通过 android的JNI调用支付宝脱机认证库本地接口时，我欲返回一个类的实例，但是却报了几个错，最后查出来了原因。在此总结下。
错误一 ：E/dalvikvm﹕JNI ERROR (app bug): accessed stale local reference
，jclass is an invalid local reference AllocObject
原因是 android的垃圾回收机制问题，新版本已经不允许全局使用findclass出来的局部引用了，
会被GC回收掉。所以必须new成全局引用才行。
需要注意的地方是：
static jclass myClass;
一，需要把jclass声明为静态的 。二，注意这个地方，用NewGlobalRef把引用设为全局的。写在
JNIEXPORT jint JNI_OnLoad(JavaVM* vm,void *reserved)
中。
jclass tmp;
tmp = (*env)->FindClass(env,"com/example/ndktest/VerifyResponse"); if( tmp == NULL ) { ALOGE("%d..Can't find class %s!\n",__LINE__, "com/example/ndktest/VerifyResponse"); return -1; } myClass = (jclass)(*env)->NewGlobalRef(env,tmp);
错误二： E/dalvikvm﹕ JNI ERROR (app bug): accessed stale global reference 0x474e386e
需要注意的地方是：
(*env)->SetObjectField(env,obj,cardNo,"12345678");
这样的写法是错误的，正确应该是：
(*env)->SetObjectField(env,obj,cardNo,(jstring)(*env)->NewSringUTF(env,"1234567890"));
给欲返回的字符串赋值，需要用(*env)->NewSringUTF(env,"1234567890"
//========================================================================
以下为我欲通过JNI返回给java层调用的支付宝脱机校验的结果，类
VerifyResponse
的定义：
package com.example.ndktest; /** * Created by yang on 2017/7/8. */ public class VerifyResponse { byte[] cardData; int cardDataLength; String cardNo=""; String cardType; int errorCode; String record; String uid; public byte[] getCardData() { return this.cardData; } public int getCardDataLength() { return this.cardDataLength; } public String getCardNo() { return this.cardNo; } public String getCardType() { return this.cardType; } public int getErrorCode() { return this.errorCode; } public String getRecord() { return this.record; } public String getUid() { return this.uid; } public void setCardData(byte[] paramArrayOfByte) { this.cardData = paramArrayOfByte; } public void setCardDataLength(int paramInt) { this.cardDataLength = paramInt; } public void setCardNo(String paramString) { this.cardNo = paramString; } public void setCardType(String paramString) { this.cardType = paramString; } public void setErrorCode(int paramInt) { this.errorCode = paramInt; } public void setRecord(String paramString) { this.record = paramString; } public void setUid(String paramString) { this.uid = paramString; } public String toString() { return "uid:" + getUid() + "," + "record:" + getRecord() + "," + "cardType:" + getCardType() + "," + "cardNo:" + getCardNo() + "," + "cardData:" + getCardData() + "," + "cardDataLength:" + getCardDataLength() + "," + "errorCode:" + new Integer(getErrorCode()).toString(); } }
在android的应用层，声明如下：
public static native VerifyResponse verifyQrcode(byte[] qrCodeOfByte, String paramPos, int amount_cent);
在用c写的JNI 层，写法如下：
jobject JNICALL jni_verify_pos_qrcode(JNIEnv *env,jobject thiz,jbyteArray qrCodeOfByte, jstring paramPos, jint amount_cent) { int ret = 0; jboolean b; jsize qrcode_len; const unsigned char* qrcode= NULL; const char* pos_param = NULL; LOGD("%s>>> ..%s..%d..enter",LOG_TAG,__FUNCTION__,__LINE__); // jclass clazz = (*env)->FindClass(env,"com/example/ndktest/VerifyResponse"); // if(clazz == 0){ // return (void*)-100; // } jobject obj = (*env)->AllocObject(env,myClass); jfieldID errorCode = (*env)->GetFieldID(env,myClass,"errorCode","I"); if(errorCode == 0){ return (void*)-101; } jfieldID cardNo = (*env)->GetFieldID(env,myClass,"cardNo","Ljava/lang/String;"); if(cardNo == 0){ ret = -104; goto END; } jfieldID uid = (*env)->GetFieldID(env,myClass,"uid","Ljava/lang/String;"); if( uid == 0){ ret = -105; goto END; } pos_param= (char*)((*env)->GetStringUTFChars(env,paramPos, &b)); qrcode = (unsigned char*)(*env)->GetByteArrayElements(env,qrCodeOfByte, NULL); qrcode_len = (*env)->GetArrayLength(env,qrCodeOfByte); if(qrcode_len > 512){ ret = -103; goto END; } LOGI("===========校验二维码开始================\n"); //拼装验证请求 VERIFY_REQUEST_V2 verify_request; //装入二进制格式的二维码 verify_request.qrcode = qrcode; //装入二进制二维码长度 verify_request.qrcode_len = qrcode_len; //装入pos_param