jelly-bean.jd revision ac6be105444e945437481f9b3e7d2742a33c7287
1page.title=Jelly Bean 2tab1=Android 4.3 3tab1.link=#android-43 4tab2=Android 4.2 5tab2.link=#android-42 6tab3=Android 4.1 7tab3.link=#android-41 8 9@jd:body 10<div id="butterbar-wrapper" > 11 <div id="butterbar" > 12 <div id="butterbar-message"> 13<a target="_blank" href="https://docs.google.com/a/google.com/forms/d/1EHLPGqhbxj2HungHRRN4_0K9TGpc-Izy-u46vBDgS8Q/viewform"> 14 Take the Android Developer Survey</a> 15 </div> 16 </div> 17</div> 18 19<style> 20#android-41 {display:none;} 21#android-42 {display:none;} 22</style> 23 24<script> 25function revealSection(hashy) { 26 if (hashy != "" && !$(hashy).is(":visible")) { 27 sectionId = $(hashy).closest(".version-section").attr("id"); 28 link = $("#title-tabs a[href$="+sectionId+"]"); 29 link.parent().addClass("selected"); 30 link.parent().siblings().removeClass("selected"); 31 32 sectionDiv = $(".version-section"+link.attr("href")); 33 if (sectionDiv.length) { 34 $(".version-section").hide(); 35 sectionDiv.show(); 36 } 37 38 $('html, body').animate({ 39 scrollTop: $(hashy).offset().top 40 }, 100); 41 } 42} 43 44$(document).ready(function() { 45 $("#title-tabs li a").each(function() { 46 $(this).click(function(){ 47 $(this).parent().addClass("selected"); 48 $(this).parent().siblings().removeClass("selected"); 49 $(".version-section").hide(); 50 $($(this).attr("href")).show(); 51 return false; 52 }); 53 }); 54 55 hashy = escapeHTML(location.hash); 56 revealSection(hashy); 57}); 58 59window.onhashchange = function () { 60 revealSection(escapeHTML(location.hash)); 61} 62 63</script> 64 65 66<!-- BEGIN ANDROID 4.3 --> 67<div id="android-43" class="version-section"> 68 69<div style="float:right;padding:0px 0px 10px 28px;width:480px;"> 70<div> 71<a href="{@docRoot}images/jb-android-43@2x.png"><img src="{@docRoot}images/jb-android-43.jpg" alt="Android 4.3 on phone and tablet" width="472"></a> 72 73</div> 74</div> 75<p>Welcome to Android 4.3, a sweeter version of <span 76style="white-space:nowrap;">Jelly Bean!</span></p> 77 78<p>Android 4.3 includes performance optimizations and great 79new features for users and developers. This document provides a glimpse of what's new for 80developers. 81 82<p>See the <a href="{@docRoot}about/versions/android-4.3.html">Android 4.3 APIs</a> 83document for a detailed look at the new developer APIs.</p> 84 85<p>Find out more about the new Jelly Bean features for users at <a 86href="http://www.android.com/whatsnew">www.android.com</a>.</p> 87 88 89<h2 id="43-performance" style="line-height:1.25em;">Faster, Smoother, More 90Responsive</h2> 91 92<p>Android 4.3 builds on the performance improvements already included in Jelly 93Bean — <strong>vsync timing</strong>, <strong>triple buffering</strong>, 94<strong>reduced touch latency</strong>, <strong>CPU input boost</strong>, and 95<strong>hardware-accelerated 2D rendering</strong> — and adds new 96optimizations that make Android even faster.</p> 97 98<p>For a graphics performance boost, the hardware-accelerated 2D renderer now 99<strong>optimizes the stream of drawing commands</strong>, transforming it into 100a more efficient GPU format by rearranging and merging draw operations. For 101multithreaded processing, the renderer can also now use <strong>multithreading 102across multiple CPU cores</strong> to perform certain tasks.</p> 103 104<p>Android 4.3 also improves <strong>rendering for shapes and text</strong>. 105Shapes such as circles and rounded rectangles are now rendered at higher quality 106in a more efficient manner. Optimizations for text include increased performance 107when using multiple fonts or complex glyph sets (CJK), higher rendering quality 108when scaling text, and faster rendering of drop shadows.</p> 109 110<p><strong>Improved window buffer allocation</strong> results in a faster image 111buffer allocation for your apps, reducing the time taken to start rendering when 112you create a window.</p> 113 114<p>For highest-performance graphics, Android 4.3 introduces support for 115<strong>OpenGL ES 3.0</strong> and makes it accessible to apps through both 116framework and native APIs. On supported devices, the hardware accelerated 2D 117rendering engine takes advantage of OpenGL ES 3.0 to optimize <strong>texture 118management</strong> and increase <strong>gradient rendering 119fidelity</strong>.</p> 120 121 122<h2 id="43-graphics">OpenGL ES 3.0 for High-Performance Graphics</h2> 123 124<p>Android 4.3 introduces platform support for <a class="external-link" 125href="http://www.khronos.org/opengles/3_X/" target="_android">Khronos OpenGL ES 3.0</a>, 126providing games and other apps with highest-performance 2D and 3D graphics 127capabilities on supported devices. You can take advantage of OpenGL ES 3.0 128and related EGL extensions using either <strong>framework APIs</strong> 129or <strong>native API bindings</strong> through the Android Native Development 130Kit (NDK).</p> 131 132<p>Key new functionality provided in OpenGL ES 3.0 includes acceleration of 133advanced visual effects, high quality ETC2/EAC texture compression as a standard 134feature, a new version of the GLSL ES shading language with integer and 32-bit 135floating point support, advanced texture rendering, and standardized texture 136size and render-buffer formats. 137 138<p>You can use the OpenGL ES 3.0 APIs to create highly complex, highly efficient 139graphics that run across a range of compatible Android devices, and you can 140support a single, standard texture-compression format across those devices.</p> 141 142<p>OpenGL ES 3.0 is an optional feature that depends on underlying graphics 143hardware. Support is already available on Nexus 7 (2013), Nexus 4, and 144Nexus 10 devices.</p> 145 146 147<h2 id="43-bluetooth" style="clear:both;">Enhanced Bluetooth Connectivity</h2> 148 149<h4 id="43-bt-le">Connectivity with Bluetooth Smart devices and sensors</h4> 150 151<p>Now you can design and build apps that interact with the latest generation 152of small, low-power devices and sensors that use <a 153href="http://www.bluetooth.com/Pages/Bluetooth-Smart-Devices.aspx" 154class="external-link" target="_android">Bluetooth Smart technology</a>. </p> 155 156<div style="float:right;margin:0px 0px 32px 0px;width:460px;"> 157<img src="{@docRoot}images/jb-btle.png" alt="" width="450" style="padding-left:1.5em;margin-bottom:0"> 158<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;margin-bottom:0;padding-left:1.5em;">Android 4.3 gives you a single, standard API for interacting with Bluetooth Smart devices. </p> 159</div> 160 161<p>Android 4.3 introduces built-in platform support for <strong>Bluetooth Smart 162Ready</strong> in the central role and provides a standard set of APIs that 163apps can use to discover nearby devices, query for GATT services, and read/write 164characteristics.</p> 165 166<p>With the new APIs, your apps can efficiently scan for devices and services of 167interest. For each device, you can check for supported GATT services by UUID and 168manage connections by device ID and signal strength. You can connect to a GATT 169server hosted on the device and read or write characteristics, or register a 170listener to receive notifications whenever those characteristics change.</p> 171 172<p>You can implement support for any GATT profile. You can read or write 173standard characteristics or add support for custom characteristics as needed. 174Your app can function as either client or server and can transmit and receive 175data in either mode. The APIs are generic, so you’ll be able to support 176interactions with a variety of devices such as proximity tags, watches, fitness 177meters, game controllers, remote controls, health devices, and more. 178</p> 179 180<p>Support for Bluetooth Smart Ready is already available on Nexus 7 (2013) 181and Nexus 4 devices and will be supported in a growing number of 182Android-compatible devices in the months ahead.</p> 183 184<h4 id="43-bt-avrcp">AVRCP 1.3 Profile</h4> 185 186<p>Android 4.3 adds built-in support for <strong>Bluetooth AVRCP 1.3</strong>, 187so your apps can support richer interactions with remote streaming media 188devices. Apps such as media players can take advantage of AVRCP 1.3 through the 189<strong>remote control client APIs</strong> introduced in Android 4.0. In 190addition to exposing playback controls on the remote devices connected over 191Bluetooth, apps can now transmit metadata such as track name, composer, and 192other types of media metadata. </p> 193 194<p>Platform support for AVRCP 1.3 is built on the Bluedroid Bluetooth stack 195introduced by Google and Broadcom in Android 4.2. Support is available right 196away on Nexus devices and other Android-compatible devices that offer A2DP/AVRCP 197capability. </p> 198 199 200<h2 id="43-profiles">Support for Restricted Profiles</h2> 201 202<div style="float:right;margin:22px 0px 0px 24px;width:340px;"> 203<img src="{@docRoot}images/jb-profiles-create-n713.png" alt="Setting up a Restricted Profile" width="340" style="margin-bottom:0"> 204<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;margin-bottom:0;">A tablet owner can set up one or more restricted profiles in Settings and manage them independently. </p> 205<img src="{@docRoot}images/jb-profiles-restrictions-n713.png" alt="Setting Restrictions in a Profile" width="340" style="margin-bottom:0;padding-top:1em;"> 206<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">Your app can offer restrictions to let owners manage your app content when it's running in a profile. </p> 207</div> 208 209<p>Android 4.3 extends the multiuser feature for tablets with <strong>restricted 210profiles</strong>, a new way to manage users and their capabilities on a single 211device. With restricted profiles, tablet owners can quickly set up 212<strong>separate environments</strong> for each user, with the ability to 213manage <strong>finer-grained restrictions</strong> in the apps that are 214available in those environments. Restricted profiles are ideal for friends and 215family, guest users, kiosks, point-of-sale devices, and more. </p> 216 217<p>Each restricted profile offers an isolated and secure space with its own 218local storage, home screens, widgets, and settings. Unlike with 219users, profiles are created from the tablet owner’s environment, based on the 220owner’s installed apps and system accounts. The owner controls which installed 221apps are enabled in the new profile, and access to the owner’s accounts is 222disabled by default. </p> 223 224<p>Apps that need to access the owner’s accounts — for sign-in, 225preferences, or other uses — can opt-in by declaring a manifest attribute, 226and the owner can review and manage those apps from the profile configuration 227settings.</p> 228 229<p>For developers, restricted profiles offer a new way to deliver more value and 230control to your users. You can implement <strong>app restrictions</strong> 231— content or capabilities controls that are supported by your app — 232and advertise them to tablet owners in the profile configuration settings. 233</p> 234 235<p>You can add app restrictions directly to the profile configuration settings 236using predefined boolean, select, and multi-select types. If you want more 237flexibility, you can even launch your own UI from profile configuration settings 238to offer any type of restriction you want. </p> 239 240<p>When your app runs in a profile, it can check for any restrictions configured 241by the owner and enforce them appropriately. For example, a media app 242might offer a restriction to let the owner set a maturity level for the profile. 