable scan-only mode from Wi-Fi advanced settings. Wi-Fi scan-only mode is not dependent on device hardware and is available as part of the Android 4.3 platform.
New sensor types allow apps to better manage sensor readings. A game rotation vector lets game developers sense the device’s rotation without having to worry about magnetic interference. Uncalibrated gyroscope and uncalibrated magnetometer sensors report raw measurements as well as estimated biases to apps.
The new hardware capabilities are already available on Nexus 7 (2013) and Nexus 4 devices, and any device manufacturer or chipset vendor can build them into their devices.

New Media Capabilities

Modular DRM framework

To meet the needs of the next generation of media services, Android 4.3 introduces a modular DRM framework that enables media application developers to more easily integrate DRM into their own streaming protocols, such as MPEG DASH (Dynamic Adaptive Streaming over HTTP, ISO/IEC 23009-1).
Through a combination of new APIs and enhancements to existing APIs, the media DRM framework provides anintegrated set of services for managing licensing and provisioning, accessing low-level codecs, and decoding encrypted media data. A new MediaExtractor API lets you get the PSSH metadata for DASH media. Apps using the media DRM framework manage the network communication with a license server and handle the streaming of encrypted data from a content library.

VP8 encoder

Android 4.3 introduces built-in support for VP8 encoding, accessible from framework and native APIs. For apps using native APIs, the platform includes OpenMAX 1.1.2 extension headers to support VP8 profiles and levels. VP8 encoding support includes settings for target bitrate, rate control, frame rate, token partitioning, error resilience, reconstruction and loop filters. The platform API introduces VP8 encoder support in a range of formats, so you can take advantage of the best format for your content.
VP8 encoding is available in software on all compatible devices running Android 4.3. For highest performance, the platform also supports hardware-accelerated VP8 encoding on capable devices.

Video encoding from a surface

Starting in Android 4.3 you can use a surface as the input to a video encoder. For example, you can now direct a stream from an OpenGL ES surface to the encoder, rather than having to copy between buffers.

Media muxer

Apps can use new media muxer APIs to combine elementary audio and video streams into a single output file. Currently apps can multiplex a single MPEG-4 audio stream and a single MPEG-4 video stream into a single MPEG-4 ouput file. The new APIs are a counterpart to the media demuxing APIs introduced in Android 4.2.

Playback progress and scrubbing in remote control clients

Since Android 4.0, media players and similar applications have been able to offer playback controls from remote control clients such as the device lock screen, notifications, and remote devices connected over Bluetooth. Starting in Android 4.3, those applications can now also expose playback progress and speed through their remote control clients, and receive commands to jump to a specific playback position.

New Ways to Build Beautiful Apps

Access to notifications

Notifications have long been a popular Android feature because they let users see information and updates from across the system, all in one place. Now in Android 4.3, apps can observe the stream of notifications with the user's permission and display the notifications in any way they want, including sending them to nearby devices connected over Bluetooth.
You can access notifications through new APIs that let you register a notification listener service and with permission of the user, receive notifications as they are displayed in the status bar. Notifications are delivered to you in full, with all details on the originating app, the post time, the content view and style, and priority. You can evaluate fields of interest in the notifications, process or add context from your app, and route them for display in any way you choose.
The new API gives you callbacks when a notification is added, updated, and removed (either because the user dismissed it or the originating app withdrew it). You'll be able to launch any intents attached to the notification or its actions, as well as dismiss it from the system, allowing your app to provide a complete user interface to notifications.
Users remain in control of which apps can receive notifications. At any time, they can look in Settings to see which apps have notification access and enable or disable access as needed. Notification access is disabled by default — apps can use a new Intent to take the user directly to the Settings to enable the listener service after installation.

View overlays

You can now create transparent overlays on top of Views and ViewGroups to render a temporary View hierarchy or transient animation effects without disturbing the underlying layout hierarchy. Overlays are particularly useful when you want to create animations such as sliding a view outside of its container or dragging items on the screen without affecting the view hierarchy.

Optical bounds layout mode

A new layout mode lets you manage the positioning of Views inside ViewGroups according to their optical bounds, rather than their clip bounds. Clip bounds represent a widget’s actual outer boundary, while the new optical bounds describe the where the widget appears to be, within the clip bounds. You can use the optical bounds layout mode to properly align widgets that use outer visual effects such as shadows and glows.

Custom rotation animation types

Apps can now define the exit and entry animation types used on a window when the device is rotated. You can set window properties to enable jump-cutcross-fade, or standard window rotation. The system uses the custom animation types when the window is fullscreen and is not covered by other windows.

Screen orientation modes

Apps can set new orientation modes for Activities to ensure that they are displayed in the proper orientation when the device is flipped. Additionally, apps can use a new mode to lock the screen to its current orientation. This is useful for apps using the camera that want to disable rotation while shooting video.

Intent for handling Quick Responses

Android 4.3 introduces a new public Intent that lets any app handle Quick Responses — text messages sent by the user in response to an incoming call, without needing to pick up the call or unlock the device. Your app can listen for the intent and send the message to the caller over your messaging system. The intent includes the recipient (caller) as well as the message itself.

Support for International Users

More parts of Android 4.3 are optimized for RTL languages.

RTL improvements

Android 4.3 includes RTL performance enhancements and broader RTL support across framework UI widgets, including ProgressBar/Spinner and ExpandableListView. More debugging information visible through theuiautomatorviewer tool. In addition, more system UI components are now RTL aware, such as notifications, navigation bar and the Action Bar.
To provide a better systemwide experience in RTL scripts, more default system apps now support RTL layouts, including Launcher, Quick Settings, Phone, People, SetupWizard, Clock, Downloads, and more.

