JNI- java.lang.UnsatisfiedLinkError: Native method not found

I'm developing an Android project using OpenCV. Some of the methods do not have Java version, so I have to use NDK to use them in my project. This is my first time using NDK, so after searching for some examples, I wrote my code, run it on my device, and received error message below: ``` 07-04 10:26:19.555 21270-21270/com.example.MyTest E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.UnsatisfiedLinkError: Native method not found: com.example.MyTest.JNIlib.readImg:()I at com.example.MyTest.JNIlib.readImg(Native Method) at com.example.MyTest.MyActivity$2.onClick(MyActivity.java:60) at android.view.View.performClick(View.java:4211) at android.view.View$PerformClick.run(View.java:17267) at android.os.Handler.handleCallback(Handler.java:615) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4898) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773) at dalvik.system.NativeStart.main(Native Method) ``` I regenerated .so files for several times, and check the naming for jni functions. I also added 'extern "C"' wrappers to jni functions. But none of those solutions worked. Notice: I always use Intellij Idea to develop JAVA programs, and since Idea doesn't support NDK, and I have to use Eclipse to get to NDK, so...this is also the first time I use Eclipse. I could have made a lot of silly mistakes. lol Below are my c++ codes and makefile. LocalMain.cpp ``` #include <stdio.h> #include <iostream> #include <opencv2/nonfree/nonfree.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/nonfree/features2d.hpp> #include <opencv2/opencv.hpp> #include <jni.h> #include <android/log.h> #include "LocalFeature.h" using namespace cv; using namespace std; int readImg() { /* do something*/ return 0; } // JNI interface functions, be careful about the naming. extern "C" { JNIEXPORT jint JNICALL Java_com_example_MyTest_JNIlib_readImg(JNIEnv * env, jobject obj); }; JNIEXPORT jint JNICALL Java_com_example_MyTest_JNIlib_readImg(JNIEnv * env, jobject obj) { return (jint)readImg(); } ``` LocalFeatures.h and LocalFeatures.cpp are not shown, but I'm sure the problem is not with them. Android.mk ``` LOCAL_PATH:= $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := nonfree_prebuilt LOCAL_SRC_FILES := libnonfree.so include $(PREBUILT_SHARED_LIBRARY) include $(CLEAR_VARS) LOCAL_MODULE := opencv_java_prebuilt LOCAL_SRC_FILES := libopencv_java.so include $(PREBUILT_SHARED_LIBRARY) include $(CLEAR_VARS) # Modify LOCAL_C_INCLUDES with your path to OpenCV for Android. LOCAL_C_INCLUDES:= E:/Java/libs/OpenCV-2.4.9-android-sdk/sdk/native/jni/include LOCAL_MODULE := mytest_lib LOCAL_CFLAGS := -Werror -O3 -ffast-math LOCAL_LDLIBS += -llog -ldl LOCAL_SHARED_LIBRARIES := nonfree_prebuilt opencv_java_prebuilt LOCAL_SRC_FILES := LocalMain.cpp \ LocalFeature.h \ LocalFeature.cpp include $(BUILD_SHARED_LIBRARY) ``` Those .cpp files and .mk files are in an Eclipse project. libmytest_lib.so, libopencv_java.so, libnonfree.so can be correctly generated. The following .java files are in an Intellij Idea project. I have copied these .so files to \lib in the Idea project. JNIlib.java ``` public class JNIlib { static { try { // Load necessary libraries. System.loadLibrary("opencv_java"); System.loadLibrary("nonfree"); System.loadLibrary("mytest_lib"); } catch( UnsatisfiedLinkError e ) { System.err.println("Native code library error.\n"); } } public static native int readImg(); } ``` Part of MainActivity.java ``` public class MyActivity extends Activity implements CameraBridgeViewBase.CvCameraViewListener2{ public View.OnClickListener onClickListener = new View.OnClickListener() { @Override public void onClick(View v) { JNIlib.readImg(); } }; /*Other irrevelant code*/ } ``` Thanks a lot!