243At run time, the app could check for the maturity setting and then manage 244content according to the preferred maturity level. </p> 245 246<p>If your app is not designed for use in restricted profiles, you can opt 247out altogether, so that your app can't be enabled in any restricted profile.</p> 248 249 250<h2 id="43-optimized-location">Optimized Location and Sensor Capabilities</h2> 251 252<p><a href="{@docRoot}google/play-services/index.html">Google Play services</a> 253offers advanced location APIs that you can use in your apps. Android 4.3 254<strong>optimizes these APIs</strong> on supported devices with new hardware and 255software capabilities that minimize use of the battery. </p> 256 257 258<div style="float:left;margin:22px 24px 36px 22px;width:250px;"> 259<a href=""><img src="{@docRoot}images/google/gps-location.png" alt="" height="160" style="padding-right:1.5em;margin-bottom:0"></a> 260</div> 261 262<p><strong>Hardware geofencing</strong> optimizes for power efficiency by 263performing location computation in the device hardware, rather than in 264software. On devices that support hardware geofencing, Google Play services 265geofence APIs will be able to take advantage of this optimization to save 266battery while the device is moving. </p> 267 268<p><strong>Wi-Fi scan-only mode</strong> is a new platform optimization that 269lets users keep Wi-Fi scan on without connecting to a Wi-Fi network, to improve 270location accuracy while conserving battery. Apps that depend on Wi-Fi for 271location services can now ask users to enable scan-only mode from Wi-Fi 272advanced settings. Wi-Fi scan-only mode is not dependent on device hardware and 273is available as part of the Android 4.3 platform.</p> 274 275<p>New sensor types allow apps to better manage sensor readings. A <strong>game 276rotation vector</strong> lets game developers sense the device’s rotation 277without having to worry about magnetic interference. <strong>Uncalibrated 278gyroscope</strong> and <strong>uncalibrated magnetometer</strong> sensors report 279raw measurements as well as estimated biases to apps. </p> 280 281<p>The new hardware capabilities are already available on Nexus 7 (2013) and 282Nexus 4 devices, and any device manufacturer or chipset vendor can build them 283into their devices.</p> 284 285 286<h2 id="43-media">New Media Capabilities</h2> 287 288<h4 id="43-modular-drm">Modular DRM framework</h4> 289 290<p>To meet the needs of the next generation of media services, Android 4.3 291introduces a <strong>modular DRM framework</strong> that enables media application 292developers to more easily integrate DRM into their own streaming protocols, such 293as MPEG DASH (Dynamic Adaptive Streaming over HTTP, ISO/IEC 23009-1).</p> 294 295<p>Through a combination of new APIs and enhancements to existing APIs, the 296media DRM framework provides an <strong>integrated set of services</strong> for 297managing licensing and provisioning, accessing low-level codecs, and decoding 298encrypted media data. A new MediaExtractor API lets you get the PSSH metadata 299for DASH media. Apps using the media DRM framework manage the network 300communication with a license server and handle the streaming of encrypted data 301from a content library. </p> 302 303<h4 id="43-vp8-encoder">VP8 encoder</h4> 304 305<p>Android 4.3 introduces built-in support for <strong>VP8 encoding</strong>, 306accessible from framework and native APIs. For apps using native APIs, the 307platform includes <strong>OpenMAX 1.1.2 extension headers</strong> to support 308VP8 profiles and levels. VP8 encoding support includes settings for target 309bitrate, rate control, frame rate, token partitioning, error resilience, 310reconstruction and loop filters. The platform API introduces VP8 encoder support 311in a range of formats, so you can take advantage of the best format for your 312content. </p> 313 314<p>VP8 encoding is available in software on all compatible devices running 315Android 4.3. For highest performance, the platform also supports 316hardware-accelerated VP8 encoding on capable devices.</p> 317 318<h4 id="43-surface">Video encoding from a surface</h4> 319 320<p>Starting in Android 4.3 you can use a surface as the input to a video 321encoder. For example, you can now direct a stream from an OpenGL ES surface 322to the encoder, rather than having to copy between buffers.</p> 323 324<h4 id="43-media-muxer">Media muxer</h4> 325 326<p>Apps can use new media muxer APIs to combine elementary audio and video 327streams into a single output file. Currently apps can multiplex a single MPEG-4 328audio stream and a single MPEG-4 video stream into a <strong>single MPEG-4 ouput 329file</strong>. The new APIs are a counterpart to the media demuxing APIs 330introduced in Android 4.2. </p> 331 332<h4 id="43-progress-scrubbing">Playback progress and scrubbing in remote control 333clients</h4> 334 335<p>Since Android 4.0, media players and similar applications have been able to 336offer playback controls from remote control clients such as the device lock 337screen, notifications, and remote devices connected over Bluetooth. Starting in 338Android 4.3, those applications can now also expose playback <strong>progress 339and speed</strong> through their remote control clients, and receive commands to 340jump to a specific <strong>playback position</strong>. </p> 341 342 343<h2 id="43-beautiful-apps">New Ways to Build Beautiful Apps</h2> 344 345 346<h3 id="43-notification-access">Access to notifications</h3> 347 348<p>Notifications have long been a popular Android feature because they let users 349see information and updates from across the system, all in one place. Now in 350Android 4.3, apps can <strong>observe the stream of notifications</strong> with the 351user's permission and display the notifications in any way they want, including 352sending them to nearby devices connected over Bluetooth. </p> 353 354<p>You can access notifications through new APIs that let you <strong>register a 355notification listener</strong> service and with permission of the user, receive 356notifications as they are displayed in the status bar. Notifications are 357delivered to you in full, with all details on the originating app, the post 358time, the content view and style, and priority. You can evaluate fields of 359interest in the notifications, process or add context from your app, and route 360them for display in any way you choose.</p> 361 362<p>The new API gives you callbacks when a notification is added, updated, and 363removed (either because the user dismissed it or the originating app withdrew it). 364You'll be able to launch any intents attached to the notification or its actions, 365as well as dismiss it from the system, allowing your app to provide a complete 366user interface to notifications.</p> 367 368<p><strong>Users remain in control</strong> of which apps can receive 369notifications. At any time, they can look in Settings to see which apps have 370notification access and <strong>enable or disable access</strong> as needed. 371Notification access is disabled by default — apps can use a new Intent to 372take the user directly to the Settings to enable the listener service after 373installation.</p> 374 375<h4 id="43-view-overlays">View overlays</h4> 376 377<p>You can now create <strong>transparent overlays</strong> on top of Views and 378ViewGroups to render a temporary View hierarchy or transient animation effects 379without disturbing the underlying layout hierarchy. Overlays are particularly 380useful when you want to create animations such as sliding a view outside of its 381container or dragging items on the screen without affecting the view 382hierarchy. </p> 383 384<h4 id="43-optical-bounds">Optical bounds layout mode</h4> 385 386<p>A new layout mode lets you manage the positioning of Views inside ViewGroups 387according to their <strong>optical bounds</strong>, rather than their clip 388bounds. Clip bounds represent a widget’s actual outer boundary, while the new 389optical bounds describe the where the widget appears to be, within the clip 390bounds. You can use the optical bounds layout mode to properly align widgets 391that use outer visual effects such as shadows and glows.</p> 392 393<h4 id="43-rotation-animation">Custom rotation animation types</h4> 394 395<p>Apps can now define the exit and entry animation types used on a window when the 396device is rotated. You can set window properties to enable 397<strong>jump-cut</strong>, <strong>cross-fade</strong>, or 398<strong>standard</strong> window rotation. The system uses the custom animation 399types when the window is fullscreen and is not covered by other windows.</p> 400 401<h4 id="43-screen-orientations">Screen orientation modes</h4> 402 403<p>Apps can set new orientation modes for Activities to ensure that they are 404displayed in the proper orientation when the device is flipped. Additionally, 405apps can use a new mode to <strong>lock the screen</strong> to its current 406orientation. This is useful for apps using the camera that want to 407<strong>disable rotation</strong> while shooting video. </p> 408 409<h4 id="43-quick-responses-intent">Intent for handling Quick Responses</h4> 410 411<p>Android 4.3 introduces a new public Intent that lets any app <strong>handle 412Quick Responses</strong> — text messages sent by the user in response to 413an incoming call, without needing to pick up the call or unlock the device. Your 414app can listen for the intent and send the message to the caller over your 415messaging system. The intent includes the recipient (caller) as well as the 416message itself. </p> 417 418 419<h2 id="43-intl">Support for International Users</h2> 420 421<div style="float:right;margin:22px 0px 0px 24px;width:380px;"> 422<img src="{@docRoot}images/jb-rtl-arabic-n4.png" alt="" width="180" style="margin-bottom:0;"> 423<img src="{@docRoot}images/jb-rtl-hebrew-n4.png" alt="" width="180" style="margin-bottom:0;padding-left:10px;"> 424<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">More parts of Android 4.3 are optimized for RTL languages.</p> 425</div> 426 427<h4 id="43-rtl">RTL improvements</h4> 428 429<p>Android 4.3 includes RTL performance enhancements and broader RTL support 430across framework UI widgets, including ProgressBar/Spinner and 431ExpandableListView. More debugging information visible through the 432<code>uiautomatorviewer</code> tool. In addition, more system UI components are 433now RTL aware, such as notifications, navigation bar and the Action Bar.</p> 434 435<p>To provide a better systemwide experience in RTL scripts, more default system 436apps now support RTL layouts, including Launcher, Quick Settings, Phone, People, 437SetupWizard, Clock, Downloads, and more.</p> 438 439<h4 id="43-localization">Utilities for localization</h4> 440 441<div style="float:right;margin:16px 12px 0px 32px;width:260px;clear:both;"> 442<img src="{@docRoot}images/jb-pseudo-locale-zz.png" alt="" width="260" style="margin-bottom:0;"> 443<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">Pseudo-locales make it easier to test your app's localization.