JniHelper的再说明

cocos2d-x引擎对jni的操作进行了封装，提供了一个非常好用的类:JniHelper，定义了一些常用的接口，该文件位于cocos/platform/android/jni目录下。

下面是源码：

/****************************************************************************
Copyright (c) 2010-2012 cocos2d-x.org
Copyright (c) 2013-2014 Chukong Technologies Inc.

http://www.cocos2d-x.org

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
****************************************************************************/
#ifndef __ANDROID_JNI_HELPER_H__
#define __ANDROID_JNI_HELPER_H__

#include 
#include 
#include "platform/CCPlatformMacros.h"

NS_CC_BEGIN

typedef struct JniMethodInfo_//这个结构体包含了JNI运行环境、调用的方法所在的类、以及调用的方法名
{
    JNIEnv *    env;
    jclass      classID;
    jmethodID   methodID;
} JniMethodInfo;

class CC_DLL JniHelper
{
public:
    static void setJavaVM(JavaVM *javaVM);
    static JavaVM* getJavaVM();
    static JNIEnv* getEnv();

    static bool setClassLoaderFrom(jobject activityInstance);
    static bool getStaticMethodInfo(JniMethodInfo &methodinfo,
                                    const char *className,
                                    const char *methodName,
                                    const char *paramCode);
    static bool getMethodInfo(JniMethodInfo &methodinfo,
                              const char *className,
                              const char *methodName,
                              const char *paramCode);

    static std::string jstring2string(jstring str);

    static jmethodID loadclassMethod_methodID;
    static jobject classloader;

private:
    static JNIEnv* cacheEnv(JavaVM* jvm);

    static bool getMethodInfo_DefaultClassLoader(JniMethodInfo &methodinfo,
                                                 const char *className,
                                                 const char *methodName,
                                                 const char *paramCode);

    static JavaVM* _psJavaVM;
};

NS_CC_END

#endif // __ANDROID_JNI_HELPER_H__

/****************************************************************************
Copyright (c) 2010-2012 cocos2d-x.org
Copyright (c) 2013-2014 Chukong Technologies Inc.

http://www.cocos2d-x.org

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
****************************************************************************/
#include "JniHelper.h"
#include 
#include 
#include 

#define  LOG_TAG    "JniHelper"
#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

static pthread_key_t g_key;

jclass _getClassID(const char *className) {
    if (nullptr == className) {
        return nullptr;
    }

    JNIEnv* env = cocos2d::JniHelper::getEnv();

    jstring _jstrClassName = env->NewStringUTF(className);

    jclass _clazz = (jclass) env->CallObjectMethod(cocos2d::JniHelper::classloader,
                                                   cocos2d::JniHelper::loadclassMethod_methodID,
                                                   _jstrClassName);

    if (nullptr == _clazz) {
        LOGE("Classloader failed to find class of %s", className);
        env->ExceptionClear();
    }

    env->DeleteLocalRef(_jstrClassName);
        
    return _clazz;
}

void _detachCurrentThread(void* a) {
    cocos2d::JniHelper::getJavaVM()->DetachCurrentThread();
}

namespace cocos2d {

    JavaVM* JniHelper::_psJavaVM = nullptr;
    jmethodID JniHelper::loadclassMethod_methodID = nullptr;
    jobject JniHelper::classloader = nullptr;

    JavaVM* JniHelper::getJavaVM() {
        pthread_t thisthread = pthread_self();
        LOGD("JniHelper::getJavaVM(), pthread_self() = %ld", thisthread);
        return _psJavaVM;
    }

    void JniHelper::setJavaVM(JavaVM *javaVM) {
        pthread_t thisthread = pthread_self();
        LOGD("JniHelper::setJavaVM(%p), pthread_self() = %ld", javaVM, thisthread);
        _psJavaVM = javaVM;

        pthread_key_create(&g_key, _detachCurrentThread);
    }

    JNIEnv* JniHelper::cacheEnv(JavaVM* jvm) {
        JNIEnv* _env = nullptr;
        // get jni environment
        jint ret = jvm->GetEnv((void**)&_env, JNI_VERSION_1_4);
        
        switch (ret) {
        case JNI_OK :
            // Success!
            pthread_setspecific(g_key, _env);
            return _env;
                
        case JNI_EDETACHED :
            // Thread not attached
            if (jvm->AttachCurrentThread(&_env, nullptr) < 0)
                {
                    LOGE("Failed to get the environment using AttachCurrentThread()");

                    return nullptr;
                } else {
                // Success : Attached and obtained JNIEnv!
                pthread_setspecific(g_key, _env);
                return _env;
            }
                
        case JNI_EVERSION :
            // Cannot recover from this error
            LOGE("JNI interface version 1.4 not supported");
        default :
            LOGE("Failed to get the environment using GetEnv()");
            return nullptr;
        }
    }

    JNIEnv* JniHelper::getEnv() {
        JNIEnv *_env = (JNIEnv *)pthread_getspecific(g_key);
        if (_env == nullptr)
            _env = JniHelper::cacheEnv(_psJavaVM);
        return _env;
    }

    bool JniHelper::setClassLoaderFrom(jobject activityinstance) {
        JniMethodInfo _getclassloaderMethod;
        if (!JniHelper::getMethodInfo_DefaultClassLoader(_getclassloaderMethod,
                                                         "android/content/Context",
                                                         "getClassLoader",
                                                         "()Ljava/lang/ClassLoader;")) {
            return false;
        }

        jobject _c = cocos2d::JniHelper::getEnv()->CallObjectMethod(activityinstance,
                                                                    _getclassloaderMethod.methodID);

        if (nullptr == _c) {
            return false;
        }

        JniMethodInfo _m;
        if (!JniHelper::getMethodInfo_DefaultClassLoader(_m,
                                                         "java/lang/ClassLoader",
                                                         "loadClass",
                                                         "(Ljava/lang/String;)Ljava/lang/Class;")) {
            return false;
        }

