Google I/O 2021 Android精华内容

上山打老虎

　　Google I/O 2021结束了, 都有什么精彩内容呢?
Android部分的Playlist附上: Android & Play at Google I/O 2021
Developer Keynote (Google I/O '21)
　　对于Android的部分来说, 主要是:
Android 12

• user safety.
  
• performance; improved app startup; customizable launch animations.
  
• user experience; widgets.
  

Create beautiful apps, easier
　　现代化的Android开发.

• Android Studio的升级.
  
• Kotlin: Kotlin Symbol Processing.
  
• Jetpack: 各种libraries和Compose.
  

Build across screens.

• 各种屏幕.
  
• Voice.
  
• Watches: Health services.
  

The top 3 things to know in Modern Android Development | Android @ Google I/O'21
　　Android开发的三个top topic:

• Jetpack: 一系列的Jetpack libraries发布了新版.
  

• Tooling: Android Studio的升级, 有了WorkManager Inspector, UI的Inspector支持了View和Compose.
  
• Kotlin.
  

What's new in Android | Keynote
　　Android 12 -> S.

• @Deprecated -> deprecated.
  
• Color.
  
• Widgets.
  
• Launch animations: 系统自带启动动画, 可以定制.
  
• Notifications: 新的template style; Trampoline(?) 优化点开notification的那个短暂延迟.
  
• Toasts: 带icon, 说明是哪个app弹的toasts; 控制个数.
  
• Picture in Picture的改善.
  
• ImageView有个setRenderEffect可以模糊照片了.
  
• 可以用theme定制模糊.
  

• list的弹力拉伸效果. (我自己起的名字, 其实人家叫stretch overscroll).
  
• Graphics: AVIF. 可以过滤支持的media类型.
  
• Privacy: 关于permission的一些改进; 剪贴板内容会有toast说明来源; foreground restrictions.
  

What’s new in Android development tools | Session
　　Android Studio版本号设计.

• Preview工具可以设置横屏, 定制尺寸, 显示blueprints, play animation. Compose的preview有交互模式.
  
• Accessibility test framework scanner.
  
• 适配多种屏幕: Layout validation.
  
• 折叠屏, 手表.
  
• 模拟器还可以模拟heart rate.
  
• snapshots test.
  
• WorkManager的tasks.
  
• Migrate to Non-Transitive R Classes...
  

What’s new in Jetpack | Session
　　解释了Jetpack的初衷和现状.
alpha和beta版本的意思.

• Experimental Annotations -> Stable.
  
• CameraX -> Stable.
  
• AppSearch -> Alpha.
  
• DataStore -> 用来取代SharedPreferences.
  

• Security Crypto -> Stable.
  
• Hilt -> Stable.
  
• WorkManager -> Stable. (Android Studio也推出了新的WorkManager Inspector.)
  
• Room -> Stable.
  

• ConstraintLayout -> Stable. MotionLayout + Motion Editor.
  
• Fragment -> Stable.
  (详见release notes: https://developer.android.com/jetpack/androidx/releases/fragment.)
  重建了FragmentManager; 新增了get result的callback; 废弃了一些API, 并且Fragment StrictMode可以检测项目中是否还在使用.
  
• Navigation -> Alpha. 现在支持多个backstacks.
  
• Google Shortcuts -> Alpha.
  
• EmojiCompat -> Alpha. (AppCompat 1.4.0以后默认包含.)
  
• Paging -> Stable.
  
• Macrobenchmark -> Alpha. (app启动和滚动效率; local/CI.)
  
• Compose integrations.
  

What's new in Jetpack Compose | Session
　　为什么我们需要一个全新的UI Toolkit呢. -> 为了适应更加现代化的开发方式.
　　faster & easier.
　　Compose将数据转换成UI.
　　Checkbox的例子:

UI完全由参数控制. -> single source of truth. 没有其他的状态需要sync.

　　把参数和回调提到方法参数中去:

• You completely describe your UI for a given state.
  
• The framework updates your UI when the state changes.
  

　　这里有个图, 推荐ViewModel暴露一个Screen状态, 集中管理, 然后下发到每个composable.

　　这样也利于测试.
　　Compose实现了material design, 提供了组件, 还有theming system.
　　有一个owl app的实现解说.
　　和传统view的interop.

State of Kotlin on Android | Session

• Kotlin变得越来越流行, 不仅app, 还有server.
  
• Kotlin Symbol Processing目前发布了alpha.
  
• 编译器的升级.
  
• 好多好多的ktx库.
  
• protobuf的支持: https://developers.google.com/protocol-buffers/docs/kotlintutorial
  
• coroutines的debugger -> coming soon. 可以在线程之间跳转, 查看信息.
  

What’s new in Android Gradle plugin | Session
　　New APIs in the Android Gradle Plugin
Using Jetpack libraries in Compose | Session
　　Jetpack Compose和Jetpack中其他库可以很好的结合使用.

Top 12 tips to get ready for Android 12 | Session
　　Getting Ready for Android 12.

• Developer Options -> App Compatibility Changes.
  
• Foreground services were designed for multi-tasking and completing a user action. -> 从后台启动foreground services将被限制.
  
• Expedited Jobs with WorkManager APIs.
  
• User may turn off the mic and camera sensors using mic and camera toggles.
  
• Apps that have not been used for an extended period will be hibernated. (permissions, storage, services)
  
• Nearby device permission. Decouple Bluetooth scanning from Location.
  
• MAC address restriction.
  
• Safe component exporting. 有intent filter就必须显式声明exported.
  
• Custom notifications deprecation.
  
• App link improvements.
  
• WebView Samesite.
  
• New stretch overscroll.