android android-gradle-plugin proguard minify shrinkresources

Execution failed for task ':app:transformClassesWithAndroidGradleClassShrinkerForDebug'

I am getting this error because I tried to reduce my apk size by referring this document

Execution failed for task ':app:transformClassesWithAndroidGradleClassShrinkerForDebug'. Warnings found during shrinking, please use -dontwarn or -ignorewarnings to suppress them.

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

How to use -dontwarn or -ignorewarnings to suppress them? Where I have to add this key.

Error stack-trace:

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$1.run(ManagedExecutorImpl.java:46)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
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:221)
        at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:217)
        at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:102)
        at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:212)
        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)
        ... 29 more

Edit

proguard-rules.pro

    # Add project specific ProGuard rules here.
# You can control the set of applied configuration files using the
# proguardFiles setting in build.gradle.
#
# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

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

# Uncomment this to preserve the line number information for
# debugging stack traces.
#-dontwarnattributes SourceFile,LineNumberTable

# If you dontwarn the line number information, uncomment this to
# hide the original source file name.
#-renamesourcefileattribute SourceFile

-dontwarn <RoundedImageView>
-dontwarn <DOMSerializer>
-dontwarn retrofit2.**
-dontwarn java.nio.file.*
-dontwarn okio.**
-dontwarn okhttp3.**
-dontwarn org.w3c.dom.bootstrap.DOMImplementationRegistry
-dontwarn  com.androidquery.**
-dontwarn com.google.**
-dontwarn com.vimeo.networking.**
-dontwarn com.squareup.retrofit2.**
-dontwarn io.supercharge.**
-dontwarn com.github..**
-dontwarn com.android.**
-dontwarn com.airbnb.**
-dontwarn org.**
-dontwarn <google-services.json>

Now getting following error, If I remove shrinkResources true from build.gradle then won't get any error. But I need to reduce the apk file size using shrinkResources, How to resolve following error.

16:29:34.995 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Caused by: org.gradle.api.GradleException: Removing unused resources requires unused code shrinking to be turned on. See http://d.android.com/r/tools/shrink-resources.html for more information.
16:29:34.995 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.errors.SyncIssueHandlerImpl.reportIssue(SyncIssueHandlerImpl.kt:53)
16:29:34.996 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.builder.errors.EvalIssueReporter$DefaultImpls.reportError(EvalIssueReporter.kt:137)
16:29:34.996 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.errors.SyncIssueHandler$DefaultImpls.reportError(SyncIssueHandler.kt)
16:29:34.996 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.errors.SyncIssueHandlerImpl.reportError(SyncIssueHandlerImpl.kt:30)
16:29:34.996 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.scope.VariantScopeImpl.useResourceShrinker(VariantScopeImpl.java:457)
16:29:34.996 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.TaskManager.createMergeResourcesTask(TaskManager.java:924)
16:29:35.003 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.TaskManager.createAndroidTestVariantTasks(TaskManager.java:1907)
16:29:35.003 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]   at com.android.build.gradle.internal.VariantManager.createTasksForVariantData(VariantManager.java:521)

Solution

With the following configuration

debug {
        minifyEnabled true
        shrinkResources true
        useProguard false
        ...
    }

you try to shrink the resources having ProGuard disabled. And since resource shrinking works only in conjunction with ProGuard you get

Removing unused resources requires unused code shrinking to be turned on.

The following configuration should remove the build error:

debug {
    minifyEnabled true
    shrinkResources true
    ...
}

If after that you get Warnings found during shrinking, please use -dontwarn or -ignorewarnings to suppress them you gonna need to edit proguard-android.txt adding the corresponding -dontwarn <package_name_with_wildcard_or_class_name>.