Android NDK项目中的未定义引用错误

Question

我想将C++文件导入我的Android项目。首先，我使用Android Studio创建了一个带有C++支持的项目。它提供了骨架项目结构。我通过CMakeLists.text文件和add_library方法加载了我的文件。我可以成功加载我的C++文件并在项目视图中看到它。当我试图从native-lib.cpp中调用mClient.cpp中的方法时，我遇到了“未定义的引用”错误。由于我没有看到任何IDE警告，我可以说我的文件已经成功加载。但它在编译时不起作用。我还尝试使用add_executable通过cmake进行加载，但也产生相同的错误。请问我的配置和设置缺少什么？我是NDK和CMake的新手。感谢你的时间。

mClinet.cpp

#include "mClient.h"

static int hello(){
    return 1;
}

mClient.h

#ifdef __cplusplus
extern "C" {
#endif

static int hello();

#ifdef __cplusplus
}
#endif
#endif

这是我的CMake.text文件。

# Sets the minimum version of CMake required to build the native
# library. You should either keep the default value or only pass a
# value of 3.4.0 or lower.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds it for you.
# Gradle automatically packages shared libraries with your APK.

# set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -UNDEBUG")

add_library( # Sets the name of the library.
             native-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             # Associated headers in the same location as their source
             # file are automatically included.
             src/main/cpp/native-lib.cpp
             src/main/cpp/mClient.cpp )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because system libraries are included in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

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 )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in the
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries(native-lib android log)

我想从我的native-lib.cpp文件中调用hello()函数。

#include <jni.h>
#include <string>
#include "mClient.h"

extern "C"
jstring
Java_com_zawmyohtet_hellondk_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {

    int myInt = hello();

    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

- Zaw Myo Htet

---

@ Eichhörnchen 如果没有 extern "C"，JNI 调用将无法工作，因为名称混淆，这是完全合法的。 - Steve M

Answer 1

移除 static。 static 意味着函数在其翻译单元之外无法访问。

- Dan Albert