在克隆代码：appium-uiautomator2-server后，按照说明文档 README.md 中所说，进行构建
gradle clean assembleE2ETestDebug assembleE2ETestDebugAndroidTest
出现错误：
FAILURE: Build failed with an exception.
* Where:
Build file '/Users/cmlanche/sourcetree/appium/appium-uiautomator2-server/app/build.gradle' line: 14
* What went wrong:
A problem occurred evaluating project ':app'.
> Failed to apply plugin [id 'com.android.application']
> Minimum supported Gradle version is 4.10.1. Current version is 4.1. If using the gradle wrapper, try editing the distributionUrl in /Users/cmlanche/sourcetree/appium/appium-uiautomator2-server/gradle/wrapper/gradle-wrapper.properties to gradle-4.10.1-all.zip
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
* Get more help at https://help.gradle.org
BUILD FAILED in 1s
错误中说，当前工程最低要求的 gradle 版本是 4.10.1，而当前的版本是 4.1。
当时我并不知道，或者说已经忘记 gradle 是怎么安装的，索性做了两件事：
gradle -v查询当前的版本号，确实显示的是 4.1chengmingdeMacBook-Pro:appium-uiautomator2-server cmlanche$ brew upgrade gradle
Updating Homebrew...
==> Auto-updated Homebrew!
Updated 2 taps (dart-lang/dart and homebrew/core).
==> New Formulae
aliyun-cli breezy embree frpc frps lazygit ospray volt zabbix-cli
==> Updated Formulae
go ✔ direnv grafana mariadb simple-scan
hugo ✔ dita-ot gromacs maxwell smimesign
swagger-codegen ✔ django-completion groonga mesa snapcraft
wget ✔ dnscrypt-proxy gsoap meson snort
ace docfx gssdp metabase sourcekitten
algernon docker gtk+3 micronaut sshguard
ansible docker-completion gupnp mmseqs2 ssllabs-scan
anyenv docker-compose-completion gupnp-av mps-youtube step
apache-arrow docker-credential-helper-ecr gupnp-tools nginx streamlink
apache-arrow-glib doctl hadolint nsd stunnel
apache-flink doitlive haproxy opam svgo
apache-spark dynare hatari open-mpi swiftformat
apr easyengine helmfile openjpeg syncthing
asciidoctor embulk ispc openttd taskell
asdf erlang istioctl pacapt tbb
atlassian-cli ethereum jemalloc paket telegraf
atomist-cli exploitdb jenkins pandoc terraform_landscape
aws-okta faas-cli jenkins-lts pegtl tgui
aws-sdk-cpp ffmpeg jfrog-cli-go php tippecanoe
awscli file-roller jmeter php-code-sniffer tmux
azure-cli fn juju php@7.1 topgrade
binaryen fonttools kafkacat php@7.2 ttfautohint
bitrise freetds kitchen-sync phpunit typescript
cake futhark krakend planck unbound
carthage fx kube-aws pmd ungit
certbot gdcm kubecfg postgis v8
cfssl get_iplayer ledger pre-commit vala
cgal gitbucket libcroco prometheus vert.x
checkstyle gitlab-runner libdazzle prototool vim
citus gjs libnotify pulumi vte3
cmark glib-networking libphonenumber putty wine
collector-sidecar gmic librealsense pyenv wireguard-go
composer gmsh libsoup rakudo-star wireguard-tools
conan gnu-getopt libvirt riff xmake
confluent-oss gnumeric libxlsxwriter rke yle-dl
conjure-up gnunet links rtv youtube-dl
cpprestsdk gnutls lmod ruby-build zabbix
crowdin gobject-introspection logtalk ruby@2.4 zig
cryfs gocr lolcat sbcl zim
dcos-cli godep lumo sdl
dhall gomplate lxc serverless
dhall-json goreleaser mackup ship
==> Deleted Formulae
pdftoedn ruby@2.3
==> Upgrading 1 outdated package:
gradle 4.1 -> 5.3.1
==> Upgrading gradle
==> Downloading https://services.gradle.org/distributions/gradle-5.3.1-all.zip
==> Downloading from https://downloads.gradle.org/distributions/gradle-5.3.1-all.zip
######################################################################## 100.0%
🍺 /usr/local/Cellar/gradle/5.3.1: 13,686 files, 236.8MB, built in 1 minute
Removing: /usr/local/Cellar/gradle/4.1... (169 files, 71.7MB)
升级完后，就可以正常使用gradle命令来打包了:
chengmingdeMacBook-Pro:appium-uiautomator2-server cmlanche$ gradle clean
Welcome to Gradle 5.3.1!
Here are the highlights of this release:
- Feature variants AKA "optional dependencies"
- Type-safe accessors in Kotlin precompiled script plugins
- Gradle Module Metadata 1.0
For more details see https://docs.gradle.org/5.3.1/release-notes.html
Starting a Gradle Daemon (subsequent builds will be faster)
> Configure project :app
NDK is missing a "platforms" directory.
If you are using NDK, verify the ndk.dir is set to a valid NDK directory. It is currently set to /Users/cmlanche/Library/Android/sdk/ndk-bundle.
If you are not using NDK, unset the NDK variable from ANDROID_NDK_HOME or local.properties to remove this warning.
WARNING: Configuration 'compile' is obsolete and has been replaced with 'implementation' and 'api'.
It will be removed at the end of 2018. For more information see: http://d.android.com/r/tools/update-dependency-configurations.html
Deprecated Gradle features were used in this build, making it incompatible with Gradle 6.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/5.3.1/userguide/command_line_interface.html#sec:command_line_warnings
BUILD SUCCESSFUL in 1m 3s
2 actionable tasks: 2 executed
其实，并不是 gradle 这个版本不能用，而是对appium-uiautomator2-server这个工程不能拿用，因为 gradle 版本和谷歌的com.android.tools.build:gradle插件是有个对应关系的，这个 server 工程中使用的是 3.3.2,其最小的 gradle 就是 4.10.1，对应关系链接: https://developer.android.google.cn/studio/releases/gradle-plugin.html#updating-gradle