jelly-bean.jd revision da31f2ea9274614da18aa2544fc43fb4ee213741
1page.title=Jelly Bean 2tab1=Android 4.2 3tab1.link=#android-42 4tab2=Android 4.1 5tab2.link=#android-41 6 7@jd:body 8<div id="butterbar-wrapper" > 9 <div id="butterbar" > 10 <div id="butterbar-message"> 11<a target="_blank" href="https://docs.google.com/a/google.com/forms/d/1EHLPGqhbxj2HungHRRN4_0K9TGpc-Izy-u46vBDgS8Q/viewform"> 12 Take the Android Developer Survey</a> 13 </div> 14 </div> 15</div> 16 17<style> 18#android-41 {display:none;} 19</style> 20 21<script> 22function revealSection(hashy) { 23 if (hashy != "" && !$(hashy).is(":visible")) { 24 sectionId = $(hashy).closest(".version-section").attr("id"); 25 link = $("#title-tabs a[href$="+sectionId+"]"); 26 link.parent().addClass("selected"); 27 link.parent().siblings().removeClass("selected"); 28 29 sectionDiv = $(".version-section"+link.attr("href")); 30 if (sectionDiv.length) { 31 $(".version-section").hide(); 32 sectionDiv.show(); 33 } 34 35 $('html, body').animate({ 36 scrollTop: $(hashy).offset().top 37 }, 100); 38 } 39} 40 41$(document).ready(function() { 42 $("#title-tabs li a").each(function() { 43 $(this).click(function(){ 44 $(this).parent().addClass("selected"); 45 $(this).parent().siblings().removeClass("selected"); 46 $(".version-section").hide(); 47 $($(this).attr("href")).show(); 48 return false; 49 }); 50 }); 51 52 hashy = escapeHTML(location.hash); 53 revealSection(hashy); 54}); 55 56window.onhashchange = function () { 57 revealSection(escapeHTML(location.hash)); 58} 59 60</script> 61 62 63 64<!-- BEGIN ANDROID 4.2 --> 65<div id="android-42" class="version-section"> 66<div style="float:right;padding:0px 0px 12px 34px;"> 67<div> 68<img src="{@docRoot}images/jb-device-2.png" alt="Android 4.2 on phone and tablet" height="348" width="400"> 69</div> 70</div> 71<p>Welcome to Android 4.2, the latest version of <span 72style="white-space:nowrap;">Jelly Bean!</span></p> 73 74<p>Android 4.2 has performance optimizations, a refreshed system UI, and great 75new features for users and developers. This document provides a glimpse of what's new for 76developers. 77 78<p>See the <a href="/about/versions/android-4.2.html">Android 4.2 APIs</a> 79document for a detailed look at the new developer APIs.</p> 80 81<p>Find out more about the new Jelly Bean features for users at <a 82href="http://www.android.com/whatsnew">www.android.com</a>.</p> 83 84 85<h2 id="42-performance" style="line-height:1.25em;">Faster, Smoother, More Responsive</h2> 86 87<p>Android 4.2 builds on the performance improvements already included in Jelly Bean 88— <strong>vsync timing</strong>, <strong>triple buffering</strong>, 89<strong>reduced touch latency</strong>, and <strong>CPU input boost</strong> 90— and adds new optimizations that make Android even faster.</p> 91 92<p>Improvements in the <strong>hardware-accelerated 2D renderer</strong> make 93common animations such as scrolling and swiping smoother and faster. In 94particular, <strong>drawing is optimized</strong> for layers, clipping and 95certain shapes (rounded rects, circles and ovals).</p> 96 97<p>A variety of <strong>WebView rendering optimizations</strong> make scrolling 98of web pages smoother and free from jitter and lags.</p> 99 100<p>Android’s <strong>Renderscript Compute</strong> is the first computation 101platform ported to run directly on a <strong>mobile device GPU</strong>. It automatically 102takes advantage of <strong>GPU computation</strong> resources whenever possible, 103dramatically improving performance for graphics and image processing. Any app using 104Renderscript on a supported device can benefit immediately from 105this GPU integration <strong>without recompiling</strong>.</p> 106 107 108<div style="float:left;margin:16px 24px 12px 0px;"> 109<a href="" target="_android"> 110<img src="{@docRoot}images/jb-nexus10-1.png" alt="10-inch tablet running Android 4.2" width="380" height="281" /></a> 111</div> 112 113<h2 id="42-ui" style="margin-top:2em;">Refined, refreshed UI</h2> 114 115<p>Android 4.2 refines the Jelly Bean user experience and brings familiar 116Android UI patterns such as status bar, system bar, and notifications window to 117all tablets.</p> 118 119<p>All screen sizes now feature the <strong>status bar</strong> on top, with 120pull-down access to <strong>notifications</strong> and a new <strong>Quick 121Settings</strong> menu. The familiar </strong>system bar</strong> appears on the 122bottom, with buttons easily accessible from either hand. The <strong>Application 123Tray</strong> is also available on all screen sizes.</p> 124 125 126<h2 id="42-multiuser" style="margin-top:2em;clear:left;">One tablet, many users</h2> 127 128<p>Now several users can <strong>share a single Android tablet</strong>, with 129each user having convenient access to a <strong>dedicated user 130space</strong>. Users can switch to their spaces with a single touch from the 131lock screen.</p> 132 133<p>On a multiuser device, Android gives each user a separate environment, 134including user-specific emulated SD card storage. Users also have their own 135homescreens, widgets, accounts, settings, files, and apps, and the system keeps 136these separate. All users share core system services, but the system ensures that 137each user's applications and data remain isolated. In effect, each of the multiple 138users has his or her own Android device.</p> 139 140<p>Users can install and uninstall apps at any time in their own environments. 