Android 中 Gradle 调用过程

在 Android 开发中，我们经常接触 gradle 文件，例如：settings.gradle、build.gradle 等等，那么新建一个项目，他们之间的先后顺序是什么呢？

What？为什么要知道这个呢，直接调用它不香吗？

香是香，但是 当你需要做一些配置的时候，比如资源配置、预处理等操作的时候，该添加到什么位置呢？只有搞清楚了调用流程，才能在正确的地方添加操作。

接下来以一个新建项目为例：

新建一个 Android 项目目录如下：

├── app
│   ├── libs
│   ├── src
│   ├── build.gradle
│   └── proguard-rules.pro
├── build
├── gradle
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── config.gradle
├── build.gradle
├── gradle.properties
├── gradlew
├── gradlew.bat
├── local.properties
└── settings.gradle

其中 config.gradle 是基础配置，统一管理依赖项，整个项目中，存在 4 个 gradle 文件，它们分别是：

1. app/build.gradle：对 app 模块所需配置信息进行管理；
2. config.gradle：对依赖配置版本信息进行统一管理；
3. build.gradle：项目根配置文件；
4. settings.gradle：配置、管理项目模块信息；

对以上 4 个文件进行日志信息输出处理：

app/build.gradle

android {
    println("app --> build.gradle --> android")
    ...

    defaultConfig {
        println("app --> build.gradle --> defaultConfig")
        ...
        println("app --> build.gradle --> defaultConfig out")
    }

    buildTypes {
        println("app --> build.gradle --> buildTypes")
        debug {
            println("app --> build.gradle --> debug")
            println("app --> build.gradle --> debug out")
        }
        release {
            println("app --> build.gradle --> release")
            ...
            println("app --> build.gradle --> release out")
        }
        println("app --> build.gradle --> buildTypes out")
    }
    compileOptions {
        println("app --> build.gradle --> compileOptions")
        ...
        println("app --> build.gradle --> compileOptions out")
    }
    kotlinOptions {
        println("app --> build.gradle --> kotlinOptions")
        ...
        println("app --> build.gradle --> kotlinOptions out")
    }
    println("app --> build.gradle --> android out")
}

dependencies {
    println("app --> build.gradle --> dependencies")
    ...
    println("app --> build.gradle --> dependencies out")
}

config.gradle

allprojects {
    println("config.gradle --> allprojects")
    repositories {
        println("config.gradle --> repositories")
        ...
        println("config.gradle --> repositories out")
    }
    println("config.gradle --> allprojects out")
}

task clean(type: Delete) {
    println("config.gradle --> clean")
    ...
    println("config.gradle --> clean out")
}

ext.deps = [
        ...
]

build.gradle

    buildscript {
    println("build.gradle --> buildscript")
    ...
    repositories {
        println("build.gradle --> repositories")
        ...
        println("build.gradle --> repositories out")
    }
    dependencies {
        println("build.gradle --> dependencies")
        ..
        println("build.gradle --> dependencies out")
    }
    println("build.gradle --> buildscript out")
}

settings.gradle

    println("settings.gradle --> start")
    ...
    println("settings.gradle --> end")

build 项目之后，日志输出信息如下：

Starting Gradle Daemon...
Gradle Daemon started in 953 ms
settings.gradle --> start
settings.gradle --> end

> Configure project :
build.gradle --> buildscript
build.gradle --> repositories
build.gradle --> repositories out
build.gradle --> dependencies
build.gradle --> dependencies out
build.gradle --> buildscript out
config.gradle --> allprojects
config.gradle --> repositories
config.gradle --> repositories out
config.gradle --> allprojects out
config.gradle --> allprojects
config.gradle --> repositories
config.gradle --> repositories out
config.gradle --> allprojects out
config.gradle --> clean
config.gradle --> clean out

> Configure project :app
app --> build.gradle --> android
app --> build.gradle --> defaultConfig
app --> build.gradle --> defaultConfig out
app --> build.gradle --> buildTypes
app --> build.gradle --> debug
app --> build.gradle --> debug out
app --> build.gradle --> release
app --> build.gradle --> release out
app --> build.gradle --> buildTypes out
app --> build.gradle --> compileOptions
app --> build.gradle --> compileOptions out
app --> build.gradle --> kotlinOptions
app --> build.gradle --> kotlinOptions out
app --> build.gradle --> android out
app --> build.gradle --> dependencies
app --> build.gradle --> dependencies out

由此可知，执行顺序如下：settings.gradle --> build.gradle --> config.gradle --> app/build.gradle ，在配置 config 信息时，要注意其实效性在 build.gradle 之后，可以避免很多不必要的错误。

最后，项目地址信息 KotlinStudy，欢迎交流学习。