使用 Gradle 和 ProGuard 构建的 Android：“输出 jar 必须在输入 jar 之后指定，否则将为空”

Question

我正在使用 Gradle 创建具有不同风格的构建。直到现在它一直运行良好，直到我想启用Proguard。我为我的发布版本启用了minifyEnabled，现在我有一个异常说：

“Caused by: org.gradle.internal.UncheckedException: java.io.IOException: The output jar [.../app/build/intermediates/multi-dex/dev/release/componentClasses.jar] must be specified after an input jar, or it will be empty.”

有人知道是什么导致了这个异常吗？我基本上想在发布我的应用程序之前启用 ProGuard。下面是我的 Gradle 文件。

lintOptions {
    abortOnError false
}

dexOptions{
    incremental true
    javaMaxHeapSize "4g"
}

defaultConfig {
        applicationId "..."
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
    }

buildTypes {

    release {
        minifyEnabled true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        signingConfig signingConfigs.release
    }

    debug {
        minifyEnabled false
        shrinkResources false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        signingConfig signingConfigs.debug
    }
}

ProGuard 规则文件。

# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in /Users/osayilgan/Development/Android/sdk/tools/proguard/proguard-android.txt
# You can edit the include path and order by changing the proguardFiles
# directive in build.gradle.
#
# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

# Add any project specific keep options here:

# If your project uses WebView with JS, uncomment the following
# and specify the fully qualified class name to the JavaScript interface
# class:
#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
#   public *;
#}

-keepnames public class * extends io.realm.RealmObject
-keep class io.realm.** { *; }
-dontwarn javax.**
-dontwarn io.realm.**

这是 proguard-android 文件。这是 Android SDK 中的默认设置。

# This is a configuration file for ProGuard.
# http://proguard.sourceforge.net/index.html#manual/usage.html

-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-verbose

# Optimization is turned off by default. Dex does not like code run
# through the ProGuard optimize and preverify steps (and performs some
# of these optimizations on its own).
-dontoptimize
-dontpreverify
# Note that if you want to enable optimization, you cannot just
# include optimization flags in your own project configuration file;
# instead you will need to point to the
# "proguard-android-optimize.txt" file instead of this one from your
# project.properties file.

-keepattributes *Annotation*
-keep public class com.google.vending.licensing.ILicensingService
-keep public class com.android.vending.licensing.ILicensingService

# For native methods, see http://proguard.sourceforge.net/manual/examples.html#native
-keepclasseswithmembernames class * {
    native <methods>;
}

# keep setters in Views so that animations can still work.
# see http://proguard.sourceforge.net/manual/examples.html#beans
-keepclassmembers public class * extends android.view.View {
   void set*(***);
   *** get*();
}

# We want to keep methods in Activity that could be used in the XML attribute onClick
-keepclassmembers class * extends android.app.Activity {
   public void *(android.view.View);
}

# For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

-keepclassmembers class **.R$* {
    public static <fields>;
}

# The support library contains references to newer platform versions.
# Don't warn about those in case this app is linking against an older
# platform version.  We know about them, and they are safe.
-dontwarn android.support.**

Answer 1

我花了很长时间才弄明白，但正如我所猜测的，这完全是关于 Proguard 的配置。

我开始挖掘控制台中的警告，并意识到 Proguard 找不到某些参考。所以将它们作为-dontwarn 添加到proguard 配置文件解决了这个问题。

就我而言，我不得不忽略下面的包；

-dontwarn java.lang.invoke**
-dontwarn org.apache.lang.**
-dontwarn org.apache.commons.**
-dontwarn com.nhaarman.**
-dontwarn se.emilsjolander.**