JNI——结构体(即java中的类)的传入与设置——NativeMethod映射表
参考:http://www.cnblogs.com/skywang12345/archive/2013/05/26/3093593.html
http://www.2cto.com/kf/201501/372701.html
java 类:
package com.skywang.ndk; public class MyInfo { private String mName; private int mAge; private float mHeight; public String toString(){ return "mName:"+mName+", mAge:"+mAge+", mHeight:"+mHeight; } } ============================================ Person.java: package com.skywang.ndk; public class Person { private String mName; private int mAge; private float mHeight; public String toString(){ return "mName:"+mName+", mAge:"+mAge+", mHeight:"+mHeight; } }
package com.skywang.ndk; import android.app.Activity; import android.os.Bundle; import android.util.Log; public class NdkParam extends Activity { public static final String TAG="skywang--NdkParam"; public static final String TAG_MY="MY_skywang--NdkParam"; /** Called when the activity is first created. */ private Person person=null; private MyInfo myinfo = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Log.d(TAG, "on create."); person = new Person(); for (int i=0; i<3; i++) { getPersonInfoByIndex(person, i); Log.d(TAG, "person["+i+"] -- "+person); } Log.d(TAG, "==============================》MyInfo.《=================================="); myinfo = new MyInfo(); for (int i=0; i<3; i++) { getMyInfoByIndex(myinfo, i); Log.d(TAG, "myinfo["+i+"] -- "+myinfo); } } // jni private native int getPersonInfoByIndex(Person person, int index); private native int getMyInfoByIndex(MyInfo myinfo, int index); static { //System.loadLibrary("ndk_param"); System.loadLibrary("ndk_param"); } }
JNI:
头文件: #include <stdlib.h> #include <string.h> #include <stdio.h> #include <jni.h> #include <assert.h> // 获取数组的大小 # define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0]))) // 指定要注册的类,对应完整的java类名 #define JNIREG_CLASS "com/skywang/ndk/NdkParam" #define JNIPAR_CLASS "com/skywang/ndk/Person" #define JNIPAR_CLASS_MYINFO "com/skywang/ndk/MyInfo" // 引入log头文件 #include <android/log.h> // log标签 #define TAG "hello_param" // 定义info信息 #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG,__VA_ARGS__) // 定义debug信息 #define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__) // 定义error信息 #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__) // jfieldID结构体,用于保存类“Person.java”的filedID struct PersonOffsets { jfieldID name; jfieldID age; jfieldID height; } gPersonOffsets; struct MyInfoOffsets { jfieldID name; jfieldID age; jfieldID height; } gMyInfoOffsets; // 与“Person.java”对应的结构体,用于保存数据,并将数据赋值给Person.java的成员 typedef struct tagPerson { char mName[10]; int mAge; float mHeight; }Person; typedef struct tagMyInfo { char mName[10]; int mAge; float mHeight; }MyInfo; // 定义了3个Person static Person gPersons[] = { {"skywang", 25, 175}, {"eman" , 30, 166}, {"Dan" , 51, 172}, }; static MyInfo gMyInfos[] = { {"liu", 25, 175}, {"gang" , 30, 166}, {"hong" , 51, 172}, }; #define GPERSON_NUM NELEM(gPersons) #define GMYINFO_NUM NELEM(gMyInfos)
