方式一：

在gradle.properties中写入：

#测试环境
ENV_TEST=test
#开发环境
ENV_DEV=dev
#生产环境
ENV_ONLINE=online
APPLICATION_ID=com.xxx.xxxx
COMPILE_SDK_VERSION=26
TARGET_SDK_VERSION=26
MIN_SDK_VERSION=15
SUPPORT_V4_SUPPORT=com.android.support:support-v4:26.1.0
SUPPORT_ANNOTATIONS=com.android.support:support-annotations:26.1.0
SUPPORT_V7_APPCOMPAT=com.android.support:appcompat-v7:26.1.0
SUPPORT_V7_RECYCLERVIEW=com.android.support:recyclerview-v7:26.1.0

使用规则，字符串直接用，整形需在后加 as int

android {
compileSdkVersion COMPILE_SDK_VERSION as int
defaultConfig {
applicationId APPLICATION_ID
minSdkVersion MIN_SDK_VERSION as int
targetSdkVersion TARGET_SDK_VERSION as int
versionCode 100
versionName "1.0.0"
multiDexEnabled true
flavorDimensions "versionCode"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}

方式二：

在根目录下的build.gradle文件下添加 buildscript{ .... } 中的内容：

buildscript {
ext.kotlin_version = '1.1.51'
ext.rxandroid = '2.0.1'
ext.anko_version = '0.8.2'
ext.support_version = '26.1.0'
ext.target_sdk_version = 26
ext.min_sdk_version = 15
ext.applicationId = 'com.beiyijinfu.rxbusdemo'
repositories {
google()
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:3.0.0'
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}

使用规则，字符串需使用“$”，整形直接用

android {
compileSdkVersion compile_sdk_version
defaultConfig {
applicationId "com.xxx.xxxx"
minSdkVersion min_sdk_version
targetSdkVersion target_sdk_version
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
implementation "com.android.support:appcompat-v7:$support_version"
implementation "io.reactivex.rxjava2:rxandroid:$rxandroid"
implementation "org.jetbrains.anko:anko-common:$anko_version"
implementation "com.android.support:recyclerview-v7:$support_version"
}

方式三：

在根目录下的build.gradle文件下添加 ext{ .... } 中的内容：

ext{
kotlin_version = '1.1.51'
rxandroid = '2.0.1'
anko_version = '0.8.2'
support_version = '26.1.0'
target_sdk_version = 26
compile_sdk_version = 26
min_sdk_version = 15
}

使用规则，字符串需使用“$rootProject.”，整形直接用rootProject.。ext可加可不加

android {
compileSdkVersion rootProject.compile_sdk_version
defaultConfig {
applicationId "com.xxx.xxxx"
minSdkVersion rootProject.ext.min_sdk_version
targetSdkVersion rootProject.ext.target_sdk_version
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$rootProject.ext.kotlin_version"
implementation "com.android.support:appcompat-v7:$rootProject.support_version"
implementation "io.reactivex.rxjava2:rxandroid:$rootProject.rxandroid"
compile "org.jetbrains.anko:anko-common:$rootProject.anko_version"
compile "com.android.support:recyclerview-v7:$rootProject.support_version"
}

方式四：

在项目根目录下创建.gradle文件，如：config.gradle，config.gradle中文件内容可以自己定义，如下示例：

ext{
kotlin_version = '1.1.51'
rxandroid = '2.0.1'
anko_version = '0.8.2'
support_version = '26.1.0'
target_sdk_version = 26
compile_sdk_version = 26
min_sdk_version = 15
}

使用规则，在build.gradle中先引用进来：

 apply from :"config.gradle"

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile "com.android.support:cardview-v7:${support_version }"
compile "com.android.support:appcompat-v7:${support_version }"
compile "com.android.support:design:${support_version }"
}