        JniHelper::classloader = cocos2d::JniHelper::getEnv()->NewGlobalRef(_c);
        JniHelper::loadclassMethod_methodID = _m.methodID;

        return true;
    }

    bool JniHelper::getStaticMethodInfo(JniMethodInfo &methodinfo,
                                        const char *className, 
                                        const char *methodName,
                                        const char *paramCode) {
        if ((nullptr == className) ||
            (nullptr == methodName) ||
            (nullptr == paramCode)) {
            return false;
        }

        JNIEnv *env = JniHelper::getEnv();
        if (!env) {
            LOGE("Failed to get JNIEnv");
            return false;
        }
            
        jclass classID = _getClassID(className);
        if (! classID) {
            LOGE("Failed to find class %s", className);
            env->ExceptionClear();
            return false;
        }

        jmethodID methodID = env->GetStaticMethodID(classID, methodName, paramCode);
        if (! methodID) {
            LOGE("Failed to find static method id of %s", methodName);
            env->ExceptionClear();
            return false;
        }
            
        methodinfo.classID = classID;
        methodinfo.env = env;
        methodinfo.methodID = methodID;
        return true;
    }

    bool JniHelper::getMethodInfo_DefaultClassLoader(JniMethodInfo &methodinfo,
                                                     const char *className,
                                                     const char *methodName,
                                                     const char *paramCode) {
        if ((nullptr == className) ||
            (nullptr == methodName) ||
            (nullptr == paramCode)) {
            return false;
        }

        JNIEnv *env = JniHelper::getEnv();
        if (!env) {
            return false;
        }

        jclass classID = env->FindClass(className);
        if (! classID) {
            LOGE("Failed to find class %s", className);
            env->ExceptionClear();
            return false;
        }

        jmethodID methodID = env->GetMethodID(classID, methodName, paramCode);
        if (! methodID) {
            LOGE("Failed to find method id of %s", methodName);
            env->ExceptionClear();
            return false;
        }

        methodinfo.classID = classID;
        methodinfo.env = env;
        methodinfo.methodID = methodID;

        return true;
    }

    bool JniHelper::getMethodInfo(JniMethodInfo &methodinfo,
                                  const char *className,
                                  const char *methodName,
                                  const char *paramCode) {
        if ((nullptr == className) ||
            (nullptr == methodName) ||
            (nullptr == paramCode)) {
            return false;
        }

        JNIEnv *env = JniHelper::getEnv();
        if (!env) {
            return false;
        }

        jclass classID = _getClassID(className);
        if (! classID) {
            LOGE("Failed to find class %s", className);
            env->ExceptionClear();
            return false;
        }

        jmethodID methodID = env->GetMethodID(classID, methodName, paramCode);
        if (! methodID) {
            LOGE("Failed to find method id of %s", methodName);
            env->ExceptionClear();
            return false;
        }

        methodinfo.classID = classID;
        methodinfo.env = env;
        methodinfo.methodID = methodID;

        return true;
    }

    std::string JniHelper::jstring2string(jstring jstr) {
        if (jstr == nullptr) {
            return "";
        }
        
        JNIEnv *env = JniHelper::getEnv();
        if (!env) {
            return nullptr;
        }

        const char* chars = env->GetStringUTFChars(jstr, nullptr);
        std::string ret(chars);
        env->ReleaseStringUTFChars(jstr, chars);

        return ret;
    }

} //namespace cocos2d

1、getStaticMethodInfo：

用来判断java类中静态函数是否存在，初始化结构体JniMethodInfo。该结构体封装了JNIEnv*和java.lang.Class、函数ID。第一个参数为JniMethodInfo，第二个参数是类的绝对路径，第三个参数是函数名，第四个参数是函数签名(参数和返回类型)。这样可以使用JNIEnv*调用CallStaticXXXMethod(jclass clazz，jmethodID methodID，...)和CallXXXMethod(jobject obj，jmethodID methodID，...)等常用函数，其中XXX代表函数返回值类型，如void、int等。

2、getMethodInfo：

用于调用Java类的非静态函数

上述两个函数会返回一个布尔值来判断当前操作是否成功，成功的话就可以调用函数了。如下：

3、CallStaticVoidMethod

void JniFun::longinWX(const char* APP_ID,const char* AppSecret)
	{
#if CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID
		JniMethodInfo minfo;
		bool isHave = JniHelper::getStaticMethodInfo(minfo,JAVA_CLASSNAME,"LoginWX","(Ljava/lang/String;Ljava/lang/String;)V");
		if (isHave)
		{
			jstring jAPP_ID = minfo.env->NewStringUTF(APP_ID);										 
			jstring jAppSecret = minfo.env->NewStringUTF(AppSecret);
			minfo.env->CallStaticVoidMethod(minfo.classID, minfo.methodID,jAPP_ID,jAppSecret);

			minfo.env->DeleteLocalRef(jAPP_ID);
			minfo.env->DeleteLocalRef(jAppSecret);
			minfo.env->DeleteLocalRef(minfo.classID); 
			cocos2d::log("JniFun call LoginWX over!");
		}
		else
		{
			//NoticeMsg::Instance().ShowLogon(false);
			cocos2d::log("JniFun call LoginWX error!");
		}
#endif
#if CC_TARGET_PLATFORM == CC_PLATFORM_IOS
        cocos2d::log("IosHelper::sendAuthRequest!");
		IosHelper::sendAuthRequest();
#endif
	}

这个时候就会调用到com/wx/Native里面的LoginWx函数了。