</p> 444</div> 445 446<p>Android 4.3 also includes new utilities and APIs for creating better RTL 447strings and testing your localized UIs. A new <strong>BidiFormatter</strong> 448provides a set of simple APIs for wrapping Unicode strings so that you can 449fine-tune your text rendering in RTL scripts. To let you use this utility more 450broadly in your apps, the BidiFormatter APIs are also now available for earlier 451platform versions through the Support Package in the Android SDK. </p> 452 453<p>To assist you with managing date formatting across locales, Android 4.3 454includes a new <strong>getBestAvaialbleDate()</strong> method that automatically 455generates the best possible localized form of a Unicode UTS date for a locale 456that you specify. It’s a convenient way to provide a more localized experience 457for your users. </p> 458 459<p>To help you test your app more easily in other locales, Android 4.3 460introduces <strong>pseudo-locales</strong> as a new developer option. 461Pseudo-locales simulate the language, script, and display characteristics 462associated with a locale or language group. Currently, you can test with a 463pseudo-locale for <strong>Accented English</strong>, which lets you see how your 464UI works with script accents and characters used in a variety of European 465languages. <!--To use the pseudo-locale, enable “Developer options” in Settings 466and then select Accented English from Language and Input settings. --></p> 467 468 469<h2 id="43-accessibility">Accessibility and UI Automation</h2> 470 471<p>Starting in Android 4.3, accessibility services can <strong>observe and 472filter key events</strong>, such as to handle keyboard shortcuts or provide 473navigation parity with gesture-based input. The service receives the events and 474can process them as needed before they are passed to the system or other 475installed apps.</p> 476 477<p>Accessibility services can declare <strong>new capability attributes</strong> 478to describe what their services can do and what platform features they use. For 479example, they can declare the capability to filter key events, retrieve window 480content, enable explore-by-touch, or enable web accessibility features. In some 481cases, services must declare a capability attribute before they can access 482related platform features. The system uses the service’s capability attributes 483to generate an opt-in dialog for users, so they can see and agree to the 484capabilities before launch.</p> 485 486<p>Building on the accessibility framework in Android 4.3, a new <strong>UI 487automation framework</strong> lets tests interact with the device’s UI by 488simulating user actions and introspecting the screen content. Through the UI 489automation framework you can perform basic operations, set rotation of the 490screen, generate input events, take screenshots, and much more. It’s a powerful 491way to automate testing in realistic user scenarios, including actions or 492sequences that span multiple apps.</p> 493 494 495<h2 id="43-enterprise-security">Enterprise and Security</h2> 496 497<h4 id="43-wpa2">Wi-Fi configuration for WPA2-Enterprise networks</h4> 498 499<p>Apps can now configure the <strong>Wi-Fi credentials</strong> they need for 500connections to <strong>WPA2 enterprise access points</strong>. Developers can 501use new APIs to configure Extensible Authentication Protocol (EAP) and 502Encapsulated EAP (Phase 2) credentials for authentication methods used in the 503enterprise. Apps with permission to access and change Wi-Fi can configure 504authentication credentials for a variety of EAP and Phase 2 authentication 505methods. </p> 506 507<h4 id="43-selinux">Android sandbox reinforced with SELinux</h4> 508 509<p>Android now uses <strong>SELinux</strong>, a mandatory access control (MAC) 510system in the Linux kernel to augment the UID based application sandbox. 511This protects the operating system against potential security vulnerabilities.</p> 512 513<h4 id="43-keychain">KeyChain enhancements</h4> 514 515<p>The KeyChain API now provides a method that allows applications to confirm 516that system-wide keys are bound to a <strong>hardware root of trust</strong> for 517the device. This provides a place to create or store private keys that 518<strong>cannot be exported</strong> off the device, even in the event of a root or 519kernel compromise.</p> 520 521<h4 id="43-keystore">Android Keystore Provider</h4> 522 523<p>Android 4.3 introduces a keystore provider and APIs that allow applications 524to create exclusive-use keys. Using the APIs, apps can create or store private 525keys that <strong>cannot be seen or used by other apps</strong>, and can be 526added to the keystore without any user interaction. </p> 527 528<p>The keystore provider provides the same security benefits that the KeyChain 529API provides for system-wide credentials, such as binding credentials to a 530device. Private keys in the keystore cannot be exported off the device.</p> 531 532<h4 id="43-seuid">Restrict Setuid from Android Apps</h4> 533 534<p>The <code>/system</code> partition is now mounted <code>nosuid</code> for 535zygote-spawned processes, preventing Android applications from executing 536<code>setuid</code> programs. This reduces root attack surface and likelihood of 537potential security vulnerabilities.</p> 538 539 540<h2 id="43-tools">New Ways to Analyze Performance</h2> 541 542<div style="float:right;margin:16px 6px 0px 32px;width:390px;"> 543<img src="{@docRoot}images/jb-systrace.png" alt="" width="390" style="margin-bottom:0;"> 544<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">Systrace uses a new command syntax and lets you collect more types of profiling data.</p> 545</div> 546 547<h4 id="43-systrace">Enhanced Systrace logging</h4> 548 549<p>Android 4.3 supports an enhanced version of the <strong>Systrace</strong> 550tool that’s easier to use and that gives you access to more types of information 551to profile the performance of your app. You can now collect trace data from 552<strong>hardware modules</strong>, <strong>kernel functions</strong>, 553<strong>Dalvik VM</strong> including garbage collection, <strong>resources 554loading</strong>, and more. </p> 555 556<p>Android 4.3 also includes new Trace APIs that you can use in your apps to mark 557specific sections of code to trace using Systrace <strong>begin/end 558events</strong>. When the marked sections of code execute, the system writes the 559begin/end events to the trace log. There's minimal impact on the performance of 560your app, so timings reported give you an accurate view of what your app is 561doing.</p> 562 563<p>You can visualize app-specific events in a timeline in the Systrace output 564file and analyze the events in the context of other kernel and user space trace 565data. Together with existing Systrace tags, custom app sections can give you new 566ways to understand the performance and behavior of your apps.</p> 567 568<div style="float:right;margin:6px 0px 0px 32px;width:380px;"> 569<img src="{@docRoot}images/jb-gpu-profile-clk-n4.png" alt="" width="180" style="margin-bottom:0;"> 570<img src="{@docRoot}images/jb-gpu-profile-cal-n4.png" alt="" width="180" style="margin-bottom:0;padding-left:10px;"> 571<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">On-screen GPU profiling in Android 4.3.</p> 572</div> 573 574<h4 id="43-gpu-profiling" >On-screen GPU profiling</h4> 575 576<p>Android 4.3 adds new developer options to help you analyze your app’s 577performance and pinpoint rendering issues on any device or emulator.</p> 578 579<p>In the <strong>Profile GPU rendering</strong> option you can now visualize 580your app’s effective framerate on-screen, while the app is running. You can 581choose to display profiling data as on-screen <strong>bar or line 582graphs</strong>, with colors indicating time spent creating drawing commands 583(blue), issuing the commands (orange), and waiting for the commands to complete 584(yellow). The system updates the on-screen graphs continuously, displaying a 585graph for each visible Activity, including the navigation bar and notification 586bar. </p> 587 588<p>A green line highlights the <strong>60ms threshold</strong> for rendering 589operations, so you can assess the your app’s effective framerate relative 590to a 60 fps goal. If you see operations that cross the green line, you 591can analyze them further using Systrace and other tools.</p> 592 593<p class="caution" style="clear:both">On devices running Android 4.2 and higher, 594developer options are hidden by default. You can reveal them at any time by 595tapping 7 times on <strong>Settings > About phone > Build number</strong> 596on any compatible Android device.</p> 597 598<h4 id="43-strictmode">StrictMode warning for file URIs</h4> 599 600<p>The latest addition to the StrictMode tool is a policy constraint that warns 601when your app exposes a <code>file://</code> URI to the system or another app. 602In some cases the receiving app may not have access to the <code>file://</code> 603URI path, so when sharing files between apps, a <code>content://</code> URI should 604be used (with the appropriate permission). This new policy helps you catch and fix 605such cases. If you’re looking for a convenient way to store and expose files to other 606apps, try using the <code>FileProvider</code> content provider that’s available 607in the <a href="{@docRoot}tools/support-library/index.html">Support Library</a>.</p> 608 609</div><!-- END ANDROID 4.3 --> 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634<!-- BEGIN ANDROID 4.2 --> 635<div id="android-42" class="version-section"> 636<div style="float:right;padding:0px 0px 12px 34px;"> 637<div> 638<img src="{@docRoot}images/jb-device-2.png" alt="Android 4.2 on phone and tablet" height="348" width="400"> 639</div> 640</div> 641<p>Welcome to Android 4.2, the latest version of <span 642style="white-space:nowrap;">Jelly Bean!</span></p> 643 644<p>Android 4.2 has performance optimizations, a refreshed system UI, and great 645new features for users and developers. This document provides a glimpse of what's new for 646developers. 647 648<p>See the <a href="{@docRoot}about/versions/android-4.2.html">Android 4.2 APIs</a> 649document for a detailed look at the new developer APIs.</p> 650 651<p>Find out more about the new Jelly Bean features for users at <a 652href="http://www.android.com/whatsnew">www.android.com</a>.</p> 653 654 655<h2 id="42-performance" style="line-height:1.25em;">Faster, Smoother, More Responsive</h2> 656 657<p>Android 4.2 builds on the performance improvements already included in Jelly Bean 658— <strong>vsync timing</strong>, <strong>triple buffering</strong>, 659<strong>reduced touch latency</strong>, and <strong>CPU input boost</strong> 660— and adds new optimizations that make Android even faster.</p> 661 662<p>Improvements in the <strong>hardware-accelerated 2D renderer</strong> make 663common animations such as scrolling and swiping smoother and faster. In 664particular, <strong>drawing is optimized</strong> for layers, clipping and 665certain shapes (rounded rects, circles and ovals).</p> 666 667<p>A variety of <strong>WebView rendering optimizations</strong> make scrolling 668of web pages smoother and free from jitter and lags.</p> 669 670<p>Android’s <strong>Renderscript Compute</strong> is the first computation 671platform ported to run directly on a <strong>mobile device GPU</strong>. It automatically 672takes advantage of <strong>GPU computation</strong> resources whenever possible, 673dramatically improving performance for graphics and image processing. Any app using 674Renderscript on a supported device can benefit immediately from 675this GPU integration <strong>without recompiling</strong>.</p> 676 677 678<div style="float:left;margin:16px 24px 12px 0px;"> 679<a href="" target="_android"> 680<img src="{@docRoot}images/jb-nexus10-1.png" alt="10-inch tablet running Android 4.2" width="380" height="281" /></a> 681</div> 682 683<h2 id="42-ui" style="margin-top:2em;">Refined, refreshed UI</h2> 684 685<p>Android 4.2 refines the Jelly Bean user experience and brings familiar 686Android UI patterns such as status bar, system bar, and notifications window to 687all tablets.