我使用 Android Studio 2.2 和 cmake 来构建 jni 文件。
我想在 jni 文件中显示日志,但收到错误消息“未定义对 `__android_log_write 的引用”。
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} )
我的两个jni文件与下面相同,没有函数名
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(Module: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:将 C 和 C++ 代码添加到您的项目。我想我可以使用log api。
我的代码或我的设置有什么问题?
Update:
我发现我的第一个 jni 库中没有问题(更新代码)。
仅在第二个库中发生错误。
例如:target_link_libraries(测试库,本机库, ...), native-lib 是第二个要加载的库。
所以native-lib不能使用log api。
现在我唯一能做的就是删除native-lib。但我真的很想知道为什么?