1. Introduction

This post would demo how to do solve the TaskExecutionException e.g. transform Classes With Android Gradle Class Shrinker For Debug as follows:

Warnings found during shrinking, please use -dontwarn or -ignorewarnings to suppress them.

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesWithAndroidGradleClassShrinkerForDebug'.
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70)
    at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)
    at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)
    at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
    at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:60)
    at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:97)
    at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:87)
    at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.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:54)
    at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
    at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:248)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:241)
    at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:230)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:123)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:79)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:104)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:98)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:626)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:581)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:98)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.gradle.tooling.BuildException: Warnings found during shrinking, please use -dontwarn or -ignorewarnings to suppress them.
    at com.android.build.gradle.internal.transforms.BuiltInShrinkerTransform.checkForWarnings(BuiltInShrinkerTransform.java:200)
    at com.android.build.gradle.internal.transforms.BuiltInShrinkerTransform.fullRun(BuiltInShrinkerTransform.java:178)
    at com.android.build.gradle.internal.transforms.BuiltInShrinkerTransform.transform(BuiltInShrinkerTransform.java:130)
    at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:222)
    at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:218)
    at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:102)
    at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:213)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
    at org.gradle.api.internal.project.taskfactory.IncrementalTaskAction.doExecute(IncrementalTaskAction.java:46)
    at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:39)
    at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:26)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:121)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
    at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:110)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:92)
    ... 32 more

2. Environments

  • Android Studio 3.1
  • Android SDK tools 26.1.1

3. The Project layout

I have setup the project with two modules as follows:

  • MyApplication Project
    • base
    • app

The base have some common android base classes and utilities. The app module is the real module for my application.And the app depends on the base.

4. The project’s build.gradle file

Here is the build.gradle of the project:

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0'
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

// Define versions in a single place
ext {
    minSdkVersion = 14
    targetSdkVersion = 26
    compileSdkVersion = 26
    buildToolsVersion = '26.0.2'

    // App dependencies
    supportLibraryVersion = '26.1.0'
    guavaVersion = '18.0'
    junitVersion = '4.12'
    mockitoVersion = '1.10.19'
    powerMockito = '1.6.2'
    hamcrestVersion = '1.3'
    runnerVersion = '1.0.1'
    rulesVersion = '1.0.1'
    espressoVersion = '3.0.1'
    roomVersion = "1.0.0"
}

5. The app module’s build.gradle file

Here is the build.gradle of the app module

apply plugin: 'com.android.application'

android {
    compileSdkVersion rootProject.ext.compileSdkVersion
    buildToolsVersion rootProject.ext.buildToolsVersion

    defaultConfig {
        applicationId "com.hdd.myapplication"
        manifestPlaceholders = [appName: "My App"]
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }
    buildTypes {
        debug {
            minifyEnabled false
            useProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            testProguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguardTest-rules.pro'
        }
        release {
            minifyEnabled true
            shrinkResources true
            zipAlignEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "com.android.support:cardview-v7:$rootProject.supportLibraryVersion"
    implementation "com.android.support:design:$rootProject.supportLibraryVersion"
    implementation "com.android.support:recyclerview-v7:$rootProject.supportLibraryVersion"
    implementation project(':base')
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
}

6. The problem

When I build the project, everything works fine. But when I run the app and deploy to an emulator, I got this Exception:

Warnings found during shrinking, please use -dontwarn or -ignorewarnings to suppress them.

Just as this picture shows: exception1

When I click the gradle build warning, I got this:

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesWithAndroidGradleClassShrinkerForDebug'.
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70)
    at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)
    at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)
    at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
    at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:60)
    ....

6. How to solve the problem?

Change the app’s build.gradle file to the following:

buildTypes {
        debug {
            minifyEnabled false

            useProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            testProguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguardTest-rules.pro'
        }
    }

That is, the key is to change the debug buildtype’s minifyEnabled to false

As the google officical document says:

To enable code shrinking with ProGuard, add minifyEnabled true to the appropriate build type in your build.gradle file.

Be aware that code shrinking slows down the build time, so you should avoid using it on your debug build if possible.

7. Other solutions

I have tested that there is another solution to this problem, You can edit the app’s build.gradle as follows:

debug {
            minifyEnabled false
            useProguard false
        ...
    }

or like this:

debug {
            minifyEnabled true
            useProguard true
        ...
    }

It’s clear that the minifyEnabled must work collaborated with the useProguard, if you set minifyEnabled to be true but turn off the useProguard, then the exception would popup.