Android JNI学习：创建一个支持native的Module

1. New Module选择Android NativeLibrary生成一个Lib，自动配置好的externalNativeBuild脚本

defaultConfig {
        minSdk 25
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        consumerProguardFiles "consumer-rules.pro"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
    }
externalNativeBuild {
        cmake {
            path "src/main/cpp/CMakeLists.txt"
            version "3.10.2"
        }
    }

2. Java编写Native函数

 public native String encJNI(String src);

3. CPP编写native层实现

extern "C"
JNIEXPORT jstring JNICALL
Java_com_lg_encnativelib_NativeLib_encJNI(JNIEnv *env, jobject thiz, jstring src) {
    const char *name = env->GetStringUTFChars(src, NULL);
    std::string res = EncImpl::doEnc(name);
    env->ReleaseStringChars(src, reinterpret_cast<const jchar *>(name));
    return env->NewStringUTF(res.c_str());
}

4. 添加新的cpp文件
   在CMakeLists.txt中添加引用

add_library(
    ...
    EncImpl.cpp ）

5. 添加目录下的所有的cpp文件

# 查找当前目录下的所有源文件
# 并将名称保存到 DIR_SRCS 变量
aux_source_directory(. DIR_SRCS)
add_library( # Sets the name of the library.
             encnativelib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             #encnativelib.cpp
             #EncImpl.cpp
             ${DIR_SRCS}
        )

6. 添加子目录的cpp文件

aux_source_directory(./third    DIR_SRCS)

7. 手把手教你如何在Android下进行JNI开发（入门）
   https://cloud.tencent.com/developer/article/1983561