android studio 使用gradle打jar包并混淆

昨天准备把写好的代码使用gradle打jar包出来，并打算加混淆。打jar包容易，结果在混淆上走了弯路。

首先打jar包的配置很简单，使用jar的task，具体代码如下：

task buildJar(type: Jar, dependsOn: ['assembleRelease']) {
    destinationDir = file('build/outputs/jar/')
    appendix = ""
    baseName = ""
    version = SDK_VERSION

    // manifest信息
    def map = ['Version': SDK_VERSION,
               'Gradle': project.gradle.gradleVersion,
               'Vendor': '',
               'Date': new Date().getDateTimeString()
        ]
    manifest.attributes(map)

    from('build/intermediates/classes/release/')
    exclude('**/BuildConfig.class')
    exclude('**/BuildConfig/$*.class')
    exclude('**/R.class')
    exclude('**/R/$*.class')
    include('**/*.class')
}

但是发现上面打出来的jar包中的代码没有被混淆，于是加混淆。使用混淆的proguard.gradle.ProGuardTask task时，发现总是报如下错误：

java.io.IOException: The output jar [....jar] must be specified after an input jar, or it will be empty.

按照上面的提示， outjars 是写在 injars 后面啊， it will be empty 是提示哪里有问题？以为是 proguard-rules.pro 文件中的配置有问题，结果把文件清空，还是报上面的错误，错误原因不得而知了。在这个问题上耗了很长时间，最终还是没有解决。

突然看到上面的 assembleRelease task想起了平常打APK时，会使用到这个task，打出来的APK会自动混淆。那这个 assembleRelease task就会依赖处理混淆的task，于是查看了输出日志：

To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/2.14.1/userguide/gradle_daemon.html.
Observed package id 'system-images;android-22;google_apis;x86' in inconsistent location 'android-sdk-windows-studio/system-images/addon-google_apis-google-22
/x86' (Expected 'android-sdk-windows-studio/system-images/android-22/google_apis/x86')
Observed package id 'system-images;android-22;google_apis;x86' in inconsistent location 'android-sdk-windows-studio/system-images/addon-google_apis-google-22
/x86' (Expected 'android-sdk-windows-studio/system-images/android-22/google_apis/x86')
Incremental java compilation is an incubating feature.                
:sdk:preBuild UP-TO-DATE                                                                                                                                                
:sdk:extractProguardFiles
:sdk:preReleaseBuild
:sdk:checkReleaseManifest
:sdk:preDebugAndroidTestBuild UP-TO-DATE
:sdk:preDebugBuild UP-TO-DATE
:sdk:preDebugUnitTestBuild UP-TO-DATE
:sdk:preReleaseUnitTestBuild UP-TO-DATE
:sdk:prepareComAndroidSupportAnimatedVectorDrawable2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportAppcompatV72510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportCompat2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportCoreUi2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportCoreUtils2510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportFragment2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportMediaCompat2510Library UP-TO-DATE      
:sdk:prepareComAndroidSupportSupportV42510Library UP-TO-DATE
:sdk:prepareComAndroidSupportSupportVectorDrawable2510Library UP-TO-DATE
:sdk:prepareReleaseDependencies
:sdk:compileReleaseAidl UP-TO-DATE      
:sdk:compileReleaseNdk UP-TO-DATE
:sdk:compileLint UP-TO-DATE
:sdk:copyReleaseLint UP-TO-DATE
:sdk:compileReleaseRenderscript UP-TO-DATE
:sdk:generateReleaseBuildConfig                 
:sdk:generateReleaseResValues UP-TO-DATE
:sdk:generateReleaseResources UP-TO-DATE
:sdk:mergeReleaseResources UP-TO-DATE      
:sdk:processReleaseManifest UP-TO-DATE
:sdk:processReleaseResources UP-TO-DATE      
:sdk:generateReleaseSources
:sdk:incrementalReleaseJavaCompilationSafeguard                 
:sdk:compileReleaseJavaWithJavac                 
:sdk:compileReleaseJavaWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.).
注: 某些输入文件使用或覆盖了已过时的 API。                                                                                                                               
注: 有关详细信息, 请使用 -Xlint:deprecation 重新编译。                                                                                                                   
:sdk:extractReleaseAnnotations                   
:sdk:mergeReleaseShaders UP-TO-DATE      
:sdk:compileReleaseShaders UP-TO-DATE
:sdk:generateReleaseAssets UP-TO-DATE
:sdk:mergeReleaseAssets UP-TO-DATE
:sdk:mergeReleaseProguardFiles UP-TO-DATE
:sdk:packageReleaseRenderscript UP-TO-DATE
:sdk:packageReleaseResources UP-TO-DATE      
:sdk:processReleaseJavaRes UP-TO-DATE
:sdk:transformResourcesWithMergeJavaResForRelease UP-TO-DATE
:sdk:transformClassesAndResourcesWithProguardForRelease                 
ProGuard, version 5.2.1
Reading input...                                                        
Reading program directory [sdk/build/intermediates/classes/release] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-media-compat/25.1.0/jars/classes.jar] (filtered)

Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-compat/25.1.0/jars/classes.jar] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-fragment/25.1.0/jars/classes.jar] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-core-ui/25.1.0/jars/classes.jar] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/animated-vector-drawable/25.1.0/jars/classes.jar] (filte
red)
Reading library jar [android-sdk-windows-studio/extras/android/m2repository/com/android/support/support-annotations/25.1.0/support-annotations-25.1.0.jar] (f
iltered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-v4/25.1.0/jars/classes.jar] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-vector-drawable/25.1.0/jars/classes.jar] (filter
ed)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/appcompat-v7/25.1.0/jars/classes.jar] (filtered)
Reading library jar [sdk/build/intermediates/exploded-aar/com.android.support/support-core-utils/25.1.0/jars/classes.jar] (filtered)
Reading library jar [/android-sdk-windows-studio/platforms/android-25/android.jar]
Reading library jar [/android-sdk-windows-studio/platforms/android-25/optional/org.apache.http.legacy.jar]
Note: duplicate definition of library class [android.net.http.HttpResponseCache]
Note: duplicate definition of library class [android.net.http.SslCertificate$DName]
Note: duplicate definition of library class [android.net.http.SslError]
Note: duplicate definition of library class [android.net.http.SslCertificate]
Note: duplicate definition of library class [org.apache.http.params.CoreConnectionPNames]
Note: duplicate definition of library class [org.apache.http.params.HttpConnectionParams]
Note: duplicate definition of library class [org.apache.http.params.HttpParams]
Note: duplicate definition of library class [org.apache.http.conn.scheme.SocketFactory]
Note: duplicate definition of library class [org.apache.http.conn.scheme.LayeredSocketFactory]
Note: duplicate definition of library class [org.apache.http.conn.scheme.HostNameResolver]
Note: duplicate definition of library class [org.apache.http.conn.ConnectTimeoutException]
Note: there were 11 duplicate class definitions.
      (http://proguard.sourceforge.net/manual/troubleshooting.html#duplicateclass)
Initializing...
Note: you're ignoring all warnings!                                     
Ignoring unused library classes...                                      
  Original number of library classes: 5857
  Final number of library classes:    383
Printing kept classes, fields, and methods...
Shrinking...
Printing usage to [sdk/build/outputs/mapping/release/usage.txt]...
Removing unused program classes and class elements...                   
  Original number of program classes: 52                                
  Final number of program classes:    48
Obfuscating...
Printing mapping to [sdk/build/outputs/mapping/release/mapping.txt]...
Writing output...
Preparing output jar [sdk/build/intermediates/transforms/proguard/release/jars/3/3/main.jar]
  Copying resources from program directory [sdk/build/intermediates/classes/release] (filtered)
Printing classes to [sdk/build/outputs/mapping/release/dump.txt]...
:sdk:transformClassesAndResourcesWithSyncLibJarsForRelease                 
:sdk:mergeReleaseJniLibFolders UP-TO-DATE
:sdk:transformNative_libsWithMergeJniLibsForRelease UP-TO-DATE      
:sdk:transformNative_libsWithSyncJniLibsForRelease UP-TO-DATE
:sdk:bundleRelease                 
:sdk:compileReleaseSources
:sdk:assembleRelease
:sdk:buildJar                 
              
BUILD SUCCESSFUL.

好家伙，被我发现了。其中从 :sdk:transformClassesAndResourcesWithProguardForRelease 这个task就可以看到，下面一堆日志是关于 ProGuard 混淆工具的，最后可以看到：

Preparing output jar [sdk/build/intermediates/transforms/proguard/release/jars/3/3/main.jar]

这个 main.jar 就是混淆后的jar包，只不过这个jar还包含了 R 类和 BuildConfig 类的信息，所以将这个信息过滤掉就可以。但问题也来了，jar包都已经打好了，怎么配置混淆？解决方法是只要把jar包当输入就行了，最终配置如下：

task buildJar(type: Jar, dependsOn: ['assembleRelease']) {
    destinationDir = file('build/outputs/jar/')
    appendix = "" // SDK的后缀名称
    baseName = "" // SDK名称
    version = SDK_VERSION // 这个常量是在gradle.properties中配置的

    // manifest信息
    def map = ['Version': SDK_VERSION,
               'Gradle': project.gradle.gradleVersion,
               'Vendor': '',
               'Date': new Date().getDateTimeString()
        ]
    manifest.attributes(map)

    from(project.zipTree('build/intermediates/transforms/proguard/release/jars/3/3/main.jar'))
    exclude('**/BuildConfig.class')
    exclude('**/BuildConfig/$*.class')
    exclude('**/R.class')
    exclude('**/R/$*.class')
    include('**/*.class')
}

OK，任务搞定。

来自：http://www.jacpy.com/2017/02/28/android-studio-gradle-make-jar-and-proguard.html