c文件: #include "ndk_param.h" /* * 根据index获取Person信息。 * 参数说明: * env : JNI 接口指针。 * claszz : Java 类对象。 * person : 输入参数,java对象 * index : 输入参数,序列号。 */ JNIEXPORT jint JNICALL getPersonInfoByIndex(JNIEnv *env, jobject clazz, jobject person, jint index) { // 若index无效,则直接返回-1。 if ((int)index<0 || (int)index>=GPERSON_NUM) return -1; // 将Person数组(gPersons)中的第index个成员赋值给pPerson指针 Person *pPerson = &gPersons[index]; // 设置java对象person的mName jstring name = (*env)->NewStringUTF(env, pPerson->mName); (*env)->SetObjectField(env, person, gPersonOffsets.name, name); // 设置java对象person的mAge (*env)->SetIntField(env, person, gPersonOffsets.age, pPerson->mAge); // 设置java对象person的mHeight (*env)->SetFloatField(env, person, gPersonOffsets.height, pPerson->mHeight); LOGD("%s index-%d mName:%s, mAge:%d, mHeight:%f\n", __func__, index, pPerson->mName, pPerson->mAge, pPerson->mHeight); return 0; } JNIEXPORT jint JNICALL getMyInfoByIndex(JNIEnv *env, jobject clazz, jobject myinfo, jint index) { // 若index无效,则直接返回-1。 if ((int)index<0 || (int)index>=GMYINFO_NUM) return -1; // 将Person数组(gPersons)中的第index个成员赋值给pPerson指针 MyInfo *pMyInfo = &gMyInfos[index]; // 设置java对象person的mName jstring name = (*env)->NewStringUTF(env, pMyInfo->mName); (*env)->SetObjectField(env, myinfo, gMyInfoOffsets.name, name); // 设置java对象person的mAge (*env)->SetIntField(env, myinfo, gMyInfoOffsets.age, pMyInfo->mAge); // 设置java对象person的mHeight (*env)->SetFloatField(env, myinfo, gMyInfoOffsets.height, pMyInfo->mHeight); LOGD("%s index-%d mName:%s, mAge:%d, mHeight:%f\n", __func__, index, pMyInfo->mName, pMyInfo->mAge, pMyInfo->mHeight); return 0; } // 初始化函数,用于获取Java中各个成员对应的fieldID。 static void nativeClassInit (JNIEnv *env) { jclass personClass = (*env)->FindClass(env, JNIPAR_CLASS); jclass myinfoClass = (*env)->FindClass(env, JNIPAR_CLASS_MYINFO); // 获取Person的mName成员对应的FieldID,并保存到gPersonOffsets中 gPersonOffsets.name = (*env)->GetFieldID(env, personClass, "mName" , "Ljava/lang/String;"); gMyInfoOffsets.name = (*env)->GetFieldID(env, myinfoClass, "mName" , "Ljava/lang/String;"); // 获取Person的mAge成员对应的FieldID,并保存到gPersonOffsets中 gPersonOffsets.age = (*env)->GetFieldID(env, personClass, "mAge" , "I"); gMyInfoOffsets.age = (*env)->GetFieldID(env, myinfoClass, "mAge" , "I"); // 获取Person的mHeight成员对应的FieldID,并保存到gPersonOffsets中 gPersonOffsets.height = (*env)->GetFieldID(env, personClass, "mHeight", "F"); gMyInfoOffsets.height = (*env)->GetFieldID(env, myinfoClass, "mHeight", "F"); } // Java和JNI函数的绑定表 static JNINativeMethod method_table[] = { { "getPersonInfoByIndex", "(Lcom/skywang/ndk/Person;I)I", (void*)getPersonInfoByIndex },//绑定 { "getMyInfoByIndex", "(Lcom/skywang/ndk/MyInfo;I)I", (void*)getMyInfoByIndex },//绑定 }; // 注册native方法到java中 static int registerNativeMethods(JNIEnv* env, const char* className, JNINativeMethod* gMethods, int numMethods) { jclass clazz; clazz = (*env)->FindClass(env, className); if (clazz == NULL) { return JNI_FALSE; } if ((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < 0) { return JNI_FALSE; } return JNI_TRUE; } int register_ndk_param(JNIEnv *env) { nativeClassInit(env); // 调用注册方法 return registerNativeMethods(env, JNIREG_CLASS, method_table, NELEM(method_table)); } // JNI_OnLoad在jni注册时,会被回调执行。 JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) { JNIEnv* env = NULL; jint result = -1; if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) { return result; } register_ndk_param(env); // 返回jni的版本 return JNI_VERSION_1_4; }