一些 build.gradle 文件的语法与其他文件不同？

Question

Started a new job and I can see that the build.gradle files's syntax is a bit different like the one using a = to assign values and the other just without it. Fx. the Google Sunflower demo app has it's implemetation statements without parentheses and my project uses parentheses and will not work otherwise.

I'd like to have all add-on versions in one place as I'm used to, and as it's of-course in the Sunflower app:

ext {
    appCompatVersion = '1.1.0'
    ...
}

but that fails in my project

What is going on?

Answer 1

Gradle is a build automation tool, which can be written in several languages, more importantly when it comes to Android Studio, Gradle files tend to be either written in Gradle's own Groovy DSL language which is heavily based on Apache Groovy's language, which is usually referred to in documentations as just Groovy, or they can be written in Kotlin DSL, which is based on its parent namesake Kotlin language, Gradle's Kotlin DSL support was announced in 2016 which is why you might find legacy projects using Groovy, while others are using Kotlin DSL.

You can tell the difference between Groovy Gradle files and Kotlin DSL Gradle files by looking at the file extension, a settings.gradle is a Groovy script and settings.gradle.kt is a Kotlin DSL script.

Note that Gradle supports interoperability between Groovy and Kotlin DSL files, meaning that, while a settings.gradle must be written in Groovy and a build.gradle.kt must be written in Kotlin DSL, it's OK to have a project that have both settings.gradle and build.gradle.kt , Gradle is smart enough to make them understand each other, although for the sake of consistency, I would recommend sticking with one DSL language for all your Gradle files.

By default when you create an Android project for the first time, the Gradle files generated for you are in Groovy.

For much, much more thorough details on the differences between the two syntaxes I highly recommend reading the Gradle docs, this page in particular which goes into migrating from Groovy to Kotlin DSL , starting from the "Prepare your Groovy scripts" section. It's handy to have it on your side whenever you're copy/pasting a Gradle fix from Stackoverflow which is written in a Gradle syntax that doesn't correspond to your Gradle file extension, although eventually you'll probably end up memorizing the little differences yourself.

Answer 2

Don't confuse build.gradle (Groovy) with build.gradle.kts (Kotlin).