Note: the entry point `XXX` is saved in the configuration, but not the descriptor class` xxx 'in Android Studio

Question

The following error appeared when I enabled minifyEnabled in android studio v1.1.0

Grade:

 package com.example.FFmpegBridge; public class FFmpegBridge { static { System.loadLibrary("xxx"); } public native void init(AVOptions options, int audio) throws IOException; static public class AVOptions { } } 

proguard-rules.pro by default:

 # Add project specific ProGuard rules here. # By default, the flags in this file are appended to flags specified # in /Users/jerikc/Library/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 *; #} 

Error:

 19:55:06.080 [INFO] [system.out] Note: the configuration keeps the entry point 'com.example.FFmpegBridge { void init(com.example.FFmpegBridge$AVOptions,int); }', but not the descriptor class 'com.example.FFmpegBridge$AVOptions' 19:55:06.086 [INFO] [system.out] Note: there were 2 references to unknown classes. 19:55:06.086 [INFO] [system.out] You should check your configuration for typos. 19:55:06.086 [INFO] [system.out] (http://proguard.sourceforge.net/manual/troubleshooting.html#unknownclass) 19:55:06.086 [INFO] [system.out] Note: there were 1 unkept descriptor classes in kept class members. 19:55:06.087 [INFO] [system.out] You should consider explicitly keeping the mentioned classes 19:55:06.087 [INFO] [system.out] (using '-keep'). 19:55:06.088 [INFO] [system.out] (http://proguard.sourceforge.net/manual/troubleshooting.html#descriptorclass) 19:55:06.088 [INFO] [system.out] Ignoring unused library classes... 19:55:06.088 [INFO] [system.out] Original number of library classes: 3686 19:55:06.089 [INFO] [system.out] Final number of library classes: 326 19:55:06.089 [INFO] [system.out] Printing kept classes, fields, and methods... 19:55:06.125 [INFO] [system.out] Shrinking... 19:55:06.313 [DEBUG] [org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter] Finished executing task ':library:proguardRelease' 19:55:06.313 [LIFECYCLE] [class org.gradle.TaskExecutionLogger] :library:proguardRelease FAILED 19:55:06.313 [INFO] [org.gradle.execution.taskgraph.AbstractTaskPlanExecutor] :library:proguardRelease (Thread[main,5,main]) completed. Took 1.17 secs. 19:55:06.314 [DEBUG] [org.gradle.execution.taskgraph.AbstractTaskPlanExecutor] Task worker [Thread[main,5,main]] finished, busy: 1.763 secs, idle: 0.013 secs 19:55:06.328 [ERROR] [org.gradle.BuildExceptionReporter] 19:55:06.328 [ERROR] [org.gradle.BuildExceptionReporter] FAILURE: Build failed with an exception. 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] * What went wrong: 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] Execution failed for task ':library:proguardRelease'. 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] > java.io.IOException: The output jar is empty. Did you specify the proper '-keep' options? 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] 19:55:06.329 [ERROR] [org.gradle.BuildExceptionReporter] * Try: 19:55:06.330 [ERROR] [org.gradle.BuildExceptionReporter] Run with --stacktrace option to get the stack trace. 19:55:06.331 [LIFECYCLE] [org.gradle.BuildResultLogger] 19:55:06.331 [LIFECYCLE] [org.gradle.BuildResultLogger] BUILD FAILED 19:55:06.331 [LIFECYCLE] [org.gradle.BuildResultLogger] 19:55:06.331 [LIFECYCLE] [org.gradle.BuildResultLogger] Total time: 12.014 secs 

How to solve a compilation error?