Android: How to generate signed APK with minifyEnabled

Question

I have an android app, I just finished working on it and am ready to publish it on PlayStore. However, to avoid someone else from directly decompiling it, I wanted to add the proguard layer of security.

I tried to generate signed apk after setting minifyEnabled to 'true'. However, android studio started showing several errors, at one point the count went beyond 800 errors. I tried searching for a solution online and got to know the main cause of this problem might be all the third party libraries I had added to my application.

One of the most popular solution to overcome this type of problem was to add the -dontwarn or -keep attribute in the proguard-rules.txt file. But, the problem persisted even after I tried following all the solutions available online, I went tried to find something on youtube but got nothing of use. Can someone please help me. Here is the app level gradel file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"
    defaultConfig {
        applicationId "com.example.android.jsontutorial"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner                     "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.1.0'
    compile 'com.android.support:design:25.1.0'
    compile 'com.android.support:support-v4:25.1.0'
    compile 'com.android.volley:volley:1.0.0'
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'com.android.support:recyclerview-v7:25.1.0'
    compile 'com.android.support:cardview-v7:25.1.0'
    //compile 'com.google.firebase:firebase-core:10.2.4'
    compile 'com.google.firebase:firebase-ads:10.0.1'
    testCompile 'junit:junit:4.12'
}
apply plugin: 'com.google.gms.google-services'
apply plugin: 'com.google.gms.google-services'

Here is the proguard-rules.txt file:

# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in C:\Users\Priyansh\AppData\Local\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 tvName to the JavaScript interface
# class:
#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
#   public *;
#}

 -dontwarn     com.squareup.picasso.**
 -dontwarn     com.android.support.**
 -dontwarn     com.android.support.**
 -dontwarn     com.android.support.**
 -dontwarn     com.android.volley.**
 -dontwarn     com.android.support.**
 -dontwarn     com.android.support.**
 -dontwarn     com.google.firebase.**

Here is the seemingly helpful information I found in the gradle console:

    Warning: there were 1341 unresolved references to classes or interfaces.
         You may need to add missing library jars or update their versions.
         If your code works fine without the missing classes, you can suppress
         the warnings with '-dontwarn' options.
         (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
Warning: there were 83 unresolved references to program class members.
         Your input classes appear to be inconsistent.
         You may need to recompile the code.
         (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedprogramclassmember)

Warning: Exception while processing task java.io.IOException: Please correct the above warnings first.
:app:transformClassesAndResourcesWithProguardForRelease FAILED

If you want to take a look at the detailed warnings then here.

Can someone please help me tackle this problem, I know like always the solution will be too stupidly simple such as a simple ReBuild, but, please help!!

P.S. I have already tried a full clean build and rebuild.

Answer 1

Add these to your proguard-rules.txt:

-keep class java.awt.event.** { *; }
-keep class org.apache.** { *; }
-keep class org.gradle.** { *; }
-keep class groovy.lang.** { *; }
-keep class javax.swing.** { *; }

This should reduce the number of errors you have. Add more keep statements until you resolve all the problems.