Sending parameters to java via c++

Question

My java class has a static function defined as follows:

public static void logEvent(final String eventName, final String jObject) {
        //Function data
    }

Now my cpp file has the following function

void PingoScreen::callApslarIntegration(){
    char* eventName="bingo";
    JniMethodInfo t;  

if (JniHelper::getStaticMethodInfo(t, "com/myapp/test/ApslarSetup","logEvent", "()V")) {
    t.env->CallStaticVoidMethod(t.classID, t.methodID);
    t.env->DeleteLocalRef(t.classID);
  }
}

How can i send two string params to the JAVA function via JNI ?

Kind Regards

===============================================================

void PingoScreen::callApsIntegration() {

    JniMethodInfo t;

    if (JniHelper::getStaticMethodInfo(t, "com/myapp/test/ApslarSetup",
            "logJSONEvent", "()V")) {

        const char* cstr1 = "Test1";
        const char* cstr2 = "Test2";

        jstring jstr1 = t.env->NewStringUTF(cstr1);
        jstring jstr2 = t.env->NewStringUTF(cstr2);

        t.env->CallStaticVoidMethod(t.classID, t.methodID,jstr1,jstr2);
        t.env->DeleteLocalRef(t.classID);
    }
}

The above function causes a crash ?

==================================

Finally got it to work

void PingoScreen::callApslarIntegration() {
    JniMethodInfo t;
    if (JniHelper::getStaticMethodInfo
                (t, "com/nbs/test/ApslarSetup",
                "logJSONEvent",
                "(Ljava/lang/String;Ljava/lang/String;)V")) {

        const char* cstr1 = "Test1";
        const char* cstr2 = "Test2";

        jstring jstr1 = t.env->NewStringUTF(cstr1);
        jstring jstr2 = t.env->NewStringUTF(cstr2);

        t.env->CallStaticVoidMethod(t.classID, t.methodID,jstr1,jstr2);
        t.env->DeleteLocalRef(t.classID);
    }
}

The crash was due to the line

if (JniHelper::getStaticMethodInfo
                    (t, "com/nbs/test/ApslarSetup",
                    "logJSONEvent",
                    "(Ljava/lang/String;Ljava/lang/String;)V"))

The signiture had to be Ljava/lang/String;Ljava/lang/String; and not Ljava/lang/String;Ljava/lang/String (notice the last semi-colon)

Tip: Use javap -s -public com.nbs.test.ApslarSetup | egrep -A 2 "logJSONEvent" to obtain signatures to use with JNI. — Tom Blodget
– Tom Blodget, Commented Dec 15, 2013 at 5:05

Dave · Accepted Answer · 2013-12-13 08:30:53Z

3

If you want to use CallStaticVoidMethod, simply pass two jstrings to it, like so:

const char* cstr1 = "Test1";
const char* cstr2 = "Test2";
jstring jstr1 = t.env->NewStringUTF(cstr1);
jstring jstr2 = t.env->NewStringUTF(cstr2);
t.env->CallStaticVoidMethod(t.classID, t.methodID, jstr1, jstr2);

You can also use CallStaticVoidMethodA or CallStaticVoidMethodV instead of simply CallStaticVoidMethod. See the documentation here.

edited Dec 13, 2013 at 8:30

answered Dec 13, 2013 at 8:11

Dave

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4 Comments

AndroidDev Over a year ago

I have edited my question with the updated function. Its causing a crash ?

Dave Over a year ago

Any error log? I'm not by a PC to test it. If the problem is in what I wrote, it's how I'm creating the jstrings, so you may find something quicker by Googling...

AndroidDev Over a year ago

Just a C stack strace that does not seem discernible to me ?

AndroidDev Over a year ago

@Dave- Thank you for your help. The problem was in my code. Thank you for your time.

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