verify_request.pos_param = pos_param; //装入本次消费金额 如果生成脱机记录时还无法确定消费金额 装入0（单位：分） verify_request.amount_cent = amount_cent; VERIFY_RESPONSE_V2 verify_response; verify_response.uid = (char*)malloc(17); verify_response.uid_len = 17; verify_response.record = (char*)malloc(2048); verify_response.record_len = 2048; verify_response.card_no = (char*)malloc(32); verify_response.card_no_len = 32; verify_response.card_data = (unsigned char*)malloc(128); verify_response.card_data_len = 128; verify_response.card_type = (char*)malloc(16); verify_response.card_type_len = 16; /** * 调用接口验证二维码的有效性 */ ret = verify_qrcode_v2(&verify_request, &verify_response); /** * 处理返回的结果 */ if(ret != SUCCESS){ switch(ret){ case MALFORMED_QRCODE: LOGI("二维码格式错误！请提示用户二维码错误。\n"); break; case QRCODE_INFO_EXPIRED: LOGI("二维码过期！请提示用户刷新二维码。\n"); break; case QRCODE_KEY_EXPIRED: LOGI("二维码密钥过期！请提示用户联网后刷新二维码再使用。\n"); break; case POS_PARAM_ERROR: LOGI("商户传入的pos_param错误，请检查传入的pos_param。\n"); break; case QUOTA_EXCEEDED: LOGI("单笔额度超限！请提示用户由于额度限制无法过闸机。\n"); break; case NO_ENOUGH_MEMORY: LOGI("内存不足，极端错误，请检查程序运行空间是否足够。\n"); break; case QRCODE_DUPLICATED: LOGI("二维码重复！验证失败。\n"); break; case SYSTEM_ERROR: LOGI("系统异常！请联系支付宝技术人员。\n"); break; default: break; } LOGI("二维码校验结束！验证失败，不放行！\n"); LOGI("===========验证二维码 结束================\n"); goto END; } LOGI("从二维码中获取到的uid: %s\n", verify_response.uid); LOGI("验证成功后，返还的脱机记录: %s\n", verify_response.record); LOGI("二维码中的卡类型为: %s\n",verify_response.card_type); LOGI("二维码中的卡号为: %s\n", verify_response.card_no); bytes_to_hex_string(print_buf, sizeof(print_buf), verify_response.card_data, verify_response.card_data_len); LOGI("二维码中的二进制卡数据(hex string形式):%s\n", print_buf); /** * 1.商户可以根据uid判断是否为同一用户重复交易 */ /** * 2.商户可以根据qrcode判断是否为重复二维码 * 此判断也可以放在校验二维码前执行，商户可以自行选择 */ /** * 3.商户需要根据卡类型、卡号、卡数据 综合判断该卡的合法性、以及是否受理该卡 * 请商户保留 可受理 的脱机记录 */ LOGI("验证成功，请放行！\n"); LOGI("response ok！\n"); (*env)->SetObjectField(env,obj,cardNo,"12345678"); //(*env)->SetObjectField(env,obj,cardNo,(jstring)(*env)->NewSringUTF(env,"1234567890")); LOGI("response ok1！\n"); END: free(verify_response.uid); free(verify_response.record); free(verify_response.card_no); free(verify_response.card_data); free(verify_response.card_type); (*env)->SetIntField(env,obj,errorCode,ret); LOGI("response ok2！\n"); //(*env)->SetObjectField(env,obj,cardNo,"12345678"); (*env)->SetObjectField(env,obj,cardNo,(jstring)(*env)->NewStringUTF(env,"12345678")); LOGI("response ok3！\n"); (*env)->ReleaseStringUTFChars(env, paramPos, pos_param); (*env)->ReleaseByteArrayElements(env,qrCodeOfByte,(jbyte*)qrcode,0); return obj; }
//定义批量注册的数组，是注册的关键部分 static const JNINativeMethod gMethods[] = { {"qrcode_test", /* func2是在java中声明的native函数名 */ "()I", /* "()V"是函数的签名，可以通过javah获取。*/ (void*)jni_check_qrcode_test }, { "initPosVerify", "(Ljava/lang/String;Ljava/lang/String;)I", (void*)jni_init_pos_verify }, { "verifyQrcode", "([BLjava/lang/String;I)Lcom/example/ndktest/VerifyResponse;", (void*)jni_verify_pos_qrcode } }; // extern "C" { JNIEXPORT jint JNI_OnLoad(JavaVM* vm,void *reserved) { JNIEnv *env =NULL; jint result = -1; static const char* kClassName="com/example/ndktest/Test"; jclass clazz,tmp; LOGD("%s>>> ..%s..%d..enter",LOG_TAG,__FUNCTION__,__LINE__); if( (*vm)->GetEnv(vm,(void**)&env,JNI_VERSION_1_4) != JNI_OK ) { return result; } clazz = (*env)->FindClass(env,kClassName); if( clazz == NULL ) { ALOGE("%d..Can't find class %s!\n",__LINE__, kClassName); return -1; } tmp = (*env)->FindClass(env,"com/example/ndktest/VerifyResponse"); if( tmp == NULL ) { ALOGE("%d..Can't find class %s!\n",__LINE__, "com/example/ndktest/VerifyResponse"); return -1; } myClass = (jclass)(*env)->NewGlobalRef(env,tmp); if( (*env)->RegisterNatives( env,clazz, gMethods, sizeof(gMethods)/sizeof(gMethods[0]) ) != JNI_OK ) { ALOGE("Failed registering methods for %s!\n", kClassName); return -1; } LOGD(">>> ..%s..%d.exit",__FUNCTION__,__LINE__); return JNI_VERSION_1_4; } // }