141To save storage space, Google Play downloads an APK only if it's not already 142installed by another user on the device. If the app is already installed, Google 143Play records the new user's installation in the usual way but doesn't download 144another copy of the app. Multiple users can run the same copy of an APK because 145the system creates a new instance for each user, including a user-specific data 146directory.</p> 147 148<p>For developers, <strong>multi-user support is transparent</strong> — 149your apps do not need to do anything special to run normally in a multi-user 150environment and there are no changes you need to make in your existing or 151published APKs. The system manages your app in each user space just as it does 152in a single-user environment. </p> 153 154 155<h2 id="42-engagement" style="clear:left; margin-top:1em;">New ways to engage users</h2> 156 157<div style="float:right;margin:22px 0px 0px 24px;width:280px;"> 158<div> 159<img src="{@docRoot}images/jb-lock-calendar.png" alt="Calendar lock screen widget" width="280" height="543" style="padding-left:1em;margin-bottom:0"> 160</div> 161<p class="image-caption" style="padding:1.5em">You can extend <strong>app widgets</strong> to run on the lock screen, for instant access to your content.</p> 162</div> 163 164<h3 id="42-lockscreen-widgets">Lock screen widgets</h3> 165 166<p>In Android 4.2, users can place <strong>app widgets</strong> directly on 167their <strong>lock screens</strong>, for instant access to favorite app content 168without having to unlock. Users can add as many as five lock screen widgets, 169choosing from widgets provided by installed apps. The lock screen displays each 170widget in its own panel, letting users swipe left and right to view different 171panels and their widgets.</p> 172 173<p>Like all app widgets, lock screen widgets can display <strong>any kind of content</strong> and 174they can accept direct user interaction. They can be entirely self-contained, 175such as a widget that offers controls to play music, or they can let users jump 176straight to an Activity in your app, after unlocking along the way as 177needed.</p> 178 179<p>For developers, lock screen widgets offer a great new way to engage users. 180They let you put your content in front of users in a location they’ll see often, 181and they give you more opportunities to bring users directly into your app.</p> 182 183<p>You can take advantage of this new capability by building a new app widget or 184by extending an existing home screen widget. If your app already includes home 185screen widgets, you can extend them to the lock screen with minimal change. To 186give users an optimal experience, you can update the widget to use the full lock 187screen area when available and resize when needed on smaller screens. You can 188also add features to your widgets that might be especially useful or convenient 189on the lock screen.</p> 190 191<h3 id="42-daydreams">Daydream</h3> 192 193<p>Daydream is an <strong>interactive screensaver mode</strong> that starts when 194a user’s device is docked or charging. In this mode, the system launches a 195daydream — a remote content service provided by an installed app — 196as the device screensaver. A user can enable Daydream from the Settings app and 197then choose the daydream to display.</p> 198 199<p>Daydreams combine the best capabilities of live wallpapers and home screen 200widgets, but they are more powerful. They let you offer the any kind of content 201in a completely new context, with user interactions such as flipping through 202photos, playing audio or video, or jumping straight into your app with a single 203touch.</p> 204 205<p>Because daydreams can start automatically when a device is charging or 206docked, they also give your app a great way to support new types of user 207experiences, such as leanback or exhibition mode, demo or kiosk mode, and 208"attract mode" — all without requiring special hardware.</p> 209 210<div style="float:left;margin:20px 30px 0px 0px;width:460px;"> 211<div> 212<img src="{@docRoot}images/jb-dream-1.png" alt="Daydream screensaver mode" height="300" style="padding-left:1em;"> 213</div> 214<p class="image-caption" style="padding:.5em .5em .5em 1.5em;"><span 215style="font-weight:500;">Daydream</span> lets you create powerful interactive screensavers that display any kind of content.</p> 216</div> 217 218<p>Daydreams are similar to Activities and can do anything that Activity 219can do — from rendering a UI hierarchy (without using RemoteViews) to 220drawing directly using Canvas, OpenGL, SurfaceTexture, and more. They can play 221video and audio and they can even accept direct user interaction. However, 222daydreams are not Activities, so they don’t affect the backstack or appear in 223Recents and they cannot be launched directly from your app.</p> 224 225<p>Implementing a daydream is straightforward and you can take advantage of UI 226components and resources that you’ve already created for other parts of your 227app. You can provide multiple daydreams in your app and you can offer distinct 228content and display settings for each.</p> 229 230<h2 id="42-external-display" style="clear:left;">External display support</h2> 231 232<p>Android 4.2 introduces platform support for <strong>external 233displays</strong> that goes far beyond mirroring — apps can now target 234unique content to any one or multiple displays that are attached to an Android 235device. Apps can build on this to deliver new kinds of interaction and 236entertainment experiences to users.</p> 237 238<h3 id="42-display-manager">Display manager</h3> 239 240<p>Apps interact with displays through a new display manager system service. 