按照步骤执行：

local.properties文件（sdk和ndk配置路径）：

## This file is automatically generated by Android Studio.
# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
#
# This file should *NOT* be checked into Version Control Systems,
# as it contains information specific to your local configuration.
#
# Location of the SDK. This is only used by Gradle.
# For customization when using a Version Control System, please read the
# header note.
sdk.dir=E\:\\AndroidSDK
ndk.dir=E\:\\AndroidNDK\\android-ndk-r14b

CMakeLists.txt文件 :

cmake_minimum_required(VERSION 3.4.1)include_directories( ${CMAKE_SOURCE_DIR}/head)
add_library(jni_more SHARED  ${CMAKE_SOURCE_DIR}/cpp/More.cpp)find_library(lib-log log)target_link_libraries(jni_more ${lib-log})

app :  build.gradle文件：

apply plugin: 'com.android.application'
android {compileSdkVersion 28defaultConfig {applicationId "com.zzm.more"minSdkVersion 19targetSdkVersion 28versionCode 1versionName "1.0"testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" externalNativeBuild{cmake{abiFilters "arm64-v8a" , "armeabi-v7a"}}} externalNativeBuild {cmake{path "src/main/jni/CMakeLists.txt"}}buildTypes {release {minifyEnabled falseproguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'}}
}
dependencies {implementation fileTree(dir: 'libs', include: ['*.jar'])implementation 'com.android.support:appcompat-v7:28.0.0'implementation 'com.android.support.constraint:constraint-layout:1.1.3'testImplementation 'junit:junit:4.12'androidTestImplementation 'com.android.support.test:runner:1.0.2'androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

MainActivity.java文件：

package com.zzm.more;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends AppCompatActivity {static {System.loadLibrary("jni_more");}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Log.i("22m",test("zengzeming"));}public static native String test(String name);
}

xxx.cpp文件：

#include "jni.h"
#include "android/log.h"
//#include "../head/more.h"
#include <stdio.h>jstring  test(JNIEnv* env,jclass ,jstring name){const char* name_char=env->GetStringUTFChars(name,false);__android_log_print(ANDROID_LOG_INFO,"22m","name : %s",name_char);return env->NewStringUTF("zengzeming");
}const  char* classPathName="com/zzm/more/MainActivity";
const JNINativeMethod methods[]={{ "test","(Ljava/lang/String;)Ljava/lang/String;",(void*)test }
};
int registerNativeMethods(JNIEnv* env, const char* className, const JNINativeMethod* gMethods,int numMethods){jclass clazz;clazz=env->FindClass(className);if(clazz==NULL){__android_log_print(ANDROID_LOG_INFO,"22m","native registration unable to find class '%s'",className);return  JNI_FALSE;}if(env->RegisterNatives(clazz,gMethods,numMethods)<0){__android_log_print(ANDROID_LOG_INFO,"22m","RegisterNatives failed for  '%s'",className);return  JNI_FALSE;}return JNI_TRUE;
}int registerNatives(JNIEnv* env){
if(!registerNativeMethods(env,classPathName,methods, sizeof(methods)/ sizeof(methods[0]))){return  JNI_FALSE;
}
return JNI_TRUE;
}typedef  union {JNIEnv* env;void* venv;
}UnionJNIEnvToVoid;jint  JNI_OnLoad(JavaVM* vm, void* ){UnionJNIEnvToVoid uenv;uenv.venv=NULL;jint  result =-1;JNIEnv* env=NULL;__android_log_print(ANDROID_LOG_INFO,"22m","JNI_OnLoad");if(vm->GetEnv(&uenv.venv,JNI_VERSION_1_6)!=JNI_OK){__android_log_print(ANDROID_LOG_INFO,"22m","ERROR: GetEnv failed");goto fail;}env=uenv.env;if(registerNatives(env)!=JNI_TRUE){__android_log_print(ANDROID_LOG_INFO,"22m","ERROR: registerNatives failed");goto fail;}result=JNI_VERSION_1_6;fail:return  result;
}

run起来的log信息:

2019-01-05 07:20:12.808 30571-30571/com.zzm.more I/22m: JNI_OnLoad
2019-01-05 07:20:13.100 30571-30571/com.zzm.more I/22m: name : zengzeming
2019-01-05 07:20:13.100 30571-30571/com.zzm.more I/22m: zengzeming