</p> 688 689<p>All screen sizes now feature the <strong>status bar</strong> on top, with 690pull-down access to <strong>notifications</strong> and a new <strong>Quick 691Settings</strong> menu. The familiar </strong>system bar</strong> appears on the 692bottom, with buttons easily accessible from either hand. The <strong>Application 693Tray</strong> is also available on all screen sizes.</p> 694 695 696<h2 id="42-multiuser" style="margin-top:2em;clear:left;">One tablet, many users</h2> 697 698<p>Now several users can <strong>share a single Android tablet</strong>, with 699each user having convenient access to a <strong>dedicated user 700space</strong>. Users can switch to their spaces with a single touch from the 701lock screen.</p> 702 703<p>On a multiuser device, Android gives each user a separate environment, 704including user-specific emulated SD card storage. Users also have their own 705homescreens, widgets, accounts, settings, files, and apps, and the system keeps 706these separate. All users share core system services, but the system ensures that 707each user's applications and data remain isolated. In effect, each of the multiple 708users has his or her own Android device.</p> 709 710<p>Users can install and uninstall apps at any time in their own environments. 711To save storage space, Google Play downloads an APK only if it's not already 712installed by another user on the device. If the app is already installed, Google 713Play records the new user's installation in the usual way but doesn't download 714another copy of the app. Multiple users can run the same copy of an APK because 715the system creates a new instance for each user, including a user-specific data 716directory.</p> 717 718<p>For developers, <strong>multi-user support is transparent</strong> — 719your apps do not need to do anything special to run normally in a multi-user 720environment and there are no changes you need to make in your existing or 721published APKs. The system manages your app in each user space just as it does 722in a single-user environment. </p> 723 724 725<h2 id="42-engagement" style="clear:left; margin-top:1em;">New ways to engage users</h2> 726 727<div style="float:right;margin:22px 0px 0px 24px;width:280px;"> 728<div> 729<img src="{@docRoot}images/jb-lock-calendar.png" alt="Calendar lock screen widget" width="280" height="543" style="padding-left:1em;margin-bottom:0"> 730</div> 731<p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">You can extend <strong>app widgets</strong> to run on the lock screen, for instant access to your content.</p> 732</div> 733 734<h3 id="42-lockscreen-widgets">Lock screen widgets</h3> 735 736<p>In Android 4.2, users can place <strong>app widgets</strong> directly on 737their <strong>lock screens</strong>, for instant access to favorite app content 738without having to unlock. Users can add as many as five lock screen widgets, 739choosing from widgets provided by installed apps. The lock screen displays each 740widget in its own panel, letting users swipe left and right to view different 741panels and their widgets.</p> 742 743<p>Like all app widgets, lock screen widgets can display <strong>any kind of content</strong> and 744they can accept direct user interaction. They can be entirely self-contained, 745such as a widget that offers controls to play music, or they can let users jump 746straight to an Activity in your app, after unlocking along the way as 747needed.</p> 748 749<p>For developers, lock screen widgets offer a great new way to engage users. 750They let you put your content in front of users in a location they’ll see often, 751and they give you more opportunities to bring users directly into your app.</p> 752 753<p>You can take advantage of this new capability by building a new app widget or 754by extending an existing home screen widget. If your app already includes home 755screen widgets, you can extend them to the lock screen with minimal change. To 756give users an optimal experience, you can update the widget to use the full lock 757screen area when available and resize when needed on smaller screens. You can 758also add features to your widgets that might be especially useful or convenient 759on the lock screen.</p> 760 761<h3 id="42-daydreams">Daydream</h3> 762 763<p>Daydream is an <strong>interactive screensaver mode</strong> that starts when 764a user’s device is docked or charging. In this mode, the system launches a 765daydream — a remote content service provided by an installed app — 766as the device screensaver. A user can enable Daydream from the Settings app and 767then choose the daydream to display.</p> 768 769<p>Daydreams combine the best capabilities of live wallpapers and home screen 770widgets, but they are more powerful. They let you offer the any kind of content 771in a completely new context, with user interactions such as flipping through 772photos, playing audio or video, or jumping straight into your app with a single 773touch.</p> 774 775<p>Because daydreams can start automatically when a device is charging or 776docked, they also give your app a great way to support new types of user 777experiences, such as leanback or exhibition mode, demo or kiosk mode, and 778"attract mode" — all without requiring special hardware.</p> 779 780<div style="float:left;margin:20px 30px 0px 0px;width:460px;"> 781<div> 782<img src="{@docRoot}images/jb-dream-1.png" alt="Daydream screensaver mode" height="300" style="padding-left:1em;"> 783</div> 784<p class="image-caption" style="padding:.5em .5em .5em 1.5em;"><span 785style="font-weight:500;">Daydream</span> lets you create powerful interactive screensavers that display any kind of content.</p> 786</div> 787 788<p>Daydreams are similar to Activities and can do anything that Activity 789can do — from rendering a UI hierarchy (without using RemoteViews) to 790drawing directly using Canvas, OpenGL, SurfaceTexture, and more. They can play 791video and audio and they can even accept direct user interaction. However, 792daydreams are not Activities, so they don’t affect the backstack or appear in 793Recents and they cannot be launched directly from your app.</p> 794 795<p>Implementing a daydream is straightforward and you can take advantage of UI 796components and resources that you’ve already created for other parts of your 797app. You can provide multiple daydreams in your app and you can offer distinct 798content and display settings for each.</p> 799 800<h2 id="42-external-display" style="clear:left;">External display support</h2> 801 802<p>Android 4.2 introduces platform support for <strong>external 803displays</strong> that goes far beyond mirroring — apps can now target 804unique content to any one or multiple displays that are attached to an Android 805device. Apps can build on this to deliver new kinds of interaction and 806entertainment experiences to users.</p> 807 808<h3 id="42-display-manager">Display manager</h3> 809 810<p>Apps interact with displays through a new display manager system service. 811Your app can enumerate the displays and check the capabilities of each, 812including size, density, display name, ID, support for secure video, and more. 813Your app can also receive callbacks when displays are added or removed or when 814their capabilities change, to better manage your content on external 815displays.</p> 816 817<h3 id="42-presentation">Presentation window</h3> 818 819<p>To make it easy to show content on an external display, the framework 820provides a new UI object called a <strong>Presentation</strong> — a type of dialog that 821represents a window for your app’s content on a specific external display. Your 822app just gives the display to use, a theme for the window, and any unique 823content to show. The Presentation handles inflating resources and rendering your 824content according to the characteristics of the targeted display.</p> 825 826<div style="margin:0 auto;width:569px;padding-top:1em;"> 827 828<img src="{@docRoot}images/external-display.png" alt="" width="555" height="351" style="padding-left:1em;margin-bottom:0"> 829 830<p class="image-caption" style="padding:1.25em">You can take full control of two or more independent displays using <strong>Presentation</strong>.</p> 831</div> 832 833<p>A Presentation gives your app full control over the remote display window and 834its content and lets you manage it based on user input events such as key 835presses, gestures, motion events, and more. You can use all of the normal tools 836to create a UI and render content in the Presentation, from building an 837arbitrary view hierarchy to using SurfaceView or SurfaceTexture to draw directly 838into the window for streamed content or camera previews.</p> 839 840<h3 id="42-preferred display">Preferred display selection</h3> 841 842<p>When multiple external displays are available, you can create as many 843Presentations as you need, with each one showing unique content on a specific 844display. In many cases, you might only want to show your content on a single 845external display — but always on the that’s best for Presentation content. 846For this, the system can help your app choose the best display to use.</p> 847 848<p>To find the best display to use, your app can query the display manager for 849the system’s <strong>preferred Presentation display</strong> and receive callbacks when that 850display changes. Alternatively, you can use the media router service, extended 851in Android 4.2, to receive notifications when a system video route changes. Your 852app can display content by default in the main Activity until a preferred 853Presentation display is attached, at which time it can automatically switch to 854Presentation content on the preferred display. Your apps can also use media 855router’s MediaRouteActionProvider and MediaRouteButton to offer standard 856display-selection UI.</p> 857 858<h3 id="42-protected-content">Protected content</h3> 859 860<p>For apps that handle protected or encrypted content, the display API now 861reports the <strong>secure video capabilities</strong> of attached displays. Your app query a 862display to find out if it offers a secure video output or provides protected 863graphics buffers and then choose the appropriate content stream or decoding to 864make the content viewable. For additional security on SurfaceView objects, your 865app can set a secure flag to indicate that the contents should never appear in 866screenshots or on a non-secure display output, even when mirrored.</p> 867 868<h3 id="42-wireless-display">Wireless display</h3> 869 870<p>Starting in Android 4.2, users on supported devices can connect to an 871external display over Wi-Fi, using <a 872href="http://www.wi-fi.org/wi-fi-certified-miracast%E2%84%A2">Miracast</a>, a 873peer-to-peer wireless display standard created by the <a 874href="http://www.wi-fi.org/">Wi-Fi Alliance</a>. When a wireless display is 875connected, users can stream any type of content to the big screen, including 876photos, games, maps, and more.</p> 877 878<p>Apps can take advantage of <strong>wireless displays</strong> in the same way as they do other 879external displays and no extra work is needed. The system manages the network 880connection and streams your Presentation or other app content to the wireless 881display as needed.