System.loadLibrary(...) couldn't find native library in my case

I want to use a existing native library from another Android project, so I just copied the NDK built library (libcalculate.so) to my new Android project. In my new Android project I created a folder libs/armeabi/ and put libcalculate.so there. There is no jni/ folder. My testing device has ARM architecture.

In my java code I load the library by:

  static{
    System.loadLibrary("calculate");
  }

When I run my new android project, I got error:

java.lang.UnsatisfiedLinkError:  ...
nativeLibraryDirectories=[/vendor/lib, /system/lib]]] couldn't find "libcalculate.so"

So, as error says, the copied native library is not in /verdor/lib or /system/lib , how to resolve this problem in my case?

(I unziped the apk package, under lib/ there is libcalculate.so)

====UPDATE=====

I also tried to create a jni/ folder under project root, and add an Android.mk file under jni/. The content of Android.mk is:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := libcalculate
LOCAL_SRC_FILES := libcalculate.so
include $(PREBUILT_SHARED_LIBRARY)

Then, under project root, I executed ndk-build . After that, the armeabi/ and armeabi-v7a/ directories are generated by ndk-build (with libcalculate.so inside the folder).

Then I run my maven build the project successfully. In the final apk package, there are:

lib/armeabi/libcalculate.so
lib/armeabi-v7a/libcalculate.so

But when I run my app, the same error throw:

java.lang.UnsatisfiedLinkError:  ...
nativeLibraryDirectories=[/vendor/lib, /system/lib]]] couldn't find "libcalculate.so"

To root cause (and maybe solve your issue in the same time), here is what you can do:

1. Remove the jni folder and all the .mk files. You don't need these nor the NDK if you aren't compiling anything.

2. Copy your libcalculate.so file inside <project>/libs/(armeabi|armeabi-v7a|x86|...) . When using Android Studio, it's <project>/app/src/main/jniLibs/(armeabi|armeabi-v7a|x86|...), but I see you're using eclipse.

3. Build your APK and open it as a zip file, to check that your libcalculate.so file is inside lib/(armeabi|armeabi-v7a|x86|...).

4. Remove and install your application

5. Run dumpsys package packages | grep yourpackagename to get the nativeLibraryPath or legacyNativeLibraryDir of your application.

6. Run ls on the nativeLibraryPath you had or on legacyNativeLibraryDir/armeabi, to check if your libcalculate.so is indeed there.

7. If it's there, check if it hasn't been altered from your original libcalculate.so file: is it compiled against the right architecture, does it contain the expected symbols, are there any missing dependencies. You can analyze libcalculate.so using readelf.

In order to check step 5-7, you can use my application instead of command lines and readelf: Native Libs Monitor

PS: It's easy to get confused on where .so files should be put or generated by default, here is a summary:

• libs/CPU_ABI inside an eclipse project

• jniLibs/CPU_ABI inside an Android Studio project

• jni/CPU_ABI inside an AAR

• lib/CPU_ABI inside the final APK

• inside the app's nativeLibraryPath on a <5.0 device, and inside the app's legacyNativeLibraryDir/CPU_ARCH on a >=5.0 device.

Where CPU_ABI is any of: armeabi, armeabi-v7a, arm64-v8a, x86, x86_64, mips, mips64. Depending on which architectures you're targeting and your libs have been compiled for.

Note also that libs aren't mixed between CPU_ABI directories: you need the full set of what you're using, a lib that is inside the armeabi folder will not be installed on a armeabi-v7a device if there are any libs inside the armeabi-v7a folder from the APK.

In gradle, after copying all files folders to libs/

jniLibs.srcDirs = ['libs']

Adding the above line to sourceSets in build.gradle file worked. Nothing else worked whatsoever.

In my case i must exclude compiling sources by gradle and set libs path

android {

    ...
    sourceSets {
        ...
        main.jni.srcDirs = []
        main.jniLibs.srcDirs = ['libs']
    }
....

The reason for this error is because there is a mismatch of the ABI between your app and the native library you linked against. Another words, your app and your .so is targeting different ABI.

if you create your app using latest Android Studio templates, its probably targeting the arm64-v8a but your .so may be targeting armeabi-v7a for example.

There is 2 way to solve this problem:

1. build your native libraries for each ABI your app support.
2. change your app to target older ABI that your .so built against.

Choice 2 is dirty but I think you probably have more interested in:

change your app's build.gradle

android {
    defaultConfig {
        ...
        ndk {
            abiFilters 'armeabi-v7a'
        }
   }
}