谷歌今天推出了首个Android P开发者预览版（也就是所谓的安卓9.0），现在可以在developer.android.com上下载。预览包括一个更新的SDK，包含Pixel，Pixel XL，Pixel 2，Pixel 2 XL和官方Android模拟器的系统映像。与去年不同，在Android P上没有用于测试Android Wear的模拟器。

Google已经连续第三年在其I / O开发者大会前的几个月发布了第一个Android主要版本的开发者预览版。 Android N（后称Android Nougat）和Android O（后称Android Oreo）的首次开发者预览分别于2016年3月和2017年3月抵达。去年，谷歌没有通过Android Beta计划发布第一个开发者预览版，通过它可以通过选定设备上的无线更新获得早期的Android版本。这与Android P保持一致 – Google仅通过手动下载和Flash进行第一次预览，强调仅供开发人员使用，不适用于日常或消费者使用。

除此之外，适用相同的规则。 这是Android的下一个版本的早期版本，Android被称为Android P，直到Google选择以该字母开头的名称。

第一次预览的目标是让开发人员尽早使用该版本，以便他们可以探索应用程序的新功能和API，测试兼容性并提供反馈，然后在5月8日至5月的I / O 2018共享更多详细信息 10.随后的开发人员预览版中将发布更多新功能和功能，并最终将通过Android Beta计划进行注册。

预览时间表如下：

3月：预览版1（初始版本，alpha）
5月：预览2（增量更新，测试版）
6月：预览版3（最终API和官方SDK，Play发布，测试版）
6月：预览版4（测试发布候选版）
7月：预览版5（发布候选版，用于最终测试）
Q3：AOSP和生态系统的最终版本

如果您想要简短版本，以下是第一个Android P开发人员预览的亮点：内置支持显示剪切（读取：凹槽），调整后的快速设置面板，带圆角的通知抽屉，内嵌回复时的通知消息 ，通知中的智能回复，用于指纹验证的一致UI以及用于限制应用程序在后台可以执行的隐私增强功能。

仍然不满意？ 以下是所有新API和功能的更长版本（还有更多内容，毕竟这只是第一次预览版）：

显示剪切支持：应用程序现在可充分利用全屏幕内容和API的最新设备屏幕，让您管理您的内容显示方式，包括检查剪切形状并请求周围的全屏布局。甚至有一个开发人员选项可以模拟任何设备上的切口。
HDR VP9视频，HEIF图像压缩和媒体API：Android P增加了对HDR VP9 Profile 2的内置支持，因此您可以在支持HDR的设备上从YouTube，Play电影和其他来源为用户提供支持HDR的电影。 HEIF（heic）图像编码已添加到平台，使您可以轻松发送和利用来自后端服务器的HEIF图像。媒体API也正在增强和重构，以便于开发和整合 – 细节将在今年晚些时候发布。
多摄像头API：您现在可以同时从两个或更多物理摄像头访问流。该API还允许您调用逻辑或融合的相机流，以便在两台或更多台相机之间自动切换。相机的其他改进包括新的会话参数，有助于减少初始捕捉期间的延迟，表面共享可让相机客户端处理各种使用情况而无需停止和启动相机流，以及用于基于显示器的闪光灯支持和访问OIS的API时间戳用于应用级图像稳定和特殊效果。
用于位图和可绘制的ImageDecoder：ImageDecoder（弃用BitmapFactory）允许您从字节缓冲区，文件或URI创建位图或绘图。它比BitmapFactory提供了几个优势，包括对精确缩放，对硬件存储器的单步解码，对解码后处理的支持以及对动画图像的解码。
改进的消息通知：新的MessagingStyle通知样式突出显示了谁正在发送消息以及如何回复。你可以显示对话，附上照片和贴纸，甚至建议聪明的回复。
JobScheduler中的数据成本敏感度：JobScheduler现在可以更好地为用户处理与网络相关的作业，并与运营商分别提供的网络状态信号进行协调。作业可以声明其估计的数据大小，信号预取以及指定详细的网络要求。运营商可以将网络报告为拥塞或未计量，然后JobScheduler根据网络状态管理工作。
使用Wi-Fi RTT的室内定位：支持IEEE 802.11mc WiFi协议的平台 – 也称为WiFi往返时间（RTT） – 可让您利用应用中的室内定位。因此，应用程序可以使用RTT API来测量到附近WiFi接入点（AP）的距离。知道与三个或更多AP的距离，可以使用1到2米的精度计算设备位置。