</p> 882 883 884<h2 id="42-native-rtl">Native RTL support</h2> 885 886<div style="float:right;margin:22px 0px 0px 24px;width:340px;"> 887<div> 888<img src="{@docRoot}images/jb-rtl.png" alt="RTL layout mirroring" width="340" height="457" style="margin-bottom:0;"> 889</div> 890<p class="image-caption" style="padding-top:1em">Developers can now <strong>mirror their layouts</strong> for RTL languages.</p> 891</div> 892 893<p>Android 4.2 introduces <strong>full native support for RTL</strong> 894(right-to-left) layouts, including layout mirroring. With native RTL support, 895you can deliver the same great app experience to all of your users, whether 896their language uses a script that reads right-to-left or one that reads 897left-to-right.</p> 898 899<p>When the user switches the system language to a right-to-left script, the 900system now provides automatic mirroring of app UI layouts and all view widgets, 901in addition to bidi mirroring of text elements for both reading and character 902input.</p> 903 904<p>Your app can take advantage of <strong>RTL layout mirroring</strong> in your app with minimal effort. 905If you want the app to be mirrored, you simply declare a new attribute in your 906app manifest and change all "left/right" layout properties to new "start/end" 907equivalents. The system then handles the mirroring and display of your UI as 908appropriate.</p> 909 910<p>For precise control over your app UI, Android 4.2 includes new APIs that let 911you manage layout direction, text direction, text alignment, gravity, and 912locale direction in View components. You can even create custom versions of 913layout, drawables, and other resources for display when a right-to-left script 914is in use.</p> 915 916<p>To help you debug and optimize your custom right-to-left layouts, the 917HierarchyViewer tool now lets you see start/end properties, layout direction, 918text direction, and text alignment for all the Views in the hierarchy.</p> 919 920 921<h2 id="42-intl">Enhancements for international languages</h2> 922 923<p>Android 4.2 includes a variety of <strong>font and character 924optimizations</strong> for international users:</p> 925<ul> 926<li>For Korean users, a new font choice is available — Nanum (나눔글꼴) 927Gothic, a unicode font designed especially for the Korean-language script.</li> 928<li>Improved support for Japanese vertical text displayed in WebViews.</li> 929<li>Improved font kerning and positioning for Indic, Thai, Arabic, and Hebrew 930default fonts.</li> 931</ul> 932 933<p>The default Android keyboard also includes an updated set of 934dictionaries:</p> 935<ul> 936<li>Improved dictionaries for French (with bigram support), English, and 937Russian</li> 938<li>New dictionaries for Danish, Greek, Finnish, Lithuanian, Latvian, Polish, 939Slovenian, Serbian, Swedish, Turkish</li> 940</ul> 941 942 943<h2 id="42-ui-tools">New ways to create beautiful UI</h2> 944 945<h3 id="42-nested-fragments">Nested Fragments</h3> 946 947<p>For more control over your UI components and to make them more modular, 948Android 4.2 lets you <strong>nest Fragments inside of Fragments</strong>. For 949any Fragment, a new Fragment manager lets you insert other Fragments as child 950nodes in the View hierarchy.</p> 951 952<p>You can use nested Fragments in a variety of ways, but they are especially 953useful for implementing dynamic and reusable UI components inside of a UI 954component that is itself dynamic and reusable. For example, if you use ViewPager 955to create fragments that swipe left and right, you can now insert fragments into 956each Fragment of the view pager.</p> 957 958<p>To let you take advantage of nested Fragments more broadly in your app, this 959capability is added to the latest version of the <strong>Android Support 960Library</strong>.</p> 961 962 963<h2 id="42-accessibility">Accessibility</h2> 964 965<p>The system now helps accessibility services <strong>distinguish between touch 966exploration and accessibility gestures</strong> while in touch-exploration mode. 967When a user touches the screen, the system notifies the service that a generic 968touch interaction has started. It then tracks the speed of the touch interaction 969and determines whether it is a touch exploration (slow) or accessibility gesture 970(fast) and notifies the service. When the touch interaction ends, the system 971notifies the service.</p> 972 973<p>The system provides a new global accessibility option that lets an 974accessibility service open the Quick Settings menu based on an action by the 975user. Also added in Android 4.2 is a new accessibility feedback type for 976<strong>Braille devices</strong>.</p> 977 978<p>To give accessibility services insight into the meaning of Views for 979accessibility purposes, the framework provides new APIs for associating a View 980as the label for another View. The label for each View is available to 981accessibility services through AccessibilityNodeInfo.</p> 982 983 984<h2 id="42-camera">Improved Camera with HDR</h2> 985 986<p>Android 4.2 introduces a <strong>new camera hardware interface and 987pipeline</strong> for improved performance. On supported devices, apps can use a 988new <strong>HDR camera scene mode</strong> to capture an image using high 989dynamic range imaging techniques. </p> 990 991<p>Additionally, the framework now provides an API to let apps check whether the 992camera shutter sound can be disabled. Apps can then let the user disable the 993sound or choose an alternative sound in place of the standard shutter sound, 994which is recommended.</p> 995 996 997<h2 id="42-renderscript">Renderscript Computation</h2> 998 999<p>In Android 4.2, Renderscript Compute introduces new scripting features, new 1000optimizations, and direct GPU integration for the highest performance in 1001computation operations.</p> 1002 1003<h3 id="42-filterscript">Filterscript</h3> 1004 1005<p>Filterscript is a subset of Renderscript that is focused on <strong>optimized 1006image processing across a broad range of device chipsets</strong>. Developers 1007can write their image processing operations in Filterscript using the standard 1008Renderscript runtime API, but within stricter constraints that ensure wider 1009compatibility and improved optimization across CPUs, GPUs, and DSPs.</p> 1010 1011<p>Filterscript is ideal for hardware-accelerating simple image-processing and 1012computation operations such as those that might be written for OpenGL ES 1013fragment shaders. Because it places a relaxed set of constraints on hardware, 1014your operations are optimized and accelerated on more types of device chipsets. 1015Any app targeting API level 17 or higher can make use of Filterscript.</p> 1016 1017<h3 id="42-rs-intrinsics">Script intrinsics</h3> 1018 1019<p>In Android 4.2, Renderscript adds support for a set of script intrinsics 1020— pre-implemented <strong>filtering primitives that are 1021accelerated</strong> to reduce the amount of code that you need to write and to 1022ensure that your app gets the maximum performance gain possible.</p> 1023 1024<p>Intrinsics are available for blends, blur, color matrix, 3x3 and 5x5 convolve, 1025per-channel lookup table, and converting an Android YUV buffer to RGB.</p> 1026 1027<h3 id="42-rs-groups">Script groups</h3> 1028 1029<p>You can now create <strong>groups of Renderscript scripts</strong> and 1030execute them all with a single call as though they were part of a single script. 1031This allows Renderscript to optimize execution of the scripts in ways that it 1032could not do if the scripts were executed individually.</p> 1033 1034<div style="float:right;padding-top:1em;width:400px;margin-left:2em;"> 1035<img src="{@docRoot}images/jb-rs-chart-versions.png" alt="Renderscipt optimizations chart" width="360" height="252" 1036style="border:1px solid #ddd;border-radius: 6px;" /> 1037<p style="image-caption">Renderscript image-processing 1038benchmarks run on different Android platform versions (Android 4.0, 4.1, and 4.2) 1039in CPU only on a Galaxy Nexus device.</p> 1040<img src="{@docRoot}images/jb-rs-chart-gpu.png" style="border:1px solid #ddd;border-radius: 6px; alt="" width="360" height="252" /> 1041<p style="image-caption">Renderscript image-processing benchmarks comparing operations run with GPU + CPU to those run in CPU only on the same Nexus 10 device.</p> 1042</div> 1043 1044<p>If you have a directed acyclic graph of Renderscript operations to run, you can 1045use a builder class to create a script group defining the operations. At 1046execution time, Renderscript optimizes the run order and the connections between 1047these operations for best performance.</p> 1048 1049 1050<h3 id="42-rs-optimization">Ongoing optimization improvements</h3> 1051 1052<p>When you use Renderscript for computation operations, you apps benefit from 1053<strong>ongoing performance and optimization improvements</strong> in the 1054Renderscript engine itself, without any impact on your app code or any need for 1055recompilation.</p> 1056 1057<p>As optimization improves, your operations execute faster and on more 1058chipsets, without any work on your part. The chart at right highlights 1059the performance gain delivered by ongoing Renderscript optimization improvements 1060across successive versions of the Android platform.</p> 1061 1062<h3 id="42-gpu-compute">GPU Compute</h3> 1063 1064<p>Renderscript Compute is the first computation platform ported to run directly on a mobile device GPU. It now 1065automatically takes advantage of <strong>GPU computation</strong> resources 1066whenver possible to improve performance. With GPU integration, even the most 1067complex computations for graphics or image processing can execute with 1068dramatically improved performance.</p> 1069 1070<p>Any app using Renderscript on a supported device can benefit immediately from 1071this GPU integration, without recompiling. The Nexus 10 tablet is the first 1072device to support this integration.</p> 1073 1074<h2 id="42-dev-options" style="clear:right;margin-top:1em;">New built-in developer options</h2> 1075 1076<p>The Android 4.2 system includes a variety of new developer options that make 1077it easier to create great looking apps that perform well. The new options expose 1078features for <strong>debugging and profiling</strong> your app from any device 1079or emulator.</p> 1080 1081<p class="caution" style="clear:right;">On devices running Android 4.2, 1082developer options are hidden by default, helping to create a better experience 1083for users. You can reveal the developer options at any time by tapping 7 times 1084on <strong>Settings</strong> > <strong>About phone</strong> > <strong>Build 1085number</strong> on any compatible Android device.</p> 1086 1087<div style="float:left;margin:20px 42px 0px 0px;width:290px;"> 1088<div> 1089<img src="{@docRoot}images/jb-dev-options-device.png" width="280" height="548"> 1090</div> 1091<p class="image-caption" style="padding:.5em">New <span 1092style="font-weight:500;">developer options</span> give you more ways to profile and debug on a device.</p> 1093</div> 1094 1095<p style="margin-top:2em;">New developer options in Android 4.2 include:</p> 1096 1097<ul> 1098<li><strong>Take bug report</strong> — immediately takes a screen shot and 1099dumps device state information to local file storage, then attaches them to a 1100new outgoing email message.</li> 1101<li><strong>Power menu bug reports</strong> — Adds a new option to the 1102device power menu and quick settings to take a bug report (see above).</li> 1103<li><strong>Verify apps over usb</strong> — Allows you to disable app 1104checks for sideloading apps over USB, while still checking apps from other 1105sources like the browser. This can speed up the development process while 1106keeping the security feature enabled.