build.gradle配置变量，在Activity中使用

apply plugin: 'com.android.application'
apply from: rootProject.file('gradle/signing.gradle')
apply plugin: 'android-checkstyle'
apply plugin: 'android-pmd'

android {
...

buildTypes {
debug {
signingConfig signingConfigs.debug
applicationIdSuffix ".debug"
buildConfigField "boolean", "SHOW_GREETINGS", "Boolean.parseBoolean(\"true\")"
buildConfigField "String", "GREETINGS", "\"Greetings, My Lord !!!\""
}
release {
signingConfig signingConfigs.releaseKeystore
buildConfigField "boolean", "SHOW_GREETINGS", "Boolean.parseBoolean(\"false\")"
buildConfigField "String", "GREETINGS", "\"Hello, World !!!\""
}
}

...
}

boolean isShowGreetings = BuildConfig.SHOW_GREETINGS;