Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease

I am trying to export apk and I want to enable Proguard but it throwing below error. I read so many answers and tried but didn't worked. Getting below error:

Warning:Exception while processing task java.io.IOException: java.lang.NullPointerException 
Error:Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease

StackTrace:

:app:transformClassesAndResourcesWithProguardForRelease
ProGuard, version 5.2.1
Warning: Exception while processing task java.io.IOException: java.lang.NullPointerException
:app:transformClassesAndResourcesWithProguardForRelease FAILED

FAILURE: Build failed with an exception.


* What went wrong:
Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease'.
> Job failed, see logs for details

* Try:
Run with --info or --debug option to get more log output.


* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
        at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:66)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:52)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:203)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:185)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:66)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:50)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:25)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:110)
        at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
        at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
        at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
        at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
        at org.gradle.initialization.DefaultGradleLauncher$4.run(DefaultGradleLauncher.java:153)
        at org.gradle.internal.Factories$1.create(Factories.java:22)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:53)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:150)
        at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:32)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:98)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:92)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:63)
        at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:92)
        at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:83)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:99)
        at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
        at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:48)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:81)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:46)
        at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:51)
        at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:28)
        at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:43)
        at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:173)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:239)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:212)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:35)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:24)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:205)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:169)
        at org.gradle.launcher.Main.doAction(Main.java:33)
        at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:55)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:36)
        at org.gradle.launcher.GradleMain.main(GradleMain.java:23)
        at org.gradle.wrapper.BootstrapMainStarter.start(BootstrapMainStarter.java:30)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:129)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)
Caused by: java.lang.RuntimeException: Job failed, see logs for details
        at com.android.build.gradle.internal.transforms.ProGuardTransform.transform(ProGuardTransform.java:196)
        at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:178)
        at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:174)
        at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:156)
        at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:173)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.doExecute(AnnotationProcessingTaskFactory.java:245)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:221)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.execute(AnnotationProcessingTaskFactory.java:232)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:210)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
        ... 60 more
Caused by: java.io.IOException: java.lang.NullPointerException
        at com.android.build.gradle.internal.transforms.ProGuardTransform.doMinification(ProGuardTransform.java:283)
        at com.android.build.gradle.internal.transforms.ProGuardTransform.access$000(ProGuardTransform.java:63)
        at com.android.build.gradle.internal.transforms.ProGuardTransform$1.run(ProGuardTransform.java:173)
        at com.android.builder.tasks.Job.runTask(Job.java:49)
        at com.android.build.gradle.tasks.SimpleWorkQueue$EmptyThreadContext.runTask(SimpleWorkQueue.java:41)
        at com.android.builder.tasks.WorkQueue.run(WorkQueue.java:223)
Caused by: java.lang.NullPointerException
        at proguard.util.FixedStringMatcher.matches(FixedStringMatcher.java:52)
        at proguard.util.OrMatcher.matches(OrMatcher.java:46)
        at proguard.classfile.util.WarningPrinter.accepts(WarningPrinter.java:89)
        at proguard.classfile.util.WarningPrinter.print(WarningPrinter.java:77)
        at proguard.KeepClassMemberChecker.checkClassSpecifications(KeepClassMemberChecker.java:76)
        at proguard.ConfigurationChecker.check(ConfigurationChecker.java:136)
        at proguard.ProGuard.execute(ProGuard.java:73)
        at com.android.build.gradle.internal.transforms.BaseProguardAction.runProguard(BaseProguardAction.java:54)
        at com.android.build.gradle.internal.transforms.ProGuardTransform.doMinification(ProGuardTransform.java:254)
        ... 5 more

Gradle file:

buildscript {
repositories {
    maven { url 'https://maven.fabric.io/public' }
   }

dependencies {
    classpath 'io.fabric.tools:gradle:1.+'
   }
}

apply plugin: 'com.android.application'
apply plugin: 'io.fabric'

repositories {
    maven { url 'https://maven.fabric.io/public' }
}

android {
compileSdkVersion 25
buildToolsVersion "25"

defaultConfig {
    applicationId "package_name"
    minSdkVersion 14
    targetSdkVersion 25
    versionCode 22
    versionName "2.3.1"
    multiDexEnabled true
}
buildTypes {
    release {
        minifyEnabled true
        shrinkResources true
        debuggable false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        buildConfigField "String", "BASE_URL", "\"http://release.com/\""
                }
    debug {
        testCoverageEnabled false
        minifyEnabled false
        shrinkResources false
        debuggable true
        versionNameSuffix '-dev'
        applicationIdSuffix '.dev'