241Your app can enumerate the displays and check the capabilities of each, 242including size, density, display name, ID, support for secure video, and more. 243Your app can also receive callbacks when displays are added or removed or when 244their capabilities change, to better manage your content on external 245displays.</p> 246 247<h3 id="42-presentation">Presentation window</h3> 248 249<p>To make it easy to show content on an external display, the framework 250provides a new UI object called a <strong>Presentation</strong> — a type of dialog that 251represents a window for your app’s content on a specific external display. Your 252app just gives the display to use, a theme for the window, and any unique 253content to show. The Presentation handles inflating resources and rendering your 254content according to the characteristics of the targeted display.</p> 255 256<div style="margin:0 auto;width:569px;padding-top:1em;"> 257 258<img src="{@docRoot}images/external-display.png" alt="" width="555" height="351" style="padding-left:1em;margin-bottom:0"> 259 260<p class="image-caption" style="padding:1.25em">You can take full control of two or more independent displays using <strong>Presentation</strong>.</p> 261</div> 262 263<p>A Presentation gives your app full control over the remote display window and 264its content and lets you manage it based on user input events such as key 265presses, gestures, motion events, and more. You can use all of the normal tools 266to create a UI and render content in the Presentation, from building an 267arbitrary view hierarchy to using SurfaceView or SurfaceTexture to draw directly 268into the window for streamed content or camera previews.</p> 269 270<h3 id="42-preferred display">Preferred display selection</h3> 271 272<p>When multiple external displays are available, you can create as many 273Presentations as you need, with each one showing unique content on a specific 274display. In many cases, you might only want to show your content on a single 275external display — but always on the that’s best for Presentation content. 276For this, the system can help your app choose the best display to use.</p> 277 278<p>To find the best display to use, your app can query the display manager for 279the system’s <strong>preferred Presentation display</strong> and receive callbacks when that 280display changes. Alternatively, you can use the media router service, extended 281in Android 4.2, to receive notifications when a system video route changes. Your 282app can display content by default in the main Activity until a preferred 283Presentation display is attached, at which time it can automatically switch to 284Presentation content on the preferred display. Your apps can also use media 285router’s MediaRouteActionProvider and MediaRouteButton to offer standard 286display-selection UI.</p> 287 288<h3 id="42-protected-content">Protected content</h3> 289 290<p>For apps that handle protected or encrypted content, the display API now 291reports the <strong>secure video capabilities</strong> of attached displays. Your app query a 292display to find out if it offers a secure video output or provides protected 293graphics buffers and then choose the appropriate content stream or decoding to 294make the content viewable. For additional security on SurfaceView objects, your 295app can set a secure flag to indicate that the contents should never appear in 296screenshots or on a non-secure display output, even when mirrored.</p> 297 298<h3 id="42-wireless-display">Wireless display</h3> 299 300<p>Starting in Android 4.2, users on supported devices can connect to an 301external display over Wi-Fi, using <a 302href="http://www.wi-fi.org/wi-fi-certified-miracast%E2%84%A2">Miracast</a>, a 303peer-to-peer wireless display standard created by the <a 304href="http://www.wi-fi.org/">Wi-Fi Alliance</a>. When a wireless display is 305connected, users can stream any type of content to the big screen, including 306photos, games, maps, and more.</p> 307 308<p>Apps can take advantage of <strong>wireless displays</strong> in the same way as they do other 309external displays and no extra work is needed. The system manages the network 310connection and streams your Presentation or other app content to the wireless 311display as needed.</p> 312 313 314<h2 id="42-native-rtl">Native RTL support</h2> 315 316<div style="float:right;margin:22px 0px 0px 24px;width:340px;"> 317<div> 318<img src="{@docRoot}images/jb-rtl.png" alt="RTL layout mirroring" width="340" height="457" style="margin-bottom:0;"> 319</div> 320<p class="image-caption" style="padding-top:1em">Developers can now <strong>mirror their layouts</strong> for RTL languages.</p> 321</div> 322 323<p>Android 4.2 introduces <strong>full native support for RTL</strong> 324(right-to-left) layouts, including layout mirroring. With native RTL support, 325you can deliver the same great app experience to all of your users, whether 326their language uses a script that reads right-to-left or one that reads 327left-to-right.</p> 328 329<p>When the user switches the system language to a right-to-left script, the 330system now provides automatic mirroring of app UI layouts and all view widgets, 331in addition to bidi mirroring of text elements for both reading and character 332input.</p> 333 334<p>Your app can take advantage of <strong>RTL layout mirroring</strong> in your app with minimal effort. 335If you want the app to be mirrored, you simply declare a new attribute in your 336app manifest and change all "left/right" layout properties to new "start/end" 337equivalents. The system then handles the mirroring and display of your UI as 338appropriate.</p> 339 340<p>For precise control over your app UI, Android 4.2 includes new APIs that let 341you manage layout direction, text direction, text alignment, gravity, and 342locale direction in View components. You can even create custom versions of 343layout, drawables, and other resources for display when a right-to-left script 344is in use.</p> 345 346<p>To help you debug and optimize your custom right-to-left layouts, the 347HierarchyViewer tool now lets you see start/end properties, layout direction, 348text direction, and text alignment for all the Views in the hierarchy.</p> 349 350 351<h2 id="42-intl">Enhancements for international languages</h2> 352 353<p>Android 4.2 includes a variety of <strong>font and character 354optimizations</strong> for international users:</p> 355<ul> 356<li>For Korean users, a new font choice is available — Nanum (나눔글꼴) 357Gothic, a unicode font designed especially for the Korean-language script.</li> 358<li>Improved support for Japanese vertical text displayed in WebViews.</li> 359<li>Improved font kerning and positioning for Indic, Thai, Arabic, and Hebrew 360default fonts.</li> 361</ul> 362 363<p>The default Android keyboard also includes an updated set of 364dictionaries:</p> 365<ul> 366<li>Improved dictionaries for French (with bigram support), English, and 367Russian</li> 368<li>New dictionaries for Danish, Greek, Finnish, Lithuanian, Latvian, Polish, 369Slovenian, Serbian, Swedish, Turkish</li> 370</ul> 371 372 373<h2 id="42-ui-tools">New ways to create beautiful UI</h2> 374 375<h3 id="42-nested-fragments">Nested Fragments</h3> 376 377<p>For more control over your UI components and to make them more modular, 378Android 4.2 lets you <strong>nest Fragments inside of Fragments</strong>. For 379any Fragment, a new Fragment manager lets you insert other Fragments as child 380nodes in the View hierarchy.</p> 381 382<p>You can use nested Fragments in a variety of ways, but they are especially 383useful for implementing dynamic and reusable UI components inside of a UI 384component that is itself dynamic and reusable. For example, if you use ViewPager 385to create fragments that swipe left and right, you can now insert fragments into 386each Fragment of the view pager.</p> 387 388<p>To let you take advantage of nested Fragments more broadly in your app, this 389capability is added to the latest version of the <strong>Android Support 390Library</strong>.</p> 391 392 393<h2 id="42-accessibility">Accessibility</h2> 394 395<p>The system now helps accessibility services <strong>distinguish between touch 396exploration and accessibility gestures</strong> while in touch-exploration mode. 397When a user touches the screen, the system notifies the service that a generic 398touch interaction has started. It then tracks the speed of the touch interaction 399and determines whether it is a touch exploration (slow) or accessibility gesture 400(fast) and notifies the service. When the touch interaction ends, the system 401notifies the service.</p> 402 403<p>The system provides a new global accessibility option that lets an 404accessibility service open the Quick Settings menu based on an action by the 405user. Also added in Android 4.2 is a new accessibility feedback type for 406<strong>Braille devices</strong>.</p> 407 408<p>To give accessibility services insight into the meaning of Views for 409accessibility purposes, the framework provides new APIs for associating a View 410as the label for another View. The label for each View is available to 411accessibility services through AccessibilityNodeInfo.</p> 412 413 414<h2 id="42-camera">Improved Camera with HDR</h2> 415 416<p>Android 4.2 introduces a <strong>new camera hardware interface and 417pipeline</strong> for improved performance. On supported devices, apps can use a 418new <strong>HDR camera scene mode</strong> to capture an image using high 419dynamic range imaging techniques. </p> 420 421<p>Additionally, the framework now provides an API to let apps check whether the 422camera shutter sound can be disabled. Apps can then let the user disable the 423sound or choose an alternative sound in place of the standard shutter sound, 424which is recommended.</p> 425 426 427<h2 id="42-renderscript">Renderscript Computation</h2> 428 429<p>In Android 4.2, Renderscript Compute introduces new scripting features, new 430optimizations, and direct GPU integration for the highest performance in 431computation operations.</p> 432 433<h3 id="42-filterscript">Filterscript</h3> 434 435<p>Filterscript is a subset of Renderscript that is focused on <strong>optimized 436image processing across a broad range of device chipsets</strong>. Developers 437can write their image processing operations in Filterscript using the standard 438Renderscript runtime API, but within stricter constraints that ensure wider 439compatibility and improved optimization across CPUs, GPUs, and DSPs.</p> 440 441<p>Filterscript is ideal for hardware-accelerating simple image-processing and 442computation operations such as those that might be written for OpenGL ES 443fragment shaders. Because it places a relaxed set of constraints on hardware, 444your operations are optimized and accelerated on more types of device chipsets. 445Any app targeting API level 17 or higher can make use of Filterscript.