Java.lang.UnsatisfiedLinkError - NDK in android gradle studio?

Question

Folder structure

app ---main ---java ----jni -----Android.mk -----Application.mk ----- hello-jni.c ---res 

in build.gradle

 apply plugin: 'com.android.application' android { compileSdkVersion 21 buildToolsVersion "22.0.1" defaultConfig { applicationId "com.example.hellojni" minSdkVersion 17 targetSdkVersion 21 sourceSets.main { jni.srcDirs = [] jniLibs.srcDir 'src/main/libs' } ndk { moduleName "hello-jni" cFlags "-std=c++11 -fexceptions" ldLibs "log" stl "gnustl_shared" abiFilter "armeabi-v7a" } task nativeLibsToJar(type: Zip, description: 'create a jar archive of the native libs') { destinationDir file("$buildDir/native-libs") baseName 'native-libs' extension 'jar' from fileTree(dir: 'libs', include: '**/*.so') into 'lib/' } tasks.withType(JavaCompile) { compileTask -> compileTask.dependsOn(nativeLibsToJar) } testApplicationId "com.example.hellojni.tests" testInstrumentationRunner "android.test.InstrumentationTestRunner" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt' } } dependencies { compile fileTree(dir: "$buildDir/native-libs", include: 'native-libs.jar') } } 

on Android.mk

  LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := hello-jni LOCAL_SRC_FILES := hello-jni.c include $(BUILD_SHARED_LIBRARY) 

at hello-jni.c

 include<com.example.hellojni.HelloJni.h> #include <string.h> #include <jni.h> jstring Java_com_example_hellojni_HelloJni_stringFromJNI( JNIEnv* env, jobject thiz ) { #if defined(__arm__) #if defined(__ARM_ARCH_7A__) #if defined(__ARM_NEON__) #if defined(__ARM_PCS_VFP) #define ABI "armeabi-v7a/NEON (hard-float)" #else #define ABI "armeabi-v7a/NEON" #endif #else #if defined(__ARM_PCS_VFP) #define ABI "armeabi-v7a (hard-float)" #else #define ABI "armeabi-v7a" #endif #endif #else #define ABI "armeabi" #endif #elif defined(__i386__) #define ABI "x86" #elif defined(__x86_64__) #define ABI "x86_64" #elif defined(__mips64) /* mips64el-* toolchain defines __mips__ too */ #define ABI "mips64" #elif defined(__mips__) #define ABI "mips" #elif defined(__aarch64__) #define ABI "arm64-v8a" #else #define ABI "unknown" #endif return (*env)->NewStringUTF(env, "Hello from JNI ! Compiled with ABI " ABI "."); } 

in java

  public class HelloJni extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setText( stringFromJNI() ); setContentView(tv); } public native String stringFromJNI(); public native String unimplementedStringFromJNI(); static { System.loadLibrary("hello-jni"); } } 

I get an unsatisfied error

  java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.example.hellojni-2/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]] couldn't find "libhello-jni.so" at java.lang.Runtime.loadLibrary(Runtime.java:366) at java.lang.System.loadLibrary(System.java:989) at com.example.hellojni.HelloJni.<clinit>(HelloJni.java:64) at java.lang.reflect.Constructor.newInstance(Native Method) at java.lang.Class.newInstance(Class.java:1572) at android.app.Instrumentation.newActivity(Instrumentation.java:1088) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388) at android.app.ActivityThread.access$800(ActivityThread.java:148) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5312) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696) 

My local.properties

 sdk.dir=F\:\\SDK ndk.dir=C\:\\NDK 

Does not generate .so files.

Answer 1

You have a few errors in the build.gradle file:

The nativeLibsToJar task was a suitable technique in early versions of plugins for Android gradle, it should not be used with at least 0.7 and may lead to errors deleting this task. Instead, if you put your .so files inside jniLibs/ABI directories (where ABI is armeabi-v7a, x86 ...), they will integrate correctly inside your APK.

Then you installed:

 jni.srcDirs = [] jniLibs.srcDir 'src/main/libs' 

Disables the built-in ndk integration from the gradle plugin and makes gradle use libs from libs instead of jniLibs . This is good, but later you define your ndk module with the ndk {} block, which is useless, remove it.

After cleaning these parts, you can call ndk-build (or ndk-build.cmd if you are using Windows) from the command line, from the root of your Android project. It will generate your .so files inside libs/ABI and they will be integrated into your APK, since jniLibs.srcDir 'src/main/libs' told gradle to get these libraries from libs .

You can verify that your .so files are integrated by opening the APK as a zip file; .So files must be present in lib/ABI .