神经网络API 1.1：支持九个新的操作 – Pad，BatchToSpaceND，SpaceToBatchND，移调，Stripping Slice，Mean，Div，Sub和Squeeze。如果您拥有Pixel 2设备，您将获得Qualcomm Hexagon HVX驱动程序，并为量化模型加速。
自动填充改进：允许密码管理员改进Autofill用户体验的新API，如更好的数据集过滤，输入清理和兼容模式。
开放移动API用于NFC支付和安全交易：应用可以使用OMAPI API访问安全元素（SE），以启用智能卡支付和其他安全服务。硬件抽象层（HAL）提供了用于枚举各种安全元素（eSE，UICC和其他）的基础API。
ART性能：ART对执行配置文件的使用已扩展为优化应用程序并减少已编译应用程序代码的内存占用量。 ART现在使用配置文件信息进行设备上的DEX文件重写，在一系列流行的应用程序中减少了高达11％。
优化的Kotlin：改进了几种编译器优化，特别是那些针对循环的编译器优化，以提取更好的性能。 Google还在与JetBrains合作优化Kotlin生成的代码。
电源效率：瞌睡，应用待机和背景限制已经完善，可进一步延长电池寿命。
针对现代Android：Google Play将需要所有应用更新于2018年11月之前针对Android Oreo（targetSdkVersion 26或更高版本），支持2019年地平线上的64位硬件。Android P将在安装应用程序的目标平台早于Android 4.2（targetSdkVersion小于17），未来的平台版本将继续增加该下限。
通过公共API提高应用程序兼容性：Google开始通过要求开发者使用公共等价物来限制对选定的非SDK界面的访问。
应用程序安全性：跨应用程序和设备进行指纹认证的更一致的用户界面。 Android现在提供了一个标准系统对话框，以提示用户触摸指纹传感器，根据设备管理文本和位置。应用程序可以使用新的FingerprintDialog API触发系统指纹对话框。 Google还在更改Network Security Configuration的默认设置以阻止所有明文流量。
用户隐私：从空闲应用程序访问麦克风，摄像头和所有SensorManager传感器将受到限制。当您的应用程序的UID空闲时，麦克风会报告空音频和传感器停止报告事件。应用程序使用的摄像头断开连接，如果应用程序试图使用它们，则会产生错误。谷歌还将通过客户端秘密启用对Android备份的加密。

谷歌正在要求开发人员将他们的应用与Android P兼容，以便他们的用户在升级时能够实现无缝过渡。 如果你发现任何错误，你可以在这里举报。

英文：

Google today launched the first Android P developer preview, available for download now at developer.android.com. The preview includes an updated SDK with system images for the Pixel, Pixel XL, Pixel 2, Pixel 2 XL, and the official Android Emulator. Unlike last year, there is no emulator for testing Android Wear on Android P.

This is the third year running that Google has released the first developer preview of the next major Android version months before its I/O developer conference. The first developer previews of Android N (later named Android Nougat) and Android O (later named Android Oreo) arrived in March 2016 and March 2017, respectively. Last year, Google did not release the first developer preview via the Android Beta Program, which lets you get early Android builds via over-their-air updates on select devices. This stays the same with Android P — Google is making the first preview available solely by manual download and flash to emphasize it is for developers only and not intended for daily or consumer use.

Other than that, the same rules apply. This is an early look at the next version of Android, which is being referred to as Android P until Google picks a name starting with that letter.

The goal of the first preview is to let developers play with the build early so they can explore new features and APIs for apps, test for compatibility, and give feedback before more details are shared at I/O 2018, scheduled for May 8 to May 10. More new features and capabilities will be released in subsequent developer previews, and eventually enrollments will be taken through the Android Beta Program.

The preview schedule is as follows:

• March: Preview 1 (initial release, alpha)
• May: Preview 2 (incremental update, beta)
• June: Preview 3 (final APIs and official SDK, Play publishing, beta)
• June: Preview 4 (release candidate for testing)
• July: Preview 5 (release candidate for final testing)
• Q3: Final release to AOSP and ecosystem

If you want the short version, here are the highlights for the first Android P developer preview: built-in support for display cutouts (read: notches), a tweaked Quick Settings panel, notification drawer with rounded corners, messages in notifications when replying inline, smart replies in notifications, a consistent UI for fingerprint authentication, and privacy enhancements to limit what apps can do in the background.

