ndk引入

0.配置：

androidstudio :
preferences->Android SDK->SDK Tools 下载NDK +CMake

1590475246611.jpg

1.新项目：

androidstudio :
file->new project->natite c++(下滑才能看见)

2.local.properties

这里查看是否有ndk.dir=/../..
如未有,则添加ndk.dir=/Users/admin/Library/Android/sdk/ndk/../

3.cpp位于main目录下,和java同级

新项目自动创建,老项目创建CMakeLists.txt
创建个xx.cpp

4.MainActivity.java来个方法测试

package main;

import android.app.Activity;
import android.app.ActivityManager;
import android.content.Context;
import android.os.Bundle;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.zhisheng.test.R;

import java.util.List;

public class MainActivity extends Activity {
    static {
        System.loadLibrary("native-lib");
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.inflate);
        (((TextView)(findViewById(R.id.tvTwoJump)))).setText(getStringJNI());
    }

    public native String getStringJNI();
}

4.cpp来个方法测试

#include <jni.h>
#include <string>


extern "C"
JNIEXPORT jstring JNICALL
//方法名:Java_包名_类名_java调用方法名
//个人理解 c++很少了解
Java_main_MainActivity_getStringJNI(JNIEnv *env, jobject thiz) {
    // TODO: implement getStringJNI()
    std::string hello = "Hello2222 from C++";
    return env->NewStringUTF(hello.c_str());
}

项目测试完成

CMakeLists.txt 上传一下哈

# 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.

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 )

# 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.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )