UIAutomator 2
While the API remains almost the same, the internal implementation has changed and we see the introduction of UIObject2//UIAutomator2简介。
UIObject2
Unlike UiObject, the UIElement is bound to a particular view instance and can become stale if the underlying view object is destroyed. As a result, it may be necessary to call findObject(BySelector) to obtain a new UiObject2 instance if the UI changes significantly.//UIElement基于一个特殊的view实例。
The Build System
UIAutomator 2 utilizes capabilities of Gradle as a build system. Previous, UIAutomator used Maven/Ant.//UIAutomator2使用的构建工具是Gradle，UIAutomator使用的构建工具是Maven/Ant。
Test Assets
Test packages produced are now APKs. Previously, UIAutomator produced .jar or .zip files. This makes UIAutomator 2 completely Android instrumentation capable.//UIAutomator产出.jar或者.zip文件，UIAutomator2产出apk文件。
ADB
ADB deals with UIAutomator 2 slightly differently.
The original version of UiAutomator ran as a shell program://ADB命令有区别。
adb shell uiautomator runtest ...
UiAutomator 2 is based on Android Instrumentation. Tests are compiled to APKs, and run in an application process:
adb shell am instrument ...