</p> 446 447<h3 id="42-rs-intrinsics">Script intrinsics</h3> 448 449<p>In Android 4.2, Renderscript adds support for a set of script intrinsics 450— pre-implemented <strong>filtering primitives that are 451accelerated</strong> to reduce the amount of code that you need to write and to 452ensure that your app gets the maximum performance gain possible.</p> 453 454<p>Intrinsics are available for blends, blur, color matrix, 3x3 and 5x5 convolve, 455per-channel lookup table, and converting an Android YUV buffer to RGB.</p> 456 457<h3 id="42-rs-groups">Script groups</h3> 458 459<p>You can now create <strong>groups of Renderscript scripts</strong> and 460execute them all with a single call as though they were part of a single script. 461This allows Renderscript to optimize execution of the scripts in ways that it 462could not do if the scripts were executed individually.</p> 463 464<div style="float:right;padding-top:1em;width:400px;margin-left:2em;"> 465<img src="{@docRoot}images/jb-rs-chart-versions.png" alt="Renderscipt optimizations chart" width="360" height="252" 466style="border:1px solid #ddd;border-radius: 6px;" /> 467<p style="image-caption">Renderscript image-processing 468benchmarks run on different Android platform versions (Android 4.0, 4.1, and 4.2) 469in CPU only on a Galaxy Nexus device.</p> 470<img src="{@docRoot}images/jb-rs-chart-gpu.png" style="border:1px solid #ddd;border-radius: 6px; alt="" width="360" height="252" /> 471<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> 472</div> 473 474<p>If you have a directed acyclic graph of Renderscript operations to run, you can 475use a builder class to create a script group defining the operations. At 476execution time, Renderscript optimizes the run order and the connections between 477these operations for best performance.</p> 478 479 480<h3 id="42-rs-optimization">Ongoing optimization improvements</h3> 481 482<p>When you use Renderscript for computation operations, you apps benefit from 483<strong>ongoing performance and optimization improvements</strong> in the 484Renderscript engine itself, without any impact on your app code or any need for 485recompilation.</p> 486 487<p>As optimization improves, your operations execute faster and on more 488chipsets, without any work on your part. The chart at right highlights 489the performance gain delivered by ongoing Renderscript optimization improvements 490across successive versions of the Android platform.</p> 491 492<h3 id="42-gpu-compute">GPU Compute</h3> 493 494<p>Renderscript Compute is the first computation platform ported to run directly on a mobile device GPU. It now 495automatically takes advantage of <strong>GPU computation</strong> resources 496whenver possible to improve performance. With GPU integration, even the most 497complex computations for graphics or image processing can execute with 498dramatically improved performance.</p> 499 500<p>Any app using Renderscript on a supported device can benefit immediately from 501this GPU integration, without recompiling. The Nexus 10 tablet is the first 502device to support this integration.</p> 503 504<h2 id="42-dev-options" style="clear:right;margin-top:1em;">New built-in developer options</h2> 505 506<p>The Android 4.2 system includes a variety of new developer options that make 507it easier to create great looking apps that perform well. The new options expose 508features for <strong>debugging and profiling</strong> your app from any device 509or emulator.</p> 510 511<p class="caution" style="clear:right;">On devices running Android 4.2, 512developer options are hidden by default, helping to create a better experience 513for users. You can reveal the developer options at any time by tapping 7 times 514on <strong>Settings</strong> > <strong>About phone</strong> > <strong>Build 515number</strong> on any compatible Android device.</p> 516 517<div style="float:left;margin:20px 42px 0px 0px;width:290px;"> 518<div> 519<img src="{@docRoot}images/jb-dev-options-device.png" width="280" height="548"> 520</div> 521<p class="image-caption" style="padding:.5em">New <span 522style="font-weight:500;">developer options</span> give you more ways to profile and debug on a device.</p> 523</div> 524 525<p style="margin-top:2em;">New developer options in Android 4.2 include:</p> 526 527<ul> 528<li><strong>Take bug report</strong> — immediately takes a screen shot and 529dumps device state information to local file storage, then attaches them to a 530new outgoing email message.</li> 531<li><strong>Power menu bug reports</strong> — Adds a new option to the 532device power menu and quick settings to take a bug report (see above).</li> 533<li><strong>Verify apps over usb</strong> — Allows you to disable app 534checks for sideloading apps over USB, while still checking apps from other 535sources like the browser. This can speed up the development process while 536keeping the security feature enabled.</li> 537<li><strong>Show hardware layers updates</strong> — Flashes hardware 538layers green when they update.</li> 539<li><strong>Show GPU overdraw</strong> — Highlights GPU overdraw 540areas.</li> 541<li><strong>Force 4x MSAA</strong> — Enables 4x MSAA in Open GL ES 2.0 542apps.</li> 543<li><strong>Simulate secondary displays</strong> — Creates one or more 544non-secure overlay windows on the current screen for use as a simulated remote 545display. You can control the simulated display’s size and density.</li> 546<li><strong>Enable OpenGL traces</strong> — Lets you trace OpenGL 547execution using Logcat, Systrace, or callstack on glGetError.