Still not satisfied? Here is the longer version of all the new APIs and features (and there is more to come; this is just the first preview, after all):

• Display cutout support: Apps can now take full advantage of the latest device screens with full-screen content and APIs let you manage how your content is displayed, including checking the cutout shape and requesting full-screen layout around it. There’s even a developer option that simulates a cutout on any device.
• HDR VP9 Video, HEIF image compression, and Media APIs: Android P adds built-in support for HDR VP9 Profile 2, so you can deliver HDR-enabled movies to your users from YouTube, Play Movies, and other sources on HDR-capable devices. HEIF (heic) images encoding has been added to the platform, making it easy to send and utilize HEIF images from your backend server. The media APIs are also being enhanced and refactored to make them easier to develop and integrate with — details are coming later this year.
• Multi-camera API: You can now access streams simultaneously from two or more physical cameras. The API also lets you call a logical or fused camera stream that automatically switches between two or more cameras. Other improvements in camera include new Session parameters that help to reduce delays during initial capture, Surface sharing that lets camera clients handle various use-cases without the need to stop and start camera streaming, and APIs for display-based flash support and access to OIS timestamps for app-level image stabilization and special effects.
• ImageDecoder for bitmaps and drawables: ImageDecoder, which deprecates BitmapFactory, lets you create a bitmap or drawable from a byte buffer, file, or URI. It offers several advantages over BitmapFactory, including support for exact scaling, single-step decoding to hardware memory, support for post-processing in decode, and decoding of animated images.
• Improved messaging notifications: The new MessagingStyle notification style highlights who is messaging and how you can reply. You can show conversations, attach photos and stickers, and even suggest smart replies.
• Data cost sensitivity in JobScheduler: JobScheduler now handles network-related jobs better for the user, coordinating with network status signals provided separately by carriers. Jobs can declare their estimated data size, signal prefetching, and specify detailed network requirements. Carriers can report networks as being congested or unmetered and JobScheduler then manages work according to the network status.
• Indoor positioning with Wi-Fi RTT: Platform support for the IEEE 802.11mc WiFi protocol — also known as WiFi Round-Trip-Time (RTT) — lets you take advantage of indoor positioning in your apps. Apps can thus use RTT APIs to measure the distance to nearby WiFi Access Points (APs). Knowing the distance to three or more APs lets you calculate the device position with an accuracy of 1 to 2 meters.
• Neural Networks API 1.1: Support for nine new ops — Pad, BatchToSpaceND, SpaceToBatchND, Transpose, Strided Slice, Mean, Div, Sub, and Squeeze. If you have a Pixel 2 device, you’ll get a Qualcomm Hexagon HVX driver with acceleration for quantized models.
• Autofill improvements: New APIs that allow password managers to improve the Autofill user experience, such as better dataset filtering, input sanitization, and compatibility mode.
• Open Mobile API for NFC payments and secure transactions: Apps can use the OMAPI API to access secure elements (SE) to enable smart-card payments and other secure services. A hardware abstraction layer (HAL) provides the underlying API for enumerating a variety of Secure Elements (eSE, UICC, and others).
• ART performance: ART’s use of execution profiles has been expanded to optimize apps and reduce in-memory footprint of compiled app code. ART now uses profile information for on-device rewriting of DEX files, with reductions up to 11 percent across a range of popular apps.
• Optimized Kotlin: Improved several compiler optimizations, especially those that target loops, to extract better performance. Google is also working with JetBrains to optimize Kotlin’s generated code.
• Power efficiency: Doze, App Standby, and Background Limits have been refined to further improve battery life.
• Targeting modern Android: Google Play will require all app updates to target Android Oreo (targetSdkVersion 26 or higher) by November 2018, with support for 64-bit hardware on the horizon for 2019. Android P will warn users with a dialog when they install an app that targets a platform earlier than Android 4.2 (targetSdkVersion less than 17), and future platform versions will continue to increment that lower bound.
• Improving app compatibility through public APIs: Google is starting to restrict access to selected non-SDK interfaces by asking developers to use the public equivalents instead.
• Security for apps: A more consistent UI for fingerprint authentication across apps and devices. Android now provides a standard system dialog to prompt the user to touch the fingerprint sensor, managing text and placement as appropriate for the device. Apps can trigger the system fingerprint dialog using a new FingerprintDialog API. Google is also changing the defaults for Network Security Configuration to block all cleartext traffic.
• Privacy for users: Access to microphone, camera, and all SensorManager sensors from apps that are idle will be restricted. While your app’s UID is idle, the microphone reports empty audio and sensors stop reporting events. Cameras used by your app are disconnected and will generate an error if the app tries to use them. Google will also enable encryption of Android backups with a client-side secret.

Google is asking developers to make their app compatible with Android P so that their users can expect a seamless transition when they upgrade. If you find any bugs, you can report them here.

由软慧人工智能AI编译自：venturebeat