android gradle build resources.arsc文件未压缩问题解决

随着google如火如荼的推出android studio IDE和gradle buld工具，很多公司要对build系统做从ant到gradle的升级，不幸的是我被分配负责该任务。

发现一个问题，gralde编译后的apk比ant要大大约1M左右，对于老大之前严格要求控制apk在10M左右的需求，只能说造化弄人。压缩包打开发现gradle build之后的apk resources.arsc没有压缩，导致apk增大很多。

于是乎，设置resource shrink 为true，结果如下：

图一：ant打包之后的详单：

图二：gradle shrinkResources false的详单

图三：gradle shrinkResources true的详单

结果发现：ant打包后的resources.arsc，从1.1M压缩到267K，还是比较狠的。

至于是否shrinkResources，没有什么效果

aapt l -v Client-release-unsigned-ant.apk ，查看apk明细：

发现ant包和gradle包的差异：

 Length   Method    Size  Ratio   Offset      Date  Time  CRC-32    Name
1158688  Deflate  273481  76%   9835381  11-17-15 15:18  04aecb3e  resources.arsc -------- <span style="color:#ff0000;">ant build apk</span>
1158508  Stored  1158508   0%   2899860  11-17-15 15:21  9222ccf9  resources.arsc   -------- <span style="color:#ff0000;">gradle build apk</span>

ant build resources.arsc是deflate method，而gradle build 的是stored method，而且size相差很大。

于是乎，寻找gradle设置deflate模式的配置开关，未果，似乎是硬编码方式，不支持dsl配置，只能从最后的apk包下手，对resources做二次压缩。下面代码：

apply plugin: 'android'


dependencies {
    compile fileTree(dir: 'libs', include: '*.jar')
    compile project(':MyProj')
}


android {
    compileSdkVersion 19
    buildToolsVersion '21.1.2'


    lintOptions {
        abortOnError false
    }


    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
            jniLibs.srcDirs = ['libs']
        }


        // Move the tests to tests/java, tests/res, etc...
        instrumentTest.setRoot('tests')


        // Move the build types to build-types/<type>
        // For instance, build-types/debug/java, build-types/debug/AndroidManifest.xml, ...
        // This moves them out of them default location under src/<type>/... which would
        // conflict with src/ being used by the main source set.
        // Adding new build types or product flavors should be accompanied
        // by a similar customization.
        debug.setRoot('build-types/debug')
        release.setRoot('build-types/release')
    }


    defaultConfig {
        multiDexEnabled true
    }


    dexOptions {
        javaMaxHeapSize "2g"
        jumboMode true
    }


    buildTypes {
        debug {
            minifyEnabled false
            proguardFile('proguard.cfg')
        }
        release {
            minifyEnabled true
            proguardFile('proguard.cfg')
        }
    }


    packagingOptions {
        exclude('META-INF/DEPENDENCIES')
        exclude('META-INF/NOTICE')
        exclude('META-INF/LICENSE')
    }


    lintOptions {
        // Or, if you prefer, you can continue to check for errors in release builds,
        checkReleaseBuilds false
        // but continue the build even when errors are found:
        abortOnError false
    }
}


import java.util.zip.ZipEntry
import java.util.zip.ZipFile
import java.util.zip.ZipOutputStream


// 打包过程中很多手工zip过程：
// 1，为了压缩resources.arsc文件而对标准产出包重新压缩
// 2，以及各子apk的纯手打apk包
// 但对于音频等文件，压缩会导致资源加载报异常
// 重新打包方法，使用STORED过滤掉不应该压缩的文件们
// 后缀名列表来自于android源码
def repackApk(originApk, targetApk){
    def noCompressExt = [".jpg", ".jpeg", ".png", ".gif",
                         ".wav", ".mp2", ".mp3", ".ogg", ".aac",
                         ".mpg", ".mpeg", ".mid", ".midi", ".smf", ".jet",
                         ".rtttl", ".imy", ".xmf", ".mp4", ".m4a",
                         ".m4v", ".3gp", ".3gpp", ".3g2", ".3gpp2",
                         ".amr", ".awb", ".wma", ".wmv"]


    ZipFile zipFile = new ZipFile(originApk)
    ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(targetApk)))
    zipFile.entries().each{ entryIn ->
        if(entryIn.directory){
            println "${entryIn.name} is a directory"
        }
        else{
            def entryOut = new ZipEntry(entryIn.name)
            def dotPos = entryIn.name.lastIndexOf('.')
            def ext = (dotPos >= 0) ? entryIn.name.substring(dotPos) : ""
            def isRes = entryIn.name.startsWith('res/')
            if(isRes && ext in noCompressExt){
                entryOut.method = ZipEntry.STORED
                entryOut.size = entryIn.size
                entryOut.compressedSize = entryIn.size
                entryOut.crc = entryIn.crc
            }
            else{
                entryOut.method = ZipEntry.DEFLATED
            }
            zos.putNextEntry(entryOut)
            zos << zipFile.getInputStream(entryIn)
            zos.closeEntry()
        }
    }
    zos.finish()
    zos.close()
    zipFile.close()
}


task repack(){


	doLast{
		print "root dir is : $rootDir"
		println "release打包之后，重新压缩一遍，以压缩resources.arsc"


		def oldApkFile = file("$rootDir/projectPath/build/outputs/apk/Client-release-unsigned.apk")


		assert oldApkFile != null : "没有找到release包！"


		def newApkFile = new File("$rootDir/projectPath/build/outputs/apk/Client-release-unsigned-repack.apk")
		print oldApkFile.absolutePath
		print newApkFile.absolutePath
		//重新打包
		repackApk(oldApkFile.absolutePath, newApkFile.absolutePath)


		assert newApkFile.exists() : "没有找到重新压缩的release包！"
	}
}

其实也可以通过java或者python程序终结对apk进行二次处理达到效果，但是不如gradle处理的自然。

done, perfect !