JNI操作二维数组

之前的文章讲解了有关JNI使用方法，这篇文章进阶一点，介绍下JNI操作二维数组的方法。有了之前文章的操作JNI的方法，这里直接上代码了。

Java代码部分

package com.testjni;

public class TestJNI
{
    private static final int ONE_DIMENSION = 3;

    private static final int TWO_DIMENSION = 2;

    public native int test2DimensionArray(int[][] aHoleList);

    static
    {
        System.load("D:\eclipseWebWorkSpace\testest\src\com\testjni\libTestJNI_amd64.dll");
    }

    public static void main(String[] args)
    {
        TestJNI testJNI = new TestJNI();

        //测试二维数组
        int[][] test = new int[ONE_DIMENSION][TWO_DIMENSION];
        System.out.println("
java before--->");
        for (int i = 0; i < ONE_DIMENSION; i++)
        {
            StringBuilder sb = new StringBuilder("test[");
            for (int j = 0; j < TWO_DIMENSION; j++)
            {
                if (j == 0)
                {
                    sb.append(i).append("] = ").append(test[i][j]).append(" ");
                }
                else
                {
                    sb.append(test[i][j]).append(" ");
                }
            }
            System.out.println(sb.toString());
        }
        int res = testJNI.test2DimensionArray(test);

        System.out.println("
java after--->res=" + res);
        for (int i = 0; i < ONE_DIMENSION; i++)
        {
            StringBuilder sb = new StringBuilder("test[");
            for (int j = 0; j < TWO_DIMENSION; j++)
            {
                if (j == 0)
                {
                    sb.append(i).append("] = ").append(test[i][j]).append(" ");
                }
                else
                {
                    sb.append(test[i][j]).append(" ");
                }
            }
            System.out.println(sb.toString());
        }
    }
}

C头文件

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

#ifndef _Included_com_testjni_TestJNI
#define _Included_com_testjni_TestJNI
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_testjni_TestJNI
 * Method:    nativeBsmGetHoleList
 * Signature: ([[I)I
 */
JNIEXPORT jint JNICALL Java_com_testjni_TestJNI_test2DimensionArray
  (JNIEnv *, jobject, jobjectArray);

#ifdef __cplusplus
}
#endif
#endif

C源码文件

#include <stdio.h>
#include "com_testjni_TestJNI.h"

#define ONE_DIMENSION 3
#define TWO_DIMENSION 2
JNIEXPORT jint JNICALL Java_com_testjni_TestJNI_test2DimensionArray(JNIEnv *env, jobject obj, jobjectArray test)
{
    int jniTest[ONE_DIMENSION][TWO_DIMENSION];
    for (int i = 0; i < ONE_DIMENSION; i++)
    {
        for (int j = 0; j < TWO_DIMENSION; j++)
        {
            jniTest[i][j] = 10 * (i + 1)+ j;
        }
    }

    printf("
jni:
");
    jintArray testArray;
    for (int i = 0; i < ONE_DIMENSION; i ++)
    {
        //从输入参数二维数组aHoleList中取出某个一维数组
        testArray = (jintArray)env->GetObjectArrayElement(test, i);
        printf("testArray[%d]=%d, %d, %d, testArray[0] addr = %d; testArray[1] addr = %d, testArray[2] addr = %d; testArray addr=%d; sizeof(jintArray)=%d
", 
            i, testArray[0], testArray[1], testArray[2], &testArray[0], &testArray[1], &testArray[2], testArray, sizeof(jintArray));
        //获取一维数组的指针
        jint *testP = env->GetIntArrayElements(testArray, NULL);
        printf("C before, testP[%d]=%d, %d, testP addr=%d
", i, testP[0], testP[1], testP);
        //改变数组的值
        for (int j = 0; j < TWO_DIMENSION; j++)
        {
             *(testP + j) = jniTest[i][j];
        }
        printf("C after, testP[%d]=%d, %d, testP addr=%d
", i, testP[0], testP[1], testP);
        env->ReleaseIntArrayElements(testArray, testP, 0);
        printf("
");
    }
    return 666;
}

运行结果

java before--->
test[0] = 0 0 
test[1] = 0 0 
test[2] = 0 0 

java after--->res=666
test[0] = 10 11 
test[1] = 20 21 
test[2] = 30 31 

jni:
testArray[0]=200, 149, 5485270, testArray[0] addr = 475516656; testArray[1] addr = 475516657, testArray[2] addr = 475516658; testArray addr=475516656; sizeof(jintArray)=8
C before, testP[0]=0, 0, testP addr=38368912
C after, testP[0]=10, 11, testP addr=38368912

testArray[1]=224, 149, 38368982, testArray[0] addr = 475516664; testArray[1] addr = 475516665, testArray[2] addr = 475516666; testArray addr=475516664; sizeof(jintArray)=8
C before, testP[1]=0, 0, testP addr=38368912
C after, testP[1]=20, 21, testP addr=38368912

testArray[2]=248, 149, 38368982, testArray[0] addr = 475516672; testArray[1] addr = 475516673, testArray[2] addr = 475516674; testArray addr=475516672; sizeof(jintArray)=8
C before, testP[2]=0, 0, testP addr=38368912
C after, testP[2]=30, 31, testP addr=38368912

总结：掌握C语言的核心知识点指针，各种操作水到渠成。