JNI实现Java调用C/C++代码详细代码示例

#ifndef JNITEST_CALCULATOR_H
#define JNITEST_CALCULATOR_H

class Calculator {
public:
    int Add(int a, int b);
};

#endif //JNITEST_CALCULATOR_H

#include "Calculator.h"

int Calculator::Add(int a, int b)
{
    return a + b;
}

cmake_minimum_required(VERSION 3.22.1)

project("jnitest")

include_directories(${CMAKE_CURRENT_SOURCE_DIR})

add_library(${CMAKE_PROJECT_NAME} SHARED
        native-lib.cpp
        Calculator.cpp)

target_link_libraries(${CMAKE_PROJECT_NAME}
        android
        log)

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

extern "C"
JNIEXPORT jint JNICALL
Java_com_cat_jnitest_MainActivity_CplusplusAdd(JNIEnv *env, jobject thiz, jint a, jint b) {
    // 这里因为jint和int的类型的范围是一样的，所以不需要转换
    Calculator cal;
    jint ret = cal.Add(a, b);
    return ret;
}

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        TextView tv = binding.sampleText;
        String str = "JNI: a + b = ";
        int add = CplusplusAdd(100, 200);
        str += String.valueOf(add);
        tv.setText(str);
    }