为Android Studio编写自定义Gradle插件的教程

Google已经建议Android开发全部转向Android Studio开发，Android Studio 是使用gradle编译、打包的，那么问题来了，gradle可是有一堆东西...，为了彻底了解gradle，今天就来学习下如何写自己的gradle插件（当然插件源码是使用groovy写的），先看如下代码目录：

如上图所示，plugin目录是插件源码目录，sample是用来测试插件的。

1、在目录plugin/src/main/groovy/com/micky/gradle/下新建插件类MyCustomPlugin.groovy

package com.micky.gradle; 

import org.gradle.api.*; 

class MyCustomPlugin implements Plugin<Project> {
  void apply(Project project) {
    project.task('myTask') << {
      println "Hi this is micky's plugin"
    }
  }
}

看看Plugin的源码，其实就是一接口

public interface Plugin<T> {
  /**
   * Apply this plugin to the given target object.
   *
   * @param target The target object
   */
  void apply(T target);
}

2、在目录plugin/src/main/resources/META-INF/gradle-plugins/下创建文件com.micky.mycustom.properties用来指定插件实现类

implementation-class=com.micky.gradle.MyCustomPlugin

特别注意下：文件名“com.micky.mycustom”即是以后我们在使用插件时的apply plugin 'java' 的java，这里我也是折腾了半天才得出的结果，坑啊。

3、一般情况下，我们还需要指定插件项目名称，在plugin目录下新建settings.gradle

rootProject.name='gradle-micky'

4、万事具备，就差编译了，编译需要在plugin目录下新建build.gradle

apply plugin: 'groovy'
apply plugin: 'maven' 

dependencies {
  compile gradleApi()
  compile localGroovy()
} 

repositories {
  mavenCentral()
} 

group='com.micky'
version='1.0.0' 

uploadArchives {
  repositories {
    mavenDeployer {
      repository(url: uri('../repo'))
    }
  }
}

在这个脚本里使用groovy插件编译groovy源码，声明gradleAPI作为即时编译依赖，apply plugin: 'maven' 是用来创建一个插件jar文件并且存储在本地maven库里，本地maven库即我们在脚本里创建的"../repo"目录
执行命令:

gradle uploadArchives

5、以上4个步骤已经编译插件并上传到了本地库中，接下来就看看怎么使用插件，在sample目录下，新建build.gradle

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.0'
  }
} 

apply plugin: 'com.micky.mycustom'

6、执行命令

myTask即我们在MyCustomPlugin.groovy代码中创建的任务。

7、自定义Task

（1）copy一份改名CustomPluginTask

在plugin\src\main\groovy\com\micky\gradle目录创建源文件 MyCustomTask.groovy

package com.micky.gradle; 

import org.gradle.api.DefaultTask
import org.gradle.api.tasks.TaskAction 

class MyCustomTask extends DefaultTask {
  @TaskAction
  void output() {
    println "Hello this is my custom task output"
  }
}

（2）修改MyCustomPlugin.groovy

package com.micky.gradle; 

import org.gradle.api.*; 

class MyCustomPlugin implements Plugin<Project> {
  void apply(Project project) {
    project.task('customTask', type: MyCustomTask)
  }
}

（3）修改plugin目录下的build.gradle，修改版本号

apply plugin: 'groovy'
apply plugin: 'maven' 

dependencies {
  compile gradleApi()
  compile localGroovy()
} 

repositories {
  mavenCentral()
} 

group='com.micky'
version='1.0.1' 

uploadArchives {
  repositories {
    mavenDeployer {
      repository(url: uri('../repo'))
    }
  }
}

执行gradle uploadArchives 编译插件包
        
（4）sample目录下的build.gradle

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.1'
  }
}
apply plugin: 'com.micky.mycustom' 

执行gradle customTask 结果如下：

8、向Plugin Task 传递参数
（1）拷贝一份上面的代码，改名为CustomPluginTaskWithParam，修改plugin\src\main\groovy\com\micky\gradle\MyCustomPlugin.groovy

package com.micky.gradle; 

import org.gradle.api.*; 

class MyCustomPluginExtension {
  def message = "From MyCustomPluginExtention"
  def sender = "MyCustomPluin"
} 

class MyCustomPlugin implements Plugin<Project> {
  void apply(Project project) {
    project.extensions.create('myArgs', MyCustomPluginExtension)
    project.task('customTask', type: MyCustomTask)
  }
}