Utilities for localization

Pseudo-locales make it easier to test your app's localization.
Android 4.3 also includes new utilities and APIs for creating better RTL strings and testing your localized UIs. A new BidiFormatter class provides a simple API for wrapping Unicode strings, so that RTL-script data is displayed as intended in LTR-locale messages and vice-versa. To let you use this utility more broadly in your apps, the BidiFormatter API is also now available for earlier platform versions through the Support Package in the Android SDK.
To assist you with managing date formatting across locales, Android 4.3 includes a new getBestDateTimePattern() method that automatically generates the best possible localized form of a Unicode UTS date for a locale that you specify. It’s a convenient way to provide a more localized experience for your users.
To help you test your app more easily in other locales, Android 4.3 introduces pseudo-locales as a new developer option. Pseudo-locales simulate the language, script, and display characteristics associated with a locale or language group. Currently, you can test with a pseudo-locale for Accented English, which lets you see how your UI works with script accents and characters used in a variety of European languages.

Accessibility and UI Automation

Starting in Android 4.3, accessibility services can observe and filter key events, such as to handle keyboard shortcuts or provide navigation parity with gesture-based input. The service receives the events and can process them as needed before they are passed to the system or other installed apps.
Accessibility services can declare new capability attributes to describe what their services can do and what platform features they use. For example, they can declare the capability to filter key events, retrieve window content, enable explore-by-touch, or enable web accessibility features. In some cases, services must declare a capability attribute before they can access related platform features. The system uses the service’s capability attributes to generate an opt-in dialog for users, so they can see and agree to the capabilities before launch.
Building on the accessibility framework in Android 4.3, a new UI automation framework lets tests interact with the device’s UI by simulating user actions and introspecting the screen content. Through the UI automation framework you can perform basic operations, set rotation of the screen, generate input events, take screenshots, and much more. It’s a powerful way to automate testing in realistic user scenarios, including actions or sequences that span multiple apps.

Enterprise and Security

Wi-Fi configuration for WPA2-Enterprise networks

Apps can now configure the Wi-Fi credentials they need for connections to WPA2 enterprise access points. Developers can use new APIs to configure Extensible Authentication Protocol (EAP) and Encapsulated EAP (Phase 2) credentials for authentication methods used in the enterprise. Apps with permission to access and change Wi-Fi can configure authentication credentials for a variety of EAP and Phase 2 authentication methods.

Android sandbox reinforced with SELinux

Android now uses SELinux, a mandatory access control (MAC) system in the Linux kernel to augment the UID based application sandbox. This protects the operating system against potential security vulnerabilities.

KeyChain enhancements

The KeyChain API now provides a method that allows applications to confirm that system-wide keys are bound to ahardware root of trust for the device. This provides a place to create or store private keys that cannot be exported off the device, even in the event of a root or kernel compromise.

Android Keystore Provider

Android 4.3 introduces a keystore provider and APIs that allow applications to create exclusive-use keys. Using the APIs, apps can create or store private keys that cannot be seen or used by other apps, and can be added to the keystore without any user interaction.
The keystore provider provides the same security benefits that the KeyChain API provides for system-wide credentials, such as binding credentials to a device. Private keys in the keystore cannot be exported off the device.

Restrict Setuid from Android Apps

The /system partition is now mounted nosuid for zygote-spawned processes, preventing Android applications from executing setuid programs. This reduces root attack surface and likelihood of potential security vulnerabilities.

New Ways to Analyze Performance

Systrace uses a new command syntax and lets you collect more types of profiling data.

Enhanced Systrace logging

Android 4.3 supports an enhanced version of theSystrace tool that’s easier to use and that gives you access to more types of information to profile the performance of your app. You can now collect trace data from hardware moduleskernel functions,Dalvik VM including garbage collection, resources loading, and more.
Android 4.3 also includes new Trace APIs that you can use in your apps to mark specific sections of code to trace using Systrace begin/end events. When the marked sections of code execute, the system writes the begin/end events to the trace log. There's minimal impact on the performance of your app, so timings reported give you an accurate view of what your app is doing.
You can visualize app-specific events in a timeline in the Systrace output file and analyze the events in the context of other kernel and user space trace data. Together with existing Systrace tags, custom app sections can give you new ways to understand the performance and behavior of your apps.
On-screen GPU profiling in Android 4.3.

On-screen GPU profiling

Android 4.3 adds new developer options to help you analyze your app’s performance and pinpoint rendering issues on any device or emulator.
In the Profile GPU rendering option you can now visualize your app’s effective framerate on-screen, while the app is running. You can choose to display profiling data as on-screen bar or line graphs, with colors indicating time spent creating drawing commands (blue), issuing the commands (orange), and waiting for the commands to complete (yellow). The system updates the on-screen graphs continuously, displaying a graph for each visible Activity, including the navigation bar and notification bar.
A green line highlights the 16ms threshold for rendering operations, so you can assess the your app’s effective framerate relative to a 60 fps goal (because 1/60th of a second equals roughly 16ms). If you see operations that cross the green line, you can analyze them further using Systrace and other tools.
On devices running Android 4.2 and higher, developer options are hidden by default. You can reveal them at any time by tapping 7 times on Settings > About phone > Build number on any compatible Android device.

StrictMode warning for file URIs

The latest addition to the StrictMode tool is a policy constraint that warns when your app exposes a file:// URI to the system or another app. In some cases the receiving app may not have access to the file:// URI path, so when sharing files between apps, a content:// URI should be used (with the appropriate permission). This new policy helps you catch and fix such cases. If you’re looking for a convenient way to store and expose files to other apps, try using theFileProvider content provider that’s available in the Support Library.

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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