问题描述

我使用Android Studio 2.2和Cmake构建JNI文件.

我想在jni文件中显示log，但获取错误消息”未定义的引用`_____ android_log_write”.

我的cmakelists.txt文件是:

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 )

add_library( # Sets the name of the library.
         test-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/test-lib.cpp )

include_directories( src/main/jni/ )

# 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( # Specifies the target library.
                   test-lib
                   native-lib
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )

和我的两个jni文件与下面没有函数名称

JNIEXPORT jstring JNICALL Java_com_cyweemotion_www_jnitest_MainActivity_stringFromJNI
    (JNIEnv *env, jobject){
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Error here");
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
};

我的build.gradle(模块:app)是

android {
    compileSdkVersion 23
    buildToolsVersion "24.0.3"
    defaultConfig {
        minSdkVersion 19
        targetSdkVersion 24
        versionCode 2
        versionName '1.02'
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.config
        }
        debug {
            jniDebuggable false
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
    productFlavors {
    }
}

根据 android文档:添加C ++代码.我想我可以使用log API.

我的代码或设置中有什么问题?

更新:

我发现在我的第一个JNI库(更新代码)中这不是问题.

它仅在第二个库中发生错误.

ex:target_link_libraries(test-lib，本地lib ，…)，本地lib是第二个要加载的库.

因此，本地lib不能使用log api.

现在，我只能做到删除本地利率.但是我真的想知道为什么?

推荐答案

我终于发现我应该分开进行链接.

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

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

以上所述是小编给大家介绍的Android NDK(cmake):"在第二个JNI库中使用log API时，对" __android_log_write"的"未定义"引用,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对77isp云服务器技术网的支持！