</li> 548</ul> 549 550<h2 id="42-platform-tech" style="padding-top:1em;clear:left;">New Platform Technologies</h2> 551 552<p>Android 4.2 includes a variety of new and <strong>enhanced platform technologies</strong> to 553support innovative communications use-cases across a broad range of hardware 554devices. In most cases, the new platform technologies and enhancements do not directly 555affect your apps, so you can benefit from them without any modification.</p> 556 557<h3 id="42-security">Security enhancements</h3> 558 559<p>Every Android release includes dozens of security enhancements to protect 560users. Here are some of the enhancements in Android 4.2:</p> 561 562<ul> 563<li><strong>Application verification</strong> — Users can choose to enable 564“Verify Apps" and have applications screened by an application verifier, prior 565to installation. App verification can alert the user if they try to install an 566app that might be harmful; if an application is especially bad, it can block 567installation.</li> 568<li><strong>More control of premium SMS</strong> — Android will provide a 569notification if an application attempts to send SMS to a short code that uses 570premium services which might cause additional charges. The user can choose 571whether to allow the application to send the message or block it.</li> 572<li><strong>Always-on VPN</strong> — VPN can be configured so that 573applications will not have access to the network until a VPN connection is 574established. This prevents applications from sending data across other 575networks.</li> 576<li><strong>Certificate Pinning</strong> — The libcore SSL implementation 577now supports certificate pinning. Pinned domains will receive a certificate 578validation failure if the certificate does not chain to a set of expected 579certificates. This protects against possible compromise of Certificate 580Authorities.</li> 581<li><strong>Improved display of Android permissions</strong> — Permissions 582have been organized into groups that are more easily understood by users. 583During review of the permissions, the user can click on the permission to see 584more detailed information about the permission.</li> 585<li><strong>installd hardening</strong> — The installd daemon does not run 586as the root user, reducing potential attack surface for root privilege 587escalation.</li> 588<li><strong>init script hardening</strong> — init scripts now apply 589O_NOFOLLOW semantics to prevent symlink related attacks.</li> 590<li><strong>FORTIFY_SOURCE</strong> — Android now implements 591FORTIFY_SOURCE. This is used by system libraries and applications to prevent 592memory corruption.</li> 593<li><strong>ContentProvider default configuration</strong> — Applications 594which target API level 17 will have “export” set to “false” by default for each 595ContentProvider, reducing default attack surface for applications.</li> 596<li><strong>Cryptography</strong> — Modified the default implementations 597of SecureRandom and Cipher.RSA to use OpenSSL. Added SSLSocket support for 598TLSv1.1 and TLSv1.2 using OpenSSL 1.0.1</li> 599<li><strong>Security Fixes</strong> — Upgraded open source libraries with 600security fixes include WebKit, libpng, OpenSSL, and LibXML. Android 4.2 also 601includes fixes for Android-specific vulnerabilities. Information about these 602vulnerabilities has been provided to Open Handset Alliance members and fixes are 603available in Android Open Source Project. To improve security, some devices 604with earlier versions of Android may also include these fixes.</li> 605</ul> 606 607<h3 id="42-bt-stack">New Bluetooth stack</h3> 608 609Android 4.2 introduces a new Bluetooth stack optimized for use with Android 610devices. The new Bluetooth stack developed in collaboration between Google and 611Broadcom replaces the stack based on BlueZ and provides improved compatibility 612and reliability. 613 614<h3 id="42-audio">Low-latency audio</h3> 615 616<p>Android 4.2 improves support for low-latency audio playback, starting from the 617improvements made in Android 4.1 release for audio output latency using OpenSL 618ES, Soundpool and tone generator APIs. These improvements depend on hardware 619support — devices that offer these low-latency audio features can 620advertise their support to apps through a hardware feature constant. New 621AudioManager APIs are provided to query the native audio sample rate and buffer 622size, for use on devices which claim this feature.</p> 623 624<h3 id="42-camera-interface">New camera hardware interface</h3> 625 626Android 4.2 introduces a new implementation of the camera stack. The camera 627subsystem includes the implementations for components in the camera pipeline 628such as burst mode capture with processing controls. 629 630<h3 id="42-nfc-interface">New NFC hardware interface and controller interface</h3> 631 632Android 4.2 introduces support for controllers based on the NCI standard from 633the NFC-Forum. NCI provides a standard communication protocol between an NFC 634Controller (NFCC) and a device Host, and the new NFC stack developed in 635collaboration between Google and Broadcom supports it. 636 637<h3 id="42-dalvik">Dalvik runtime optimizations</h3> 638 639<p>The Dalvik runtime includes enhancements for performance and security across 640a wider range of architectures:</p> 641<ul> 642<li>x86 JIT support from Intel and MIPS JIT support from MIPS</li> 643<li>Optimized garbage-collection parameters for devices with > 512MB</li> 644<li>Default implementations of SecureRandom and Cipher.RSA now use OpenSSL</li> 645<li>SSLSocket support for TLSv1.1 and TLSv1.2 via OpenSSL 1.0.1</li> 646<li>New intrinsic support for StrictMath methods abs, min, max, and sqrt</li> 647<li>BouncyCastle updated to 1.47</li> 648<li>zlib updated to 1.27</li> 649<li>dlmalloc updated to 2.8.6</li> 650</ul> 651 652</div> <!