在Android开发过程中，偶尔需要自己写一些脚本来优化构建步骤。比如修改版本号，生成JAR包等。

1. 关于task的Action与configuration的区别

gradle中任务执行一般分为三个阶段，分别是初始化，配置，和执行阶段。比如下面的一个脚本:

ext.employee = 'Miss Wang'
task greet(group:'android-developer', description:'i am new to android world.') {        
     logger.quiet "task config start!"    
     employee='Donald Trump'   
     logger.quiet "task config finished!"   

    doLast {       
         logger.quiet "task running"        
         println "hello, " + employee    
    }
}

doLast部分就是任务greet的Action部分，而doLast外面的，就是任务greet的配置部分。配置部分先于执行部分执行。

2. 实例:从配置文件中读取版本号

ext.versionFile = file('version.properties')

task loadVersion {
    project.version = readVersion()
}

task hello << {
    println 'version = $project.version'
}

MyProjectVersion readVersion() {
    logger.quiet "Reading the version file"
    if (!versionFile.exists()) {
        throw new GradleException("Required version file does not exist:$versionFile.canonicalPath")
    }

    Properties versionProps = new Properties()
    versionFile.withInputStream { stream ->
        versionProps.load(stream)
    }

    new MyProjectVersion(versionProps.major.toInteger(), versionProps.minor.toInteger(),
            versionProps.release.toBoolean())
}

class MyProjectVersion {    
    Integer major    
    Integer minor    
    Boolean release    
    MyProjectVersion(Integer major, Integer minor)  {        
        this.major = major        
        this.minor = minor        
        this.release = Boolean.FALSE    
    }    
    MyProjectVersion(Integer major, Integer minor, Boolean release) {                                                    
        this(major, minor)        
        this.release = release    
    }    

    @Override    String toString() {        
                "$major.$minor${release ? '' : '-SNAPSHOT'}"    
     }
}

运行需要在根目录下建立version.properties文件，否则会抛出异常 Required version file does not exist。

3. 自定义任务

task generateConfigFile(type: GenerateUserConfigFile) {
    userName 'Donald Trump'
    major 'computer'
    interest 'write'
    destFile new File("hello.txt")
}

class GenerateUserConfigFile extends DefaultTask {

    @Input
    String userName

    @Input
    String major

    @Input
    String interest

    @OutputFile
    File destFile

    GenerateUserConfigFile() { }

    @TaskAction
    void actionNow() {
        ant.propertyfile(file:destFile){
            entry(key: 'userName', type: 'string', operation: '=', value: userName)
            entry(key: 'major', type: 'string', operation: '=', value: major)
            entry(key: 'interest', type: 'string', operation: '=', value: interest)
        }
    }
}

执行./gradlew -q generateConfigFile即可生成配置文件hello.txt。

#Fri, 11 Nov 2016 22:14:53 +0800

userName=Donald Trump
major=computer
interest=write

4. 使用gradle自带的任务

task createFiles << {
    def f1 = new File("hello1.txt")
    def f2 = new File("hello2.txt")
    f1.withObjectOutputStream { stream ->
        stream << "hello,world."
    }
    f2.withObjectOutputStream { stream->
        stream << "hello,android."
    }
}

task zipTest(type:org.gradle.api.tasks.bundling.Zip, dependsOn: [createFiles]) {
    logger.quiet "zip test now!"
    delete 'hello.zip'
    from(rootDir) {
        include 'hello1.txt'
        include 'hello2.txt'
    }
    archiveName 'hello.zip'
}