（2）修改plugin\src\main\groovy\com\micky\gradle\MyCustomTask.groovy

package com.micky.gradle; 

import org.gradle.api.DefaultTask
import org.gradle.api.tasks.TaskAction 

class MyCustomTask extends DefaultTask {
  @TaskAction
  void output() {
    println "Sender is ${project.myArgs.sender},\nmessage: ${project.myArgs.message}"
  }
}

（3）修改plugin/build.gradle

apply plugin: 'groovy'
apply plugin: 'maven' 

dependencies {
  compile gradleApi()
  compile localGroovy()
} 

repositories {
  mavenCentral()
} 

group='com.micky'
version='1.0.2' 

uploadArchives {
  repositories {
    mavenDeployer {
      repository(url: uri('../repo'))
    }
  }
}

执行gradle uploadArchives 编译插件包

（4）修改sample/build.gradle

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.2'
  }
} 

apply plugin: 'com.micky.mycustom'

（5）执行gradle customTask，结果如下：

（6）在gradle文件配置参数

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.2'
  }
} 

apply plugin: 'com.micky.mycustom' 

myArgs {
  sender='Micky Liu'
  message='Gradle is so simple.'
}

（7）执行gradle customTask，结果如下：

8、向Plugin Task 传递嵌套试复杂参数
（1）拷贝一份上面的代码，改名为CustomPluginTaskWithNestParam，修改plugin\src\main\groovy\com\micky\gradle\MyCustomPlugin.groovy

package com.micky.gradle; 

import org.gradle.api.*; 

class MyNestPluginExtension {
  def receiver = "Kate Zhou"
  def email = "KateZhou@gmail.com"
} 

class MyCustomPluginExtension {
  def message = "From MyCustomPluginExtention"
  def sender = "MyCustomPluin"
} 

class MyCustomPlugin implements Plugin<Project> {
  void apply(Project project) {
    project.extensions.create('myArgs', MyCustomPluginExtension)
    project.myArgs.extensions.create('nestArgs', MyNestPluginExtension)
    project.task('customTask', type: MyCustomTask)
  }
}

（2）修改MyCustomPlugin.groovy

package com.micky.gradle; 

import org.gradle.api.DefaultTask
import org.gradle.api.tasks.TaskAction 

class MyCustomTask extends DefaultTask {
  @TaskAction
  void output() {
    println "Sender is ${project.myArgs.sender} \nmessage: ${project.myArgs.message}"
    println "Receiver is ${project.myArgs.nestArgs.receiver} \nemail: ${project.myArgs.nestArgs.email}"
  }
} 

（3）修改plugin/build.gradle

apply plugin: 'groovy'
apply plugin: 'maven' 

dependencies {
  compile gradleApi()
  compile localGroovy()
} 

repositories {
  mavenCentral()
} 

group='com.micky'
version='1.0.3' 

uploadArchives {
  repositories {
    mavenDeployer {
      repository(url: uri('../repo'))
    }
  }
}

（4）执行gradle uploadArchives 编译插件包
（5）修改sample/build.gradle

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.3'
  }
} 

apply plugin: 'com.micky.mycustom' 

myArgs {
  sender='Micky Liu'
  message='Gradle is so simple.'
}

（6）执行执行gradle customTask，结果如下：

（7）在gradle文件配置参数

buildscript {
  repositories {
    maven {
      url uri('../repo')
    }
  } 

  dependencies {
    classpath group: 'com.micky',
      name: 'gradle-micky',
      version: '1.0.3'
  }
} 

apply plugin: 'com.micky.mycustom' 

myArgs {
  sender='Micky Liu'
  message='Gradle is so simple.'
  nestArgs {
    receiver='David Chen'
    email='David@126.com'
  } 

}

（8）执行gradle customTask，结果如下：

源码地址：https://github.com/mickyliu945/GradleCustomPlugin