        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        buildConfigField "String", "BASE_URL", "\"http://test.com/\""
        jackOptions {
            enabled false
        }
    }   
}
productFlavors {

}

dexOptions {
    javaMaxHeapSize "2048M"
    jumboMode true
}

sourceSets {
    main { assets.srcDirs = ['src/main/assets', 'src/stage'] }
    stage {
        res.srcDirs = ['src/stage/res', 'src/main/res/mipmap', 'src/stage/res/mipmap', 'src/stage/res/values']
    }
    release { java.srcDirs = ['src/release/java', 'src/release/java/'] }
    debug { res.srcDirs = ['src/debug/res', 'src/debug/res/drawable'] }
}
}

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])

compile 'com.android.support:appcompat-v7:25.1.0'
compile "com.android.support:support-v4:25.0.0"
compile 'com.android.support:design:25.0.0'
compile 'com.android.support:multidex:1.0.1'
compile 'com.android.volley:volley:1.0.0'
compile 'com.squareup.picasso:picasso:2.5.2'
compile 'com.google.android.gms:play-services-analytics:10.0.0'
compile 'com.google.android.gms:play-services-gcm:10.0.0'
compile 'com.github.freshdesk:hotline-android:1.1.+'
compile 'com.appsflyer:af-android-sdk:4+@aar'
compile('cn.trinea.android.view.autoscrollviewpager:android-auto-scroll-view-pager:1.1.2') {
    exclude module: 'support-v4'
}


compile('com.crashlytics.sdk.android:crashlytics:2.6.5@aar') {
    transitive = true;
}

compile 'com.pusher:pusher-java-client:1.4.0'
}

Proguard File:

# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in F:\android studio\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 *;
#}




# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in /Applications/Android Studio.app/sdk/tools/proguard/proguard-android.txt
# You can edit the include path and order by changing the ProGuard
# include property in project.properties.
#
# 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 *;
#}

# Obfuscation parameters:
#-dontobfuscate
-useuniqueclassmembernames
-keepattributes SourceFile,LineNumberTable
-allowaccessmodification

# Ignore warnings:
#-dontwarn org.mockito.**
-dontwarn org.junit.**
-keepclasseswithmembers class * {
    @junit.** *;
}

#-dontwarn com.robotium.**
#-dontwarn org.joda.convert.**

# Ignore warnings: We are not using DOM model
-dontwarn com.fasterxml.jackson.databind.ext.DOMSerializer
# Ignore warnings: https://github.com/square/okhttp/wiki/FAQs
-dontwarn com.squareup.okhttp.internal.huc.**
# Ignore warnings: https://github.com/square/okio/issues/60
-dontwarn okio.**
# Ignore warnings: https://github.com/square/retrofit/issues/435
-dontwarn com.google.appengine.api.urlfetch.**

# Keep the pojos used by GSON or Jackson
-keep class com.futurice.project.models.pojo.** { *; }

# Keep GSON stuff
-keep class sun.misc.Unsafe { *; }
-keep class com.google.gson.** { *; }

# Keep Jackson stuff
-keep class org.codehaus.** { *; }
-keep class com.fasterxml.jackson.annotation.** { *; }

# Keep these for GSON and Jackson
-keepattributes Signature
-keepattributes *Annotation*
-keepattributes EnclosingMethod

# Keep Retrofit
-keep class retrofit.** { *; }
-keepclasseswithmembers class * {
    @retrofit.** *;
}
-keepclassmembers class * {
    @retrofit.** *;
}

# Keep Picasso
-keep class com.squareup.picasso.** { *; }
-keepclasseswithmembers class * {
    @com.squareup.picasso.** *;
}
-keepclassmembers class * {
    @com.squareup.picasso.** *;
}
-keepclassmembers class * {
    @com.squareup.picasso.Utils.** *;
}
-keepattributes SourceFile,LineNumberTable
-keep class com.parse.*{ *; }
-dontwarn com.parse.**
-dontwarn com.squareup.picasso.**
-dontwarn com.demach.konotor.service.**
-keepclasseswithmembernames class * {
}
-keep class javax.naming.** { *; }
-keepclasseswithmembers class * {
    @javax.naming.** *;
}
-dontwarn javax.naming.**
-keep class junit.** { *; }
-keepclasseswithmembers class * {
    @junit.** *;
}
-dontwarn junit.**


