C++给Java写程序

柔情只为你懂 2023-10-06 20:00 12阅读 0赞

创建一个Java项目，编码选择utf8  
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编译Java文件生成.h文件  
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将.h文件拷贝到C++项目中  
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实现方法  
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编译生成解决方案，并复制路径E:\\VS2017\\edoyun\\x64\\Release  
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运行输入结果  
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进阶：实现手动注册一个实现的方法  
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完整代码如下：

package eDoYun;
    
    public class NativeClass {
        
    	public native int nativeAdd(int a, int b);
    
    	public native double nativefAdd(double a, double b);
    
    	public static void main(String[] args) {
        
    		System.loadLibrary("edoyun");// 要生成的C++模块
    
    		NativeClass a = new NativeClass();
    
    		a.nativeAdd(10, 20);
    
    		a.nativefAdd(1.234, 2.345);
    	}
    }

// dllmain.cpp : 定义 DLL 应用程序的入口点。
    #include "pch.h"
    #include"eDoYun_NativeClass.h"
    
    BOOL APIENTRY DllMain( HMODULE hModule,
                           DWORD  ul_reason_for_call,
                           LPVOID lpReserved
                         )
    {
        
        switch (ul_reason_for_call)
        {
        
        case DLL_PROCESS_ATTACH:
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
        }
        return TRUE;
    }
    
    //实现方式1：通过命名规则绑定
    JNIEXPORT jint JNICALL Java_eDoYun_NativeClass_nativeAdd
    (JNIEnv *, jobject, jint a, jint b) {
        
    	//打印日志和a,b的值
    	printf("%s(%d):%s a=%d b=%d\r\n", __FILE__, __LINE__, __FUNCTION__, a, b);
    	return a + b;
    }
    
    //实现方式2：手动注册方法绑定
    JNIEXPORT jdouble JNICALL nativefAdd
    (JNIEnv *, jobject, jdouble a, jdouble b) {
        
    	//打印日志和a,b的值
    	printf("%s(%d):%s a=%f b=%f\r\n", __FILE__, __LINE__, __FUNCTION__, a, b);
    	return a + b;
    }
    
    
    JNIEXPORT jint JNICALL 
    JNI_OnLoad(JavaVM* vm, void* reserved) {
        
    	jint result = -1;
    	JNIEnv* env = NULL;
    	if (vm->GetEnv((void**)&env, JNI_VERSION_1_1) != JNI_OK) {
        
    		printf("%s(%d):%s\r\n", __FILE__, __LINE__, __FUNCTION__);
    	}
    	jclass clz = env->FindClass("eDoYun/NativeClass");
    	if (clz == NULL) {
        
    		printf("%s(%d):%s\r\n", __FILE__, __LINE__, __FUNCTION__);
    		return -1;
    	}
    
    	JNINativeMethod methods[] = {
        
    		{
        (char*)"nativefAdd",(char*)"(DD)D",(void*)&nativefAdd}//"(DD)D"两个参数都是double返回值也是double
    	};
    
    	//注册
    	result = env->RegisterNatives(clz, methods, sizeof(methods) / sizeof(JNINativeMethod));
    	if (result != 0) {
        
    		printf("%s(%d):%s\r\n", __FILE__, __LINE__, __FUNCTION__);
    		return -1;
    	}
    
    	return JNI_VERSION_1_1;
    }

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