-- END ANDROID 4.2 --> 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677<!-- BEGIN ANDROID 4.1 --> 678<div id="android-41" class="version-section"> 679 680<div style="float:right;width:320px;padding:0px 0px 0px 34px;clear:both"> 681<div> 682<img src="{@docRoot}images/jb-android-4.1.png" height="426" width="320"> 683</div> 684</div> 685<p>Welcome to Android 4.1 the first version of Jelly Bean!</p> 686 687<p>Android 4.1 is the fastest and smoothest version of Android yet. We’ve made 688improvements throughout the platform and added great new features 689for users and developers. This document provides a glimpse of what's new for developers. 690 691<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> 692 693<p>Find out more about the Jelly Bean features for users at <a href="http://www.android.com/whatsnew">www.android.com</a>.</p> 694 695 696<h2 id="performance">Faster, Smoother, More Responsive</h2> 697 698<p>Android 4.1 is optimized to deliver Android's best performance and lowest touch latency, in an effortless, intuitive UI.</p> 699 700<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> 701 702<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> 703 704<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> 705 706<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> 707 708 709<div style="float:left;margin:12px 24px 0px 0px;"> 710<img src="{@docRoot}images/jb-accessibility-focus-250.png" width="240px" height="469"> 711</div> 712 713<div style="width:85%;padding-top:16px;"> 714<h2 id="accessibility">Enhanced Accessibility</h2> 715 716<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> 717 718<p>Accessibility services can link their own <strong>tutorials</strong> into the Accessibility settings, to help users configure and use their services.</p> 719 720<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> 721 722</div> 723 724<div style="clear:both;padding-top:1px;"> 725 726<h2 id="intl">Support for International Users</h2> 727 728<div style="clear:both;padding-top:16px;float:right;"> 729 730<div style="float:right;margin-left:18px;fpadding-top:90px;padding-bottom:60px"> 731<img src="{@docRoot}images/jb-r2l.png" width="280" height="356"> 732</div> 733</div> 734 735<h3>Bi-Directional Text and Other Language Support</h3> 736 737<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> 738 739<p>Other types of new language support include:</p> 740<ul> 741<li>Additional Indic languages: Kannada, Telugu, and Malayalam</li> 742<li>The new Emoji characters from Unicode version 6.0</li> 743<li>Better glyph support for Japanese users (renders Japanese-specific versions of glyphs when system language is set to Japanese)</li> 744<li>Arabic glyphs optimized for WebViews in addition to the Arabic glyphs for TextViews</li> 745<li>Vertical Text support in WebViews, including Ruby Text and additional Vertical Text glyphs</li> 746<li>Synthetic Bold is now available for all fonts that don't have dedicated bold glyphs</li> 747</ul> 748 749<h3>User-installable keymaps</h3> 750 751<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> 752 753<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> 754</div> 755 756 757<h2 id="ui">New Ways to Create Beautiful UI</h2> 758 759 760<div style="float:right;margin:22px 0px 0px 24px;width:280px;"> 761<div> 762<!-- <img src="{@docRoot}images/jd-notif-cd.png" style="width:200px"> --> 763<img src="{@docRoot}images/jb-notif-ex1.png" width="280" height="548"> 764</div> 765<p class="image-caption" style="padding:.5em">Developers can create custom notification styles 766like those shown in the examples above to display rich content and actions.</p> 767</div> 768 769<h3>Expandable notifications</h3> 770 771<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> 772 773<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> 774 775<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> 776 777<ul> 778<li>BigTextStyle — a notification that includes a multiline TextView object.</li> 779<li>BigInboxStyle — a notification that shows any kind of list such as messages, headlines, and so on.</li> 780<li>BigPictureStyle — a notification that showcases visual content such as a bitmap.</li> 781</ul> 782 783<p>In addition to the templated styles, you can create your own notification styles <strong>using any remote View</strong>.</p> 784 785<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> 786 787<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> 788 789<div style="float:left;margin:66px 30px 0px 0px;width:280px;"> 790<div> 791<img src="{@docRoot}images/jb-appwidgets.png" width="280" height="548"> 792</div> 793<p class="image-caption" style="padding:.5em"><span 794style="font-weight:500;">App Widgets</span> can resize automatically to fit the home screen and load different content as their sizes change.