报错：Caused by: org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Cannot verify the signature of ‘/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/appium-uiautomator2-server/apks/appium-uiautomator2-server-v4.21.1.apk’. Original error: Error: A JNI error has occurred, please check your installation and try again
Exception in thread “main” java.lang.UnsupportedClassVersionError: com/android/apksigner/ApkSignerTool has been compiled by a more recent version of the Java Runtime (class file version 53.0), this version of the Java Runtime only recognizes class file versions up to 52.0

原因：安装android sdk时bulid-tools版本30以上和jdk1.8的不匹配，所以需要将bulid-tools版本降为30以下的

安装Android Studio开发工具，在该工具里安装android sdk,降低版本的方法：

步骤1：

启动Android Studio，点击Configrue

步骤2，选择SDK Manager

步骤3：选择SDK Tools 选择build-tools勾选Show Package detill

步骤4：选择自己需要的版本