java.lang.UnsatisfiedLinkError：dlopen在64位而不是32位上失败，而.so应该在x86中构建

Question

I am trying to use JNI in Android Studio, I added the JNI function under the sample native-lib.cpp which created by Android Studio by default (after adding C++ support)

However, I am facing an error

java.lang.UnsatisfiedLinkError: No implementation found for boolean com.example.user.project.Tracker.isTracking_0(boolean) (tried Java_com_example_user_project_Tracker_isTracking_10 and Java_com_example_user_project_Tracker_isTracking_10__Z)

I also tried to add this to MainActivity

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

but I will get another exception

java.lang.UnsatisfiedLinkError: dlopen failed: "/data/app/com.example.user.project/lib/x86/libtracker.so" is 64-bit instead of 32-bit

I can see that my library has been built successfully, this is the track message it shows when build

Build tracker x86 [1/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/fhog.cpp.o [2/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/tracker.cpp.o [3/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/ctracker.cpp.o [4/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/native-lib.cpp.o [5/5] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/x86/libtracker.so Build tracker mips [1/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/tracker.cpp.o [2/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/fhog.cpp.o [3/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/ctracker.cpp.o [4/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/native-lib.cpp.o [5/5] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/mips/libtracker.so Build tracker x86_64 [1/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/tracker.cpp.o [2/5] Building CXX object CMakeFiles/tracker.dir/src/main /cpp/fhog.cpp.o [3/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/ctracker.cpp.o [4/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/native-lib.cpp.o [5/5] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/x86_64/libtracker.so Build tracker armeabi [1/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/tracker.cpp.o [2/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/fhog.cpp.o [3/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/ctracker.cpp.o [4/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/native-lib.cpp.o [5/5] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi/libtracker.so Build tracker armeabi-v7a [1/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/tracker.cpp.o [2/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/fhog.cpp.o [3/5] Building CXX object CMakeFiles/tracker.dir/src/main/cpp/ctracker.cpp.o [4/5] Building CXX object CMakeFiles/tracker .dir/src/main/cpp/native-lib.cpp.o [5/5] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi-v7a/libtracker.so

This is my CMakeLists

set (pathToOpenCv /home/user/OpenCV-android-sdk3.2)
set (pathToProject /home/user/AndroidStudioProjects/project)

cmake_minimum_required(VERSION 3.4.1)

set(CMAKE_VERBOSE_MAKEFILE on)

include_directories(${pathToOpenCv}/sdk/native/jni/include)

FILE(GLOB_RECURSE cppfiles "src/main/cpp/*.cpp")

add_library(lib_opencv SHARED IMPORTED)

add_library(tracker SHARED ${cppfiles})

set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION ${pathToProject}/app/src/main/jniLibs/${ANDROID_ABI}/libopencv_java3.so)

find_library(
              log-lib
              log )
target_link_libraries( tracker
                       ${log-lib}
                       lib_opencv
                       )

This is my native-lib.cpp

#include <jni.h>
#include <string>
extern "C"
JNIEXPORT jboolean JNICALL Java_com_example_user_project_Tracker_isTracking_10
        (JNIEnv *env, jboolean boolean) {
    printf("\n c-boolean: %d ", boolean);
    if (boolean == JNI_TRUE) {
        printf("true");
    } else {
        printf("false");
    }
    boolean = false;
    return boolean;
};

So what could be the reason that Android studio cannot find the method from my .so library, and appear java.lang.UnsatisfiedLinkError? Also, I don't why my x86 library is 64bit instead of 32bit.

Thanks

UPDATE

Just double check the android log, I think it does not load the tracker library properly. I think now the 64 bits error is the major problem. Update the issue title

java.lang.UnsatisfiedLinkError: dlopen failed: "/data/app/com.example.user.project/lib/x86/libtracker.so" is 64-bit instead of 32-bit

In build.gradle I have set the abiFilter, and my AVD is x86 device

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
    defaultConfig {
        applicationId "com.example.user.project"
        minSdkVersion 23
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
    }

    sourceSets.main {
        jniLibs.srcDir 'src/main/jniLibs'
        jni.srcDirs = []
    }



    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }

    defaultConfig {
        ndk {
            abiFilters "armeabi", "armeabi-v7a", "x86", "x86_64", "mips"
        }

    }
}

// call regular ndk-build(.cmd) script from app directory


dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
    compile project(':openCVLibrary320')
}

Answer 1

Here is what caused your problem:

sourceSets.main {
    jniLibs.srcDir 'src/main/jniLibs'
    jni.srcDirs = []
}

These definitions do not coexist safely with externalNativeBuild .

Essentially, in the new Android Studio jni.srcDirs is not relevant. It finds which C/++ files to use by analyzing your cmake or ndk-build logs. But even when you use externalNativeBuild , AS copies the binaries it finds in jniLibs to the final APK. Somehow a wrong version of the libtracker.so got stuck in the src/main/jniLibs/x86 directory. It is important to remember that build or rebuild won't normally remove/update binaries there.