JNI / Android：用C ++调用Java中的非静态方法？

Question

I have got the following JNI method which currently calls a static Java method:

void bindToMarketBillingServiceJNI(const char *  inappID)
    {
        JniMethodInfo t;

        if (JniHelper::getStaticMethodInfo(t
            , "com/mycompany/games/js/TestsDemo"
            , "bindToMarketBillingService"
            , "(Ljava/lang/String;)V"))
        {
            jstring stringArg1;

            if (! inappID)
            {
                stringArg1 = t.env->NewStringUTF("1");
            }
            else
            {
                stringArg1 = t.env->NewStringUTF(inappID);
            }

            t.env->CallStaticVoidMethod(t.classID, t.methodID, stringArg1);

            t.env->DeleteLocalRef(stringArg1);
            t.env->DeleteLocalRef(t.classID);

        }
    }

Here is my Java method :

public static void bindToMarketBillingService(final String mSku)
    {

// Some code....

}

Everything works fine.

But now, I want to make my Java method NON STATIC. I thought that I just had to change:

• JniHelper::getStaticMethodInfo to JniHelper::getMethodInfo
• t.env->CallStaticVoidMethod to t.env->CallVoidMethod
• 'public static void bindToMarketBillingService(final String mSku)' to 'public void bindToMarketBillingService(final String mSku)'

But it crashes... (crash log below)

Anybody knows how to solve this issue ?

Thanks !!

08-20 11:54:11.009: A/libc(9379): Fatal signal 11 (SIGSEGV) at 0x0c1f4072 (code=1)
08-20 11:54:11.109: D/dalvikvm(31592): GC_CONCURRENT freed 735K, 12% free 9743K/10951K, paused 4ms+7ms
08-20 11:54:11.184: D/dalvikvm(1976): GC_CONCURRENT freed 1720K, 35% free 28243K/43399K, paused 5ms+13ms
08-20 11:54:11.194: I/ApplicationPolicy(1976): getActualApplicationStateEnabled() : true
08-20 11:54:11.219: D/PJ_MainApplication(9698): onApplicationCreate -> Now
08-20 11:54:11.334: D/dalvikvm(31592): GC_CONCURRENT freed 273K, 9% free 9981K/10951K, paused 3ms+3ms
08-20 11:54:11.409: D/PJ_CrashManager(9698): registerHandler -> Current handler class = com.android.internal.os.RuntimeInit$UncaughtHandler
08-20 11:54:11.469: I/DEBUG(9331): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
08-20 11:54:11.469: I/DEBUG(9331): Build fingerprint: 'samsung/GT-I9100/GT-I9100:4.0.3/IML74K/XWLPG:user/release-keys'
08-20 11:54:11.469: I/DEBUG(9331): pid: 9379, tid: 9403  >>> com.audioguidia.games.js <<<
08-20 11:54:11.469: I/DEBUG(9331): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0c1f4072
08-20 11:54:11.474: I/DEBUG(9331):  r0 00000000  r1 10000000  r2 fffffffc  r3 4cbb9ef0
08-20 11:54:11.474: I/DEBUG(9331):  r4 00273f98  r5 4c7f7fc4  r6 51134ad4  r7 415077f8
08-20 11:54:11.474: I/DEBUG(9331):  r8 00000001  r9 0c1f4071  10 4cbb9ee4  fp 51134a58
08-20 11:54:11.474: I/DEBUG(9331):  ip ffffffec  sp 51134a58  lr 4096864d  pc 40968aac  cpsr 00000030
08-20 11:54:11.474: I/DEBUG(9331):  d0  0000000000000000  d1  3f80000000000000
08-20 11:54:11.474: I/DEBUG(9331):  d2  0000000000000000  d3  0000000000000000
08-20 11:54:11.474: I/DEBUG(9331):  d4  0000000000000000  d5  3f80000000000000
etc....

Answer 1

Changing just the call on the env object is not sufficient.

First your new instance method should be declared in the Java class like: public void myMethod(...) (ie no static keyword here).

Secondly you need a java object reference to call an instance method, not just the class. ie you would do something like (please note I am using C syntax):

jmethodID midCallBack = (*env)->GetMethodID(env, thisClass, "myMethod", "()V");
if (NULL == midCallBack) return;

// Call back the method (which returns void), based on the Method ID
(*env)->CallVoidMethod(env, thisObj, midCallBack);

See section "5.3 Callback Instance Methods and Static Methods" at this link for more information

Answer 2

If you want to call non-static method, you have to create an object of that class and after that only call member method. Code looks like this

jmethodID constructor = env->GetMethodID(cls, "<init>", "()V"); //this is for defaul c-tor
jobject object = env->NewObject(cls, constructor);
//getting your method id
env->CallVoidMethod(object, methodId/*,your parameters*/); 

Answer 3

I just made a static method in java that call not static method:

static public void startActivity() {
    try {
        Activity mother = QtNative.activity();
        Intent intent = new Intent(mother, MainActivity.class);
        mother.startActivity(intent);
    } catch (Exception e) {
        Log.e(msgTag, e.toString());
        e.printStackTrace();
    }
}

And I called from C++ like this:

void FacebookAndroid::startAndroidFacebook() {
QAndroidJniObject::callStaticMethod<void>("org.qtproject.example.MainActivity",
                                          "startFacebookActivity",
                                          "()V");
}