</li> 1107<li><strong>Show hardware layers updates</strong> — Flashes hardware 1108layers green when they update.</li> 1109<li><strong>Show GPU overdraw</strong> — Highlights GPU overdraw 1110areas.</li> 1111<li><strong>Force 4x MSAA</strong> — Enables 4x MSAA in Open GL ES 2.0 1112apps.</li> 1113<li><strong>Simulate secondary displays</strong> — Creates one or more 1114non-secure overlay windows on the current screen for use as a simulated remote 1115display. You can control the simulated display’s size and density.</li> 1116<li><strong>Enable OpenGL traces</strong> — Lets you trace OpenGL 1117execution using Logcat, Systrace, or callstack on glGetError.</li> 1118</ul> 1119 1120<h2 id="42-platform-tech" style="padding-top:1em;clear:left;">New Platform Technologies</h2> 1121 1122<p>Android 4.2 includes a variety of new and <strong>enhanced platform technologies</strong> to 1123support innovative communications use-cases across a broad range of hardware 1124devices. In most cases, the new platform technologies and enhancements do not directly 1125affect your apps, so you can benefit from them without any modification.</p> 1126 1127<h3 id="42-security">Security enhancements</h3> 1128 1129<p>Every Android release includes dozens of security enhancements to protect 1130users. Here are some of the enhancements in Android 4.2:</p> 1131 1132<ul> 1133<li><strong>Application verification</strong> — Users can choose to enable 1134“Verify Apps" and have applications screened by an application verifier, prior 1135to installation. App verification can alert the user if they try to install an 1136app that might be harmful; if an application is especially bad, it can block 1137installation.</li> 1138<li><strong>More control of premium SMS</strong> — Android will provide a 1139notification if an application attempts to send SMS to a short code that uses 1140premium services which might cause additional charges. The user can choose 1141whether to allow the application to send the message or block it.</li> 1142<li><strong>Always-on VPN</strong> — VPN can be configured so that 1143applications will not have access to the network until a VPN connection is 1144established. This prevents applications from sending data across other 1145networks.</li> 1146<li><strong>Certificate Pinning</strong> — The libcore SSL implementation 1147now supports certificate pinning. Pinned domains will receive a certificate 1148validation failure if the certificate does not chain to a set of expected 1149certificates. This protects against possible compromise of Certificate 1150Authorities.</li> 1151<li><strong>Improved display of Android permissions</strong> — Permissions 1152have been organized into groups that are more easily understood by users. 1153During review of the permissions, the user can click on the permission to see 1154more detailed information about the permission.</li> 1155<li><strong>installd hardening</strong> — The installd daemon does not run 1156as the root user, reducing potential attack surface for root privilege 1157escalation.</li> 1158<li><strong>init script hardening</strong> — init scripts now apply 1159O_NOFOLLOW semantics to prevent symlink related attacks.</li> 1160<li><strong>FORTIFY_SOURCE</strong> — Android now implements 1161FORTIFY_SOURCE. This is used by system libraries and applications to prevent 1162memory corruption.</li> 1163<li><strong>ContentProvider default configuration</strong> — Applications 1164which target API level 17 will have “export” set to “false” by default for each 1165ContentProvider, reducing default attack surface for applications.</li> 1166<li><strong>Cryptography</strong> — Modified the default implementations 1167of SecureRandom and Cipher.RSA to use OpenSSL. Added SSLSocket support for 1168TLSv1.1 and TLSv1.2 using OpenSSL 1.0.1</li> 1169<li><strong>Security Fixes</strong> — Upgraded open source libraries with 1170security fixes include WebKit, libpng, OpenSSL, and LibXML. Android 4.2 also 1171includes fixes for Android-specific vulnerabilities. Information about these 1172vulnerabilities has been provided to Open Handset Alliance members and fixes are 1173available in Android Open Source Project. To improve security, some devices 1174with earlier versions of Android may also include these fixes.</li> 1175</ul> 1176 1177<h3 id="42-bt-stack">New Bluetooth stack</h3> 1178 1179Android 4.2 introduces a new Bluetooth stack optimized for use with Android 1180devices. The new Bluetooth stack developed in collaboration between Google and 1181Broadcom replaces the stack based on BlueZ and provides improved compatibility 1182and reliability. 1183 1184<h3 id="42-audio">Low-latency audio</h3> 1185 1186<p>Android 4.2 improves support for low-latency audio playback, starting from the 1187improvements made in Android 4.1 release for audio output latency using OpenSL 1188ES, Soundpool and tone generator APIs. These improvements depend on hardware 1189support — devices that offer these low-latency audio features can 1190advertise their support to apps through a hardware feature constant. New 1191AudioManager APIs are provided to query the native audio sample rate and buffer 1192size, for use on devices which claim this feature.</p> 1193 1194<h3 id="42-camera-interface">New camera hardware interface</h3> 1195 1196Android 4.2 introduces a new implementation of the camera stack. The camera 1197subsystem includes the implementations for components in the camera pipeline 1198such as burst mode capture with processing controls. 1199 1200<h3 id="42-nfc-interface">New NFC hardware interface and controller interface</h3> 1201 1202Android 4.2 introduces support for controllers based on the NCI standard from 1203the NFC-Forum. NCI provides a standard communication protocol between an NFC 1204Controller (NFCC) and a device Host, and the new NFC stack developed in 1205collaboration between Google and Broadcom supports it. 1206 1207<h3 id="42-dalvik">Dalvik runtime optimizations</h3> 1208 1209<p>The Dalvik runtime includes enhancements for performance and security across 1210a wider range of architectures:</p> 1211<ul> 1212<li>x86 JIT support from Intel and MIPS JIT support from MIPS</li> 1213<li>Optimized garbage-collection parameters for devices with > 512MB</li> 1214<li>Default implementations of SecureRandom and Cipher.RSA now use OpenSSL</li> 1215<li>SSLSocket support for TLSv1.1 and TLSv1.2 via OpenSSL 1.0.1</li> 1216<li>New intrinsic support for StrictMath methods abs, min, max, and sqrt</li> 1217<li>BouncyCastle updated to 1.47</li> 1218<li>zlib updated to 1.27</li> 1219<li>dlmalloc updated to 2.8.6</li> 1220</ul> 1221 1222</div> <!-- END ANDROID 4.2 --> 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247<!-- BEGIN ANDROID 4.1 --> 1248<div id="android-41" class="version-section"> 1249 1250<div style="float:right;width:320px;padding:0px 0px 0px 34px;clear:both"> 1251<div> 1252<img src="{@docRoot}images/jb-android-4.1.png" height="426" width="320"> 1253</div> 1254</div> 1255<p>Welcome to Android 4.1 the first version of Jelly Bean!</p> 1256 1257<p>Android 4.1 is the fastest and smoothest version of Android yet. We’ve made 1258improvements throughout the platform and added great new features 1259for users and developers. This document provides a glimpse of what's new for developers. 1260 1261<p>See the <a href="{@docRoot}about/versions/android-4.1.html">Android 4.1 APIs</a> document for a detailed look at the new developer APIs.</p> 1262 1263<p>Find out more about the Jelly Bean features for users at <a href="http://www.android.com/whatsnew">www.android.com</a>.</p> 1264 1265 1266<h2 id="performance">Faster, Smoother, More Responsive</h2> 1267 1268<p>Android 4.1 is optimized to deliver Android's best performance and lowest touch latency, in an effortless, intuitive UI.</p> 1269 1270<p>To ensure a consistent framerate, Android 4.1 extends <strong>vsync timing</strong> across all drawing and animation done by the Android framework. Everything runs in lockstep against a 16 millisecond vsync heartbeat — application rendering, touch events, screen composition, and display refresh — so frames don’t get ahead or behind.</p> 1271 1272<p>Android 4.1 also adds <strong>triple buffering</strong> in the graphics pipeline, for more consistent rendering that makes everything feel smoother, from scrolling to paging and animations.</p> 1273 1274<p>Android 4.1 reduces touch latency not only by <strong>synchronizing touch</strong> to vsync timing, but also by actually <strong>anticipating</strong> where your finger will be at the time of the screen refresh. This results in a more reactive and uniform touch response. In addition, after periods of inactivity, Android applies a <strong>CPU input boost</strong> at the next touch event, to make sure there’s no latency.</p> 1275 1276<p><strong>Tooling</strong> can help you get the absolute best performance out of your apps. Android 4.1 is designed to work with a new tool called <strong>systrace</strong>, which collects data directly from the Linux kernel to produce an overall picture of system activities. The data is represented as a group of vertically stacked time series graphs, to help isolate rendering interruptions and other issues. The tool is available now in the <a href="{@docRoot}tools/index.html">Android SDK</a> (Tools R20 or higher)</p> 1277 1278 1279<div style="float:left;margin:12px 24px 0px 0px;"> 1280<img src="{@docRoot}images/jb-accessibility-focus-250.png" width="240px" height="469"> 1281</div> 1282 1283<div style="width:85%;padding-top:16px;"> 1284<h2 id="accessibility">Enhanced Accessibility</h2> 1285 1286<p>New APIs for accessibility services let you handle gestures and manage <strong>accessibility focus</strong> as the user moves through the on-screen elements and navigation buttons using accessibility gestures, accessories, and other input. The Talkback system and explore-by-touch are redesigned to use accessibility focus for easier use and offer a complete set of APIs for developers.</p> 1287 1288<p>Accessibility services can link their own <strong>tutorials</strong> into the Accessibility settings, to help users configure and use their services.</p> 1289 1290<p>Apps that use standard View components <strong>inherit support</strong> for the new accessibility features automatically, without any changes in their code. Apps that use custom Views can use new accessibility node APIs to indicate the parts of the View that are of interest to accessibility services. </p> 1291 1292</div> 1293 1294<div style="clear:both;padding-top:1px;"> 1295 1296<h2 id="intl">Support for International Users</h2> 1297 1298<div style="clear:both;padding-top:16px;float:right;"> 1299 1300<div style="float:right;margin-left:18px;fpadding-top:90px;padding-bottom:60px"> 1301<img src="{@docRoot}images/jb-r2l.png" width="280" height="356"> 1302</div> 1303</div> 1304 1305<h3>Bi-Directional Text and Other Language Support</h3> 1306 1307<p>Android 4.1 helps you to reach more users through support for <strong>bi-directional text</strong> in TextView and EditText elements. Apps can display text or handle text editing in left-to-right or right-to-left scripts. Apps can make use of new Arabic and Hebrew locales and associated fonts.