How to resolve the java.lang.UnsatisfiedLinkError in NDK in Android?

Question

I am new in ndk development in android.I have gone through the file system of ndk android. Here, explaining what i have done. 1) i have created a folder named "jni" then create 2 file named Android.mk and ndkfoo.c.

In Android.mk

LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) # Here we give our module name and source file(s) LOCAL_MODULE := ndkfoo LOCAL_SRC_FILES := ndkfoo.c include $(BUILD_SHARED_LIBRARY)

and in ndkfoo.c

#include <string.h> #include <jni.h> jstring Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction(JNIEnv* env, jobject javaThis) { return (*env)->NewStringUTF(env, "Hello from native code!"); }

then i have created NdkFooActivity class, in which i have written

// load the library - name matches jni/Android.mk static { System.loadLibrary("ndkfoo"); }

But now when i build from cygwin in xp it creates .so file successfully then i run as android application. It gives me java.lang.UnsatisfiedLinkError in LOGCAT.

So, Please let me know where i am wrong.

Thanks in Advance,

Are you sure the class where you declared invokeNativeFunction() is actually com.mindtherobot.samples.ndkfoo.NdkFooActivity? You can post all the code — ognian
– ognian, Commented Jul 17, 2010 at 19:14
Specifically, please include the declaration of the native method in the .java file. Show the "package" and "class" declarations too. Also, add a JNI_OnLoad function to your shared library and put some logging there so you can make sure the library is being loaded successfully. — fadden
– fadden, Commented Jul 19, 2010 at 17:47
Check for this declaration in the ndkfoo.c Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction, this should change to your package name like Java_com_your_package_ndkfoo_NdkFooActivity_invokeNativeFunction — pradeep
– pradeep, Commented Apr 30, 2011 at 11:31

StarDust · Accepted Answer · 2011-03-09 08:33:56Z

I think you forgot to change the package name.

Java_com_mindtherobot_samples_ndkfoo

It should be your package what you have specified creating project.

Daniel Rodriguez · Accepted Answer · 2012-12-13 23:47:32Z

21

Also(just ran into this issue), please note that System.loadLibrary() will always throw an exception if you are testing on the Intel Atom x86 emulator. It works just fine on regular Android emulators and debugging on a physical device.

answered Dec 13, 2012 at 23:47

Daniel Rodriguez

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5 Comments

Bhavesh Patadiya Over a year ago

@Daniel Rodriguez : Thank you soooooooooo much. :) :) :)

Daniel Rodriguez Over a year ago

Trial an error. Many debugging hours were lost to bring you this answer.

CCJ Over a year ago

...unless the library you're loading was compiled for x86

2013Asker Over a year ago

It's also worth noting that this problem can be solved by compiling for all architectures as shown on stackoverflow.com/a/12607739/2264920

Yirga Over a year ago

How do you know if the emulator is Intel Atom x86 or regular emulator?

18446744073709551615 · Accepted Answer · 2012-01-20 06:53:35Z

11

Although this has not been the OP's problem, I had the same java.lang.UnsatisfiedLinkError because of missing

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

answered Jan 20, 2012 at 6:53

18446744073709551615

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1 Comment

ademar111190 Over a year ago

normally it causes the follow problem: 'java.lang.ExceptionInInitializerError java.lang.UnsatisfiedLinkError: Library xyz... not found'

SomeCallMeTim · Accepted Answer · 2010-09-25 06:23:49Z

There's a good chance the signature is wrong, as others have mentioned.

If you run the javah utility, you can find the exact signature. From the bin folder in your project, where the .apk is and the root of the Java class hierarchy is generated, run:

javah -o jni_sig.h com.mindtherobot.whatever.your.package.is.NdkFooActivity

...and, if you got the package name and class name correct, it will write out a header (called jni_sig.h) with the correct function signature(s) for any native functions. Copy that to your header and .c file, adding parameters as needed, and it should work correctly.

Thanks. On my system, it needs to be run from the Classes sub directory.