</p> 795</div> 796 797<div style="padding-top:1px;clear:right;"> 798 799 800<h3>Resizable app widgets</h3> 801 802<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> 803 804<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> 805 806<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> 807 808<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> 809 810</div> 811 812<h3>Simplified task navigation</h3> 813 814<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> 815 816<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> 817 818<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> 819 820<h3>Easy animations for Activity launch</h3> 821 822<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> 823 824<h3>Transitions to Lights Out and Full Screen Modes</h3> 825 826<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> 827 828<h3>New types of remoteable Views</h3> 829 830<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> 831 832<h3>Live wallpaper preview</h3> 833 834<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> 835 836<h3>Higher-resolution contact photos</h3> 837 838<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> 839 840 841<h2 id="input">New Input Types and Capabilities</h2> 842 843<h3>Find out about devices being added and removed</h3> 844 845<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> 846 847<h3>Query the capabilities of input devices</h3> 848 849<p>Android 4.1 includes APIs that let apps and games take full advantage of all input devices that are connected and available.</p> 850 851<p>Apps can query the device manager to enumerate all of the input devices currently attached and learn about the capabilities of each.</p> 852 853<h3>Control vibrator on input devices</h3> 854 855<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> 856 857 858<h2 id="graphics">Animation and Graphics</h2> 859 860<h3>Vsync for apps</h3> 861 862<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> 863 864<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> 865 866<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> 867 868<h3>New animation actions and transition types</h3> 869 870<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> 871 872<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> 873 874<p>A new transition type in LayoutTransition enables you to automate animations in response to all layout changes in a ViewGroup.</p> 875 876 877<h2 id="connectivity">New Types of Connectivity</h2> 878 879<h3>Android Beam</h3> 880 881<p>Android Beam is a popular NFC-based technology that lets users instantly share, just by touching two NFC-enabled phones together.</p> 882 883<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> 884 885<h3>Wi-Fi Network Service Discovery</h3> 886 887<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> 888 889<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> 890 891<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> 892 893<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> 894 895<h3>Wi-Fi Direct Service Discovery</h3> 896 897<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> 898 899<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> 900 901<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> 902 903<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> 904 905<h3>Network Bandwidth Management</h3> 906 907<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> 908 909 910<h2 id="media">New Media Capabilities</h2> 911 912<h3>Media codec access</h3> 913 914<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> 915 916<h3>USB Audio</h3> 917 918<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> 919 920<h3>Audio record triggering</h3> 921 922<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> 923 924<h3>Multichannel audio</h3> 925 926<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> 927 928<p>Android 4.1 also adds built-in support for encoding/decoding AAC 5.1 audio.</p> 929 930<h3>Audio preprocessing</h3> 931 932<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> 933 934<h3>Audio chaining</h3> 935 936<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> 937 938<h3 id="media-router">Media Router</h3> 939 940<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> 941 942<h2 id="renderscript">Renderscript Computation</h2> 943 944<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> 945 946<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> 947 948 949<h2 id="browser">Android Browser and WebView</h2> 950 951<p>In Android 4.1, the Android Browser and WebViews include these enhancements:</p> 952<ul> 953<li>Better HTML5 video user experience, including touch-to-play/pause and smooth transition from inline to full screen mode. </li> 954<li>Improved rendering speed and reduced memory usage for better scrolling and zooming performance.</li> 955<li>Improved HTML5/CSS3/Canvas animation performance.</li> 956<li>Improved text input.</li> 957<li>Updated JavaScript Engine (V8) for better JavaScript performance.</li> 958<li>Support for the updated HTML5 Media Capture specification (the "capture" attribute on input type=file elements).</li> 959</ul> 960 961 962<h2 id="google">Google APIs and services</h2> 963 964<p>To extend the capabilities of Android even further, several new services for Android are available.</p> 965 966<h3 id="gcm">Google Cloud Messaging for Android</h3> 967 968<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> 969 970<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> 971 972<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> 973 974<h3>App Encryption</h3> 975 976<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> 977 978<h3>Smart App Updates</h3> 979 980<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> 981 982<h3 id="gps">Google Play services</h3> 983 984<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> 985 986<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> 987 988<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> 989 990<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> 991 992</div> <!-- END ANDROID 4.1 --> 993 994 995 996 997 998 999