</p> 1308 1309<p>Other types of new language support include:</p> 1310<ul> 1311<li>Additional Indic languages: Kannada, Telugu, and Malayalam</li> 1312<li>The new Emoji characters from Unicode version 6.0</li> 1313<li>Better glyph support for Japanese users (renders Japanese-specific versions of glyphs when system language is set to Japanese)</li> 1314<li>Arabic glyphs optimized for WebViews in addition to the Arabic glyphs for TextViews</li> 1315<li>Vertical Text support in WebViews, including Ruby Text and additional Vertical Text glyphs</li> 1316<li>Synthetic Bold is now available for all fonts that don't have dedicated bold glyphs</li> 1317</ul> 1318 1319<h3>User-installable keymaps</h3> 1320 1321<p>The platform now supports <strong>user-installable keyboard maps</strong>, such as for additional international keyboards and special layout types. By default, Android 4.1 includes 27 international keymaps for keyboards, including Dvorak. When users connect a keyboard, they can go to the Settings app and select one or more keymaps that they want to use for that keyboard. When typing, users can switch between keymaps using a shortcut (ctrl-space).</p> 1322 1323<p>You can create an app to <strong>publish additional keymaps</strong> to the system. The APK would include the keyboard layout resources in it, based on standard Android keymap format. The application can offer additional keyboard layouts to the user by declaring a suitable broadcast receiver for ACTION_QUERY_KEYBOARD_LAYOUTS in its manifest. </p> 1324</div> 1325 1326 1327<h2 id="ui">New Ways to Create Beautiful UI</h2> 1328 1329 1330<div style="float:right;margin:22px 0px 0px 24px;width:280px;"> 1331<div> 1332<!-- <img src="{@docRoot}images/jd-notif-cd.png" style="width:200px"> --> 1333<img src="{@docRoot}images/jb-notif-ex1.png" width="280" height="548"> 1334</div> 1335<p class="image-caption" style="padding:.5em">Developers can create custom notification styles 1336like those shown in the examples above to display rich content and actions.</p> 1337</div> 1338 1339<h3>Expandable notifications</h3> 1340 1341<p>Notifications have long been a unique and popular feature on Android. Developers can use them to place important or time-based information in front of users in the notification bar, outside of the app’s normal UI.</p> 1342 1343<p>Android 4.1 brings a major update to the Android notifications framework. Apps can now display <strong>larger, richer notifications</strong> to users that can be expanded and collapsed with a pinch or swipe. Notifications support <strong>new types of content</strong>, including photos, have configurable priority, and can even include multiple actions.</p> 1344 1345<p>Through an improved <strong>notification builder</strong>, apps can create notifications that use a larger area, up to 256 dp in height. Three <strong>templated notification styles</strong> are available:</p> 1346 1347<ul> 1348<li>BigTextStyle — a notification that includes a multiline TextView object.</li> 1349<li>BigInboxStyle — a notification that shows any kind of list such as messages, headlines, and so on.</li> 1350<li>BigPictureStyle — a notification that showcases visual content such as a bitmap.</li> 1351</ul> 1352 1353<p>In addition to the templated styles, you can create your own notification styles <strong>using any remote View</strong>.</p> 1354 1355<p>Apps can add up to three <strong>actions</strong> to a notification, which are displayed below the notification content. The actions let the users respond directly to the information in the notification in alternative ways. such as by email or by phone call, without visiting the app.</p> 1356 1357<p>With expandable notifications, apps can give more information to the user, effortlessly and on demand. Users remain in control and can long-press any notification to get information about the sender and optionally disable further notifications from the app.</p> 1358 1359<div style="float:left;margin:66px 30px 0px 0px;width:280px;"> 1360<div> 1361<img src="{@docRoot}images/jb-appwidgets.png" width="280" height="548"> 1362</div> 1363<p class="image-caption" style="padding:.5em"><span 1364style="font-weight:500;">App Widgets</span> can resize automatically to fit the home screen and load different content as their sizes change.</p> 1365</div> 1366 1367<div style="padding-top:1px;clear:right;"> 1368 1369 1370<h3>Resizable app widgets</h3> 1371 1372<p>Android 4.1 introduces improved App Widgets that can <strong>automatically resize</strong>, based on where the user drops them on the home screen, the size to which the user expands them, and the amount of room available on the home screen. New App Widget APIs let you take advantage of this to <strong>optimize your app widget content</strong> as the size of widgets changes.</p> 1373 1374<p>When a widget changes size, the system notifies the host app’s widget provider, which can reload the content in the widget as needed. For example, a widget could display larger, richer graphics or additional functionality or options. Developers can still maintain control over maximum and minimum sizes and can update other widget options whenever needed. </p> 1375 1376<p>You can also supply separate landscape and portrait layouts for your widgets, which the system inflates as appropriate when the screen orientation changes.</p> 1377 1378<p>App widgets can now be displayed in third party launchers and other host apps through a new bind Intent (AppWidgetManager.ACTION_APPWIDGET_BIND).</p> 1379 1380</div> 1381 1382<h3>Simplified task navigation</h3> 1383 1384<p>Android 4.1 makes it easy for you to manage the “Up” navigation that’s available to users from inside of your apps and helps ensure a consistent experience for users.</p> 1385 1386<p>You can <strong>define the intended Up navigation</strong> for individual Activity components of your UI by adding a new <strong>XML attribute</strong> in the app’s manifest file. At run time, as Activities are launched, the system extracts the Up navigation tree from the manifest file and automatically creates the Up affordance navigation in the action bar. Developers who declare Up navigation in the manifest no longer need to manage navigation by callback at run time, although they can also do so if needed.</p> 1387 1388<p>Also available is a new <strong>TaskStackBuilder</strong> class that lets you quickly put together a synthetic task stack to start immediately or to use when an Activity is launched from a PendingIntent. Creating a synthetic task stack is especially useful when users launch Activities from remote views, such as from Home screen widgets and notifications, because it lets the developer provide a managed, consistent experience on Back navigation.</p> 1389 1390<h3>Easy animations for Activity launch</h3> 1391 1392<p>You can use a new helper class, <strong>ActivityOptions</strong>, to create and control the animation displayed when you launch your Activities. Through the helper class, you can specify custom animation resources to be used when the activity is launched, or request new zoom animations that start from any rectangle you specify on screen and that optionally include a thumbnail bitmap.</p> 1393 1394<h3>Transitions to Lights Out and Full Screen Modes</h3> 1395 1396<p>New system UI flags in View let you to cleanly transition from a normal application UI (with action bar, navigation bar, and system bar visible), to "lights out mode" (with status bar and action bar hidden and navigation bar dimmed) or "full screen mode" (with status bar, action bar, and navigation bar all hidden). </p> 1397 1398<h3>New types of remoteable Views</h3> 1399 1400<p>Developers can now use <strong>GridLayout</strong> and <strong>ViewStub</strong> views in Home screen widgets and notifications. GridLayout lets you structure the content of your remote views and manage child views alignments with a shallower UI hierarchy. ViewStub is an invisible, zero-sized View that can be used to lazily inflate layout resources at runtime.</p> 1401 1402<h3>Live wallpaper preview</h3> 1403 1404<p>Android 4.1 makes it easier for users to <strong>find and install Live Wallpapers</strong> from apps that include them. If your app includes Live Wallpapers, you can now start an Activity (ACTION_CHANGE_LIVE_WALLPAPER) that shows the user a preview of the Live Wallpaper from your own app. From the preview, users can directly load the Live Wallpaper.</p> 1405 1406<h3>Higher-resolution contact photos</h3> 1407 1408<p>With Android 4.1, you can store <strong>contact photos</strong> that are as large as <strong>720 x 720</strong>, making contacts even richer and more personal. Apps can store and retrieve contact photos at that size or use any other size needed. The maximum photo size supported on specific devices may vary, so apps should <strong>query the built-in contacts provider</strong> at run time to obtain the max size for the current device. </p> 1409 1410 1411<h2 id="input">New Input Types and Capabilities</h2> 1412 1413<h3>Find out about devices being added and removed</h3> 1414 1415<p>Apps can <strong>register to be notified</strong> when any new input devices are attached, by USB, Bluetooth, or any other connection type. They can use this information to change state or capabilities as needed. For example, a game could receive notification that a new keyboard or joystick is attached, indicating the presence of a new player.</p> 1416 1417<h3>Query the capabilities of input devices</h3> 1418 1419<p>Android 4.1 includes APIs that let apps and games take full advantage of all input devices that are connected and available.</p> 1420 1421<p>Apps can query the device manager to enumerate all of the input devices currently attached and learn about the capabilities of each.</p> 1422 1423<h3>Control vibrator on input devices</h3> 1424 1425<p>Among other capabilities, apps can now make use of any <strong>vibrator service</strong> associated with an attached input device, such as for <strong>Rumble Pak</strong> controllers.</p> 1426 1427 1428<h2 id="graphics">Animation and Graphics</h2> 1429 1430<h3>Vsync for apps</h3> 1431 1432<p>Extending vsync across the Android framework leads to a more consistent framerate and a smooth, steady UI. So that apps also benefit, Android 4.1 <strong>extends vsync timing</strong> to all drawing and animations initiated by apps. This lets them optimize operations on the UI thread and provides a stable timebase for synchronization.</p> 1433 1434<p>Apps can take advantage of vsync timing for free, through Android’s <strong>animation framework</strong>. The animation framework now uses vsync timing to automatically handle synchronization across animators.</p> 1435 1436<p>For specialized uses, apps can access vsync timing through APIs exposed by a new Choreographer class. Apps can request invalidation on the next vsync frame — a good way to schedule animation when the app is not using the animation framework. For more advanced uses, apps can post a callback that the Choreographer class will run on the next frame. </p> 1437 1438<h3>New animation actions and transition types</h3> 1439 1440<p>The animation framework now lets you define start and end actions to take when running ViewPropertyAnimator animations, to help synchronize them with other animations or actions in the application. The action can run any runnable object. For example, the runnable might specify another animation to start when the previous one finishes.</p> 1441 1442<p>You can also now specify that a ViewPropertyAnimator use a layer during the course of its animation. Previously, it was a best practice to animate complicated views by setting up a layer prior to starting an animation and then handling an onAnimationEnd() event to remove the layer when the animation finishes. Now, the withLayer() method on ViewPropertyAnimator simplifies this process with a single method call.</p> 1443 1444<p>A new transition type in LayoutTransition enables you to automate animations in response to all layout changes in a ViewGroup.