Elis Popescu · Accepted Answer · 2012-12-11 20:41:44Z

Maybe not relevant anymore but as far as I know you also need to add the "lib" prefix to your native library name. In your case you need to change the Android.mk to "LOCAL_MODULE := libndkfoo" and keep "System.loadLibrary("ndkfoo");" as it is. Check the ndk sample code.

Justin Buser · Accepted Answer · 2012-03-01 05:21:55Z

I'm pretty sure that should be:

JNIEXPORT jstring JNICALL Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction(JNIEnv* env, jobject javaThis) { return (*env)->NewStringUTF(env, "Hello from native code!"); }

Which SDK are you targeting and which version of the NDK do you have? Does the error you're getting say that it couldn't load the library at all or that there was an unimplemented method? Either way make sure you don't have android:hasCode="false" set on the application tag in your manifest.

You can also open up the APK file after a build using winrar or something similar to make sure that the libndkfoo.so file is actually being included with the package.

Either way if you aren't declaring the native function in NdkFooActivity you will get that error, i.e.

public static native String invokeNativeFunction();

SRedouane · Accepted Answer · 2013-08-11 21:23:36Z

JNIEXPORT jstring JNICALL Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction(JNIEnv* env, jobject javaThis) { return (*env)->NewStringUTF(env, "Hello from native code!"); }

the problem is that you compile for a target processor and execute in other. if you compile in ARM(armeabi) then execute in armeabi based emulator. create a file called application.mk in same folder as Android.mk and put inside it one of this:

APP_ABI := x86
APP_ABI := armeabi
APP_ABI := mips
APP_ABI := armeabi x86 mips //to compile in all target and you will get 3 *.so files

then compile->run. it should work.

Sajal Saha · Accepted Answer · 2012-11-25 08:41:30Z

Create a file Application.mk in jni folder.Copy following line and paste it to Application.mk and save.Now build the project with your cgywin and run again

APP_ABI := armeabi armeabi-v7a

Jagdeep Singh · Accepted Answer · 2013-06-11 05:58:12Z

The method name Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction

may be not same as that of your package name or class name. To make this naming of method exactly same you must use javah.

This will make a header file which will be having the same method name that is required.To make this header file go to the classes folder in the bin of your project(make sure you have created the java file with static method and build it properly) by this command in your terminal

~/workspace/Android_Example2/bin/classes$

In this directory write the following command

sudo javah -jni com.NDK.android_example2.MainActivity

Change the package name and class name according to your project.This will create a com_NDK_android_example2_MainActivity.h in your classes folder.

Simply move this file into your jni folder. In this file, there will be static methods that you have created in the MainActivity.java file but they are just declared not implemented that you will implement in your C file.

NOTE: While Coping the method check that the method parameters are need to be declared, so make them declare in your C file.

Hope this help.

Vinayakkumar · Accepted Answer · 2013-07-28 10:01:02Z

Replace this

Java_com_mindtherobot_samples_ndkfoo_NdkFooActivity_invokeNativeFunction

With

Java_your_packege_name_your_Activity_Name_invokeNativeFunction

Example if your package is com.pack and Activity Name name is MainActivity then

Java_com_pack1_MainActivity_invokeNativeFunction

Don't forget to add reference in Activity.

// load the library - name matches jni/Android.mk

static { System.loadLibrary("ndkfoo"); } public native String invokeNativeFunction();

Repeat all these step it should work :)

Awesomeness · Accepted Answer · 2013-03-29 12:58:50Z

I also had a java.lang.UnsatisfiedLinkError error. I verified everything mention in above answers but was still getting the error. I eventually discovered that the JNI method names cannot have underscores.

Example: Java_com_example_app_NativeLib_print_out_stuff <- generates java.lang.UnsatisfiedLinkError: print_out_stuff

Rename the print_out_stuff function to something without underscores: Java_com_example_app_NativeLib_printOutStuff <- works

karyochi · Accepted Answer · 2013-03-29 15:22:30Z

here's a tutorial how to use native code: here

make sure you dont have any spaces in your project path. also you cant use an underscore in your package or project name.

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