cocos2d 中使用jni C++ 调用 Java 方法

1.简单数据类型例子

假设我们Java中有这么一个open的静态方法，它没有参数，有一个int的返回值。怎么在C++中调用它呢？

package cb.CbCCBLE;
public class CbCCBLECentralManager {
    public static final String TAG = "CbCCBLECentralManager Android";
    public static int open()
    {
    	Log.d(TAG,"open");
    	return 1;
    }
}

#if defined(ANDROID)
#include "platform/android/jni/JniHelper.h"
#include <jni.h>
int CbCCBLECentralManager::open()
{
    JniMethodInfo minfo;
    bool isHave = JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "open", "()I");
    if (! isHave)
    {
        CCLOG("FAIL: CbCCBLECentralManager - open");
        return 0;
    }
    
    int result = minfo.env->CallStaticIntMethod(minfo.classID, minfo.methodID);

    return result;
}
#endif

参数和返回值都会用特殊简写来代替，不是int，比如I代表int。完整的参数对于如下：

表格中提到的简单类型如果是多个的话用比如是：

public class CbCCBLECentralManager {
    public static final String TAG = "CbCCBLECentralManager Android";
    public static int open(int a, int b)
    {
    	Log.d(TAG,"open");
    	return 1;
    }
}

C++调用就如下了：

JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "open", "()II");

注意下CallStaticIntMethod，因为我们调用的是静态的返回int的方法，所以用了这个，要根据调用的方法不同而使用不同的东西，具体参考：  http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/functions.html#wp2556

2.看一个字符串的例子，字符串会有点麻烦：

Java：

public static int scanPeripheralWithName(String name, long duration)
    {
    	Log.d(TAG,"scanPeripheralWithName name:" + name + " duration:" + duration);
    	return 1;
    }

int CbCCBLECentralManager::scanPeripheralWithName(std::string name, long duration)
{
    JniMethodInfo minfo;
    bool isHave = JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "scanPeripheralWithName", "(Ljava/lang/String;J)I");
    if (! isHave)
    {
        CCLOG("FAIL: CbCCBLECentralManager - scanPeripheralWithName");
        return 0;
    }
    jstring jname = minfo.env->NewStringUTF(name.c_str());
    jlong jDuration = (long)duration;
    int result = minfo.env->CallStaticIntMethod(minfo.classID, minfo.methodID,jname, jDuration);
    
    return result;
}

要注意的是CallStaticIntMethod的最后2个参数，我们传进去了一个jstring和一个jlong。什么是jstring呢？是这样的：

jni有自己的数据类型，一般是j开头，用它们作为java 和 c++的中间媒体。

3.看一个数组例子

返回字符串的例子：

 public static String[] getAllPeripherals()
    {
        Log.d(TAG,"getAllPeripherals");
        String[] resultArray = {"testPeripheral1", "testPeripheral2"}; //just for test
        return resultArray;
    }

std::vector<std::string> CbCCBLECentralManager::getAllPeripherals()
{
    std::vector<std::string> stdResult;
    
    JniMethodInfo minfo;
    bool isHave = JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "getAllPeripherals", "()[Ljava/lang/String;");
    if (! isHave)
    {
        CCLOG("FAIL: CbCCBLECentralManager - getAllPeripherals");
        //return stdResult;
        return stdResult;
    }
    
    jobjectArray jResult = static_cast<jobjectArray>(minfo.env->CallStaticObjectMethod(minfo.classID, minfo.methodID));

    jsize resultSize = minfo.env->GetArrayLength(jResult);
    
    jsize index = 0;
    while(index < resultSize)
    {
        jstring eachElement = (jstring)minfo.env->GetObjectArrayElement(jResult, index);
        std::string stdString = JniHelper::jstring2string(eachElement);
        stdResult.push_back(stdString);
        ++index;
    }
    
    return stdResult;

}

传入字符串的例子：

public static int scanPeripheralWithServiceUUIDs(String[] serviceUUIDs, long duration)
    {
       Log.d(TAG,"scanPeripheralWithServiceUUIDs:" + duration);
    }

int CbCCBLECentralManager::scanPeripheralWithServiceUUIDs(std::vector<std::string>serviceUUIDs,long duration){
    JniMethodInfo minfo;
    bool isHave = JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "scanPeripheralWithServiceUUIDs", "([Ljava/lang/String;J)I");
    if (! isHave)
    {
        CCLOG("FAIL: CbCCBLECentralManager - scanPeripheralWithServiceUUIDs");
        return 0;
    }
    jint size = serviceUUIDs.size();
    jclass StringObject = minfo.env->FindClass("java/lang/String");
    jobjectArray jServiceUUIDsArray = minfo.env->NewObjectArray( size, StringObject, NULL);
    jlong jDuration = (long)duration;
    for(int i = 0; i < serviceUUIDs.size(); i++)
    {
        jstring serviceUUID = minfo.env->NewStringUTF(serviceUUIDs[i].c_str());
        minfo.env->SetObjectArrayElement(jServiceUUIDsArray, i, serviceUUID);
    }
    int result = minfo.env->CallStaticIntMethod(minfo.classID, minfo.methodID, jServiceUUIDsArray, jDuration);
    
    return result;
}

4.看一个自定义class的例子

package OurBLE;


public class OurBlePeripheralAdvertisementData
{
    public String deviceName;
public String getDeviceName(){
    	return deviceName;
    }
}

 public static OurBlePeripheralAdvertisementData getPeripheralAdvertisementData(String peripheralId)
    {
        Log.d(TAG,"getPeripheralAdvertisementData");
        OurBlePeripheralAdvertisementData result = new OurBlePeripheralAdvertisementData();
        result.deviceName = "deviceName1";
        return result;
    }

CbCCBLEPeripheralAdvertisementData CbCCBLECentralManager::getPeripheralAdvertisementData(std::string peripheralId)
{
    CbCCBLEPeripheralAdvertisementData data = CbCCBLEPeripheralAdvertisementData();
    JniMethodInfo minfo;
    bool isHave = JniHelper::getStaticMethodInfo(minfo, "cb/CbCCBLE/CbCCBLECentralManager", "getPeripheralAdvertisementData", "(Ljava/lang/String;)LOurBLE/OurBlePeripheralAdvertisementData;");
    if (! isHave)
    {
        CCLOG("FAIL: CbCCBLECentralManager - getPeripheralAdvertisementData");
        return data;
    }
    jstring jPeripheralId = minfo.env->NewStringUTF(peripheralId.c_str());
    jobject result = minfo.env->CallStaticObjectMethod(minfo.classID, minfo.methodID, jPeripheralId);
    
    jclass CbCCBLEPeripheralAdvertisementDataClass = minfo.env->FindClass("OurBLE/OurBlePeripheralAdvertisementData");
    jmethodID deviceNameMId = minfo.env->GetMethodID(CbCCBLEPeripheralAdvertisementDataClass, "getDeviceName", "()Ljava/lang/String;");  
    jstring jDeviceName = (jstring)minfo.env->CallObjectMethod(result, deviceNameMId);
    
    //deviceName
    data.deviceName = JniHelper::jstring2string(jDeviceName);

    return data;
}

主要这里还用了些FindClass，GetMethodID, CallObjectMethod API，这样class就能传递了。

jni真的是无所不能啊。 《cocos2d 中使用jni Java 调用 C++ 方法》