</p> 1445 1446 1447<h2 id="connectivity">New Types of Connectivity</h2> 1448 1449<h3>Android Beam</h3> 1450 1451<p>Android Beam is a popular NFC-based technology that lets users instantly share, just by touching two NFC-enabled phones together.</p> 1452 1453<p>In Android 4.1, Android Beam makes it easier to share images, videos, or other payloads by <strong>leveraging Bluetooth for the data transfer</strong>. When the user triggers a transfer, Android Beam hands over from NFC to Bluetooth, making it really easy to manage the transfer of a file from one device to another.</p> 1454 1455<h3>Wi-Fi Network Service Discovery</h3> 1456 1457<p>Android 4.1 introduces support for multicast <strong>DNS-based service discovery</strong>, which lets applications find and connect to services offered by peer devices over Wi-Fi networks — including mobile devices, printers, cameras, media players, and others. Developers can take advantage of Wi-Fi network service discovery to build cross-platform or multiplayer games and application experiences.</p> 1458 1459<p>Using the service discovery API, apps can create and register any kind of service, for any other NSD-enabled device to discover. The service is advertised by multicast across the network using a human-readable string identifier, which lets user more easily identify the type of service. </p> 1460 1461<p>Consumer devices can use the API to scan and discover services available from devices connected to the local Wi-Fi network. After discovery, apps can use the API to resolve the service to an IP address and port through which it can establish a socket connection.</p> 1462 1463<p>You can take advantage of this API to build new features into your apps. For example, you could let users connect to a webcam, a printer, or an app on another mobile device that supports Wi-Fi peer-to-peer connections. </p> 1464 1465<h3>Wi-Fi Direct Service Discovery</h3> 1466 1467<p>Ice Cream Sandwich introduced support for Wi-Fi Direct, a technology that lets apps <strong>discover and pair directly</strong>, over a high-bandwidth peer-to-peer connection. Wi-Fi Direct is an ideal way to share media, photos, files and other types of data and sessions, even where there is no cell network or Wi-Fi available.</p> 1468 1469<p>Android 4.1 takes Wi-Fi Direct further, adding API support for <strong>pre-associated service discovery</strong>. Pre-associated service discovery lets your apps get more useful information from nearby devices about the services they support, before they attempt to connect. Apps can initiate discovery for a specific service and filter the list of discovered devices to those that actually support the target service or application.</p> 1470 1471<p>For example, this means that your app could discover only devices that are “printers” or that have a specific game available, instead of discovering all nearby Wi-Fi Direct devices. On the other hand, your app can advertise the service it provides to other devices, which can discover it and then negotiate a connection. This greatly simplifies discovery and pairing for users and lets apps take advantage of Wi-Fi Direct more effectively.</p> 1472 1473<p>With Wi-Fi Direct service discovery, you can create apps and <strong>multiplayer games</strong> that can share photos, videos, gameplay, scores, or almost anything else — all without requiring any Internet or mobile network. Your users can connect using only a direct p2p connection, which avoids using mobile bandwidth.</p> 1474 1475<h3>Network Bandwidth Management</h3> 1476 1477<p>Android 4.1 helps apps <strong>manage data usage</strong> appropriately when the device is <strong>connected to a metered network</strong>, including tethering to a mobile hotspot. Apps can query whether the current network is metered before beginning a large download that might otherwise be relatively expensive to the user. Through the API, you can now get a clear picture of which networks are sensitive to data usage and manage your network activity accordingly.</p> 1478 1479 1480<h2 id="media">New Media Capabilities</h2> 1481 1482<h3>Media codec access</h3> 1483 1484<p>Android 4.1 provides low-level access to platform hardware and software codecs. Apps can query the system to discover what <strong>low-level media codecs</strong> are available on the device and then and use them in the ways they need. For example, you can now create multiple instances of a media codec, queue input buffers, and receive output buffers in return. In addition, the media codec framework supports protected content. Apps can query for an available codec that is able to play protected content with a DRM solution available on the device.</p> 1485 1486<h3>USB Audio</h3> 1487 1488<p>USB audio output support allows hardware vendors to build hardware such as <strong>audio docks</strong> that interface with Android devices. This functionality is also exposed with the Android <strong>Open Accessory Development Kit</strong> (ADK) to give all developers the chance to create their own hardware.</p> 1489 1490<h3>Audio record triggering</h3> 1491 1492<p>Android now lets you <strong>trigger audio recording</strong> based on the completion of an audio playback track. This is useful for situations such as playing back a tone to cue your users to begin speaking to record their voices. This feature helps you sync up recording so you don’t record audio that is currently being played back and prevents recordings from beginning too late.</p> 1493 1494<h3>Multichannel audio</h3> 1495 1496<p>Android 4.1 supports <strong>multichannel audio</strong> on devices that have hardware multichannel audio out through the <strong>HDMI port</strong>. Multichannel audio lets you deliver rich media experiences to users for applications such as games, music apps, and video players. For devices that do not have the supported hardware, Android automatically downmixes the audio to the number of channels that are supported by the device (usually stereo).</p> 1497 1498<p>Android 4.1 also adds built-in support for encoding/decoding AAC 5.1 audio.</p> 1499 1500<h3>Audio preprocessing</h3> 1501 1502<p>Developers can apply <strong>preprocessing effects</strong> to audio being recorded, such as to apply noise suppression for improving speech recording quality, echo cancellation for acoustic echo, and auto gain control for audio with inconsistent volume levels. Apps that require high quality and clean audio recording will benefit from these preprocessors.</p> 1503 1504<h3>Audio chaining</h3> 1505 1506<p>MediaPlayer supports <strong>chaining audio streams together</strong> to play audio files without pauses. This is useful for apps that require seamless transitions between audio files such as music players to play albums with continuous tracks or games.</p> 1507 1508<h3 id="media-router">Media Router</h3> 1509 1510<p>The new APIs MediaRouter, MediaRouteActionProvider, and MediaRouteButton provide standard mechanisms and UI for <strong>choosing where to play media</strong>. Support is built-in for wired headsets and a2dp bluetooth headsets and speakers, and you can add your own routing options within your own app.</p> 1511 1512<h2 id="renderscript">Renderscript Computation</h2> 1513 1514<p>Android 4.1 extends Renderscript computation to give you more flexibility. You can now <strong>sample textures</strong> in your Renderscript compute scripts, and <strong>new pragmas</strong> are available to define the floating point precision required by your scripts. This lets you enable <strong>NEON instructions</strong> such as fast vector math operations on the CPU path, that wouldn’t otherwise be possible with the full IEEE 754-2008 standard.</p> 1515 1516<p>You can now <strong>debug</strong> your Renderscript compute scripts on <strong>x86-based emulator and hardware devices</strong>. You can also define multiple root-style kernels in a single Renderscript source file.</p> 1517 1518 1519<h2 id="browser">Android Browser and WebView</h2> 1520 1521<p>In Android 4.1, the Android Browser and WebViews include these enhancements:</p> 1522<ul> 1523<li>Better HTML5 video user experience, including touch-to-play/pause and smooth transition from inline to full screen mode. </li> 1524<li>Improved rendering speed and reduced memory usage for better scrolling and zooming performance.</li> 1525<li>Improved HTML5/CSS3/Canvas animation performance.</li> 1526<li>Improved text input.</li> 1527<li>Updated JavaScript Engine (V8) for better JavaScript performance.</li> 1528<li>Support for the updated HTML5 Media Capture specification (the "capture" attribute on input type=file elements).</li> 1529</ul> 1530 1531 1532<h2 id="google">Google APIs and services</h2> 1533 1534<p>To extend the capabilities of Android even further, several new services for Android are available.</p> 1535 1536<h3 id="gcm">Google Cloud Messaging for Android</h3> 1537 1538<p>Google Cloud Messaging (GCM) is a service that lets developers send <strong>short message data</strong> to their users on Android devices, without needing a proprietary sync solution. </p> 1539 1540<p>GCM handles all the details of <strong>queuing messages and delivering them</strong> efficiently to the targeted Android devices. It supports message <strong>multicasting</strong> and can reach up to 1000 connected devices simultaneously with a single request. It also supports message <strong>payloads</strong>, which means that in addition to sending tickle messages to an app on the device, developers can send up to 4K of data. </p> 1541 1542<p>Google Cloud Messaging is completely <strong>free for all developers</strong> and sign-up is easy. See the <a href="{@docRoot}google/gcm/index.html">Google Cloud Messaging</a> page for registration, downloads, and documentation.</p> 1543 1544<h3>App Encryption</h3> 1545 1546<p>Starting with Android 4.1, Google Play will help protect application assets by encrypting all paid apps with a device-specific key before they are delivered and stored on a device.</p> 1547 1548<h3>Smart App Updates</h3> 1549 1550<p>Smart app updates is a new feature of Google Play that introduces a better way of delivering <strong>app updates</strong> to devices. When developers publish an update, Google Play now delivers only the <strong>bits that have changed</strong> to devices, rather than the entire APK. This makes the updates much lighter-weight in most cases, so they are faster to download, save the device’s battery, and conserve bandwidth usage on users’ mobile data plan. On average, a smart app update is about <strong>1/3 the size</strong> of a full APK update.</p> 1551 1552<h3 id="gps">Google Play services</h3> 1553 1554<p>Google Play services helps developers to <strong>integrate Google services</strong> such as authentication and Google+ into their apps delivered through Google Play.</p> 1555 1556<p>Google Play services is automatically provisioned to end user devices by Google Play, so all you need is a <strong>thin client library</strong> in your apps.</p> 1557 1558<p>Because your app only contains the small client library, you can take advantage of these services without a big increase in download size and storage footprint. Also, Google Play will <strong>deliver regular updates</strong> to the services, without developers needing to publish app updates to take advantage of them.</p> 1559 1560<p>For more information about the APIs included in Google Play Services, see the <a href="http://developers.google.com/android/google-play-services/index.html">Google Play services</a> developer page.</p> 1561 1562</div> <!-- END ANDROID 4.1 --> 1563 1564 1565 1566 1567 1568 1569