-keep public class * extends java.lang.Exception
-keep public class * extends android.support.v7.app.ActionBarActivity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgent
-keep public class * extends android.preference.Preference
-keep public class * extends android.support.v4.app.Fragment
-keep public class * extends android.support.v4.app.DialogFragment
-keep public class * extends android.app.Fragment
-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 public class * extends android.view.View {
 public <init>(android.content.Context);
 public <init>(android.content.Context, android.util.AttributeSet);
 public <init>(android.content.Context, android.util.AttributeSet, int);
 public void set*(...);
}

-keepclasseswithmembers class * {
 public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
 public <init>(android.content.Context, android.util.AttributeSet, int);
}

-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>;
}

-keep class android.support.v4.app.** { *; }
-keep interface android.support.v4.app.** { *; }
-keep class com.actionbarsherlock.** { *; }
-keep interface com.actionbarsherlock.** { *; }
# 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.**
-dontwarn com.google.ads.**
-dontwarn com.google.android.gms.ads.**

-keep class com.google.android.gms.ads.** { *; }

-dontwarn com.demach.**
-dontwarn com.freshdesk.hotline.**

-keep class com.demach.** { *; }
-keep class com.freshdesk.hotline.** { *; }
#-keep class com.google.gson.demach.** {
#    *;
#}
# Application classes that will be serialized/deserialized over Gson

-keep class cn.trinea.android.** { *; }
-keepclassmembers class cn.trinea.android.** { *; }
-dontwarn cn.trinea.android.**

-keep class com.crashlytics.** { *; }
-dontwarn com.crashlytics.**

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

#volley
-keep class org.apache.commons.logging.**
-keep class com.android.volley.** { *; }
-dontwarn com.android.volley.**


#GAID
-keep class * extends java.util.ListResourceBundle {
    protected Object[][] getContents();  }

-keep public class com.google.android.gms.common.internal.safeparcel.SafeParcelable {
        public static final *** NULL;      }

-keepnames @com.google.android.gms.common.annotation.KeepName class *
-keepclassmembernames class * {
        @com.google.android.gms.common.annotation.KeepName *;
}

-keepnames class * implements android.os.Parcelable {
       public static final ** CREATOR;
}

#pusher
-keep class com.pusher.client.** { *; }
-keepclassmembers class com.pusher.client.** { *; }
-dontwarn com.pusher.client.**

-keep class pusher.java.client.** { *; }
-keepclassmembers class pusher.java.client.** { *; }
-dontwarn pusher.java.client.**

-dontwarn org.slf4j.**

#GAID
-keep public class com.google.** { *; }
-dontwarn com.google.**

-dontwarn com.appsflyer.AFKeystoreWrapper
-dontwarn uk.co.chrisjenx.calligraphy.CalligraphyConfig
-dontwarn uk.co.chrisjenx.calligraphy.CalligraphyUtils
-dontwarn uk.co.chrisjenx.calligraphy.CalligraphyConfig
-dontwarn uk.co.chrisjenx.calligraphy.CalligraphyUtils

If anyone has any solution please share here.

add the below to your ProGuard rules

-ignorewarnings

-keep class * {
    public private *;
}

and rebuild your project.

try this at your proguard-rules.pro

-ignorewarnings
-keep class * {
    public private *;
}

Only -ignorewarnings this line solved my problem.

Also Add the following line to <ProjectRoot>/android/gradle.properties to Obfuscating Dart Code:

extra-gen-snapshot-options=--obfuscate

Please refer this and this for more information.

Also If you using Firebase Auth please add it to proguard-rules.pro file:

-keep class com.google.firebase.** { *; }

Sharing my /android/app/proguard-rules.pro file

#Flutter Wrapper
-keep class io.flutter.app.** { *; }
-keep class io.flutter.plugin.**  { *; }
-keep class io.flutter.util.**  { *; }
-keep class io.flutter.view.**  { *; }
-keep class io.flutter.**  { *; }
-keep class io.flutter.plugins.**  { *; }
-ignorewarnings

Hope someone will help this

You can try this keep class com.xyz.** { *; } -dontwarn com.xyz.**

Close the project and Android Studio. Open the project again, rebuild the project. And then you can try to generate the APK. That's worked for me. Though wired!

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

Please remove this line of code in your gradle. This worked for me.