编译生成.so文件

1.新建带c++支持的Android工程。demo编译运行无误

2.在CMakeLists.txt中添加，生成.so文件可以拷贝出去供其他工程使用

# For more information about using CMake with Android Studio, read the
# documentation: http://www.51sjk.com/Upload/Articles/1/0/268/268069_20210708022713721.html

# Sets the minimum version of CMake required to build the native library.

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 them for you.
# Gradle automatically packages shared libraries with your APK.
#设置生成的so动态库最后输出的路径
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI})

#在add_library之前设置
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).
             native-lib.cpp )

3.动态注册native方法名称，这样可以注册其他工程的包路径

// native方法
static jstring JNICALL native_get_String(JNIEnv *env, jobject obj, jobject content) {

}

/**
 * 注册的native调用的方法
 */
static const JNINativeMethod gMethods[] = {
        {"stringFromJNI",  "(Landroid/content/Context;)Ljava/lang/String;", (jstring *) native_get_String}
};

/**
 * 注册方法到JVM中
 * System.loadLibrary会自动调用JNI_OnLoad，在此进行动态注册
 *
 * @param jvm
 * @param reserved
 * @return
 */
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *jvm, void *reserved) {
    // 防止动态调试
    ptrace(PTRACE_TRACEME, 0, 0, 0);

    JNIEnv *env = NULL;//注册时在JNIEnv中实现的，所以必须首先获取它
    jint result = JNI_FALSE;

    //获取env指针
    if (jvm->GetEnv((void **) &env, JNI_VERSION_1_6) != JNI_OK) {//从JavaVM获取JNIEnv，使用1.6的版本
        return result;
    }

    //获取类引用，写类的全路径（包名+类名）
    jclass clazz = env->FindClass("com.mobile.encrypt.api.whitebox.EncryptUtils");
    if (clazz == NULL) {
        return result;
    }

    //注册方法
    if (env->RegisterNatives(clazz, gMethods, sizeof(gMethods) / sizeof(gMethods[0])) < 0) {
        return result;
    }
    //成功
    result = JNI_VERSION_1_6;
    return result;
}

4.获取方法签名，在build的?/build/intermediates/classes/debug/目录下获取定义native方法名称工具类的class文件。使用javap -s ?xxx.class获取方法签名

5.CMakeLists.txt添加多c++源文件

6.gradle配置

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