Android Studio ignoring APP_ABI for ndk-build even after setting abiFilters correctly

Issue

I'm working on an Android app that has a native library dependency being built with ndk-build. The library in turn, depends on a prebuilt static library (.a) that I add into the root Android.mk as below. I intend to build only for armeabi-v7a and arm64-v8a.

ifeq ($(TARGET_ARCH), arm)
    LOCAL_SRC_FILES := lib/mylib_arm.a
else ifeq ($(TARGET_ARCH), arm64)
    LOCAL_SRC_FILES := lib/mylib_arm64.a
else
    $(error platform not supported!)
endif

When I tried to build the project, the build failed at the task :app:externalNativeBuildCleanDebug, with the following error.

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:externalNativeBuildCleanDebug'.
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:151)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$3.accept(ExecuteActionsTaskExecuter.java:148)
    at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:191)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:141)
    at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionStateTaskExecuter.execute(ResolveBeforeExecutionStateTaskExecuter.java:75)
    at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:62)
    at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:108)
    at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionOutputsTaskExecuter.execute(ResolveBeforeExecutionOutputsTaskExecuter.java:67)
    at org.gradle.api.internal.tasks.execution.ResolveAfterPreviousExecutionStateTaskExecuter.execute(ResolveAfterPreviousExecutionStateTaskExecuter.java:46)
    at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:94)
    at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:46)
    at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:95)
    at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57)
    at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56)
    at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36)
    at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:73)
    at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:52)
    at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:49)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:416)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:406)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
    at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102)
    at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36)
    at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:49)
    at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:43)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:355)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:343)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:336)
    at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:322)
    at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:134)
    at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:129)
    at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:202)
    at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:193)
    at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:129)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.lang.Thread.run(Thread.java:748)
Caused by: org.gradle.internal.UncheckedException: Build command failed.
Error while executing process /home/sourav/android/sdk/ndk/20.0.5594570/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/sourav/code/app/app/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/sourav/code/app/app/src/main/jni/Application.mk APP_ABI=x86 NDK_ALL_ABIS=x86 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/sourav/code/app/app/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/sourav/code/app/app/build/intermediates/ndkBuild/debug/lib clean}

/home/sourav/code/app/app/src/main/jni/mylib/Android.mk:12: *** platform not supported!.  Stop.

Upon further inspection, I found out that the build was being invoked as follows

/home/sourav/android/sdk/ndk/20.0.5594570/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/sourav/code/app/app/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/sourav/code/app/app/src/main/jni/Application.mk APP_ABI=x86 NDK_ALL_ABIS=x86 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/sourav/code/app/app/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/sourav/code/app/app/build/intermediates/ndkBuild/debug/lib clean}

Clearly, Gradle is failing to read the APP_ABI correctly from Appilcation.mk. I have tried setting abifilters in all possible locations, as you can see below.

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.app"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            // For ndk-build, instead use the ndkBuild block.
            ndkBuild {
                // Sets optional flags for the C++ compiler.
                abiFilters "armeabi-v7a", "arm64-v8a"
            }
        }

        ndk {
            abiFilters "armeabi-v7a", "arm64-v8a"
        }

    }
    buildTypes {
        release {
            ndk {
                abiFilters "armeabi-v7a", "arm64-v8a"
            }
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }

        debug {
            ndk {
                abiFilters "armeabi-v7a", "arm64-v8a"
            }
        }
    }
    externalNativeBuild {
        ndkBuild {
            path file('src/main/jni/Android.mk')
        }
    }
}

Despite all my efforts, the build keeps failing on the same step, and I can see that the app is still trying to build for APP_ABI = x86 despite clearly being instructed not to do so.

Any help would be appreciated ! TIA.

Solution

Just in case someone stumbles across the same problem, after trying everything (including Build > Clean Project), the above issue was solved by deleting the .gradle folder in the root project directory and building again.

Answered By - Sourav Banerjee