LOCAL_SHARED_LIBRARIES crashes my app

Question

I am trying to use a C library (apriltag) in my android app (4.4) using the NDK. I prebuilt the library using the android toolchain. After that, I followed this tutorial ( link ) to use apriltag in my C++ module.

My android.mk :

include $(CLEAR_VARS)
LOCAL_MODULE := apriltag_prebuilt_lib
LOCAL_SRC_FILES := $(LOCAL_PATH)/prebuilt/libapriltag.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := gle_main
...
LOCAL_LDLIBS := -landroid -llog -lEGL -lGLESv2
LOCAL_SHARED_LIBRARIES += apriltag_prebuilt_lib
LOCAL_STATIC_LIBRARIES := cpufeatures android_native_app_glue ndk_helper

However, as soon as I reference it in another module, my app cannot even start. Android monitor tells me that process has died. If I comment the line LOCAL_SHARED_LIBRARIES I can start it but cannot use apriltag in my module...

Also, it works on Android 7. With this device I get the invalid DT_NEEDED entry "app/build/.../libapriltag.so" error for libgle_main.so (the c++ module that uses apriltag).

Any ideas to get it work on my Android 4.4 device ?

EDIT 1: I've added to my Activity :

static {
    System.loadLibrary("apriltag");
    System.loadLibrary("gle_main");
}

But now, I get this error :

java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "sqrt" referenced by "/data/app/com.laas.lumus_app-1/lib/arm/libapriltag.so"

I guess it is related to the math library so I added to my gle_main and my apriltag_prebuilt_lib .

LOCAL_LDLIBS += -lm

Nothing changed.

Now, the app doesnt start on the 4.4 AND the 7.0 device.

Thank you in advance.

Answer 1

Because you are using a prebuilt shared library, libapriltag.so . You have to let gradle add it to your apk also, and then you can use it into gle_main . You have to add this line to your module/build.gradle script

android{
    sourceSets.main{
         jniLibs.srcDir 'path_to_libapriltag'
}

Answer 2

最后，我决定将所有源文件放入我的项目中，以使用Android Studio而不是使用外部工具链来完全构建它。