在Android studio 3.3 版项目中使用cmake调用C/C++

前提

原因：由于本人在网上找了很多都是老版本的，不能用，于是就自己摸索。
本文环境
andriod studio 3.3

环境配置

网上搜索android studio 并下载，这些步骤，可以自行百度.

1. 点击File->Project Structure ，看下图，如果没有安卓NDK 点击可以自动下载.
   

创建工程

点击Finish

创建MakeLists.txt

不懂的可以百度搜索CMake的含义

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.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.


aux_source_directory(src/main/cpp MainCPP)

add_library( # Sets the name of the library.
             test_lib #.so库名 可自定义

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
            ${MainCPP} ) #源文件所在目录
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries 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 this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
                       test_lib #.so库名 可自定义
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

创建c++文件

在main 目录下添加一个cpp的目录
并创建文件
Test.cpp Test.h

#include "Test.h"

#include 
#include "Test2.h"


extern  "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_Test_1lib_getStr(JNIEnv *env, jclass type, jstring str_) {
    //const jchar* jcstr = (env)->GetStringChars(jstr, 0);
    // TODO

    return env->NewStringUTF("12313");
//    return (*env)->NewStringUTF(env, "1111111");
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_myapplication_Test_1lib_getStr2(JNIEnv *env, jclass type, jstring str_) {
    //const char *str = env->GetStringUTFChars(str_, 0);

    // TODO

    //env->ReleaseStringUTFChars(str_, str);

    return env->NewStringUTF(GetTest2String().c_str());
}

创建一个java的类

package com.example.myapplication;

public class Test_lib {
    static {
        System.loadLibrary("test_lib");
    }
    public static  native String getStr(String str);
    public static  native String getStr2(String str);
}

java 调用c++

生成so

点击 Build->Make Project 生成so
然后点击run 就可以了。