Send MotionEvent from Java to JNI

问题

Is it possible to send MotionEvent from Java to C++ through JNI?

I have a method in C++ that should receive a pointer to AInputEvent to send it to the Game class:

JNIEXPORT void JNICALL
Java_com_game_ActivityMain_onTouch(JNIEnv *jenv, jclass obj,jobject event) {
    AInputEvent* inputEvent=(AInputEvent*)event;
    game->OnInput(inputEvent);
    }
};

in Java I declared the native method as:

public static native void onTouch(MotionEvent event);

but the application crashes when I tab on the screen.

Edit:

I guess this can't be done since Java TouchEvent and JNI AInputEnvent is not the same type. so what should I do?

Edit 2: I created a struct in JNI side and fill its fields by calling methods, is this the best scenario?

jclass eventClss=jenv->GetObjectClass(event);
jmethodID methodId = jenv->GetMethodID(eventClss, "getX", "()F");
float x = jenv->CallFloatMethod(event, methodId);

回答1:

I understood both AInputEvent and MotionEvent are different type and can't be cast to each other, so I send MotionEvent as jobject and accessed its method and fields using the JNI Environment.

JNIEXPORT void JNICALL
Java_com_game_ActivityMain_onTouch(JNIEnv *jenv, jclass obj,jobject motionEvent) {
    jclass motionEventClass=jenv->GetObjectClass(motionEvent);

    jmethodID pointersCountMethodId = jenv->GetMethodID(motionEventClass,"getPointerCount", "()I");
    int pointersCount = jenv->CallIntMethod(motionEvent, pointersCountMethodId);
    jmethodID getActionMethodId = jenv->GetMethodID(motionEventClass, "getAction", "()I");
    int32_t action = jenv->CallIntMethod(motionEvent, getActionMethodId);

    jmethodID getXMethodId = jenv->GetMethodID(motionEventClass, "getX", "(I)F");
    float x0 = jenv->CallFloatMethod(motionEvent, getXMethodId,0);

    jmethodID getYMethodId = jenv->GetMethodID(motionEventClass, "getY", "(I)F");
    float y0 = jenv->CallFloatMethod(motionEvent, getYMethodId,0);

    float x1=0;
    float y1=0;
    if(pointersCount>1){
        x1 = jenv->CallFloatMethod(motionEvent, getXMethodId,1);
        y1 = jenv->CallFloatMethod(motionEvent, getYMethodId,1);
    }

    States::MotionEvent inputEvent;
    inputEvent.PointersCount=pointersCount;
    inputEvent.Action=action;
    inputEvent.X0=x0;
    inputEvent.Y0=y0;
    inputEvent.X1=x1;
    inputEvent.Y1=y1;
    game->OnMotionEvent(inputEvent);
}

来源：https://stackoverflow.com/questions/57828868/send-motionevent-from-java-to-jni

标签

android

java-native-interface