Linux 下 编写 JNI 代码

Java 代码 TestJNI.java

public class TestJNI {
    
    
    private native int testJniAdd(int v1, int v2);

    public void test() {
    
    
        System.out.println("The result: " + testJniAdd(2, 3));
    }

    public static void main(String[] args) {
    
    
        TestJNI instance = new TestJNI();
        instance.test();
    }

    static {
    
    
        System.load("～/JNITest/libtestJniLib.so");
    }
}

javah 生成 TestJNI.h 头文件

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class TestJNI */

#ifndef _Included_TestJNI
#define _Included_TestJNI
#ifdef __cplusplus
extern "C" {
    
    
#endif
/*
 * Class:     TestJNI
 * Method:    testJniAdd
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_TestJNI_testJniAdd
  (JNIEnv *, jobject, jint, jint);

#ifdef __cplusplus
}
#endif
#endif

TestJNI.c 代码实现

#include "TestJNI.h"

/*
 * Class:     TestJNI
 * Method:    testJniAdd
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_TestJNI_testJniAdd
  (JNIEnv * env, jobject obj, jint v1, jint v2) {
    
    
    return v1 + v2;
}

在 Android NDK 下编译so

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE := testJniLib
LOCAL_SRC_FILES := TestJNI.c

include $(BUILD_SHARED_LIBRARY)

在 Linux gcc 下编译so

#!/bin/sh

gcc -I '～/java/include' -I '～/java/include/linux' TestJNI.c -shared -o libtestJniLib.so