[移动开发] Android ndk开发入门集锦一

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[移动开发]Android ndk开发入门集锦一

1、搭建NDK环境

1.1首先配置ndk环境变量如下图输出如何配置ndk环境变量这里不再赘述请自行百度

1.2.如果没有ndk环境需要在AndroidStudio中下载如下图

?1.3通过这里下载NDK下载?选择自己对应电脑系统位数下载即可比如32bit或者64bit 这里不再赘述如下图所示下载好解压默认一般放在Android sdk根目录

1.4 NDK版本选择
?

2、添加c++支持库

新建一个Project工程选择c++ 然后选择对应的版本这里需要注意是你的c++Standard支持库与ndk版本一致否则会出现编译异常点击finish就会开始构建项目

3、配置app/build.gradle文件

配置app build.gradle 主要配置ndk的 path 和 ndk版本号以及abiFilters 芯片支持类型

abiFilters 'armeabi-v7a', 'arm64-v8a'

?3.1选择对应cmake版本

??3.2CmakeLists.txt文件

# 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 3.10.2) 对应cmake版本号

# Declares and names the project.

project("myapplication") 项目名称


# 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.
             face-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
        face-lib.cpp Facer.h Facer.cpp)
#这里指添加cpp文件 h头文件你的加载库文件
# 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 )
//这里指找到cmake库名字

# 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.
                       face-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )
//关联ndk动态链接so库

4、编写jni代码 cpp文件

#include <jni.h>  导入jni头文件
#include <string>  导入字符串库
#include "Facer.h"  导入Facer.h头文件

extern "C" JNIEXPORT jstring JNICALL
//这里必须全路径否则就会找不到对应的类 包名+类名+方法名
Java_com_example_myapplication_Facer_getFacer(JNIEnv *env, jclass clazz, jstring top,
                                              jstring bottom, jstring right,jstring brow,jstring eyes,
                                          jstring hand) {
    Facer facer(//使用 env->GetStringUTFChars将jstring转化为string
            env->GetStringUTFChars(top, 0),
            env->GetStringUTFChars(bottom, 0),
            env->GetStringUTFChars(right,0),
            env->GetStringUTFChars(brow, 0),
            env->GetStringUTFChars(eyes, 0),
            env->GetStringUTFChars(hand, 0)
    );

    return env->NewStringUTF(facer.getFace().c_str());//返回对应字符串
}

5、添加头文件

//
// Created by zm-pc on 2022/7/2.
//

#include <iostream> 

using namespace std;

#ifndef MY_APPLICATION_FACE_H
#define MY_APPLICATION_FACE_H


class Facer {
public:
    Facer(const string &top="-",const  string &bottom="-",const  string &right="%",
          const string &brow="~", const string &eyes=".",const string &hand="$");

    ~Facer();

public:
    string top;
    string bottom;
    string right;
    string brow;
    string eyes;
    string hand;
public:
    void printFace();
    string getFace();


};


#endif //MY_APPLICATION_FACE_H