Undefined reference to AAssetManager_fromJava

问题

I am trying to access assets from an android apk using AAssetManager. However, I keep getting "Undefined reference to AAssetManager_fromJava" even though I've included asset_manager.h and asset_manager_jni.h Other functions from asset_manager.h, like AAssetManager_openDir(mgr, "") etc also can't be referenced.

Here's the complete code

#define EXPORT_API

#include <string.h>
#include <jni.h>
#include <android\log.h>

#include <sys\types.h>
#include <android\asset_manager.h>
#include <android\asset_manager_jni.h>

#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, "com.devin - native", __VA_ARGS__)

JNIEnv* env=0;

#ifdef __cplusplus
extern "C" {
#endif

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* pvt){
    LOGD("JNI_OnLoad() called");
    vm->AttachCurrentThread(&env, 0);
    return JNI_VERSION_1_2;
}

EXPORT_API void LoadAsset(char* filename, jobject assetManager){
    AAssetManager* mgr = AAssetManager_fromJava(env, assetManager);
        /* More stuff */
}

#ifdef __cplusplus
};
#endif

This code is in a .cpp file and being compiled with NDK R8. Am I doing something terribly wrong here?

回答1:

My mistake. I didn't have "android" library added to the linker. I have actually setup NDK dev environment on Visual Studio Express and "android" library wasn't added to my project by default.

If you are using makefiles, be sure to add -landroid to your LOCAL_LDLIBS when using native AssetManager.

回答2:

Android Studio developers, İf you have ExternalNativeBuild file which is called "CMakeList.txt" you must append this code to the file CMakeList.txt

find_library( # Sets the name of the path variable.
          android-lib

          # Specifies the name of the NDK library that
          # you want CMake to locate.
          android )
target_link_libraries( 
                   ${log-lib}
                    ${android-lib})

if you also have native lib you can add easily like this

target_link_libraries( native-lib
                   ${log-lib}
                    ${android-lib})

It should work!

回答3:

I added the following to gradle.build

android.ndk { ldLibs.addAll(["android", "log"]) }

回答4:

I fixed it by adding following to Android.mk

LOCAL_SHARED_LIBRARIES += libandroid

回答5:

find_library( # Sets the name of the path variable.
    log-lib

    # Specifies the name of the NDK library that
    # you want CMake to locate.
    log
)

find_library(android-lib android)

target_link_libraries( # Specifies the target library.
    hll
    ${log-lib}
    ${android-lib}
    # Links the target library to the log library
    # included in the NDK.
)

来源：https://stackoverflow.com/questions/12552208/undefined-reference-to-aassetmanager-fromjava

标签

android

android-ndk

android-assets